Pentair MT125 User manual

Model MT125 Natural Propane
125K (33 kW) with cord 461092 461093
240 VAC NATURAL GAS/LP GAS
FOR YOUR SAFETY - READ BEFORE OPERATING
• IF YOU DO NOT FOLLOW THESE INSTRUCTIONS EXACTLY, A FIRE OR EXPLOSION MAY RESULT,
CAUSING PROPERTY DAMAGE, PERSONAL INJURY OR LOSS OF LIFE.
• IMPROPER INSTALLATION, ADJUSTMENT, ALTERATION, SERVICE OR MAINTENANCE CAN
CAUSE PROPERTY DAMAGE, PERSONAL INJURY OR DEATH. INSTALLATION AND SERVICE
MUST BE PERFORMED BY A QUALIFIED INSTALLER, SERVICE AGENCY OR THE GAS SUPPLIER.
• DO NOT PLACE ARTICLES ON OR AGAINST THIS APPLIANCE.
• DO NOT USE OR STORE FLAMMABLE MATERIALS NEAR THIS APPLIANCE.
• DO NOT SPRAY AEROSOLS IN THE VICINITY OF THIS APPLIANCE WHILE IT IS IN OPERATION.
• DO NOT TRY TO LIGHT ANY APPLIANCE.
• DO NOT TOUCH ANY ELECTRICAL SWITCH; DO NOT USE ANY PHONE IN YOUR BUILDING.
• IMMEDIATELY CALL YOUR GAS SUPPLIER FROM A NEIGHBOR’S PHONE.
FOLLOW THE GAS SUPPLIER’S INSTRUCTIONS.
• IF YOU CANNOT REACH YOUR GAS SUPPLIER, CALL THE FIRE DEPARTMENT.
Pentair Water Australia Pty. Ltd.s AU/NZ – Head Office
1-21 Monash Drive, Dandenong South, Victoria 3175 – Australia • 1300.137.344 • Fax [phone]
1620 Hawkins Ave., Sanford, NC 27330, USA • [phone] • [phone]
10951 W. Los Angeles Ave., Moorpark, CA 93021, USA • [phone] • [phone]
For additional free copies of this manual; call AUS: 1300 137 344 - NZ: 0800 654 112.
FOR YOUR SAFETY – This product must be installed
and serviced by authorized personnel, qualified in
pool/spa heater installation. Improper installation and/
or operation can create carbon monoxide gas and
flue gases which can cause serious injury, property
damage,or death. As an additional measure of safety,
Pentair Water Australia Pty. Ltd. strongly recommends
installation of suitable Carbon Monoxide detectors in
the vicinity of this heater. Improper installation and/or
operation will void the warranty.
OWNER:
Retain For
Future
Reference
(FOR OUTDOOR USE ONLY*) INSTALLATION AND USER’S GUIDE
MASTERTEMP 125 POOL AND SPA HEATER (AUSTRALIA)
Notice: MasterTemp Heaters are designed for use with NATURAL
and PROPANE gas only.
(*) For heater indoor use, see page 21.
ATTENTION INSTALLER: PLEASE GIVE THIS MANUAL
TO THE OWNER AND/OR OPERATOR ONCE INSTALLATION
IS COMPLETE.
www.pentairwater.com.au - www.pentair.com
WHAT TO DO IF YOU SMELL GAS

MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide 460906 Rev. D 8/2020
2
To identify the heater, see rating plate on the inner front panel of the heater. There are two designators for each heater,
one is the Model Number and the other is the Heater Identication Number (HIN).
a. HeaterIdenticationNumber(HIN)
The following example simplies the identication system:
1) MT : MasterTemp
2) Model Size : 125 : Input rating (Mega Joule [MJ]/hr)
3) Construction : (HD = Heavy Duty Model)
4) Fuel Type : (LP = Propane gas or N = Natural gas)
MT 125 HD
MT = MASTERTEMP
MODEL SIZE = MJ INPUT = Mega Joule [MJ] / HR
H. I. N.
HEATER IDENTIFICATION NUMBER
ID DESIGNATOR FOR PENTAIR WATER POOL AND SPA
MASTERTEMP™ 125 HEATER
Example:
123 4
FUEL TYPE = N = NATURAL GAS
LP = PROPANE GAS
125 (125 MJ /HR)
HD = HEAVY DUTY MODEL
N
Heater Identification Information
Heater Identification Information
HEATER IDENTIFICATION INFORMATION — (HIN)
The heater data rating plate is located on the inner front panel of the heater. To access the data rating
plate, unbolt and remove the side door access panel as shown below.
Heater Data Rating Plate Location
Door Acess Panel
Top Panel
Door Acess Panel
AUSTRALIAONLY
GAS SAFETY CERTIFICATION
DO NOT REMOVE
TM

