HTP MC50 Installation manual

120 Braley Rd. P.O. Box 429 East Freetown, MA 02717-0429 www.htproducts.com
LP-171 Rev. 3.3.15
MC Series Gas-Fired
Circulating Heater
INSTALLATION
START-UP
MAINTENANCE
PARTS
Models
MC50 / MC80
MC99 / MC120
When installing models manufactured after July 7, 2008, you will notice additional selections on the control installer menu that will not
apply to this unit. DO NOT CHANGE THESE FACTORY SETTINGS. Refer to the Control Program Reference Chart within this manual
for selections that apply to this model.
This manual must be used by a qualified installer/service technician. Read all instructions in this manual before installing. Perform steps
in the given order. Failure to comply could result in substantial property damage, severe personal injury, or death.
NOTICE: HTP reserves the right to make product changes or updates without notice and will not be held liable for typographical errors
in literature.
NOTE TO CONSUMER: PLEASE KEEP ALL INSTRUCTIONS FOR FUTURE REFERENCE.

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LP-171 Rev. 3.3.15
IF THE INFORMATION IN THIS MANUAL IS NOT FOLLOWED EXACTLY, A FIRE OR EXPLOSION MAY RESULT, CAUSING
PROPERTY DAMAGE, PERSONAL INJURY, OR LOSS OF LIFE. DO NOT STORE GASOLINE OR OTHER FLAMMABLE VAPORS
AND LIQUIDS IN THE VICINITY OF THIS OR ANY OTHER HEATER.
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. Installation and service must be provided by a qualified installer,
service agency, or the gas supplier.

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LP-171 Rev. 3.3.15
The following defined terms are used throughout this manual to bring attention to the presence of hazards of various risk
levels, or to important product information.
DANGER indicates an imminently hazardous situation which, if not avoided, will result in death or serious injury.
WARNING indicates a potentially hazardous situation which, if not avoided, could result in death or serious injury.
CAUTION indicates a potentially hazardous situation which, if not avoided, may result in minor or moderate injury.
CAUTION used without the safety alert symbol indicates a potentially hazardous situation which, if not avoided, may result in property
damage.
FOREWORD
This manual is intended to be used in conjunction with other literature provided with the MC Series Gas-Fired Heater. This includes all
related control information. It is important that this manual, all other documents included with this system, and additional publications
including the National Fuel Gas Code, ANSI Z223.1-2002, be reviewed in their entirety before beginning any work.
Installation should be made in accordance with the regulations of the Authority Having Jurisdiction, local code authorities, and utility
companies which pertain to this type of water heating equipment.
Authority Having Jurisdiction (AHJ) –The Authority Having Jurisdiction may be a federal, state, local government, or individual such
as a fire chief, fire marshal, chief of a fire prevention bureau, labor department or health department, building official or electrical
inspector, or others having statutory authority. In some circumstances, the property owner or his/her agent assumes the role, and at
government installations, the commanding officer or departmental official may be the AHJ.
NOTE: HTP, Inc. reserves the right to modify product technical specifications and components without prior notice.
FOR THE INSTALLER
This heater must be installed by qualified and licensed personnel. The installer should be guided by the instructions furnished with the
heater, and with local codes and utility company requirements. In the absence of local codes, preference should be given to the
National Fuel Gas Code, ANSI Z223.1-2002.
INSTALLATIONS MUST COMPLY WITH:
Local, state, provincial, and national codes, laws, regulations and ordinances.
The latest version of the National Fuel Gas Code, ANSI Z223.1, from American Gas Association Laboratories, 8501 East Pleasant
Valley Road, Cleveland, OH 44131.
In Canada –CGA No. B149 (latest version), from Canadian Gas Association Laboratories, 55 Scarsdale Road, Don Mills, Ontario,
Canada M3B 2R3. Also, Canadian Electrical Code C 22.1, from Canadian Standards Association, 5060 Spectrum Way, Suite 100,
Mississauga, Ontario, Canada L4W 5N6.
Code for the installation of Heat Producing Appliances (latest version), from American Insurance Association, 85 John Street, New
York, NY 11038.
This manual must only be used by a qualified heating installer/service technician. Read all instructions in this manual before installing.
Perform steps in the order given. Failure to comply could result in severe personal injury, death or substantial property damage.

