[Adlerberts-Protege]

Getting to learn a lot about this unit the last couple days. Here is the problem.

The pressure switch is opening up when the blower fan kicks on to push across the heat exchanger. This unit has a pressure switch with the usual hose that connects to the draft inducer, and a second that goes to a port connected into the heat exchanger itself.

I guess my question is. Could there be a breach in the heat exchanger causing the switch to open up once the blower hits it? It only happens about 1 out of 20 fires, otherwise runs as normal. But only happens once the fan kicks on.

 

[Adlerberts-Protege]

I thank you Runncool for sending me the service manual for the unit. Looks like it can flash E17 for pressure switch opening or for the thermal fuse opening due to high temp.

Like I said before, the pressure switch is opening about 3 to 4 seconds after the fan kicks in, but it isn't due to high temp. The only thing opening is the pressure switch, the thermal fuse is staying closed. hmmmmm

 

[Adlerberts-Protege]

I'm not familiar with this system, but can you tee into the pressure switch tubing that goes to the HX and see if the pressure changes when the blower comes on?

I emailed you the service manual on this unit.

Yessir, I am positive that it does as that is the only reason the switch opens. I am guessing I have some breach in the HX then??? I did a visual inspection and it looks solid. I definitely will tee in when I go back though and verify. I am also going to bring a new pressure switch with me to eliminate that as an issue. Any idea how to find out the specs of the pressure switch?? I snapped a picture of the number on it, but not sure who to show it too.

 

[Adlerberts-Protege]

No I do not. I only briefly scanned the manual and did not see a rating on the pressure switch.

I even tried to google the pressure switch part number and only came up with a picture.

I know, pretty dumb design on their part. I will try and cross-reference the number on Monday.

 

[Adlerberts-Protege]

Kind of a bump!!

Anyone else want to chime in on this and to add and/or correct to my thinking?

This pressure switch only opens up once the system has cycled to the fan coming on via the thermal disc...easy stuff right?? The fan blows across the heat exchanger, then the pressure switch opens. Must be a breach in the heat exchanger somewhere correct?? How else could the fan kicking on affect the pressures of said tubing connected to the heat exchanger?

Both run directly into the circuit board, so it could possibly be board related but I can almost guarantee this board isn't going to be cheap. Anybody else want to look over that service manual and see if I am missing something?

 

[Adlerberts-Protege]

I know you are trying to get other guys ideas on this problem, but if you will indulge me …………….

Do you have a combustion analyzer?

A change in O2 when the blower starts during a combustion test is a possible chance you have a compromised HX.

I do not like to condemn a HX for this, but with your pressure switch issue, it might be an added test to confirm your findings.

As I stated before, I would also want to tee into the tubing that goes to the HX and see if there is an actual change in pressure on this side of the switch when the blower comes on.

O.K. I will now shut up now and let others respond.

Side note: Others probably do not have this service manual as I could not post it to your thread, because we are in an “OPEN” forum.

Trust me, I appreciate it!! 10x over.

I do have a combustion analyzer, will give it a try. And I will tee into the tubing between HX and switch, when I go back.

Scenario for you though. Let's say the pressure does drop when the blower comes on (which it has to IMO, otherwise why would the switch be opening), but the 02 readings are fine? Where do I go from there?

Edit: Maybe I should just sell him a mini-split and get rid of this discontinued unit?

 

[Adlerberts-Protege]

I don’t see that happening if there is a large enough crack or hole to cause the “pressure” the switch is looking at to change enough to open the switch.

This doesn’t fit your scenario, (pressure switch “opens” when blower starts), but I would also be double checking the inducer motor side of this equation too.

Could the inducer be slowing down (over amping possibly) after a short run time that just happens to coinside with the blower coming on?

Possible, but I don't see why it would slow down or over amp once the fan kicks on. Also, it only does it about 1 out of 10 startups, and with a larger temp difference it does ramp up after about 90 seconds to higher stage. I just don't know enough about these damn things.

 

[Adlerberts-Protege]

I would have to go back pre-2011 to get tech support it appears.

 

[Adlerberts-Protege]

Not sure if this applies, but Goodman GMN inducers had the PS tap directly in line with the impeller and it would get caked up with crud. Just a thought.... I cleaned a lot of em with a small drill bit.

Cleaned out all connections/entrance points. I have a feeling I can take everything apart and give it a thorough cleaning, solve the problem for a while. But is this unit worth it?

 

[Adlerberts-Protege]

Have you changed out the pressure switch? They have rubber diaphragms that get old and can cause intermittent issues. They don’t cost much and it’s worth a try. And yes the inducer can overheat and stop working if the bearings are worn. I’d try the pressure switch then look at the inducer possibly the cause assuming vents are clear of obstructions. Have you checked the flue pipe for obstructions?


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I am going to change out the pressure switch and see what happens. If the inducer was worn out then he wouldn't be having these intermittent issues, and it definitely wouldn't happen right when the fan kicks on. Flue is unobstructed.