64659-001 REV. A 07/06/18
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DESCRIPTION OF SYSTEM AND COMPONENTS
System Description
iHEAT is an electronically controlled gas/air modulation system that can be utilized by P250 or P265
burners to provide a variable heat source for an appliance. The components of the system include: a
fan-assisted gas burner, a modulating gas valve, and an electronic control module that varies the speed
of the burner fan and the gas flow rate through the gas valve.
The thermostat on the OEM’s appliance controls the temperature by sending a variable electrical signal
to the iHEAT control, which responds to the signal by adjusting the speed of the combustion air blower
and by changing the gas flow to the burner via a variable voltage to the modulating gas valve. These
changes in combustion air and gas flow result in a variable heat source that responds to the appliance’s
call for heat.
Component Functions
iHEAT control – The control receives a 4-20 mA input signal from the appliance’s thermostat. Based on
the value of this input, the control generates outputs to the combustion air blower (combustion air) and
the modulating gas valve (gas flow). The proper ratio of combustion air to gas is specific for the type of
gas used, natural or propane. The ratios are stored in the memory of the control and are selected by
positioning dip switches accessed through an opening on the face of the iHEAT control. See setup
information for the proper settings of the switches. The control also incorporates a series of lights that
signify the operating state of the system and assist in the diagnosis of the system should it require
repair. In the event of improper combustion air blower speed, the control will act to shut off the flow of
gas by de-energizing the ignition control. The solenoid portion of the gas valve is powered by the
ignition control and no gas will flow.
Combustion air blower – The purpose of the combustion air blower is to provide the proper amount of
air to the heating zone of the burner. The speed of the combustion air blower is controlled and
monitored by the iHEAT control. The RPM is measured through a 3-wire plug connecting the combustion
air blower to the control. There is also an adjustable air shutter on the inlet side of the blower. Refer to
the Setup section for the recommended air shutter setting.
Modulating gas valve – The gas valve used in the iHEAT system has two functions built into one valve
body. The first function is a solenoid valve that, when energized, allows gas to flow to the burner. The
second function is the modulation of gas flow to the burner. Based on an input voltage from the iHEAT
control, the modulating portion of the valve will vary the gas flow between an upper set point and a
lower set point. The valve is designed with flange connections on the inlet and outlet making it easy to
service should this become necessary.
