Pentair Pool Products MiniMax NT Low NOx Series User manual

Rev. B 4-5-02 P/N 472089
1
1
FOR YOUR SAFETY - READ BEFORE OPERATING
Warning: If you do not follow these instructions exactly, a fire or explosion may
result, causing property damage, personal injury or loss of life.
For additional free copies of this manual; call [phone].
Do not store or use gasoline or other flammable vapors and
liquids in the vicinity of this or other appliances.
For Your
Safety
Warning: Improper installation, adjustment, alteration, service or maintenance can
cause property damage, personal injury or death. Installation and service must be
performed by a licensed qualified installer, service agency or the gas supplier.
MiniMax®NT Low NOx Series
POOL & SPA HEATERS
OPERATION & INSTALLATION MANUAL
WARNING
WHAT TO DO IF YOU SMELL GAS
•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.
WARNING
U.S. Patent Numbers
6,295,980
5,318,007 - 5,228,618
5,201,307 - 4,595,825
Pentair Pool Products, Inc.
1620 Hawkins Ave., Sanford, NC 27330 •[phone]
10951 W. Los Angeles Ave., Moorpark, CA 93021 •[phone]
1
To
Consumer
Retain For
Future
Reference

P/N 472089 Rev. B 4-5-02
2
Table of Contents
Introduction ............................................................................................................... 3
Important Notices ...................................................................................................................................................................... 3
Code Requirements ................................................................................................................................................................... 3
Warranty Information ................................................................................................................................................................. 4
Operation .................................................................................................................... 4
Safety Rules .............................................................................................................................................................................. 4
HSI (Hot-Surface Ignition) Lighting/Operation - Natural Gas ..................................................................................................... 5
Installation Instructions ............................................................................................ 6
Specifications ............................................................................................................................................................................ 6
Installation — Electrical ............................................................................................................................................................. 7
Installation — Remote Hook-Ups (2 and 3 Wire) ....................................................................................................................... 8
Installation — Operating Controls .............................................................................................................................................. 9 - 10
Installation — Troubleshooting (Controls) .................................................................................................................................. 10 - 11
Installation — Wiring Diagram ................................................................................................................................................... 12
Installation — Water Connections.............................................................................................................................................. 13
Installation — Plumbing ............................................................................................................................................................. 13
Installation — Gas Line ............................................................................................................................................................. 14
Pipe Sizing Chart/Gas Pressure Requirements ......................................................................................................................... 14
Regulated Manifold Pressure Test ............................................................................................................................................. 14
Venting — Indoor Installations ................................................................................................................................................... 15 - 18
Venting — Outdoor Installations ................................................................................................................................................ 19
Basic Operation — General Description .................................................................................................................................... 20
Basic Operation — Safety Controls ........................................................................................................................................... 21
Basic Operation — HSI Ignition Module .................................................................................................................................... 22
Maintenance ............................................................................................................................ 23
Maintenance Instructions ........................................................................................................................................................... 23
Pressure Relief Valve ................................................................................................................................................................ 23
Maintenance (Water Treatment) ................................................................................................................................................ 24
Trouble Shooting ....................................................................................................... 25
Troubleshooting (General) ......................................................................................................................................................... 25
Troubleshooting (Service Checks - Ignition Module) ................................................................................................................. 25
MiniMax NT Low NOx Parts List & Exploded View (Dual Voltage) ............................................ 26-27
Warranty Information ................................................................................................. Back Cover

Rev. B 4-5-02 P/N 472089
3
MiniMax®NT Low NOx
Pool and Spa Heaters
Congratulations on your purchase of a MiniMax NT Low NOx 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 MiniMax NT Low NOx is a compact, lightweight, efficient, induced-draft,
gas fired high performance pool and spa heater that can be directly connected to schedule 40 PVC pipe. The
MiniMax NT Low NOx, also comes equipped with the Pentair multifunction temperature controller which
shows, at a glance, the proper functioning of the heater. All HSI (hot-surface ignition) MiniMax NT Low
NOx heaters are designed with a direct ignition device (HSI) which eliminates the need for a standing pilot.
The MiniMax NT Low NOx requires an external power source (120/240 VAC 60 Hz) to operate.
IMPORTANT NOTICES
...For the installer and operator of the MiniMax NT Low NOx 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 any more information, or if you have any questions
regarding to this pool heater, please contact Pentair Pool Products, Inc. at [phone].
These heaters are designed for the heating of swimming pools and spas, and should never be employed for
use as space heating boilers, general purpose water heaters, in non-stationary installations, or for the heating
of salt water.
Do not use the heater to protect pools or spas from freezing if the final maintenance temperature desired is
below 60° F. as this will cause condensation related problems.
CODE REQUIREMENTS
The installation must conform with local codes or in the absence of local codes with the latest National Fuel
Gas Code, ANSI Z223.1, and the latest edition of the National Electrical Code, NFPA 70.
Installation in Canada to be made in accordance with the latest CAN/CGA-B149.1 or .2 and CSA C22.1
Canadian Electric Code, part 1.
Introduction

