24
5 - HYDRONIC PIPING
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.
5.7 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
baseboard 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.
5.10 Domestic Hot Water Mode
GMCB150 & GMCB200 or GMHB125 with Indirect Tank
WARNING
Burn, Scald Hazard! Water temperature over 120°F
(49°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.
!
• This boiler has domestic hot water priority. Demand at tap
or shower will override any central heating requirement.
•
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. (GMCB150 & GMCB200 Combi
Boilers 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.
•
Install (field supplied) domestic water pressure relief valve
as required by authority having jurisdiction.
5.8 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.
5.9 Pump Protection (Automatic pump exercise)
Pump will automatically operate for 1 minute in every 24
hours to prevent seizing.
PN 240012363 REV. B [03/29/2019]
