Heater expert in the house??

[tilerite]

I have a Tappan electronic gas furnace in my attic. This thing has been given us trouble since we moved in the house in 2002. The house was built in the late 90’s. Anyway, we have an issue with the unit that has plagued us for the past few winters. When turned on, the inducer motor comes on first, followed by the glow plugs firing up. Next, the gas valve opens to fire up the unit but after a few second, it shuts down. This only happens on cold nights. Once morning comes, everything cycles properly and the unit functions as its supposed to.

There is no diagnostic code so my heater tech has been trying to figure out the problem by process of elimination. Last week, he determined that a pressure safety switch was not functioning properly, so he replaced it. Two days later, same problem again. I even replaced the thermostat, which was necessary anyway. Problem still exists. He is baffled, as am I. I need a fresh perspective from somebody who may be able to think outside the box. I hate this thing. We had to replace the motherboard and glow plugs when we first moved here. Now this. All ideas are welcome. Thanks!

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[MudMaker]

Rick..
Tappan.. that doesn't sound good... After Happy Hour, and dinner, I'll add to your dilema.. How is your gas line run? I mean is there a possibility that water has gotten into the line and may be restricting gas flow during colder times?? Gas pressure ain't that great, and you are talkin bout the attic - brrrrrrr... Just a thought.. :)

aaaa.. do you have this problem in the summer? Oh - fergit it... :lol1: am I far enough outside the box??

[cx]

I would have your repair guy put a pressure guage in the line and leave it for you to observe when the failures occur. It could be that the pressure to your house or unit actually is below the requirement of the pressure switch and that could occur only at some times of the day due to supply and demand on your, or the utility's system.

That pressure is very low and requires a gauge that most folks don't carry around in their truck, but furnace repair guy should have one. I had to make my own for working on all my RV gas stuff.

You might also be able to persuade your utility company to do that test on your behalf.

My opinion; worth price charged.

[tilerite]

These are supposed to be the best heater/ac experts in my area, but I'm starting to wonder. They are decent, honest people so I don't feel like I'm getting hosed but this is getting ridiculous. I'll pass on the advice when he calls me. I actually mentioned the gas line thing last winter and he told me that it wasn't the problem.

[MudMaker]

I actually mentioned the gas line thing last winter and he told me that it wasn't the problem.

Good then... we can rule that out... :)
Sorry Rick.. being a smart a$$ just comes natural to me.... :rolleyes:

[tilerite]

I think its a gas issue. My wife thinks its not. We got a fault code that read; ignition failure (check ground), which I think could be a false reading caused by a gas flow issue.

[Boilermaker 98]

Rick:

I think your gas line is undersized. What leads me to believe this is that you say it quits working on the coldest night which is when th gas usage is the greatest. When the gas pressure in the main drops, it will drop on your side of the meter as well. Since we are talking inches of water as the pressure measurement, I would say you need to increase your gas line from the meter to the burner.

[madronatile]

If brian didn't nail it,

JB like forum for heating guys (http://forums.invision.net/index.cfm?CFID=4649971&CFTOKEN=4e37a06-5b3c8a1d-900b-407b-81c3-2a38d249dc9c&CFApp=2&)

[Mountain Tile]

Gotta agree with CX and Frank, your not getting enough pressure, or the gas line thats installed is the improper size and type. Did a job last summer, where the hvac guy was pissed at the builder for moving the location of the propane tank, making it a longer run, saying that now he would need to run a different line. I worked for a builder for years, and frequently had to trouble shoot the heaters. 9 times out of ten if it fired up and then shut off, it was a problem with the gas supply. How long of a run is your supply line?

[Brian in San Diego]

I haven't been involved much in residential stuff (except a job or two for neighbors) in years, however, even in our industrial systems the utilization of electronics brings many problems into the mix. Grounding (or rather lack thereof) is one of our more frequent problems. I would make sure that the circuit is properly grounded and the "pigtail" going to the furnace is properly grounded as well. I am always very suspect when people start changing "motherboards" and the like. Earlier in my career I had close to forty chillers under contract with a total of probably close to 200 "boards" contained within those systems. In a five year period I replaced a total of three boards. A great number of problems are electrical in nature and grounding or a lack thereof can often be the culprit.

I would check tightness of all connections and verify the presence of ground wires where they belong.