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LP-171 Rev. 3.3.15
The latest version of the National Electrical Code, NFPA No. 70.
NOTE: The gas manifold and controls met safe lighting and other performance criteria when undergoing tests specified in ANSI
Z21.10.3 –latest edition.
The hydronic supply and return connections of these products are for installation in closed loop systems ONLY! Use of this
product in any manner other than described in this manual may result in premature product failure, substantial property damage, severe
personal injury, or death. Damage or failure of this product (or the system in which it is installed) due to unauthorized use IS NOT
COVERED BY WARRANTY.
TABLE OF CONTENTS
PART 1 –GENERAL SAFETY INFORMATION..........................................................................................................................6
A. PRECAUTIONS..........................................................................................................................................................................6
B. IMPROPER COMBUSTION........................................................................................................................................................7
C. GAS............................................................................................................................................................................................7
D. WHEN SERVICING THE HEATER.............................................................................................................................................7
E. HEATER SYSTEM......................................................................................................................................................................7
F. WATER CHEMISTRY*................................................................................................................................................................7
G. WINTERIZING............................................................................................................................................................................8
PART 2 –BEFORE YOU START................................................................................................................................................8
A. WHAT’S IN THE BOX .................................................................................................................................................................8
B. HOW THE HEATER OPERATES...............................................................................................................................................8
C. OPTIONAL EQUIPMENT .........................................................................................................................................................10
PART 3 –PREPARE HEATER LOCATION..............................................................................................................................10
A. BEFORE LOCATING THE HEATER ........................................................................................................................................10
B. LEVELING ................................................................................................................................................................................11
C. CLEARANCES FOR SERVICE ACCESS.................................................................................................................................12
D. RESIDENTIAL GARAGE, CLOSET, AND ALCOVE INSTALLATIONS....................................................................................12
E. EXHAUST VENT AND INTAKE PIPE.......................................................................................................................................12
F. PREVENT COMBUSTION AIR CONTAMINATION..................................................................................................................13
G. REMOVING AN EXISTING HEATER FROM AN EXISTING COMMON VENT SYSTEM........................................................13
PART 4 –PREPARE HEATER..................................................................................................................................................14
A. REMOVE HEATER FROM BOX...............................................................................................................................................14
B. WALL MOUNTING CONSIDERATIONS...................................................................................................................................14
C. WALL MOUNTING INSTRUCTIONS........................................................................................................................................15
D. INSTALLATION STEPS............................................................................................................................................................15
PART 5 –HEATER PIPING.......................................................................................................................................................15
A. GENERAL PIPING INFORMATION..........................................................................................................................................15
B. RELIEF VALVE.........................................................................................................................................................................16
C. SEPARATE LOW WATER CUTOFF........................................................................................................................................17
D. BACKFLOW PREVENTER.......................................................................................................................................................17
E. SYSTEM WATER PIPING METHODS .....................................................................................................................................17

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F. CIRCULATORS.........................................................................................................................................................................17
G. HYDRONIC PIPING WITH CIRCULATORS, ZONE VALVES, AND MULTIPLE HEATERS....................................................18
H. CIRCULATOR SIZING..............................................................................................................................................................18
I. ZONING WITH ZONE VALVES..................................................................................................................................................19
J. ZONING WITH CIRCULATORS................................................................................................................................................19
K. MULTIPLE HEATERS...............................................................................................................................................................19
L. FILL AND PURGE HEATING SYSTEM ....................................................................................................................................20
M. PIPING DETAILS .....................................................................................................................................................................21
PART 6 –PIPING WITH OPTIONAL VISION 1 SYSTEM.........................................................................................................28
A. VISION 1 SYSTEM PIPING......................................................................................................................................................28
B. ZONING WITH ZONE VALVES USING VISION 1....................................................................................................................28
C. ZONING WITH CIRCULATORS USING VISION 1...................................................................................................................28
D. PIPING DETAILS WITH THE VISION 1 SYSTEM....................................................................................................................29
PART 7 –VENTING, COMBUSTION AIR, AND CONDENSATE REMOVAL...........................................................................39
A. GENERAL.................................................................................................................................................................................39
B. APPROVED MATERIALS FOR EXHAUST VENT AND INTAKE PIPE ....................................................................................40
C. REQUIREMENTS FOR INSTALLATION IN CANADA..............................................................................................................40