P/N 472089 Rev. B 4-5-02
4
Operation
This instruction manual provides operating
instructions, installation and service information
for the MiniMax NT Low NOx high performance
heater. The information in this manual applies to
the MiniMax NT Low NOx 200, 250, 300, and
400 natural gas models.
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 MiniMax NT Low NOx.
History and experience has shown that most heater
damage is caused by improper installation practices.
SAFETY RULES
1. Spa or hot tub water temperatures should never
exceed 104° F. A temperature of 100° F. is
considered safe for a healthy adult. Special
caution is suggested for young children.
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 100° F. can cause fetal damage during the
first three months of pregnancy (resulting in the
birth of a brain-damaged or deformed child).
Pregnant women should stick to the 100° F.
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 4° F.
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.
Should overheating occur or the gas supply fail to shut off, turn off the manual gas control valve to the
appliance. 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.
WARNING
WARRANTY INFORMATION
The MiniMax NT Low NOx pool heater is sold
with a limited factory warranty. Specific details are
described on the back cover of this manual and a
copy of the warranty and warranty registration
card are included with the product.Return the
warranty registration card after filling in the serial
number from the rating plate inside the heater.
Pentair Pool Products’ 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
specifications of the heater without incurring an
obligation to update the current heater equipment.
Operation

Rev. B 4-5-02 P/N 472089
5
Operation (Lighting)
FOR YOUR SAFETY: READ BEFORE LIGHTING
A. This heater is equipped with an ignition device
which automatically lights the main burners.
Do not try to light the burners by hand.
B. BEFORE OPERATING, smell all around
the heater area for gas. Be sure to smell next
to the floor because some gas is heavier than
air and will settle on the floor.
WHAT TO DO IF YOU SMELL GAS
- Do not try to light any heater.
- 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.
C. Use only your hand to push in or turn the gas
control knob. Never use tools. If the knob will
not push in or turn by hand, don't try to repair it.
Call a qualified service technician. Forced or
attempted repair may result in a fire or explosion.
D. 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 the control system and any gas
control which has been under water.
E. The MiniMax NT Low NOx incorporates the
Pentair temperature controller to aid you in the
operation of the heater, and to assist in
diagnosing a failure in the heater’s function.
MINIMAX NT LOW NOx HSI ELECTRONIC IGNITION LIGHTING/OPERATION - NATURAL GAS
1.STOP! Read the safety information above.
2. Set the thermostat to the lowest setting.
3. Turn off electric power to the heater.
4. This heater is equipped with an ignition device
which automatically lights main burners. Do
not try to light the burners by hand.
5. Remove the control access door.
6. Push in gas control knob slightly and turn clock-
wise to “OFF”. (If not on “OFF” position.)
7. Wait five (5) minutes to clear out any gas. If you
then smell gas, STOP! Follow "B" in the safety
information above. If you don't smell gas, go to the
next step.
8. Turn knob on gas control counterclockwise
to “ON”; see Figure 1.
If you do not follow these instructions exactly, a fire or explosion may result causing personal injury, loss of life
and property damage.
Do not attempt to light the heater if you suspect a natural gas leak. Lighting the heater can result in a fire or
explosion which can cause personal injury, death, and property damage.
WARNING
9. Replace the control access door.
10. Turn on the electrical power to the heater.
11. Set the thermostat to the desired setting.
12. If the heater will not operate, follow the instruc-
tions "To Turn Off Gas To Heater" and call your
service technician or gas supplier.
OPERATING INSTRUCTIONS
TO TURN OFF GAS TO APPLIANCE
1. Set the thermostat to lowest setting.
2. Turn off all electric power to the heater if
service is to be performed.
3. Remove control access door.
4. Push in gas control knob slightly and turn
clockwise to "OFF". Do not force.
5. Replace control access door.
Gas control knob shown in “ON” position.
Figure 1.
OFF
ON
Gas
Inlet

P/N 472089 Rev. B 4-5-02
6
Installation Instructions
IMPORTANT NOTICE: These installation instructions are designed for use by qualified 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.
SPECIFICATIONS
24.05
2 in. SOCKET
"A" DIM.
8.84
6.64
30.63
LEG
LEG
14.50
3.50
4.875
MODEL
200
250 24.63
21.63
"A" DIM.
15.50
300
400 34.13
27.63
7.35
24.05
"A" DIM.
8.84
6.64
30.63
LEG
LEG
14.50
3.50
4.875
INDOOR VENT ADAPTOR
4 in. Kit
P/N 460506
5 in. Kit
P/N 460507
15.50
7.35
Ø4.88
Ø5.88
4 in. Kit
P/N 460506
2.00
5 in. Kit
P/N 460507
MODEL
200
250 24.63
21.63
"A" DIM.
300
400 34.13
27.63
OUTDOOR VENTILATION
INDOOR VENTILATION
Figure 2.
Figure 3.
DIMENSIONS IN INCHES
DIMENSIONS IN INCHES