Brian

[tilerite]

Brian
If grounding was the problem, I would think it wouldn't happen only at night. Thats why I still lean towards the problem having to do with the gas line, as others have stated.
Speaking of the gas line however, my gas stove and gas fireplace operate perfectly. Does one thing have to do with the other?

[cx]

Does one thing have to do with the other?Not necessarily. Furnace is the largest gas draw and most likely to indicate a possible supply problem. Would also depend upon the sizing of each and all of the supply lines. Might be some are OK and only the furnace is undersized. If the problem has to do with undersized lines at all.

Has the system ever worked properly, or has this problem been manifest from day one? Or do you know if the original owners had this same problem?

Plumber aughta know how to size the gas lines in new construction. Inspector would not likely have caught an undersized condition, though. But an undersize condition should have been a problem from day one.

Brian the HVAC guy should be able to speak more authoritatively on that.

Y'all use natural gas or LP?

My opinion; worth price charged.

[tilerite]

Thats what I thought, CX. After the initial problems when we first moved in (new motherboard, realignment of tubes that direct gas flow to the glow plugs, we stayed problem free for prolly 3-4 years before the newest problem began occurring last winter. And its natural gas, not propane.

[cx]

Well, sounds like the initial installation was adequate, then.

Still possible that it's a gas flow problem, though, but still not enough to effect the stove or fireplace.

Or it could be an electronics problem. Mother board bein' askeered of the dark, or somethin'. :)

But I'd certainly wanna check all the connections, specially the grounding, like Brian suggested. Bad grounds can cause all manner of weird and intermittent problems with electronic systems.

My opinion; worth price charged.

[Brian in San Diego]

Rick,

The temperature in the attic may have something to do with the problem and that could be a crack in one of the electronic circuits that is O.K. when warm (expanded) or not when cold (contracted). If it's O.K. in the day time start the system earlier in the evening and see if it takes you further into the night w/o failing. I have my doubts that this is a gas supply problem. I'm leaning toward intermittant (the worst kind) electrical problem. Is the furnace circuit a dedicated circuit? I have had problems in some of our systems where electrical noise was the culprit. If the circuit isn't dedicated and you have something else on that circuit that introduces "noise" on the line it could cause a problem. A large inductive load on a line can create noise. Maybe at night you turn on something that is introducing that noise. If you have a UPS backup for your computer, you might try putting it in the attic and plugging the furnace into that. UPS systems "condition" the line and would tend to remove anything that may cause noise. Many don't realize that you in essence have a mini-computer in your furnace and in certain environments they can be finicky.

Brian

[MudMaker]

Hey Rick.. Just thought of somethin..
Have you ever seen Chevy Chase's" Christmas Vacation"??? :rolleyes:

[tilerite]

Hey Rick.. Just thought of somethin.. Have you ever seen Chevy Chase's" Christmas Vacation"???

More times than I care to mention, Frank.

[Brian in San Diego]

Rick,

Do you have a voltmeter? to see if the thermostat or more accurately the wiring is the problem you could get some jumper wires and hook the meter to the white wire coming from the t-stat and the other on the common side of the transformer. With a call for heat you will see approx. 24 vac on your meter. if the furnace goes off but the meter stays at 24 vac then the t-stat or it's wiring isn't the problem. One clue you've provided is that your guy replaced a part and it worked for a couple of days. To replace any part there is associated wiring that gets moved and relocated. In doing so if there were loose wires they could be disturbed enough to get things to work. Then a couple of days go by and the vibration from the furnace causes the intermittant to return. I think you or someone needs to check ALL the wiring connections to see if there are any loose connectors or marginal wires. Usually there are a number of wire nuts in a terminal box. When the furnace cuts out does the main fan continue to run? How long? Does the combustion air fan continue to run? if the combustion motor continues to run and the gas valve shuts off I would suspect a faulty flame sensor or associated wiring. There has to be a flame sensor somewhere. If the sensor is heated by the pilot flame then the main gas valve shuts off (to prevent raw gas from being released into the furnace). I still haven't figured out the correlation between cold nights and a furnace not working other than the theory I already floated. I guess your flame sensor could be marginally in the flame and on cold nights the flame isn't sufficient to indicate a flame. The flame sensor is generally a probe the thickness of a pencil lead in a ceramic type holder. Generally a white wire is attached to it and it runs back to the gas valve. If there's a crack in the ceramic and the sensor shorts to ground it will shut the gas valve down. (we're talking millivolts here.)