D. EXHAUST VENT AND INTAKE PIPE LOCATION....................................................................................................................41
E. ROTATING THE FLUE ADAPTER ...........................................................................................................................................44
F. EXHAUST VENT AND INTAKE PIPE SIZING ..........................................................................................................................45
G. LONGER VENT RUNS.............................................................................................................................................................45
H. EXHAUST VENT AND INTAKE PIPE INSTALLATION ............................................................................................................46
I. VENTING DRAWINGS...............................................................................................................................................................46
PART 8 –GAS PIPING..............................................................................................................................................................48
A. GAS CONNECTION .................................................................................................................................................................48
B. GAS PIPING .............................................................................................................................................................................50
C. CHECK INLET GAS PRESSURE.............................................................................................................................................50
D. GAS VALVE..............................................................................................................................................................................51
PART 9 –FIELD WIRING..........................................................................................................................................................52
A. INSTALLATION MUST COMPLY WITH:..................................................................................................................................52
B. FIELD WIRING..........................................................................................................................................................................52
C. LINE VOLTAGE WIRING..........................................................................................................................................................52
D. THERMOSTAT.........................................................................................................................................................................52
PART 10 –FIELD WIRING –VISION 1 OPTION ......................................................................................................................55
PART 11 –START-UP PREPARATION....................................................................................................................................57
A. CHECK/CONTROL WATER CHEMISTRY...............................................................................................................................57
B. FREEZE PROTECTION (WHEN USED) ..................................................................................................................................58
C. FILL AND TEST WATER SYSTEM ..........................................................................................................................................58
D. AIR PURGING PROCEDURE FOR HEAT EXCHANGER........................................................................................................58
E. PURGE AIR FROM WATER SYSTEM.....................................................................................................................................59
F. CHECK FOR GAS LEAKS........................................................................................................................................................60

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LP-171 Rev. 3.3.15
G. CHECK THERMOSTAT CIRCUIT(S) .......................................................................................................................................60
H. CONDENSATE REMOVAL ......................................................................................................................................................60
I. FINAL CHECKS BEFORE STARTING HEATER.......................................................................................................................60
PART 12 –START-UP PROCEDURE.......................................................................................................................................61
A. OPERATING INSTRUCTIONS.................................................................................................................................................61
B. ADJUSTING THE SET POINT..................................................................................................................................................61
C. STATUS MENU........................................................................................................................................................................62
D. TEST MODE.............................................................................................................................................................................62
PART 13 –START-UP PROCEDURES WITH VISION 1 OPTION ...........................................................................................62
A. PROGRAMMING THE VISION I OPTION................................................................................................................................63
B. VISION 1 PROGRAM ACCESS................................................................................................................................................63
C. VISION 1 PROGRAM NAVIGATION........................................................................................................................................63
PART 14 –TROUBLESHOOTING ............................................................................................................................................65
A. ERROR CODE..........................................................................................................................................................................65
B. HEATER ERROR......................................................................................................................................................................65
C. HEATER FAULT.......................................................................................................................................................................65
PART 15 –MAINTENANCE ......................................................................................................................................................67
A. MAINTENANCE PROCEDURES..............................................................................................................................................67
B. MAINTENANCE SCHEDULE FOR THE SERVICE TECHNICIAN ...........................................................................................68
C. COMBUSTION CHAMBER COIL CLEANING INSTRUCTIONS ..............................................................................................68
D. MAINTENANCE SCHEDULE FOR THE OWNER....................................................................................................................69
HEATER START-UP REPORT..................................................................................................................................................74
MAINTENANCE REPORT.........................................................................................................................................................74
MAINTENANCE NOTES ........................................................................................................................................................................................78
HTP CUSTOMER INSTALLATION RECORD FORM ............................................................................................................................................. 79
PART 1 –GENERAL SAFETY INFORMATION
A. PRECAUTIONS
This heater is for indoor installations only. Clearance to combustible materials: 0” top, bottom, sides and back. Front must have room
for service, 24” recommended. (A combustible door or removable panel is acceptable front clearance.) This heater has been approved
for closet installation. This heater is designed to be wall mounted. Do not install on the floor. Category IV vent systems only.