Rev. B 4-5-02 P/N 472089
7
Installation (Electrical)
ELECTRICAL, for MiniMax NT Low NOx Heaters
Electrical Rating 60 Hz 120 / 240 Volts AC, single phase
NOTE
The MiniMax NT Low NOx heater is prewired for 240 volt AC connection using the “RED/BROWN” female connector and the
“WHITE” common male connector; see below, Figure 4. If you require the heater to be connected to 120 volts AC, remove
the “RED/BROWN” female connector from the “WHITE” common connector; now locate the “BLUE” female connector and
plug it into the “WHITE” common connector.
When connecting the home wiring to the “Line Terminal Block” inside the junction box, follow the polarity as shown below.
Connecting to 120 VAC, make sure that you connect the positive wire to the positive terminal (L), the neutral wire is
connected to the neutral terminal (N) and the ground is connected to the ground terminal (GND); see below, Figure 5.
NOTE
If any of the original wiring supplied with this heater must be replaced, installer must supply (No. 18 AWG, 600V, 105° C. U.L.
approved AWM low energy stranded) copper wire or it’s equivalent. Thermal fuse wiring must be replaced with 18 AWG, 600V,
150° C. temp. rating.Interconnecting wiring to appliance must conform to the National electrical Code or supersede local
(wiring) codes.
In Canada: wires must be CSA approved.
WARNING
The heater must be electrically grounded and bonded in accordance with local codes or, in the absence
of local codes, with the latest national electrical codes ANSI/NFPA No. 70.
In Canada: CSA standard C22.1 Canada Electrical Code Part 1 and/or local codes.
Always use crimp type connectors when connecting two wires.
LINE TERMINAL BLOCK
RED/BROWN
FM CONNECTOR
FOR USE WITH
240 VOLT AC
BLUE
FM CONNECTOR
FOR USE WITH
120 VOLT AC
WHITE
COMMON MALE
CONNECTOR
TERMINAL BLOCK
FOR AC INPUT
120 / 240 VOLT SINGLE
PHASE "See Figure 2"
L
N
GREEN WIRE
WHITE WIRE
BLACK WIRE
GROUND
CONNECTION
NEUTRAL / WHITE 120VAC
LINE #1 FOR 240 VOLT AC
POSITIVE LINE FOR 120 VOLTS AC
LINE #2 FOR 240 VOLT AC
INTERNAL
FACTORY WIRES
Figure 4.
Figure 5.

P/N 472089 Rev. B 4-5-02
8
Installation (Remotes)
Figure 6.
Figure 7.
SPA COM POOL TPROBE
OUT RETURN 24 VAC HILMT IGNITION MOD
EXT SWITCH
THERMOSTAT CIRCUIT BOARD
JUMPER REQUIRED IF NO 2 WIRE REMOTE SWITCH
POOL/OFF/SPA
FRONT PANEL
THERMOSTAT SELECT SWITCH
TFUSE VALVE
PRESS
SPA COM POOL TPROBE
OUT RETURN 24 VAC HILMT IGNITION MOD
EXT SWITCH
THERMOSTAT CIRCUIT BOARD
JUMPER REQUIRED IF NO 2 WIRE REMOTE SWITCH
POOL/
OFF/SPA
FRONT PANEL
THERMOSTAT SELECT SWITCH
TFUSE VALVE
REMOTE POOL/OFF/SPA
THERMOSTAT SELECT SWITCH
PRESS
NOTE: When connecting a remote control to the MiniMax NT Heater, you must install the low voltage
thermostat wires in separate conduit from ANY line voltage wires. Failure to follow these
instructions will cause the thermostat relay to react erratically..
REMOTE SWITCH DUAL THERM IID ONLY
3 Wire Remote
2 Wire Remote

