Central Heating System; Domestic Hot Water Mode; Frost Protection Mode; Pump Protection - UTICA BOILERS MAH-125 Installation, Operation And Maintenance Manual

5.8 Central Heating System

Boiler is designed for use in a sealed central heating system.
Design the system to operate with flow temperatures of up to
176°F (80° C), take pump head, expansion tank size, mean
radiator temperature, etc. into account.
Boiler is supplied with the following components: Pressure
relief valve - 30.0 psi (2.1 bar). Boiler internal pressure switch
will shut boiler off at 43.5 psi /3.0 bar.
Pressure gauge - to indicate the system pressure to be
maintained.
By-pass - Boiler incorporates an automatic by-pass,
However, where all radiators are fitted with thermostatic
radiator valves, an external by-pass must be fitted.

5.9 Domestic Hot Water Mode

Utica Boiler MAC-150 & 205 and MAH-125 & 165 with
indirect tank
!
WARNING
Burn, Scald Hazard! Water temperature over 125°F
(51°C) can cause severe burns and scalding. See
User's Manual before setting water temperature.
Failure to follow these instructions could result in death
or serious injury.
• Priority is given to the domestic hot water supply.
Demand at tap or shower will override any central heating
requirement.
FIGURE 5-7
5 - HYDRONIC PIPING
• Flow of water will operate the DHW flow switch which
requests the 3 way valve to change position. This will allow
the pump to circulate the primary water through the DHW
plate heat exchanger. (MAC-150 & 205 only)
• Combustion fan will then come on and begin to run at
ignition speed.
• Once the fan reaches ignition speed the control board will
allow power to flow to the spark generator and gas valve
creating ignition in the combustion chamber. The flame
sensor will acknowledge the presence of the flame in the
combustion chamber and send a signal to the control
board.
• Temperature sensors will send a signal to the control board
allowing the control board to increase/ decrease the speed
of the fan. The combustion fan will in turn modulate the
gas rate accordingly.
• When the domestic hot water demand ceases the burner
will extinguish, unless there is a demand for central
heating.

5.10 Frost Protection Mode

Frost protection mode is integrated into the appliance when
left in domestic hot water or central heating position. If the
temperature falls below 41°F / 5° C boiler will fire on its
minimum setting until flow temperature of 86°F / 30° C is
reached.

5.11 Pump Protection

Pump will automatically operate for 1 minute in every 24 hours
to prevent seizing.
21
240011941 REV B, [03/31/2018]