Operating Instructions; Testing For Gas Leaks And Purging The Gas Supply; Boiler Operation; Central Heating Mode - UTICA BOILERS MAHF-125 Installation, Operation & Maintenance Manual

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.
• This appliance is equipped with an ignition device
which automatically lights burner. Do NOT try to
light this burner by hand.
• Before operating smell all around appliance area for
gas. Be sure to smell next to floor because some
gas is heavier than air and will settle to the floor.
• Use only your hand to turn the gas shutoff
valve. Never use tools. If valve will not turn by
hand, do not try to repair it, call a qualified service
technician. Force or attempted repair may result in
fire or explosion.
• Do not use this appliance if any part has been
under water. Immediately call a qualified service
technician to inspect appliance and to replace any
part of control system and any gas control which
has been under water.
CAUTION
!
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.
10.1 Testing For Gas Leaks And Purging The Gas
Supply
• With boiler gas service cock closed (spindle flats at right
angles to valve). Pressure test gas supply and inlet pipe
work connection to boiler gas service cock for soundness.
• Loosen screw of pressure inlet gas test port on gas valve.
See section 13.4 Gas Valve. Verify gas supply is ON.
Open boiler service cock to purge.
• Retighten test port screw and test for gas leaks. Close
boiler gas shutoff device.

10.2 Boiler Operation

Domestic hot water supply always takes priority over central
heating.
Demand for hot water required during central heating period,
boiler automatically switches to hot water mode until demand
is satisfied i.e. storage water is to required temperature.
This interruption in central heating is only when demand for
hot water is present and should not be noticed by the User.

10 - OPERATING INSTRUCTIONS

10.3 Central Heating Mode

1.
2.
3.
4.
5.

10.4 Domestic Hot Water Mode

• When a tap is opened and water flow is sensed by DHW
• Water in the boiler is diverted from central heating system
• Combustion fan will come on at ignition speed, closing
• Flame sensor will acknowledge presence of flame in
• After initial stabilization period, the control board monitors
• Domestic call for heat ends when tap is closed and DHW
• There is no anti-cycling mode after a DHW call for heat if

10.5 Frost Protection

Boiler monitors supply and return water temperatures to
enable frost protection which automatically turns boiler and
pump on.
If water in boiler falls below 41°F (5°C), providing boiler is
connected to power, boiler will operate until water temperature
in the system reaches approximately 86°F (30°C).
Frost protection is for boiler only and not for complete Central
Heating System.

10.6 Pump

If electricity is connected to the boiler, regardless if power is
"On" or "Off" and has not operated for 24 hours for heating
or hot water, boiler pump will operate automatically for one
minute every 24 hours.

10.7 Low Water Pressure Sensor (Internal)

This device protects primary exchanger from damage. It will not
allow boiler to run in a LOW water pressure situation. Low water
condition occurs when water pressure drops below 7.0 psi (0.5
bar).
45
With demand for heating, pump circulates water through
the primary circuit.
Combustion fan comes on at ignition speed, closing the air
pressure switch, allowing power to spark generator and
gas valve, creating ignition in the combustion chamber.
Flame sensor acknowledges presence of flame in
combustion chamber sending a signal to the control board.
After initial stabilization period the control board monitors
supply and return temperatures and modulates fan speed
and gas rate accordingly.
Once boiler satisfies CH call for heat, the unit will
shutdown and enter 3 minute anti-cycling mode. The
boiler pump will operate for 3 minutes to dissipate any
residual heat.
If there is a subsequent CH call for heat, boiler will wait 3
minutes to operate.
flow switch, domestic hot water call for heat is initiated.
to domestic hot water heat exchanger to heat incoming
domestic water.
the air pressure switch, allowing power to flow to
spark generator and gas valve, creating ignition in the
combustion chamber.
combustion chamber and send a signal to the control
board.
supply and return temperatures and modulates fan speed
and gas rate accordingly.
flow switch does not see water flow.
there is demand.
240012565 REV A, [05/15/2019]