Brian

[MudMaker]

Hey Rick.. Just thought of somethin.. Have you ever seen Chevy Chase's" Christmas Vacation"???

Just in case you missed it.. Is it the switch?? Ya know like with the lights in Christmas Vacation?? :lol1:

[tilerite]

The wiring has been checked before but at this point, I think we need to start from scratch. Last night, the heater ran all night. Tonight, same issue again. Gas fireplace is keeping the house warm.

[MudMaker]

Hey Rick.. have you tried these guys (http://www.frigidaire.com/contact_us_other.asp) yet?? :)

[tilerite]

No Frank, can't say that I have.

[MudMaker]

That's your contact for Tappan.. :) maybe they can help ya

[tilerite]

Brian, I'll pass your suggestion to my heater guy. Thanks. Hopefully, he'll stop by tomorrow.
Everyone else, thanks for the help!! :)

[tilerite]

Well, we replaced the motherboard and so far, all is working fine. Bottom line, this is a piece of garbage unit that will need to be replaced at some point. :cry:

[tilerite]

Heater failed again. My heater guy has checked every single thing that has been discussed here and is baffled. It works, then it doesn't work then it works. All wiring and harnesses are fine. Electricity is normal. Gas is normal. He suggested I replace my electronic thermostat with the original circular type that I used to have (before these issues began). He said there is an outside chance that this could rectify the problem. If that doesn't work, he's bringing in the Tappan rep. Suggestions????

[Brian in San Diego]

Rick,

It's extremely difficult to troubleshoot from afar but I would not have suspected the motherboard. I think I mentioned that earlier...technicians are likely to replace things they don't understand. I have seen it countless times...good boards being replaced because the technician didn't understand the various functions of the board. I don't know what other suggestions to make but doubt that replacing the thermostat is going to help. Get yourself a voltmeter and the next time there's a "call" for heating measure the voltage between the white wire from the thermostat and the common terminal. You need 24 VAC at that point. If you have the 24 vac and the heater isn't coming on then the problem is not the thermostat. You could however have a break in the thermostat wire. I have seen where the original installer wrapped the stat wire around a nail in the wall and over the years it rubbed enough to cause a break in the wire. If either the red or white wire going to the thermostat had that happen and it touched intermittantly you could get the problem you have described. I think it's probably a wiring problem of a short of the flame sensor.

I don't know the qualifications of your service tech but maybe it's time to try another who might have an unbiased and fresh approach to the problem. Sometimes techs can get "locked in" to a theory and either refuse or just can't let go of it. I know...I've been there.

Brian

[tilerite]

Brian
I understand what you are saying. Believe it or not, the person who I use is the foremost heater/ac expert in the area. His knowledge and education is excellent and before he opened his own business, many years ago, he used to train and certify other techs in the area. I have spent the last two days watching him go through a checklist of things in my unit, things that kept showing the motherboard to be the problem. The voltmeter has been used over and over. My wife, who for years was a manager in industrial laundry machinery business, and who herself has a deep knowledge of mechanical parts, motherboards, wiring, etc, is also baffled. There just isn't much left to check out at this point. He's hoping that perhaps the electronic thermostat may be incompatible with my unit though he admits this would be the first time he has seen such a problem. At this point, we're just trying to think outside the box.

[kilroy]

hey Rick...
You didn't happen to put an Eagles sticker on that unit? If so, that could be your problem. They kind of run hot and then just shut off cold. Like stomping Pittsburgh only to tie the 1-8 Bengles?
:D

[tilerite]

Can we avoid football talk for now?? :tongue:

[Brian in San Diego]

Can't be any worse than the Chargers! What's the difference betwen a dollar bill and the Chargers? You can get four quarters out of a dollar. What do you call thirty millionaires watching the Super Bowl on TV? The San Diego Chargers. Thank you very much...I'll be here all week.

[tilerite]

:lol1: :lol1: :lol1:

[MudMaker]

Did you ever contact the Tappan people and ax them??

[tilerite]

Yes, we did. Their rep made suggestions that were already implemented. We have literally run out of ideas. The heater has worked for the last two nights though. Go figure.