Rev. B 4-5-02 P/N 472089
9
Installation (Operating Controls)
Knob Stopper
Screw A
OPERATING (CONTROLS)
Dual Temperature Control System
For convenience and economy all MiniMax NT
Heaters are equipped with two thermostats on the
front of the heater control panel; see Figure 8.
Figure 8.
Figure 9.
THERMOSTAT KNOB STOPPER
Each thermostat is equipped with a mechanical stop that
can be locked or unlocked with use of a screwdriver to
prevent temperatures in excess of that desired by the user;
see Figure 9.
The maximum setting can be adjusted by loosening the screw
"A" and turning the stopper dial to desired maximum setting.
Lock the setting by tightening the screw. The Mechanical
stop is under the knob. Ensure that the knob is stopping at the
correct position when the knob is rotated clockwise from a
lower temperature position. (See Thermostat Adjustment.)
NOTE
To eliminate error due to piping heat losses,
measure pool temperature with an accurate
thermometer directly at the pool or spa.
THERMOSTAT ADJUSTMENT
The knob with locking feature eliminates the need for
constant thermostat adjustments. Set the knob pointer to
the desired pool or spa temperature.
If further adjustment is needed, rotate the knob until the
desired temperature is obtained. This knob position
corresponding to your desired maximum pool or spa
temperature may now be preset (locked) by the knob
stopper which prevents the knob from being turned beyond
the maximum temperature you set.
POWER (THERMOSTAT SELECT) SWITCH
The Pool/Off/Spa switch allows the heater to be turned off
when heating is not desired.
1. “Pool” position - Maintains selected pool
temperature.
2. “Off” position - Heater will not come on regardless
of drop in pool or spa temperature.
3. “Spa” position - This allows separate control of spa
water temperature.
INDICATOR LIGHT DESCRIPTION
The MiniMax NT Heater provides nine status indicator lights, six can be seen from the front of the control panel which
help you understand the operation of the heater. If something should go wrong, the lights will aid in troubleshooting the
problem. Three additional lights can be seen after opening the control panel. These three lights give the service technician
advanced troubleshooting capability. All the LED lights are green with the exception of the red service LED.
POWER LIGHT (POWER)
The light is on at all times, in any switch position, indicating
24 VAC power is being supplied to the control circuit. If it
fails to light, no other light will be on. Possible causes are:
a) external power to the heater is disconnected, check
service panel circuit breaker or fuses; b) local circuit
breaker inside the transformer has tripped -- investigate
cause before resetting; c) transformer has failed.
THERMOSTAT (TSTAT)
This light is on when the thermostat contacts close, signaled
by the water temperature falling below the setpoint, calling
for the heater to fire to maintain the desired water
temperature.
AUXILIARY (AUX)
This light is on when it indicates the remote switch contacts
are closed. This allows you to observe if your remote switch
is properly closing the heater control circuit. When shipped
from the factory a jumper is installed to maintain closed
circuit in the absence of a remote switch.
PRESSURE (PRESS)
This light is on when Spa/Pool Selector switch is on,
indicates the circulation pump is running properly. If
pressure light fails to light, the pump may have lost its
prime or water flow may be restricted by an inadvertently
closed valve or clogged filter or pump basket. If you have
determined that there is no water flow restriction to the
heater, you should call a qualified serviceman.

P/N 472089 Rev. B 4-5-02
10
Installation (Operating Controls, cont’d.)
PWR TSTAT RMT PRESS
SRVE
HI TEMP TFUSE
GAS VALVE
MV
MV
IGNITION MODULE
IND GND VAL
MV HEAT
CLOSE IF
NO MV
THERMOSTAT
RELAY
REMOTE PRESS TFUSE
HI TEMP
LIMIT SWITCHESBREAKER
CIRCUIT
TRANSFORMER
INCOMING
LINE VOLTAGE
THERMOSTAT CIRCUIT BOARD
LIMIT SWITCHES
HI TEMP
NO MV
CLOSE IF
THERMOSTAT CIRCUIT BOARD
TRANSFORMER
LINE VOLTAGE
INCOMING
PWR
CIRCUIT
BREAKER
TSTAT RMT
RELAY
THERMOSTAT
REMOTE
PRESS
SRVE
PRESS HI TEMP
MVTFUSE
TFUSE
HEAT
IGNITION MODULE
IND GND VAL GAS VALVE
MV
MV
WATER AT SELECTED TEMPERATURE.... NORMAL OPERATION
THERMOSTAT CALLING FOR HEAT - PUMP OFF(NO PRESSURE) BLOCKS FIRING
NORMAL OPERATION
SYMBOL TABLE
LED LIT LED OFF
SWITCH OR DEVICE
OPEN CIRCUIT
(BLOCK CURRENT)
SWITCH OR DEVICE
CLOSED CIRCUIT
(PASS CURRENT)
THERM
AUX
PRESS
HEAT
POWER
SERVICE
FRONT PANEL LEDS
FRONT PANEL LEDS
HEAT
PRESS
AUX
THERM
SERVICE
POWER
OR POOL/OFF/SPA THERMOSTAT SELECT SWITCH OFF.... NORMAL OPERATION
HEAT (HEAT)
The heat light is on any time the thermostat has
signaled a call for heat which initializes the ignition
safety firing circuit -- the light comes on to indicate
successful firing of the main burners.
SERVICE (SERVICE)
The service light is off during normal operation of
heater. The light only comes on if a problem with a
control has occurred or when the heater is first
firing. The problem must be investigated by the
serviceman prior to attempts to fire the heater again.
The diagrams that follow give examples of troubleshooting a malfunctioning heater using the assistance of
the indicator lights.
TROUBLESHOOTING (CONTROLS)
Example of troubleshooting with the assistance of the indicator lights.

