Direct Gas Make-Up Air
58
Troubleshooting
Direct Gas-Fired Heat
Problem: Heater does not modulate correctly. Maxitrol SC Series system.
Is fan operating correctly?
Yes
No
Refer to Troubleshooting, Supply Fan.
Is the burner operating and lit?
Yes
No
Refer to Troubleshooting, Direct Gas-Fired Heat.
24 VAC at terminals 38 and 39?
Yes
No
Transformer TR6 faulty.
Replace transformer.
Remove the wire from terminal T1
and T2 on the Maxitrol Amplifier
(AMP). Place a jumper wire across
the terminals. 24 VDC at terminals on
modulating valve (MOD)?
Yes
No
Amplifier (AMP) faulty.
Replace amplifier
With the jumper wire installed on
terminals T1 and T2 on the Maxitrol
Amplifier (AMP), is the burner operating
at high fire?
Yes
No
High fire adjustment not set correctly.
Adjust high fire setting.
Reference Start-Up: Direct Gas-Fired Heating, Industrial or
Commercial Pilot Systems.
Inlet gas pressure too low to provide high fire.
Increase inlet gas
pressure to above the minimum input for maximum output value.
Modulating valve (MOD) stuck.
Tap valve gently to loosen.
Modulating valve (MOD) faulty.
Replace modulating valve.
Reconnect wires to Terminals T1 and
T2. Analog input signal connected to
terminals 5 and 6?
Yes
No
Connect analog signal.
Is the J3 jumper set to 0V Start?
Yes
No
Set the J3 jumper to 0V Start to allow the main portion of the
burner to ignite at low fire.
Does the signal provided to terminals 5
and 6 match the DIP switch setting?
Yes
No
If a 4-20ma signal is supplied, set DIP switches to mA. If a
0-10 VDC signal is supplied, set DIP switches to Volts
.
Remove the wires from terminals T1
and T2 on the Maxitrol Amplifier (AMP).
Check resistance between the two
wires. Is the resistance in the range of
900-1300 ohms?
Yes
No
Discharge temperature sensor (TS2) wired incorrectly.
Correct
wiring.
Discharge temperature sensor (TS2) faulty.
Replace discharge
temperature sensor.
A discharge temperature sensor failure will usually result in a reading
of infinite or zero resistance between the two wires.
Everything is working properly, consult factory.