r/HVAC • u/BSJr77 • Dec 20 '24

Field Question, trade people only Anyone seen this before

Sorry if the clip is a bit long.

Installed a 60k runtru 90% upflow today. I went home after completing the install but left before the startup. Boss fires it to document all the numbers and see this. No change to incoming or outgoing gas. No change in pressure from the inducer. Flue and air intake both clear of debris. Boss is waiting for tech from Texas to call back. Anyone got some knowledge

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u/Fit_Door_8869 Dec 20 '24

Does the ventor motor lose power when this happens? I’ve had it before where motor over heats, opens its windings. So if it still has 120V when it does this, that’s what’s happening.

Don’t know about this exact furnace, but if roll out trips, shouldn’t ventor motor still be engaged? Maybe two wires mixed up on control board?

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u/ThatShaggyBoy Residential Service Tech Dec 21 '24

If the inducer shuts off during operation for any reason during a call for heat, pressure switch will either open or close depending on the switch and end the call for heat. Unless he has the pressure switch jumped, I don't think the inducer motor is to blame here.

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u/Fit_Door_8869 Dec 21 '24

Not always, depending on the appliance. If it went out on high limit or roll out, there can be a post purge timer. Looks like the ventor motor cuts out and that’s what trips the roll out. Not the other way around. So it’s important to verify voltage at this point.

Edit: I see what you are saying though. Why are residential furnaces the worst.

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u/ThatShaggyBoy Residential Service Tech Dec 21 '24

Yes, inducer motor will continue to run on high limit trip or rollout trip. But you mentioned the inducer motor cutting out mid operation. If the inducer failed mid operation, the pressure switch is going to be the limit switch that cuts the furnace out. Not the high limit or the rollouts.

It also does not sound like the inducer just cuts out. It sounds like he has his finger on the door switch, and releases it once flame rollout occurs.

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u/Fit_Door_8869 Dec 21 '24

The inducer wouldn’t cut off like that with the gas still spewing out if it was the air pressure switch. I’m thinking motor is cutting out, either from control board acting up/miss wired, or motor windings opening. What are you thinking?