Help- stumped! Control board, limit switch, or something else??

[EdInKentucky]

The furnace working ok for several days after you opened the basement window 3" is good information.

But .. sounds like there is still negative pressure in the basement, even with that window open 3".
2 possibilities come to my mind ..
1. the return duct in the basement, is somehow pulling a lot of air out of the basement.
2. there is a "chimney effect" flowing air between the basement and the attic, possibly through walls

And it is clear that something changed, to cause this negative pressure in the basement, since the furnace did fine for 7 years.

Possible negative pressure in the space where the furnace is ... is the main reason why furnaces are often installed as "closed combustion" ... using 2 pipes to the outside, one to supply combustion air, the other to conduct exhaust gases to the outside, and the combustion area being sealed.

If this problem persists, it's possible your furnace can be converted to "closed combustion" without a lot of expense.

If that's not cheap and easy to do, you might consider a new high-efficiency furnace.
Your existing furnace is probably 80% efficient max, since it's a non-condensing type.
And it has 7 years of use on it ... not a lot, but it's not new.

A new condensing furnace will increase efficiency to the high 90's, noticeably reducing your gas bill.
Get a good USA made, known-brand furnace, avoid the exotic brands with lots of proprietary parts.
Consider Trane, Carrier, etc.

A new two-pipe furnace, properly installed, won't be affected by strong negative pressures in the basement.
It might even qualify for a tax credit.

 

[WyrTwister]

These all sound like reasonable ideas .

God bless
Wyr

 

[RMSTU]

Thanks, EdInKentucky. Those are ideas worth considering. I’ve got a request in (waiting for a return call) for a complete Home Energy Audit from the gas company. Maybe they can track down the source of the negative air pressure.

I’ve also done a temp rise test and it seems to be within the manufacturer’s range. An HVAC guy told me to check that during a phone conversation. He was completely stumped over the phone.

What about the possibility of a cracked heat exchanger? Any chance that may be causing the issue? If there’s a chance, how do I check for it?

Is there a chance that the vents or the combustion hole or a combination could have been slightly undersized from the beginning (7 yrs ago), and after 7 years, it’s staring to show?

 

[WyrTwister]

I would , in the mean time , plug in a carbon monoxide detector , near the furnace .

I would really look into the present outside air / combustion air situation .

Also , while you are waiting on the gas company to do a report , you might be pricing a furnace change out , as a worst case scenario . We installed a 90% or 92% , two stage Goodman gas furnace , maybe 20 years ago & have been happy with it .

To get enough CFM of air movement for 4 ton of A/C , the furnace is oversize . That is no problem . with the 2 stage tstat , it never has to go into 2nd stage . Unless we turn the tstat way down when we go out of town . Upon return , move the tstat up to " normal " and it kicks into high flame and REALLY puts out the heat .

It is a condensing furnace and the venting is PVC , easy to work with and inexpensive . But it has to have a drain for both the A-Coil and the furnace condensation .

Best of luck to you and Merry Christmas .

God bless
Wyr

 

[EdInKentucky]

I agree, definitely install a carbon monoxide detector in the basement near the furnace.

And ... since the temp rise is right, a cracked heat exchanger is unlikely ... although always possible.

But ... a cracked heat exchanger would not explain the negative pressure in the basement.

That's the problem to solve.

If the gas company does an energy audit using the "blower door" method, that might be able to quickly find the source of the negative pressure.

Really though, with gas prices being high now, and probably for quite a while .... you should seriously consider a 90+ efficiency replacement furnace, with closed combustion.

One that has a 2-stage burner and variable blower speed .. you will like it.

 

[timnuroomremodeling]

Realize this is an older post, but I had a similar code thrown on a Bryant system. Solved the issue by cleaning the flame sensor probe with #0000 steel wool. I'm pretty sure that's one of the code 1-4 solutions. Simple cheap maintenance fix that's worth trying.

 

[pjones]

Have you recently rearranged furniture, or moved items, possibly blocking a return air grill somewhere?

Board is a possible cause. You could pull it out and check for damage. You can’t always see the damage but often you can see indications of the issues so it’s worth a look.

I’m not on site to see the unit myself but from what you describe it leads me to disagree with your HVAC technician, I believe the negative pressure is an issue worth resolving and may be related to this issue that you are having. Sometimes it will work ok for years then one small thing changes and escalates an issue just enough to make it start causing problems.

Make sure that combustion air grill is clean and unblocked. With the negative pressure you describe you should feel a strong draft coming through it. Your furnace should not be in a negative pressure room for many reasons. There is usually bug screen installed in these that gets plugged up.

Get a CO monitor installed now if you don’t have one installed yet. Don’t wait to do this. In your situation this needs to be done.

 

[pjones]

What are the other error code descriptions for the 14,33,34 that you mentioned? (Did I get those numbers right? I’m going off memory here)

 

[pjones]

What are the other error code descriptions for the 14,33,34 that you mentioned? (Did I get those numbers right? I’m going off memory here)

Searched them... also check that the pressure switch port is clear and not obstructed.