Rev. B 4-5-02 P/N 472089
11
PRESS
PRESS
HEATER FIRING - NORMAL OPERATION
NOTE: SERVICE LED LIT FLAGS PROBLEM, TFUSE LED OFF SHOWS PROBLEM
PRESS
PRESS
THERMOSTAT CALLING FOR HEAT - BLOWN THERMAL FUSE BLOCKS FIRING
FRONT PANEL LEDS
HEAT
PRESS
AUX SERVICE
TRANSFORMER
THERM POWER
INCOMING
LINE VOLTAGE
FRONT PANEL LEDS
PRESS
HEAT
AUX
THERMOSTAT
PWR
CIRCUIT
BREAKER
TSTAT
RELAY
RMT
REMOTE
TRANSFORMER
THERM
INCOMING
LINE VOLTAGE
THERMOSTAT
PWR
BREAKER
CIRCUIT
TSTAT
RELAY RMT
REMOTE
THERMOSTAT CIRCUIT BOARD
NO MV
CLOSE IF
IGNITION MODULE
SRVE
HI TEMP
LIMIT SWITCHES
HI TEMP
TFUSE MV
IND
TFUSE
GND
THERMOSTAT CIRCUIT BOARD
GAS VALVE
HEAT
VAL
MV
MV
IGNITION MODULE
SRVE
CLOSE IF
NO MV
HI TEMP
LIMIT SWITCHES
HI TEMP
TFUSE MV
IND
TFUSE
GND GAS VALVE
HEAT
VAL
MV
MV
POWER
SERVICE
IS IN THERMAL FUSE CIRCUIT
SYMBOL TABLE
LED LIT LED OFF
SWITCH OR DEVICE
OPEN CIRCUIT
(BLOCK CURRENT)
SWITCH OR DEVICE
CLOSED CIRCUIT
(PASS CURRENT)
TROUBLESHOOTING (CONTROLS) - Continued
Installation (Operating Controls, cont’d.)

P/N 472089 Rev. B 4-5-02
12
Installation (Dual Voltage Wiring)
MiniMax NT Low NOx - HSI Electronic Ignition Wiring Diagram
(DUAL VOLTAGE w/6800 Control Board)
GRN
IGN MODULE
IGNITOR
HOT SURFACE
BURNER
GND VAL TH IGN L2 L1 IGN/240
MiniMax NT Low NOx Dual Voltage W/6800 Control Board Wiring Diagram
ORG
WHT
GRN
ORG
RED
THERMAL FUSE
WHT
BLU
RED
SWITCH
WATER PRESSURE
SPST EXTERNAL SWITCH
GAS VALVE
RED
WHT
BLU
RED
HIGH LIMIT
115˚F
1 2 3 4 5
3 2 1
GRN
AIR PRESS. SW.
BLU
RED
WHT
BLOCK TERM BLOCK
TERM
WHT
WHT
BLK
WHT
BLK
WHT
ORG
ORG
WHT
WHT
WHT WHT
BLOWER
BLK/WHT
BLK
RED/WHT
RED
PUR
ORG
WHT
BLK
WHT
IGN/120 FS
WHT BLK
120 VAC
OR
240 VAC
BLK
WHT
BLK
YEL
CON-FEM(BLU)
CON-MAL(WHT)
LOW GAS
F1
F2
24 VAC
WHT
POOL
JUMPER REQUIRED
J6
PROBE
TEMP.
VLV
TPROBE
J5
J8
24V
J4 J7
IGN MODULE
J10 J11
IND
PRESSURE SW.
IF ORIGINAL FACTORY WIRING MUST BE REPLACED, INSTALLER MUST SUPPLY UL/CSA APPROVED WIRE
WITH 18 AWG, 600V, 105˚ C TEMP. RATING.
ORG
ORG
SW/HL/TFUSE
J9
POOL
SPA COM
WHT WHT
ORG
BLK
WHT
WHT
GRN
GRN
OFF SPA
J2 J3
THERMAL FUSE WIRING MUST BE REPLACED WITH INTERCONNECTING WIRING TO APPLIANCE MUST CONFORM TO THE NATIONAL ELECTRICAL CODE OR SUPERSEDE LOCAL(WIRING) CODES.
WHT
WHT
WHT
WHT
IF NO REMOTE SWITCH
RED
RED/WHT
BLK
BLK/WHT
WHT
WHT WHT BLK YEL BLU
ORG
ORG
HIGH LIMIT
150˚F
18 AWG, 600V, 150˚ C TEMP. RATING.
FOR 120 VAC
CON-FEM(BRN)
FOR 240 VAC
ATTACH GROUND WIRE HERE
GRN
(ON THE SIDE JACKET) GREEN SCREW
PUR
ORG
YEL
BLK
WHT
FROM
TRANSFORMER
BLK
WHT
BLK
WHT
WHT
BLU
WHT
YEL
472082 REV.B
P4 P7 P10 P11
MV
MV
P9
P1
P2
THERMOSTAT
CIRCUIT BOARD
(6800)