INSTALLER –Read all instructions in this manual before installing. Perform steps in the order given.
USER –This manual is for use only by a qualified heating installer/service technician. Refer to user’s information manual for your
reference. Have this heater serviced/inspected by a qualified service technician annually.
FAILURE TO ADHERE TO THE GUIDELINES ON THIS PAGE AND HAVE THIS HEATER SERVICED/INSPECTED ANNUALLY
CAN RESULT IN SUBSTANTIAL PROPERTY DAMAGE, SEVERE PERSONAL INJURY, OR DEATH.
NOTE: When inquiring about service or troubleshooting, reference the model and serial numbers from the heater rating label.

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LP-171 Rev. 3.3.15
DO NOT USE THIS HEATER IF ANY PART HAS BEEN SUBMERGED IN WATER. Immediately call a qualified service technician.
The heater MUST BE replaced if it has been submerged. Attempting to operate a heater that has been submerged could create
numerous harmful conditions, such as a potential gas leakage causing a fire and/or explosion, or the release of mold, bacteria, or other
harmful particulates into the air. Operating a previously submerged heater could result in property damage, severe personal injury, or
death.
NOTE: Heater damage due to flood or submersion is considered an Act of God, and IS NOT covered under product warranty.
Be sure to disconnect electrical power before opening heater cabinet or performing service. Failure to do so could result in an electrical
shock that could result in property damage, serious personal injury, or death.
NOTE: If the heater is exposed to the following, do not operate until all corrective steps have been made by a qualified serviceman:
1. FIRE
2. DAMAGE
3. WATER
Any claims for damage or shortage in shipment must be filed immediately against the transportation company by the consignee.
Due to the low water content of the heater, improper sizing of the heater with regard to heating system load will result in excessive
cycling and accelerated component failure. HTP DOES NOT warrant failures caused by improperly sized heater applications. DO NOT
oversize the heater to the system. Modular heater installations greatly reduce the likelihood of heater oversizing.
B. IMPROPER COMBUSTION
Do not obstruct combustion and ventilating air flow. Adequate air must be provided for safe operation. Failure to keep the exhaust vent
and intake pipe clear of ice, snow, or other debris could result in property damage, serious personal injury, or death.
C. GAS
Should overheating or gas supply fail to shut off, do not turn off or disconnect electrical supply to circulator. Instead, shut off the gas
supply at a location external to the heater.
D. WHEN SERVICING THE HEATER
To avoid electric shock, disconnect electrical supply before performing
maintenance.
To avoid severe burns, allow heater to cool.
E. HEATER SYSTEM
Do not use petroleum-based cleaning or sealing compounds in a heater
system. Gaskets and seals in the system may be damaged. This can
result in substantial property damage.
Do not use “homemade cures” or “patent medicines”. Substantial
property damage, damage to heater, and/or serious personal injury may
result.
Continual fresh make-up water will reduce heater life. Mineral buildup
reduces heat transfer, overheats the stainless steel heat exchanger, and
causes failure. Addition of oxygen by make-up water can cause internal
corrosion in system components. Leaks in the heater or piping must be
repaired at once.
If you have an old system with cast iron radiators, thoroughly flush the
system (without heater connected) to remove sediment. The high-efficiency heat exchanger can be damaged by build-up or
corrosion due to sediment.
When the heater is used to supply potable water, do not connect it to any heating system or component(s) previously used
with a non-potable water-heating heater.
NOTE: Damages resulting from incorrect installation or from use of products not approved by HTP, Inc. ARE NOT covered by warranty.
F. WATER CHEMISTRY*
Sodium less than 20mGL.

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LP-171 Rev. 3.3.15
Water pH between 6.0 and 8.0
oMaintain water pH between 6.0 and 8.0. Check with litmus paper or have it chemically analyzed by water treatment
company.
oIf the pH differs from above, consult local water treatment company for treatment needed.
Hardness less than 7 grains
oConsult local water treatment companies for unusually hard water areas (above 7 grains hardness).
Chlorine concentration less than 100 ppm
oUsing chlorinated fresh water should be acceptable as levels are typically less than 5 ppm.
oDo not connect the heater to directly heat swimming pool or spa water.
oDo not fill heater or operate with water containing chlorine in excess of 100 ppm.
