Heil DC90 startup operation sequence question

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Old 10-28-17, 01:42 PM
J
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Question Heil DC90 startup operation sequence question

I have a DC90 gas furnace.
I had some problems with it starting, and it's going now. I want to confirm the startup sequence and if this seems correct.

Thermostat on, emergency switch on, gas valve on.
1- Furnace Draft Inducer Blower comes on. Confirmed outside it is blowing out the pipe.
2- Click sound.
3 - Igniter glows. This is one of the Silicon Carbide igniters
4 - Flame starts. This is a small flame, right at the igniter.
5 - Furnace lights. Full flame.

In step 4, is it typical to get a small flame, like a pilot light works, before the main gas comes on?
Is there a sensor that detects this?

I flipped the switch on the gas valve a couple of times, and the furnace came on. Not sure if it is going or not.
This is the first time I've used the heat this season.

I know there is a flame sensor, although I can't seem to spot it by the
 
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Old 10-28-17, 02:34 PM
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It is very possible to have a small pilot light. That's called intermittent ignition.
The igniter can double as a flame sensor.

To be of further help I need the full model number. DC90 is only a group.
It can be found on the inside wall near the burner on an ID tag.
 
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Old 10-30-17, 07:42 AM
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NTGM075EGA3 for the furnace and the gas valve being used is a sv9501m2726.
Are these the model numbers you are looking for?

The furnace is working, but it seems that every once in a while it goes through a couple of cycles for the burners to come on.
I am wondering if it could be the sensor, or the gas valve, since the pilot flame is lit.
 

Last edited by Joseph Kennedy; 10-30-17 at 09:23 AM.
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Old 10-30-17, 11:10 AM
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The SV in the gas valve signifies the Honeywell smart valve. They were problems all by themselves.
You may just have a dirty pilot orifice not allowing for a full pilot flame.

Here is the Honeywell sheet on them. The diagnostic routines are at the bottom.
honeywell/combustion/universal_smart_valve/install/69_1270.pdf
 
 

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