Rev. B 4-5-02 P/N 472089
13
PLUMBING CONNECTIONS
The MiniMax NT Low NOx heater has the unique
capability of direct schedule 40 PVC plumbing
connections. A set of bulkhead fittings is included with
the MiniMax NT Low NOx to insure conformity with
Pentair’s recommended PVC plumbing procedure.
Other plumbing connections can be used.
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.
MANUAL BY-PASS
Where the flow rate exceeds the maximum 120
GPM, a manual bypass should be installed and
adjusted. After adjustments are made, the valve
handle should be removed to avoid tampering.
WATER CONNECTIONS
Reversible Inlet/Outlet Connection
The MiniMax NT Low NOx heater is factory
assembled with right side inlet/outlet water
connections. The inlet/outlet header can be reversed
for left side water connections without removing the
heat exchanger.
Reversing Water Connections
Tools required:
1/4 in. Screw Driver
9/16 in. Socket and Wrench
1/2 in. & 9/16 in. Open Wrench
1. Remove the right and left large inspection plates.
2. Disconnect all wires from the high-limit
switches except the short jumper wire.
3. Disconnect the pressure switch wiring.
4. Remove the temperature sensing bulb from the
inlet/outlet header. Note: If needed, you may cut
the wire ties holding them together.
5. Remove the 16 bolts holding the main inlet/
outlet head and return head in place, exchange
the heads, using the new tube seals supplied
with the heater, re-install the 16 bolts using
moderate torque.
6. Install the temperature sensing probe by passing
the wires through the hole provided on the left
side of the brace panel. Route wires through the
support bracket.
7. Reconnect all the high limit wires and the
pressure switch wiring, routing the wires
through the same hole as the thermostat sensor
wires.
8. Re-install the two large inspection plates on the
appropriate side.
PLUMBING
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
siphon.
CAUTION
Exercise care when installing chemical feeders so
as to not allow back siphoning of chemical into the
heater, filters or pump.
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Installation (Plumbing)
BELOW POOL INSTALLATION
If the heater is below water level, the pressure
switch must be adjusted. This adjustment must be
done by a qualified service technician. See Page 21,
Figure 21.
PUMP
FILTER
POOL
HEATER
CHECK
VALVE
MANUAL
BY-PASS
TO
POOL
GATE
VALVE
CHECK
VALVE
FROM
POOL
Figure 10.

P/N 472089 Rev. B 4-5-02
14
Installation (Gas Line)
GAS CONNECTIONS
GAS LINE INSTALLATIONS
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 1, shows which size pipe is
required for the distance from the gas meter to the
heater. The table is for natural gas at a specific
gravity of .65.
When sizing gas lines, calculate three (3) additional
feet 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.
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.
The heater and any other gas appliances must be
disconnected from the gas supply piping system
during any pressure testing on that system, (greater
that ½ PSIG).
The heater and its gas connection must be leak
tested before placing the heater in operation. Do not
use flame to test the gas line. Use soapy water or
another nonflammable method.
A manual main shut-off valve must be installed
externally to the heater.
Pipe Sized For Length Of Run In Equivalent Feet
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REGULATED MANIFOLD PRESSURE TEST
1. Attach the manometer to the heater jacket.
2. Shut off the main gas valve.
3. Remove 1/8 in. NPT plug on the outlet side of the
valve and screw in the fitting from the manometer kit.
4. Connect the manometer hose to the fitting.
5. Turn on the heater.
6. The manometer must read 4 in. WC for natural gas,
while operating.
7. For adjustment, remove the Regulator Adjustment
Cap and using a screwdriver turn the screw clock-
wise to increase - counterclockwise to decrease gas
pressure.
Table 1.
Natural
Maximum inlet gas pressure 10 in. WC
Minimum inlet gas pressure **5 in. WC
Normal manifold pressure 4 in. WC
*All Readings are taken with the heater fired. Any adjustments
or readings made with heater off will give incorrect readings.
** 6 WC for 400 model
OFF
ON
Regulator Adjustment Cap
1/8" NPT Plug
(Manifold Press)
1/8" NPT Plug
(Inlet Press)
Figure 11.
CAUTION
The use of Flexible Connectors (FLEX) is NOT
recommended as they cause high gas pressure drops.
MINIMAX NT LOW NOx GAS PRESSURE REQUIREMENTS*
WARNING
Do not install the gas line union inside the heater
cabinet. This will void your warranty.

Rev. B 4-5-02 P/N 472089
15
INDOOR VENTING—General Requirements
The vent pipe must be the same size or larger. The MiniMax NT Low NOx heaters are capable of a 360-degree
discharge rotation and operate with a positive vent static pressure and with a vent gas temperature less than
400° F. The total length of the horizontal run must not exceed the length that is listed below in the tables.
Please note the allowable vent runs for each stack pipe diameter are different and can not be exceeded.
Note that each 90-degree elbow reduces the maximum horizontal vent run by 8 feet and each 45-degree elbow
in the vent run reduces the maximum vent run by 4 feet. See the tables below for the maximum vent lengths
using a 90-degree and 45-degree elbows. The MiniMax NT Low NOx induced-draft pool and spa heater uses
positive pressure to push flue gases through the vent pipe to the outside. This requires a completely sealed vent
system—single wall vent pipe with sealed-seams and joints may be used. Flue gases under positive pressure
may escape into the dwelling with any cracks or loose joints in the vent pipe, or improper vent installation.
The vent pipe must be of a sealed-seam construction such as those listed for use with category III appliances.
Alternately, single wall or double-wall type B duct which has had duct seams and joints permanently sealed
using cements or other suitable means which are rated for use at the flue gas temperatures of 325° F. and are
permanent are acceptable. The use of listed thimbles, roof jacks and/or side vent terminals are required; and the
proper clearances to combustible materials must be maintained in accordance with type of vent pipe employed—
in the absence of a clearance recommendation by the vent pipe manufacturer, the requirements of the Uniform
Mechanical Code should be met. The ventilation air requirements for the MiniMax NT Low NOx heater and
can be found on page 17. It is recommended that vent runs over 18 feet be insulated to reduce condensation
related problems and/or the use of a condensate trap in the vent run close to the heater may be necessary in
certain installations such as cold climates. The MiniMax NT Low NOx is suitable for through-the-wall venting.
Recommended sources for Side-wall vent hood terminals include: The Field Controls Co. (2308 Airport Road,
Kingston, NC 28501, [phone]) and Tjernlund Products Inc. (1601 Ninth Street, White Bear Lake, MN
55110, [phone])—consult manufacturer for model information and availability.
CAUTION
Do NOT combine exhaust vent pipes to a common exhaust vent in multiple unit installations. Run separate vent pipes.
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Installation (Indoor)