*NOTE: It is recommended to clean heat exchanger at least once a year to prevent lime scale buildup. To clean the heat
exchanger, follow the maintenance procedure in Part 15, Section B of this manual.
Hardness: 7 grains
Chloride levels: 100 ppm
pH levels: 6-8
TDS: 2000 ppm
Sodium: 20 mGL
G. WINTERIZING
NEVER use any toxic chemical, including automotive, standard glycol antifreeze, or ethylene glycol made for hydronic (non-potable)
systems. These chemicals can attack gaskets and seals in heaters, are poisonous if consumed, and can cause injury or death.
Consider piping and installation when determining heater location.
To winterize the heater, drain the entire system. Then apply air pressure to the drain valve and allow air and water to escape from the
purge valve (see piping instructions).
Once you have evacuated as much water as possible, pump non-toxic, NSF food grade propylene glycol, FDA rated as GRAS
(Generally Recognized As Safe), into the system. Consult the glycol manufacturer for specific instructions on concentration percentage
as well as freeze and burst protection methods. Check the volume and concentration of antifreeze to assure protection is adequate to
protect the entire system from freezing. When pumping, allow air and remaining water to escape from purge valve. When the stream
coming out of the purge valve matches the color of the non-toxic glycol, the system is adequately filled.
Finally, it is recommended to start the circulation pump and allow the system to circulate for at 30 minutes to completely blend any
trapped water that might be in the system with the glycol.
PART 2 –BEFORE YOU START
A. WHAT’S IN THE BOX
Also included with the heater:
Temperature and Pressure Relief Valve
Pressure and Temperature Gauge
Intake PVC Tee with Screens
Exhaust PVC Coupling with Screens
Plastic hose and Instructions for Purging Heat Exchanger
Installation Manual
Warranty
B. HOW THE HEATER OPERATES
Modulation Condensing Technology is an intelligent system that delivers highly efficient water heating, while maximizing efficiency
by measuring the data parameters of your system.
Stainless Steel Heat Exchanger
The highly efficient and durable stainless steel heat exchanger is designed to extract the last bit of energy from flue gas before it is
exhausted.

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LP-171 Rev. 3.3.15
Modulating Combustion System
Modulation during operation is based on supply temperature and desired temperature set point. The set point used for the control
depends upon the programmed central heating curve. The heating curve slope can be changed by the installer to better fit system
needs. The control monitors the system to regulate burner output during operation to match system demand. This increase in efficiency
allows for substantial fuel savings.
Gas Valve
The gas valve senses suction from the blower, allowing gas to flow only if the gas valve is energized and combustion air is flowing.
Swirl Plate System
The gas valve swirl plate controls air and gas flow into the burner, assuring better mixing for improved combustion.
Supply Water Temperature Sensor
This sensor monitors heater output water temperature (system outlet/supply). The control module adjusts the heater firing rate so the
outlet/supply temperature is correct.
Return Water Temperature Sensor
This sensor monitors the return water temperature (system inlet/return). The control module reduces or increases heater input,
depending on how close the inlet/return water temperature is to the outlet water temperature.
Temperature and Pressure Gauge
Allows the user to monitor system temperature and pressure.
Control
The integrated control system monitors inlet/return and outlet/supply water temperature and regulates fan speed to regulate the unit’s
BTU output. This allows the unit to deliver the required amount of heated energy and nothing more.
Flue Pipe Adapter
The flue pipe adapter may be positioned so that the installer is able to find a position that will best facilitate the exhaust and combustion
air pipe connections with the least number of elbows in even the most challenging of situations.
Burner
Constructed of metal fiber and high grade stainless steel, the burner uses pre-mixed air and gas and provides a wide range of firing
rates.
Electrical Field Connections with Terminal Strips
The electrical cover plate allows access to the line voltage and low voltage terminal strips. Attach line voltage conduits to the three
holes at the right of the line voltage terminal strip for power, CH pump and DHW pump. Route low voltage wires through the opening to
the left of the low voltage terminal strip (see Field Wiring Instructions, Part 9).
Condensate Drain Connection
As this is a condensing high efficiency appliance, the unit has a condensate removal system. Condensate is nothing more than water
vapor, derived from combustion products and similar to an automobile when it is initially started. It is very important that the condensate
line slopes away from the heater and down to a suitable inside drain.