460906 Rev. D 8/2020 MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide
3
Congratulations on your purchase of a MasterTemp 125 high performance heating system. Proper installation and
service of your new heating system and correct chemical maintenance of the water will ensure years of enjoyment. The
MasterTemp 125 heater is a compact, lightweight, efcient, induced-draft, gas red high performance pool and spa heater
that can be directly connected to schedule 40 PVC pipe. The heater also comes equipped with the Pentair multifunction
temperature controller which shows, at a glance, the proper functioning of the heater. All MasterTemp®125 heaters are
designed with a direct ignition device, HSI (hot-surface ignition), which eliminates the need for a standing pilot. The
MasterTemp®125 heater requires an external power source (240 VAC 50 Hz) to operate.
SPECIALINSTRUCTIONSTOOWNER:Retain this manual for future reference. This instruction manual provides
operating instructions, installation and service information for the MasterTemp 125 high performance heater. The
information in this manual applies to all MasterTemp®125 heater models. READANDREVIEWTHISMANUAL
COMPLETELY, it is very important that the owner/installer read and understand the section covering installation
instructions, and recognize the local and state codes before installing the MasterTemp®125 heater. Its use will reduce
service calls and chance of injury and will lengthen product life. History and experience has shown that most heater
damage is caused by improper installation practices.
IMPORTANT NOTICES
For the installer and operator of the MasterTemp pool and spa heater: The manufacturer’s warranty may be void
if, for any reason, the heater is improperly installed and/or operated. Be sure to follow the instructions set forth in
this manual. If you need more information or if you have any questions regarding to this pool heater, please contact
Pentair Water Australia Pty. Ltd. AU/NZ, AUS – at 1300 137 344 or + 61 3 9709 5800.
WARRANTY INFORMATION
The MasterTemp 125 pool heater is sold with a limited factory warranty. Specicdetailsaredescribedonthewar-
rantyregistrationcardwhichisincludedwiththeproduct. Return the warranty registration card after lling in the
serial number from the rating plate inside the heater.
Pentair’shighstandardsofexcellenceincludea policy of continuous product improvementresulting in your
state-of-the-artheater.Wereservetherighttomakeimprovementswhichchangethespecicationsoftheheater
withoutincurringanobligationtoupdatethecurrentheaterequipment.
Theseheatersaredesignedfortheheatingofchlorine,bromineorsaltsystemswimmingpoolsandspasorin
non-stationaryinstallations,andshouldneverbeemployedforuseasspaceheatingboilersorgeneralpurpose
waterheaters.Themanufacturer’swarrantymaybevoidif,foranyreason,theheaterisimproperlyinstalled
and/oroperated.Besuretofollowtheinstructionssetforthinthismanual.
CAUTION
OPERATING THIS HEATER CONTINUOUSLY AT WATER TEMPERATURE BELOW 20° C (68° F). WILL CAUSE HARMFUL
CONDENSATION AND WILL DAMAGE THE HEATER AND VOID THE WARRANTY. Do not use the heater to protect pools
or spas from freezing if the final maintenance temperature desired is below 20° C (68° F), as this will cause condensation
related problems.
Warning and Safety Instructions
IMPORTANT SAFETY INSTRUCTIONS
READ AND FOLLOW ALL INSTRUCTIONS
SAVE THESE INSTRUCTIONS
MasterTemp 125 High Performance Heater
Warning and Safety Instructions

MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide 460906 Rev. D 8/2020
4Warnings and Safety Instructions
CODE REQUIREMENTS
• Manufacturer’s Gas Installation Instructions
AS/NZS 5263.1.12:2019
• Local Gas Fitting Regulations,
• Municipal Building Codes,
• S.A.A. Wiring Code,
• Local Electrical Regulations
• Any other statutory regulations
• SANS 10087-1 or SANS 827
AUSTRALIA ONLY
GAS SAFETY CERTIFICATION
DO NOT REMOVE
TM
WARNING
Should overheating occur or the gas supply fail to shut off, turn off the manual gas control valve to the heater. Do not
use this heater if any part has been under water. Immediately call a qualified service technician to inspect the heater
and to replace any part of control system and gas control which has been under water.
1. Spa or hot tub water temperatures should never exceed 40° C. A temperature of 37° C. is considered safe for a healthy adult. Special
caution is suggested for young children. Prolonged immersion in hot water can induce hyperthermia.
2. Drinking of alcoholic beverages before or during spa or hot tub use can cause drowsiness which could lead to unconsciousness and
subsequently result in drowning.
3. Pregnant women beware! Soaking in water above 37° C. can cause fetal damage during the rst three months of pregnancy (resulting
in the birth of a brain-damaged or deformed child). Pregnant women should stick to the 37° C. maximum rule.
4. Before entering the spa or hot tub, the user should check the water temperature with an accurate thermometer. Spa or hot tub
thermostats may err in regulating water temperatures by as much as 3° C.
5. Persons with a medical history of heart disease, circulatory problems, diabetes or blood pressure problems should obtain their
physician’s advice before using spas or hot tubs.
6. Persons taking medication which induce drowsiness, such as tranquilizers, antihistamines or anticoagulants should not use spas or
hot tubs.
Installation must be in accordance with the following:
CONSUMER INFORMATION AND SAFETY
WARNING
The U.S. Consumer Product Safety Commission warns that carbon monoxide is an “invisible killer”. Carbon monoxide
is a colorless and odorless gas.
WARNING
The U.S. Consumer Product Safety Commission warns that elevated water temperature can be hazardous.
See below for water temperature guidelines before setting temperature.
1. Carbon monoxide is produced by burning fuel, including natural gas and propane.
2. Proper installation, operation and maintenance of fuel-burning appliances in the home is the most important factor in reducing carbon
monoxide poisoning.
3. Be sure that fuel burning appliances such as heaters are installed by professionals according to manufacturer’s instructions and codes.
4. Always follow the manufacturer’s directions for safe operation.
5. Have the heating system (including vents) inspected and serviced annually by a trained service technician.
6. Examine vents regularly for improper connections, visible cracks, rust or stains.
7. Install battery-operated carbon monoxide alarms. The alarms should be certied to the requirements of the most recent UL, IAS,
CSA and IAPMO standard for carbon monoxide alarms. Test carbon monoxide alarms regularly and replace dead batteries.
WARNING DO NOT MODIFY THIS APPLIANCE
DANGER
CARBON MONOXIDE GAS IS DEADLY – Exhaust from this pool heater contains toxic levels of carbon monoxide, a dangerous,
poisonous gas you cannot see or smell.

460906 Rev. D 8/2020 MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide
5
GENERAL SPECIFICATIONS
NOTICE:
• Combustion air contaminated by corrosive chemical fumes can damage the heater and will void the warranty.
• The Combination Gas Control Valve on this heater differs from most appliance gas controls. If it must be replaced,
for safety reasons replace it only with an identical gas control.
• The access door panels must be in place to provide proper ventilation. Do not operate the heater for more than five (5)
minutes with the access door panels removed.
• This heater is design certified by IAPMO as complying with the Standard for Gas Fired Pool Heaters, and is intended
for use in heating fresh water swimming pools or spas.
• The heater is designed for the heating of chlorine, bromine or salt system swimming pools and spas. It should NOT be
used as a space heating boiler, or general purpose water heater. The heater requires an external 240 VAC
single-phase electric power source.
• The heater should be located in an area where leakage of the heater or connections will not result in damage to the
area adjacent to the heater or to the structure. When such locations cannot be avoided, it is recommended that a
suitable drain pan, adequately drained, be installed under the heater. The pan must not restrict air flow.
• The heater may not be installed within 1.5 M (5 ft.) of the inside surface of a pool or spa unless it is separated by a solid
fence, wall or other permanent barrier.
CONSUMER INFORMATION AND SAFETY (CONTINUED)
WARNING
The Consumer Product Safety Commission warns that carbon monoxide is an “invisible killer”. Carbon monoxide is a
colorless and odorless gas.
1. Carbon monoxide is produced by burning fuel, including natural gas and propane.
2. Proper installation, operation and maintenance of fuel-burning appliances in the home is the most important
factor in reducing carbon monoxide poisoning.
3. Be sure that fuel burning appliances such as heaters are installed by professionals according to manufacturer’s
instructions and codes.
4. Always follow the manufacturer’s directions for safe operation.
5. Have the heating system (including vents) inspected and serviced annually by a trained service technician.
6. Examine vents regularly for improper connections, visible cracks, rust or stains.
7. Install battery-operated carbon monoxide alarms. The alarms should be certied to the requirements of the
most recent UL, IAS, CSA and IAPMO standard for carbon monoxide alarms. Test carbon monoxide alarms
regularly and replace dead batteries.
Warning and Safety Instructions

MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide 460906 Rev. D 8/2020
6
The MasterTemp 125Heater is designed and manufactured to provide many years of safe and reliable service when installed,
operated and maintained according to the information in this manual. Throughout this manual, safety warnings and cautions
are identified by the “ “ symbol. Be sure to read and comply with all of the warnings and cautions.
WARNING — This heater is equipped with an unconventional gas control valve that is factory set with
a manifold pressure of of 11 ± 5 Pa. Improper installation, adjustment, alteration, service or
maintenance can cause property damage, personal injury or loss of life. Installation or service must
be performed by a qualified installer, service agency or the gas supplier. If this control is replaced, it
must be replaced with an identical control.
Do not attempt to adjust the gas flow by adjusting the regulator setting.
WARNINGS AND SAFETY INSTRUCTIONS
CARBON MONOXIDE GAS IS DEADLY
READ OWNERS MANUAL COMPLETELY BEFORE OPERATING
THIS PRODUCT MUST BE INSTALLED AND SERVICED BY A PROFESSIONAL SERVICE
TECHNICIAN, QUALIFIED IN POOL HEATER INSTALLATION. Some jurisdictions require that
installers be licensed. Check with your local building authority about contractor licensing requirements.
Improper installation and/or operation could create carbon monoxide gas and flue gases which could
cause serious injury or death. Improper installation and/or operation will void the warranty.
Exhaust from this pool heater contains toxic levels of carbon monoxide, a dangerous, poisonous gas
you cannot see or smell. Symptoms of carbon monoxide exposure or poisoning include dizziness,
headache, nausea, weakness, sleepiness, muscular twitching, vomiting and inability to think clearly.
IF YOU EXPERIENCE ANY OF THE ABOVE SYMPTOMS, IMMEDIATELY TURN OFF THE POOL
HEATER, LEAVE THE VICINITY OF THE POOL OR SPA AND GET INTO FRESH AIR IMMEDIATELY.
THE POOL HEATER MUST BE THOROUGHLY TESTED BY A GAS PROFESSIONAL BEFORE
RESUMING OPERATION.
EXCESSIVE CARBON MONOXIDE EXPOSURE CAN CAUSE BRAIN DAMAGE OR DEATH.
• NEVER use this pool heater indoors without specified ventilation system (and properly installed
vent pipe).
• NEVER use this pool heater in the home or in partly enclosed areas (such as garages), unless
the specified ventilation system is used. If used outdoors, install far from open windows, doors,
vents and other openings.
• Pentair strongly recommends that all vents, pipes and exhaust systems be initially and
periodically tested for proper operation. This testing can be accomplished by using a hand-held
carbon monoxide meter and/or by consulting with a gas professional.
• Pool heaters must be used in conjunction with carbon monoxide detectors installed near the
pool heater. The carbon monoxide detectors must be periodically inspected for proper operation so
DANGER —
WARNING — FOR YOUR SAFETY
This product must be installed and serviced by a professional service technician, qualified in pool
heater installation. Some jurisdictions require that installers be licensed. Check with your local building
authority about contractor licensing requirements. Improper installation and/or operation could create
carbon monoxide gas and flue gases which could cause serious injury or death. Improper installation
and/or operation will void the warranty.
Warnings and Safety Instructions

460906 Rev. D 8/2020 MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide
7
WARNINGS AND SAFETY INFORMATION (CONTINUED)
WARNING — Risk of fire or explosion from incorrect fuel use or faulty fuel conversion. Do not try to run a
heater set up for natural gas on propane gas or vice versa. Only qualified service technicians should
attempt to convert heater from one fuel to the other. Do not attempt to alter the rated input or type of
gas by changing the orifice. If it is necessary to convert to a different type of gas, consult your Pentair
dealer. Serious malfunction of the burner can occur which may result in loss of life. Any additions,
changes, or conversions required in order for the appliance to satisfactorily meet the application needs
must be made by a Pentair dealer or other qualified agency using factory specified and approved
parts. The heater is available for use with natural gas or LP (propane) gas only. It is not designed to
operate with any other fuels. Refer to the nameplate for the type of gas the heater is equipped to use.
• Use heater only with the fuel for which it is designed.
• If a fuel conversion is necessary, refer this work to a qualified service technician or gas supplier
before putting the heater into operation.
WARNING — Risk of explosion if unit is installed near propane gas storage. Propane (LP) gas is heavier than
air. Consult local codes and fire protection authorities about specific installation requirements and
restrictions. Locate the heater away from propane gas storage and filling equipment as specified by
the Standard for the Storage and Handling of Liquefied Petroleum Gases (latest edition).
WARNING — Risk of fire. Do not place articles on, near or against the heater.
WARNING — Risk of burn hazard. To reduce the risk of injury, do not touch the side heater vent cover when the
heater is operating. Side heater vent covers are HOT and can burn when touched causing personal
injury. Do not allow children to play on or around heater or associated equipment. The average
temperature of the heaters flue exhaust is 204 degrees Celsius (°C).
WARNING — Risk of asphyxiation if exhaust is not correctly vented. Follow venting instructions exactly
when installing heater. Do not use a draft hood with this heater, as the exhaust is under pressure
from the burner blower and a draft hood will allow exhaust fumes to blow into the room housing the
heater. The heater is supplied with an integral venting system for outdoor installation.
CAUTION — Label all wires prior to disconnection when servicing controls. Wiring errors can cause improper
and dangerous operation. Wiring errors can also destroy the control board.
• Connect heater to 240 Volt, 50 Hz., Single Phase power only.
• Verify proper operation after servicing.
• Do not allow children to play on or around heater or associated equipment.
• Never allow children to use the pool or spa without adult supervision.
• Read and follow other safety information contained in this manual prior to operating this pool
heater.
Vent
Cover
Warning and Safety Instructions

MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide 460906 Rev. D 8/2020
8
P/N 460906 Rev. D 8/2020
Contents
Heater Identification Information ........................................................................................... 2
Warning and Safety Information ............................................................................................ 3
Important Notices ........................................................................................................................................... 3
Warranty Information ...................................................................................................................................... 3
Code Requirements........................................................................................................................................ 4
Consumer Information and Safety Information............................................................................................... 4 - 8
General Specifications.................................................................................................................................... 9
Section 1. Installation Instructions ........................................................................................ 10
Heater Description.......................................................................................................................................... 10
Sequence of Operation................................................................................................................................... 10
Putting the Heater into Service....................................................................................................................... 10
Specifications ................................................................................................................................................. 11
Plumbing Connections.................................................................................................................................... 12
Water Connections ......................................................................................................................................... 12
Multiple Heater Installation ............................................................................................................................. 13
Valves............................................................................................................................................................. 14
Manual By-Pass ............................................................................................................................................. 14
Below Pool Level Installation.......................................................................................................................... 14
Automatic By-Pass ......................................................................................................................................... 15
Gas Connections ............................................................................................................................................ 16
Sediment Traps ............................................................................................................................................. 16
Testing Gas Leaks and Pressure / Inlet Gas Pressure Requirements ........................................................... 17
Outdoor Heater Installation (Australia) .......................................................................................................... 18
Heater Clearances - Outdoor (Installation Venting Guidelines) ..................................................................... 19-20
Indoor Venting — General Requirements....................................................................................................... 21
Heater Clearances — General Requirements .............................................................................................. 21
Outside Vent Cover Removal ......................................................................................................................... 21
Vent Installation (Indoor Installation or Outdoor Shelter)................................................................................ 22
Vertical Venting (maximum elbows) ............................................................................................................... 22-25
Horizontal Venting .......................................................................................................................................... 26
Horizontal or Vertical Venting - Using Single-Wall Stainless Gas Vent......................................................... 27
Connecting Single-wall Stainless Steel Vent to the Heater ........................................................................ 28-29
Horizontal or Vertical Venting Flexible Duct (Flex-Vent) ................................................................................ 30
Combustion Air Supply ................................................................................................................................... 31
Direct Air Intake Exhaust Duct using 7.62 cm (3 in) PVC Pipe (Indoor Installation)....................................... 32
Control Panel Positioning ............................................................................................................................... 33
Final Installation Check .................................................................................................................................. 33
Contents
Customer Service
If you have questions about ordering Pentair replacement parts, and pool products, please use the following
contact information.
Customer Service and Technical Support, AUS (9 AM - 5PM, Mon - Fri, Australia Wide)
Phone: [phone] - Fax: [phone]
New Zealand (9 AM - 5PM, Mon - Fri, NZST) Phone: [phone] - Fax: [phone]
National Dealer Locator - Phone: [phone]
[e-mail] - www.pentair.com.au

460906 Rev. D 8/2020 MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide
9
Contents (Continued)
Section 1. Installation Instructions (Continued) ......................................................................... 34
Electrical Connections............................................................................................................................................... 34
Fireman’s Switch Connection/Remote Control Connections................................................................................. 35
MasterTemp 125 Heater Terminal Board/Control and Connection Wiring Diagram ............................................. 35
Heater Bonding ........................................................................................................................................................ 36
Connecting the MasterTemp Heater to the IntelliCenter Control System Load Center via RS-485.......................... 37
Connecting the RS-485 Cable from the Heater to the Load Center...................................................................... 38
Heater Wiring Diagram (3-Wire System)............................................................................................................... 40
Heater Electrical Schematic Ladder Diagram........................................................................................................ 41
Section 2. Operations.............................................................................................................. 42
Basic System Operation............................................................................................................................................ 42
HSI (Hot-Surface Ignition) Lighting/Operation........................................................................................................... 42
Start-Up and Operation Before Start-Up ................................................................................................................... 42
Operating Instructions .............................................................................................................................................. 43
To Turn Off Gas to Appliance............................................................................................................................ 43
Safety Controls/Air Flow Switch (AFS)...................................................................................................................... 44
Water Pressure Switch.......................................................................................................................................... 44
High Limits (Safety Device) ................................................................................................................................... 44
Operation of Ignition Module (ICM) ....................................................................................................................... 45
Diagnostic Indicator........................................................................................................................................... 45
Error PS Message................................................................................................................................................. 45
Control Panel............................................................................................................................................................. 46
Menu Navigation ....................................................................................................................................................... 46
Operating the Heater................................................................................................................................................. 46
Menu ..................................................................................................................................................................... ... 47
Section 3. Troubleshooting ..................................................................................................... 48
Initial Troubleshooting / Error and Fault Codes......................................................................................................... 49
Troubleshooting Instruction....................................................................................................................................... 50
Troubleshooting Chart (Important Read Me First)..................................................................................................... 50
Heater Will Not Fire - A ......................................................................................................................................... 51
Heater Will Not Fire - B ......................................................................................................................................... 52
IGN is On (Alarms: AGS, AFS, HLS, PS, EO1, or 126 ............................................................................................. 53
Diagnostic Alarms: AGS, AFS, HLS, PS, EO1, or 126.............................................................................................. 54
Diagnostic Alarms: ERR SFS.................................................................................................................................... 55
Burner Troubleshooting............................................................................................................................................. 56
Heat Exchanger Troubleshooting.............................................................................................................................. 56
Section 4. Maintenance ........................................................................................................... 57
Care and Maintenance / De-Iiming The Heater......................................................................................................... 57
Pressure Relief Valve (Not Factory Installed) ........................................................................................................... 57
After Start-Up (Checking Water Flow)....................................................................................................................... 58
After Start-Up / Spring, Fall and Winter Operation .................................................................................................... 58
Maintaining Pool Temperature .................................................................................................................................. 59
Energy Saving Tips ................................................................................................................................................... 59
Chemical Balance ..................................................................................................................................................... 59-60
Section 5. Replacement Parts ................................................................................................ 61-65
Contents

MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide 460906 Rev. D 8/2020
10
HEATER DESCRIPTION
Figure 1 shows a diagram of the heater showing how it operates.
Precisely matched orice plates meter the air and gas into the mixer.
The blower draws the air and gas through the mixer and forces it into
the burner’s ame holder. A sealed heat exchanger surrounds the ame
holder, discharging exhaust gases out the ue.
Two inch PVC water piping connects directly to the manifold/header on
the heat exchanger using 1.5” PVC slip unions provided with the heater.
The outer manifold remains cool; no heat sinks are required. A thermal
regulator and an internal bypass regulate the water ow through the heat
exchanger to maintain the correct outlet temperature. The heater operator
control panel board assembly is located on top of the heater.
SEQUENCE OF OPERATION
An electronic temperature sensing thermistor in the manifold adapter inlet controls the heater operation. When the inlet
water temperature drops below the temperature set on the operatingcontrol, the burnercontroller supplies power to the
combustion airblower through a series of safetyinterlocks. The interlocks consist of;
• the pressureswitch (PS), which senses that the pump is running,
• the highlimitswitch (HLS), which opens if the heat exchanger outlet temperature goes above 55° C (131° F), and
• the airowswitch (AFS), which senses the pressure drop across the air metering orice,
• the automatic gasshut-off (AGS) switch, which opens if the heat exchanger outlet temperature goes above 60° C
(140° F).
• the inlettemperaturecontrolswitch, which opens if the inlet temperature goes above 45° C (110° F).
• the stackuesensor (SFS), which shuts down the heater if the ue gas temperature reaches 249° C (480° F).
The air ow switch (AFS) senses the pressure drop across the air metering orice. As soon as there is sufcient air ow,
the AFS closes, closing the circuit to the hotsurfaceigniter (HSI), which ignites the fuel mixture. On a call for heat, the
blower and HSI are energized. In about 20 seconds, the gas valve opens and ignition occurs. The HSI then switches to a
sensing mode and monitors the ame. The heater is equipped with a digital operating control that enables the user to pre-
set the desired pool and spa water temperatures. The control enables the user to select between pool and spa heating, and
features a digital display that indicates the water temperature.
PUTTING THE HEATER INTO SERVICE
If the heater is installed below the level of the pool, or more than two feet above pool level, the pressure switch setting
should be adjusted. See WATER PRESSURE SWITCH, in the SAFETY CONTROLS Section (page 44).
Before putting the heater into service for the rst time, follow the instructions under “BEFORESTART-UP”(page42) in the front
ofthismanual.Checkforproperoperationoftheheaterbyfollowingthestepsunder“OPERATIONINSTRUCTIONS,”seepage43.
Damagetoequipmentcausedbyimproperinstallationorrepairwillvoidthewarranty.
Section 1. Installation Instructions
Section 1. Installation
Gas
Air
Mixer
Blower
Inlet
(Cold
Water)
Exhaust
Heating Coils
Outlet
(Mixed
Water)
Burner
Figure 1.
This product must be installed and serviced by a professional service technician, qualied in pool heater installation.
Pentair strongly recommends that all vents, pipes and exhaust systems be initially and periodically tested for proper
operation. This testing can be accomplished by using a hand-held carbon monoxide meter and/or by consulting with
a gas professional. Pool heaters must be used in conjunction with carbon monoxide detectors installed near the pool
heater. The carbon monoxide detectors must be periodically inspected for proper operation so as to insure continued
safety. Broken or malfunctioning carbon monoxide detectors must be replaced immediately. If not tted on the heater,
the installer must installed any safety devices according to the current
local codes.

460906 Rev. D 8/2020 MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide
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Section 1. Installation Instructions
DIMENSIONS IN INCHES
Figure 2.
5.5"
14cm
20.85"
52.95cm
21"
53 cm
29.43"
74.76
23"
58.4cm
10.87"
27.6cm
10.87"
28.cm
17.5"
44.5cm
ELECTRICAL
CONDUIT PORT
FRONT VIEWTOP VIEW
EXHAUST SIDE VIEWPLUMBING SIDE VIEW
These installation instructions are designed for use by qualied personnel only, trained especially for installation of this
type of heating equipment and related components. Some states require installation and repair by licensed personnel.
If this applies in your state, be sure your contractor bears the appropriate license. See Figure 2 for Outdoor and Indoor
Installations.
SPECIFICATIONS (DIMENSIONS IN CENTIMETERS AND INCHES)

MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide 460906 Rev. D 8/2020
12
PLUMBING CONNECTIONS
The MasterTemp®125 heater has the capability of direct
schedule 40 PVC plumbing connections. A set of bulkhead
ttings is included with the heater to insure conformity with
Pentair’s recommended PVC plumbing procedure. Other
plumbing connections can be used. See Figure 3 for plumbing
connections.
CAUTION
Before operating the heater on a new installation, turn on
the circulation pump and bleed all the air from the filter
using the air relief valve on top of the filter. Water should
flow freely through the heater. Do not operate the heater
unless water in the pool/spa is at the proper level. If a
manual by-pass is installed, temporarily close it to insure
that all air is purged from the heater.
WATER CONNECTIONS
The heater requires proper water ow and pressure for its
operation. See Figure 4 for the recommended installation. The
lter pump discharges to the lter, the lter discharges to the
heater, and the heater discharges directly to the pool or spa.
A manual bypass valve should be installed across the heater
when the pump ow exceeds 70 GPM (265 LPM ). See
“WATERFLOWRATE”Table1onpage14 for setting of
the manual by-pass valve.
Make sure that the outlet plumbing from the heater contains
no shut-off valves or other ow restrictions that could prevent
ow through the heater (except for pool installations as noted
below, or winterizing valves where needed). To switch ow
between the pool and spa, use a diverter valve. Do not use
any valve that can shut off the ow.
Install the chemical feeder downstream of the heater. Install a chemical resistant one-way check valve between the
heater and the chemical feeder to prevent back-siphoning through the heater when the pump is off.
NOTICE: MULTIPLE HEATER INSTALLATION: Seepage13,formultipleMasterTemp125heaterandFlowMeter
installations.
NOTICE: If the heater is plumbed in backwards, it will cycle continuously. Make sure piping from lter is not reversed
when installing heater.
Connect the heater directly to 3.81 cm (1.5”) PVC pipe, using the integral unions provided. Heat sinks are not required.
The low thermal mass of the heater will prevent overheating of the piping connected to the pump even if the heater shuts
down unexpectedly. If you are using a exible corrugated hose for above ground systems, use only Pentair approved
exible hose kits: P/N 155151 (1.8 cm - 6 ft.) and P/N 155005 (36.5 cm -12 ft.).
Occasionally a two-speed pump will not develop enough pressure on the low speed to operate the heater. In this case, run
the pump at high speed only to operate the heater. If this does not solve the problem, do not try to run the heater. Instead,
correct the installation.
Do not operate the heater while an automatic pool cleaner is also operating. If the circulation pump suction is plugged
(for example by leaves), there may not be adequate ow to the heater. Do not rely on the pressure switch in this case.
Pool
Main
Drain
Spa
From Pool 3-Way
Valve
3-Way
Valve
3-Way
Valve
Chlorinator
Heater
Pump
Check Valve
Filter
Figure 4.
Section 1. Installation Instructions
PUMP
FILTER
HEATER
MANUAL
BY-PASS
TO
POOL
GATE
VALVE
FROM
POOL
FROM
FILTER
Figure 3.

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13
Check Va
lves and Flow Meters
are optional on heater inlets
but help with system
balancing
Figure 6. Four MasterTemp® 125 Heaters Plumbing Hydraulic Diagram
INLET PORT
(COLD WATER)
OUTLET PORT
(HOT WATER)
OUTLET TO POOL
INLET FROM
PUMP/FILTER
OUTLET
TO POOL
OUTLET
TO POOL
OUTLET
TO POOL
OUTLET
TO POOL
All plumbing on multiple heater installations must be done in parallel. See Figure 5 and Figure 6.
To prevent heater overheating and to ensure heater longevity, water ow to each heater must be balanced for
optimum operation. To meet recommended ow rates, be sure all installed pipes are installed in accordance with local
and state codes. To allow for proper operation and service clearance, maintain spacing to adjacent heaters. Heaters
installed too close to one another may encounter operational issues associated with exhaust fumes.
MULTIPLE HEATER INSTALLATION
OPTIONAL
2" Ball Valve Bypass
Extend 12” (305 mm)
past end heater inlet
for hydraulic balancing
Extend 12” (305 mm)
past end heater inlet
for hydraulic balancing
Figure 5. Two MasterTemp® 125 Heaters Plumbing Hydraulic Diagram
FILTER
Check Valves and Flow Meters
are optional on heater inlets
but help with system
balancing
INLET PORT
(COLD WATER)
OUTLET PORT
(HOT WATER)
60-80 GPM/Unit (recommended).
Balance flow to each heater.
OUTLET TO POOL
INLET FROM
PUMP/FILTER
OUTLET
TO POOL
OUTLET
TO POOL
Section 1. Installation Instructions

MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide 460906 Rev. D 8/2020
14
BELOW POOL LEVEL INSTALLATION
If the heater is below water level, the pressure switch must be
adjusted. This adjustment must be done by a qualied service
technician. See following CAUTION before installation.
CAUTION
BELOW OR ABOVE POOL INSTALLATION
The WATER PRESSURE RELIEF VALVE SWITCH is set in the factory at 21 kPa (± 5 kPa) (3 ± 0.7 psi). This setting is for
a heater installed at pool level. If the heater is to be installed more than 0.3 m (1ft.) above or below, the water pressure
switch must be adjusted by a qualified service technician. See page 57.
FLOW SWITCH
If the heater is installed more than 1.5 m (5)’ above the pool or more than 1.2 m (4’) below the pool level, you will be
beyond the limits of the pressure switch and a flow switch must be installed. Locate and install the flow switch externally
on the outlet piping from the heater, as close as possible to the heater. Connect the flow switch wires in place of the
water pressure switch wires.
Section 1. Installation Instructions
VALVES
When any equipment is located below the surface of the pool or spa, valves should be placed in the circulation piping
system to isolate the equipment from the pool or spa. Check valves are recommended to prevent back-siphoning.
Back-siphoning is most likely to occur when the pump stops, creating a pressure-suction differential. Do NOT sanitize the
pool by putting chlorine tablets or sticks into the skimmer(s). When the pump is off, this will cause a high concentration
of chlorine to enter the heater, which could cause corrosion damage to the heat exchanger.
CAUTION
Exercise care when installing chemical feeders so as to not allow back siphoning of chemical into the heater, filters or
pump. When chemical feeders are installed in the circulation of the piping system, make sure the feeder outlet line is
down stream of the heater, and is equipped with a positive seal noncorrosive “Check Valve”, (P/N R172288), between
the feeder and heater.
MANUAL BY-PASS
Where the water ow rate exceeds the maximum 70 GPM (265 LPM),
a manual bypass should be installed and adjusted. After installing the
valve, adjust the valve to bring the ow rate within the acceptable range.
Then remove the valve handle or lock it in place to avoid tampering.
See Figure 7.
Table 1.
See page 57 for Pressure Relief Valve (optional)
Cool water in
Warm water out
OUTLET TO POOL
INLET TO HEATER
1. Set Manual By-Pass Valve.
2. Remove Handle.
Figure 7.
Model Min. LPM (GPM) Max. LPM (GPM) *
125 76 (20) 265 (70)
* DO NOT EXCEED THE MAXIMUM RECOMMENDED FLOW RATE
FOR THE CONNECTING PIPING.
PRESSURE
RELIEF
VALVE

460906 Rev. D 8/2020 MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide
15
Section 1. Installation Instructions
AUTOMATIC BY-PASS
Figure 8 shows a plumbing diagram for an automatic BY-PASS (IntelliValve®). This in conjunction with an IntelliFlo
VSF pump can provide added longevity of the heater and increased cost savings of operation. A 3-Port valve with an
IntelliValve actuator is installed at the heater inlet. A check valve is installed at the heater oulet so that water cannot
ow back into the heater. See instructions for Automatic Bypass valve kit (P/N 462048) for setting the open and closed
position of the IntelliValve.
WARM WATER OUT
CHECK VALVE
INTELLIVALVE
VALVE
COLD WATER IN
HOT WATER
OUT TO POOL
COLD
WATER
IN
Figure 8.

MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide 460906 Rev. D 8/2020
16
GAS CONNECTIONS
GAS LINE INSTALLATIONS
The gas supply must be installed in accordance with the Gas Installation Code, AS/NZS 5263.1.12:2019
and all applicable local codes. Before installing the gas line, be sure to check which gas the heater has been designed to
burn. This is important because different types of gas require different gas pipe sizes. The rating plate on the heater will
indicate which gas the heater is designed to burn. Table 2 below shows the recommended gas inlet pipe sizes required
for the distance from the gas meter to the heater. The table is for natural gas at a specic gravity of .65 and propane at
a specic gravity of 1.55.
When sizing gas lines, calculate 0.9 additional meters of straight pipe for every elbow used. When installing the gas line,
avoid getting dirt, grease or other foreign material in the pipe as this may cause damage to the gas valve, which may result in
heater failure.
The gas meter should be checked to make sure that it will supply enough gas to the heater and any other appliances that
may be used on the same meter. Insufcient gas supply will cause the heater to operate below its designed performance or
not at all. The gas line from the meter will usually be of a larger size than the gas valve supplied with the heater. Therefore
a reduction of the connecting gas pipe will be necessary. Make this reduction as close to the heater as possible. If the
gas pressure is not adjusted to the correct working pressure, the heater will be over gassed and cause serious damage
within minutes. This damage is not covered under the heater warranty.
Install a manual shut-off valve that conforms with Type1orType2asperAG201and/orAS4617standards and a
sediment trap/drip leg and union located outside the heater panels, see Figure 9. Do not use a restrictive gas cock.
The heater and any other gas appliances must be disconnected from the gas supply piping system during any pressure
testing on that system, (greater than 6.0 kPa). The heater and its gas connection must be leak tested before placing the
heater in operation. Donotuseametotestthegasline. Use soapy water or another nonammable method.
NOTE
A manual main shut-off valve must be installed externally to the heater.
WARNING
DO NOT INSTALL THE GAS LINE UNION INSIDE THE HEATER CABINET. THIS WILL VOID YOUR WARRANTY.
SEDIMENT TRAPS
Install a sediment trap and union located outside
the heater panels in accordance with National code
requirements. Do not use a restrictive gas cock. The
sediment trap shall be either a tee tting with a capped
nipple in the bottom outlet which can be removed for
cleaning, as shown in Figure 9, or an other device
recognized as an effective sediment trap. All gas
piping should be tested after installation in accordance
with local codes.
Figure 9.
Section 1. Installation Instructions
Manual
Shut-off
Valve
Sediment
Trap
Union
At least 9"
At least 3"
1" Dia. or larger
(See "Recommended
Pipe Sizes" Chart)
18–24" of 3/4"
Gas line from
Valve
Bell
Reducer

460906 Rev. D 8/2020 MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide
17
Section 1. Installation Instructions
TESTING GAS LEAKS AND GAS PRESSURE
THE MASTERTEMP HEATER IS INTENDED FOR INSTALLATIONWITH A METERED GAS PRESSURE REGULATOR.
Before operating the heater, the heater and its gas connections must be leak tested. DoNOTuseanopenametotest
forleaks. Test all gas connections for leaks with soapy water.
The gas valve must be completely disconnected from the gas supply piping system during any pressure testing of that
system at test pressures in excess of 6.0 kPa.
TESTING THE GAS PRESSURE THROUGH THE COMBINATION GAS CONTROL VALVE
WARNING
Risk of fire and explosion. Alteration, service, or maintenance of the Combination Gas Control Valve can lead to fire or explosion,
causing loss of life, personal injury, and/or property damage. DO NOT ATTEMPT TO ADJUST THE GAS CONTROL VALVE.
Figure 10.
1. Shut off the gas supply to the heater.
2. Loosen the small screw inside the pressure tap as shown in Figure 10.
3. Connect the manometer hose.
4. Open the gas supply to the heater.
5. Turn on the heater.
6. Take the gas pressure reading.
7. Turn off the heater.
8. Shut off the gas supply to the heater.
9. Disconnect the manometer hose.
10. Tighten the small screw inside the pressure tap.
Description Type Gas Supply Pressure
Natural Gas 1.0 kPa 6.0 Kpa
Propane Gas 2.5 kPa 6.0 pKa
NOTE: The minimum value approved for input adjustment. Do not exceed the
maximum supply pressure.
All readings must be taken while heater is operating. Any adjustments or
readings made while heater is off will result in performance problems.
INLET GAS PRESSURE REQUIREMENTS
CAUTION! This appliance is equipped with an unconventional gas control valve that is factory set with a manifold
pressure of 11 ± 5 kPa. Installation or service must be performed by a qualied installer, service agency, or the gas
supplier. If this control valve is replaced, it must be replaced with an identical control. The combination gas valve
incorporates dual shut-off valves and a negative-pressure regulator. For proper operation, the regulated pressure at the
outlet manifold of the valve must be 11 ± 5 kPa below the reference pressure at the blower mixer inlet, and the gas
valve ‘VENT’ tap must be connected to the end cap air orice as shown in Figure 9 (page 16).DONOTattemptto
adjustthegasinputbyadjustingtheregulatorsetting.Thecorrectgasregulatorsettingisrequiredtomaintain
propercombustionandmustNOTbealtered.
Lightly loosen the
small screw inside the pressure tap,
and attach/connect the manometer hose.
Table 2.

MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide 460906 Rev. D 8/2020
18 Section 1. Installation Instructions
OUTDOOR HEATER INSTALLATION (AUSTRALIA)
Thefollowinginformationisforheaterslocatedoutdoors,usingthebuilt-instacklessventingsystem.
WARNING
CARBON MONOXIDE GAS IS DEADLY – Exhaust from this pool heater contains carbon monoxide, a dangerous, poisonous
gas you cannot see or smell. Symptoms of carbon monoxide exposure or poisoning include dizziness, headache, nausea,
weakness, sleepiness, muscular twitching, vomiting and inability to think clearly. IF YOU EXPERIENCE ANY OF THE ABOVE
SYMPTOMS, IMMEDIATELY TURN OFF THE POOL HEATER, LEAVE THE VICINITY OF THE POOL OR SPA AND GET INTO
FRESH AIR IMMEDIATELY. THE POOL HEATER MUST BE THOROUGHLY TESTED BY A GAS PROFESSIONAL BEFORE
RESUMING OPERATION.
EXCESSIVE CARBON MONOXIDE EXPOSURE CAN CAUSE BRAIN DAMAGE OR DEATH.
Locate the heater in an open, unroofed area and on a level surface
that is protected from drainage or run-off. Install the heater in an area
where leaves or other debris will not collect on or around the heater.
It is recommended that a non-combustible base be a platform under
the heater constructed of hollow masonry blocks, not less than 100
millimeters (mm) thick (laid with ends unsealed and joints matched
for air circulation). Cover blocks with 0.75 mm (min.) galvanized
sheet metal, see Figure 11.
To avoid damage to the electronic components in the heater, take care
to prevent prolonged exposure to driving sources of water (such as
lawn sprinklers, heavy roof runoff, hoses, etc.). Avoid operation in
persistent, extreme, moist or salty environments.
In extreme weather, shut down the heater and disconnect the power
to it until the weather has moderated. In areas subject to hurricanes or
very high winds, purchase the Bolt Down Bracket Kit, P/N 460738,
see Figure 12.
Figure 11.
Lead
Anchor
For Heater mounting
bolts and clamps,
purchase separately
Bolt Down Bracket Kit,
Part No. 460738.
WARNING
Risk of explosion if a unit burning propane gas is installed in a pit or other low spot. Propane is heavier than air. Do not
install the heater using propane in pits or other locations where gas might collect. Consult your local building code officials to
determine installation requirements and specific installation restrictions of the heater relative to propane storage tanks and filling
equipment. Installation must meet the requirements for the Standard for the Storage and Handling of Liquid Petroleum Gases.
Consult local codes and fire protection authorities about specific installation restrictions.
Figure 12.
CAUTION: DO NOT install the heater within
1.5 M (5 ft.) of the inside surface of a pool or spa,
unless it is separated by a solid fence, wall or
other permanent barrier.
SHEET
METAL
BLOCKS
Hollow masonry blocks, not less than 100 mm (4 in) thick, (laid with ends unsealed and joints
matched for air circulation). Cover blocks with 0.75 mm (0.03 in) minimum) galvanized sheet metal.
150 mm
(6 in) Min.
BASE FOR USE ON
COMBUSTIBLE
FLOORS
Masonry blocks,
not less than 100 mm (4 in) thick
150 mm
(6 in) Min.

460906 Rev. D 8/2020 MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide
19
Section 1. Installation Instructions
Figure 13.
HEATER CLEARANCES – OUTDOOR
IMPORTANT!
• In an outdoor installation it is important to ensure water is diverted from overhanging eves with a proper
gutter/drainage system. The heater must be set on a level foundation for proper drainage.
• This unit shall not be operated outdoors at temperatures below -7o C.
The heater shall be located such that the heater’s ue terminal shall
comply with the Australian standard. (See Figure 15, page 21):
a) At least 300 mm below eaves, balconies and other projections
(Figure 13). * Where eaves have openings into the house or roof
space, the clearance required is 1500mm.
b) At least 150 mm from a return wall.
c) At least 300 mm from an external corner.
d) At least 1000 m from a gas meter.
e) At least 500 mm from an electricity meter or fuse box. The
prohibited area extends below the electricity meter or fuse to ground
level.
f) At least 75 mm from a drain pipe or soil pipe.
g) At least 150 mm horizontally from any building structure or obstruction facing a terminal.
h) At least 300 mm from any other ue terminal or combustion air intake.
i) At least 1500 mm from an openable window, door, non-mechanical air inlet, or any other opening into a
building with the exception of sub-oor ventilation.
j) At least 1000 mm from a mechanical air inlet, including a spa blower.
k) At least 1500 mm below an openable window, door, non-mechanical air inlet, or any other opening into a
building with the exception of sub-oor ventilation.
Where the heater is to be installed under a covered area, or in a recess, one of the following options shall
be applied to achieve ready dispersion of combustion products and avoidance of nuisance:
a) The covered area or recess shall be open on at least two sides and the terminal shall be located to
ensure a free ow of air across it is achieved; or
b) When on side is open, the ue terminal shall be within 500 mm of the opening, and discharging in the
direction of the opening. There shall be no other ue terminals, gas meter, electricity meter, fuse box or
openings into the building along the wall within the 500 mm distance. The ue terminal shall be located to
ensure that a free ow of air across it is achieved.
Orient the heater for convenient access to the water connections and the gas and electrical connections.
Check local building codes for setback (property line) requirements.
300 m or more

MASTERTEMP 125 Pool and Spa Heater Installation and User’s Guide 460906 Rev. D 8/2020
20
WARNING
Risk of fire and explosion. Do not spray aerosols in the vicinity of the heater while it is in operation. Chemicals should
not be stored near the heater installation. Combustion air can be contaminated by corrosive chemical fumes which
can damage the heater and will void the warranty.
CAUTION
If installing the heater next to or near an air conditioning unit
or a heat pump, allow a minimum of 1000 mm between the air
conditioning unit and the heater.
Figure 14.
VENTING GUIDELINES
OUTDOOR INSTALLATION
Vent Termination:
Must be installed at least 1500 mm away from
the building wall openings, and at the following
distances away from any door, window, or
gravity air inlet.
The heater must also have no obstructions above it.
Check local building codes
for setback requirements.
Air Inlet
Property Line
1500 mm
1500 mm
1500 mm
1500 mm
SIDE VIEW
Building
Window
Exhaust Grill
(Vent)
1500 mm
1500 mm
Section 1. Installation Instructions