P/N 472089 Rev. B 4-5-02
16
INDOOR INSTALLATION (USA ONLY)
OUTDOOR SHELTER INSTALLATION (CANADA)
See page 17 for (Indoor) Vent Adaptors
All products of combustion and vent gases must be
completely removed to the outside atmosphere through
a vent pipe which is connected to the stack adaptor. A
vent pipe extension of the same size must be connected
to the indoor stack adaptor and extended at least 2 feet
higher than highest point of the roof within a 10 foot
horizontal radius, and at least 3 ft. higher than the point
at which it passes through the roof, or as permitted by
local code; see Figures 12 and 13. The vent should
terminate with an approved vent cap (weather cap) for
protection against rain or blockage by snow. Double-
wall vent pipe and an approved roof jack shall be
employed through the roof penetration.
The heater must be located as close as practical to a
chimney or gas vent.
CAUTION
The heater should be installed at least 5 feet away
from the pool or spa.
The heater must be placed in a suitable room on a non-
combustible floor or on a non-combustible base and in
an area where leakage from heat exchanger or water
connections will not result in damage to the area
adjacent to the heater or the structure. When such
locations cannot be avoided, it is recommended that a
suitable drain pan with adequate drainage, be installed
under the heater. The pan must not restrict air flow.
Installations in basements, garages, or underground
structures where flammable liquids may be stored must
have the heater elevated 18 inches from the floor using
a non-combustible base. The following minimum
clearances from combustible materials must be
provided.
Side Front Back Top
Water Connection 18 in. 24 in. - -
Remaining 6 in. - 6 in. -
Ceiling Clearance - - - 18 in.*
*To ceiling or roof.
;;;
;;;
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Vent
Cap
Ridge
Chimney
3 ft. min.
2 ft. min.
10 ft.
Roof
Jack
AIR SUPPLY
VENTILATION
AIR SUPPLY
GAS COMBUSTION
OPTIONAL SIDE WALL VENT NT
VENT CAP AND
RISER FURNISHED
BY INSTALLER
Installation (Indoor)
The heater should not be installed closer than 6 inches to
any fences, walls or shrubs at any side or back, nor
closer than 18 inches at the plumbing side. A minimum
clearance of 24 inches must be maintained at the front of
the heater.
DOOR
6"
6"
24"
18"
Figure 14.
Figure 12.
Figure 13.

Rev. B 4-5-02 P/N 472089
17
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Installation (Indoor)
NOTE
The heater requires two uninterrupted air supply
openings; one for ventilation and one to supply
oxygen for proper gas combustion. The air supply
openings should be sized according to Table 2.
Air supply requirements below apply to all
MiniMax NT Low NOx heaters*.
CAUTION
Chemicals should not be stored near the heater
installation. Combustion air can be contaminated by
corrosive chemical fumes which can void the warranty.
*NOTE
The openings listed in Table 2 are free open vent
area—if the vents incorporate restrictive louvers,
the vent openings must be increased to
compensate for the area blocked by the louvers
(or grills).
b) Construct a non-combustible base from masonry
blocks as illustrated, see Figure 15.
I NSTALLATION ON FLOORS CONSTRUCTED
OF COMBUSTIBLE MATERIALS
The heater may be placed on a “combustible floor”
using either of the two methods listed below:
a) Use Listed Factory Non-combustible Base Kit
for use on combustible floors.
INDOOR VENT ADAPTORS
(FITS ALL MODELS)
The proper draft hood and adapter must be installed on
the heater as shown below and on pages 15 and 16:
BASE FOR USE ON COMBUSTIBLE FLOORS
24 GA. (MIN.) GALVANIZED SHEET METAL.
FOR AIR CIRCULATION). COVER BLOCKS WITH
(LAID WITH ENDS UNSEALED AND JOINTS MATCHED
HOLLOW MASONARY BLOCKS, NOT LESS THAN 4" THICK
SHEET METAL
BLOCKS
6" Min.
6" Min.
Figure 15.
Indoor Vent
Adaptor
Table 2.