If the condensate outlet on the heater is lower than the drain, you must use a condensate removal pump (kit p/n 554200 available from
HTP.) In addition, local authorities may require a condensate neutralizer to neutralize the condensate. Condensate neutralizers are
made up of lime crystals, marble or phosphate chips. Neutralizers can be installed in the field by the installer and purchased from HTP
(p/n N1100).
It is also very important not to expose the condensate line to freezing temperatures or any type of blockage. Plastic tubing must be the
only material used for the condensate line. Steel, brass, copper or other materials will be subject to corrosion or deterioration. A second
vent may be necessary to prevent condensate line vacuum lock on a long horizontal run. Also, an increase in pipe size may be
necessary to allow condensate to drain properly. Support of the condensation line may be necessary to avoid blockage of the
condensate flow.
Spark Ignition
The burner flame is ignited by applying a high voltage to the system spark electrode. This causes a spark from electrode to ground.
The Vision 1 Optional System
By controlling the temperature delivered to the central heating circuits based on outside temperature, the Vision 1 System allows the
installer to take this highly efficient heater and make it even more efficient. The Vision 1 System is also a two temperature system,
using one temperature for central heating and the other for use with an indirect water heater. This allows the user to increase the
temperature supplied to the indirect water heater to get a faster recovery by prioritizing the flow at a higher temperature than may be
needed for the central heating circuits (this requires two separate circulators). You must follow the piping, wiring, and programming
instructions located in the Vision One section of this manual.

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C. OPTIONAL EQUIPMENT
Below is a list of optional equipment available from HTP. These additional options may be purchased through your HTP distributor:
Indirect Tank Sensor (Part # 7250P-325)
Outdoor sensor (Part # 7250P-319)
2” Stainless Steel Outside Termination Vent Kit (V500)
3” Stainless Steel Outside Termination Vent Kit (V1000)
2” PVC Concentric Vent Kit (Part # KGAVT0501CVT)
3" PVC Concentric Vent Kit (Part # KGAVT0601CVT)
3” Polypro Vent Kit (Part # 8400P-001)
3” Polypro Pipe (33’ length Part # 8400P-002, 49.5’ length Part # 8400P-003)
Alarm System (Part # 7350P-602) (to monitor any failure)
Condensate Pump (Part # 7250P-320)
Condensate Neutralizer (Part # 554200)
Vision 1 Outdoor Sensing System (Part # 7250P-622)
PART 3 –PREPARE HEATER LOCATION
Carefully consider installation when determining heater location. Please read the entire manual before attempting installation. Failure to
properly take factors such as heater venting, piping, condensate removal, and wiring into account before installation could result in
wasted time, money, and possible property damage and personal injury.
A. BEFORE LOCATING THE HEATER
Incorrect ambient conditions can lead to damage to the heating system and put safe operation at risk. Ensure that the heater installation
location adheres to the information included in this manual. Failure to do so could result in property damage, serious personal injury, or
death.
Failure of heater or components due to incorrect operating conditions IS NOT covered by product warranty.
1. Installation Area (Mechanical Room) Operating Conditions
Ensure ambient temperatures are higher than 32oF/0oC and lower than 104oF/40oC.
Prevent the air from becoming contaminated by the products, places, and conditions listed in this manual, Part 3, Section F.
Avoid continuously high levels of humidity
Never close existing ventilation openings
The service life of the heater’s exposed metallic surfaces, such as the casing, as well as internal surfaces, such as the heat exchanger,
are directly influenced by proximity to damp and salty marine environments. In such areas, higher concentration levels of chlorides from
sea spray coupled with relative humidity can lead to degradation of the heat exchanger and other heater components. In these
environments, heaters must not be installed using direct vent systems which draw outdoor air for combustion. Such heaters must be
installed using room air for combustion. Indoor air will have a much lower relative humidity and, hence, potential corrosion will be
minimized.
This heater is certified for indoor installations only. Do not install the heater outdoors. Failure to install this heater indoors could result in
substantial property damage, severe personal injury, or death.
2. Check for nearby connections to:
System water piping
Venting connections
Gas supply piping
Electrical power
Condensate drain
3. Check area around heater. Remove any combustible materials, gasoline, and other flammable liquids.