
7
IDH MAINTENANCE INSTRUCTIONS
!WARNING!: Heaters should be fully serviced annually to ensure proper
performance. Maintenance should be performed by trained personnel
only. Incorrect maintenance may result in improper operation and
serious injury.
HIGH LIMIT SWITCH
It is recommended that the limit switch should be checked every heating season to ensure the switch
limits the temperature to 250oF (IDH400QR) 290°F (IDH400QRC) (This can be done by restricting the
air
flow through the unit. After tests are complete, remove all restrictions.
FAN SWITCH
The fan switch has been selected to allow for preheating of the heat exchanger to ensure that
only heated air is allowed to enter the space. Upon satisfying the need for heat, the fan switch will
continue to run the supply fan until the heat exchanger has cooled sufficiently. This feature will
help prolong the life of your heat exchanger.
FUEL FILTER
Replace cartridge (48164 or 48164A)once every week of normal usage or sooner, depending
upon fuel quality.
FLAME DETECTOR
BURNER
The electrode spacing must be checked and adjusted, if necessary after every nozzle
change. Nozzle should be replaced annually or sooner if burner cannot be set up to
operate properly. Nozzle size and type are marked on the rating plate.
ELECTRICAL
Ensure all conduit (BX) connectors are tight. Check inside connections in control box to ensure
good connections. Check marrettes.
FAN
Check for dust or dirt build up on blades. Check for tightness of the set screw. Run heater to
check for fan vibration. Replace fan blade if vibration is noticeable.
MOTORS
No lubrication is necessary since the bearings are the sealed type. Clean motor of existing dust or dirt.
FUEL SYSTEM
Periodically remove fuel tank drain plug and clean tank. Do not store unit containing
furnace oil for long periods. The quality of fuel oil will affect light off at low ambient
temperatures, #1 fuel oil or kerosene are recommended for temperatures below
-10o C/8oF. (see page 8 for recommended settings if using #2 fuel oil in cold temperature)
FUEL PUMP
Check fuel pump pressure on a regular basis. This can be checked at the bleeder screw.
ADD 10 LBS TO THIS READING TO GET THE TRUE PRESSURE.
There is a pressure loss when fuel passes through solenoid valve. Example: IDH400 pressure
should be read at the port as 150 PSI, then the reading at nozzle line will then be 140.
HEAT EXCHANGER
If a smokey condition continues even after adjusting the air band assembly, the heat exchanger
should be thoroughly cleaned as per next page.
To test the cad cell, start the burner and before the safety lock-out timing period ends,
disconnect the cad cell wires from the F-F terminals on the control. Next, jumper the F-F
terminals with a piece of wire. This will allow the burner to continue running so that you will be
able to check the cad cell resistance during the run cycle. If you did not get the F-F terminals
on the control jumpered before the burner locked out, wait 3-5 minutes before attempting this
again. With the burner running, connect the ohmmeter across the cad cell leads. Your signal
should be between 250-1200 ohms. If higher, please clean the cad cell eye or replace.