P/N 472089 Rev. B 4-5-02
18
Detail H
INDOOR INSTALLATIONS
MINIMAX NT LOW NOx VENTING GUIDELINES
;;; ;;;
vent terminated at least 24" above any object within 10 ft.
Vent Cap
Ridge
Chimney
3 ft. min.
2 ft. min.
10 ft.
4'
7'
4'
Air Supply Ventilation
Air Supply Combustion
Vent Hood
Walkway
3'
1' min. 1' min.
1' min. above grade
Vent Hood
Vent Hood
E
H
D
F
G G
F
BC
A
must extend at least 3 ft. higher than the point at which it passes through the roof, or as permitted by local code. must use a double-wall vent pipe through the roof penetration. must terminate with an approved (listed) roof jack, storm collar, and vent/weather cap.
must be not less than 7 ft.above public walkways. must be at least 3 ft.above any outside air intake located within a 10 ft.radius. must NOT be within 3 ft. of an inside corner of the structure. must be at least 1 ft.above grade. must be located the following distances away from any door, window, or gravity air inlet:
4 ft. below 4 ft. horizontally 1 ft. above
Air Supply See Air Supply Requirements Table.
B
A
D E
F
J
K
L
C
G
Vent termination for side wall installations:
must be the same diameter as the vent connector. must be suitable for use with category III appliances which have flue gas temperatures of less than 400 deg. F. may use a single wall vent pipe with permanently sealed seams and joints.
Vent pipe extension:
Vent for roof penetration installations:
L
JK
Recommended sources for side wall Vent Hood; see page 15, Section Venting.
(Table 2 on page 17.)
Figure 17.
Installation (Indoor)

Rev. B 4-5-02 P/N 472089
19
VENTILATION
OUTDOOR INSTALLATION ONLY (Outdoor Shelter Installation in Canada, see page 16)
For outdoor installation with built in vent, the heater must be placed in a suitable area on a level, noncombustible
surface. Do not install the heater under an overhang with clearances less than 3 feet from the top of the heater. The
area under an overhang must be open on three sides.
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.
Maintain minimum clearances as indicated below. Install a minimum of 4 feet below, and 4 feet horizontally from any
opening to a building, see Figure 18.
IMPORTANT!
When locating the heater, consider that high winds can roll over or deflect off adjacent buildings
and walls. Normally, placing the heater at least three feet from any wall will minimize downdraft.
NOTE
This unit shall not be operated outdoors at temperatures below -20o F. for natural gas.
Installation (Outdoor)
MINIMAX NT VENTING GUIDELINES
OUTDOOR INSTALLATION
B
C
D
ECheck local building codes
for setback requirements.
Property Line
4'
1'
4'
4'
Walkway
3'
A
E
Figure 18.
CAUTION
If installing the heater next to or near an air conditioning unit or a heat pump, allow a minimum of 24 in.
between the air conditioning unit and the heater.

P/N 472089 Rev. B 4-5-02
20
GENERAL DESCRIPTION
The MiniMax NT Low NOx Pool and Spa Heater is a fan-assisted induced draft appliance. The MiniMax
NT Low NOx is available in 200,000, 250,000, 300,000 and 400,000 btu/hr. capacities and are certified for
both indoor and outdoor installations. The MiniMax NT Low NOx version natural gas pool heater must be
used for installations in the South Coast Air Quality Management District (SCAQMD)—these heaters are
certified to comply with SCAQMD Rule 1146.2 and also meet Ventura Co. APCD Rule 74.11.1.
The MiniMax NT Low NOx is designed to operate both in stackless outdoor installations and in indoor
stack vent installations—the indoor installation may be made using Kit 460506 or 460507; see pages 6 and 17,
vertical vent pipe or with a horizontal vent pipe and a Listed side-wall vent.
BASIC SYSTEM OPERATION
TO OPERATE HEATER
1. Start pump, make sure the pump is running and is primed, to close water pressure switch and
supply power to heater.
2. Set thermostat to lowest setting .
3. Set the thermostat rocker switch to the center “OFF” position.
4. Open the access doors.
5. Push in the gas control knob slightly and turn the knob clockwise to “OFF”.
6. Wait (5) minutes to clear out any gas. If you then smell gas STOP. Follow the safety information
(stated earlier in the lighting instructions section). If you don’t smell gas, go to the next step.
7. Turn the knob on the gas control counter clockwise to the “ON” position.
8. Replace the doors.
9. Push the thermostat select switch to “POOL” or “SPA” to start the heater.
10. Set the thermostat to the desired temperature.
a. Fan motor starts, which closes draft proving switch.
b. Ignition module is energized and the prepurge cycle is started approximately 15 seconds.
c. Check for powering up the (glow coil) hot-surface ignitor by viewing through the opening holes
on the face plate.
11. The ignitor will warm up and then gas valve opens to ignite the main burners.
12. Heater will operate until desired temperature is reached.
Basic Operation