[SOLVED] Ignition Problem Fix for Armstrong Ultra SX-80 Furnace

[Roy Zimmerman]

------------------------------------------------------------------------

--------

A friend of mine just spent $100 having her Armstrong Ultra SX-80 furnace fixed. According to the repairman, this is a common problem with this model and is easily fixed by the homeowner -- so I thought I'd post the fix here and, hopefully, save some future reader a few bucks.

Her problem was that the furnace would not light. This unit has an electronic ignition that will not function unless conditions are OK in the combustion area. When the thermostat calls for heat, the combustion fan motor turns on, drawing in fresh outside air. The pressure caused by the fan is detected by a separately mounted pressure switch. If the switch is not activated, no ignition.

The pressure switch is connected to the combustion area by an 18 inch length of 1/4 inch rubber hose. It turns out that there is a lot of condensation in the combustion chamber in the area of the hose fitting and particles of rust can clog that fitting. Once the serviceman realized the pressure switch wasn't activating, the first thing he did was pull the hose off the fitting near the fan and ran a wire down the fitting bore to clean it. He reattached the hose, hit the power switch and the furnace fired right up. Total time: 10 minutes, tops.

I now know what to do next time -- and I expect there will be a next time.

Hopefully, I've saved you a service call.

[kjpro]

As I have already told you, he fix a symptom not the problem.

[Anthony Diodati]

[m Ransley]

i get the same thieg when the coons nest - no fere

[CBhvac]

Lack of vac would indeed, but what he describes is another larger problem that needs to be addressed, and while anyone can hack in a fix, the real tech will find the real problem, and repair the unit, not put a patch on it. That was a patch...nothing more.

Case in point. I had a customer that had (key word, HAD) a 3 year old Rheem

90% condensing furnace. He had allowed his cousin, who had a friend in the trade who had a friend...and so on, install it for him. I got called out for a no heat call. When I got there, the unit was installed BELOW grade, in a crawlspace and had been flooded. I priced out a new unit. Period. The maker of the unit even states in clear letters, not to run the unit if it has been exposed to water. He of course, declined and called his buddy of a buddy of a buddy back out who basically, disabled all the safetys, vac'd out the primary heat exchanger and blocked the drain at somepoint. I got called back about a month later. The home had caught on fire....sorta...the lower floor joists were found to be smoldering one morning since the drain had blocked up, filled the primary heat exchanger with water again, the inducer motor had been rigged to run all the time, and the roll outs had been bypassed. The flame was NOT going into the heat exchanger, but instead were rolling out into the vented side, and the heat was scorching the joists. He had no real legal means to go after the guy that installed or "repaired" it since he was not licenced or insured, and is now the owner of a properly installed unit, above grade, with all permits and inspections done. Sometimes, JUST because you got it to run, does not mean its running correctly, or that you solved the real problem.

[vairxpert]

If the inducer was rigged to run all the time, how did the furnace continue to operate after the first cycle in which the pressure switch failed to open?

George

[vairxpert]

Piss poor design. Look at the inducer housing. Is it covered with flaking black paint? Guess what...the inside is painted too! The paint flakes off and plugs up the port. Just popping a wire through the port will fix the problem but odds are it will come back shortly. The replacement inducer assemblies are no longer painted.

[StephenM]

Ignore the posting name, changed it for a sec in alt.hvac and havent bothered to change it back.

Simple...it was rigged on a standard peanut relay...When W was hot, it started the inducer. I might...and thats might, have some pics of that one around...if I do, you can see what a mess it was. He had a couple of old TI sequencers in there as well, that didnt belong.

[vairxpert]

Why did he go through all that trouble instead of just letting the control board do its job? Or was the exchanger plugged to the point the pressure switch didn't prove, so he basically hardwired the inducer and used a relay in place of the pressure switch that would make and break on W in order to fool the computer? Now that would be Sweeet!!

Oh and if you're reading this, Stormin'...please don't get any ideas!

George

[Anthony Diodati]

So IOW there should not have been a lot of condensation in the combustion chamber in the area of the hose fitting,causeing the rust in the first place? Tony D.

[Anthony Diodati]

[CBHVAC]

Yup...exactly. I had a similar problem child not too long ago..an older Armstrong. I got this call about a unit that the other tech had said he "cant get that computer control anymore" and wondered if I could look at it. It worked sometimes, and most times not. It was a mess, in a crawlspace, and the vent was rusted, doors off, blower door switch hardwired, blower overheat limit hardwired, an extra relay or 4 in there..a bad HSI, and the best part was, once I got the HSI working, I had to prove what else was wrong, and start over. So..first things first, I get the thing to fire, and lo and behold, it does...problem is that the inducer and the blower came on at the same time. Turn the AC on....inducer was on..go freaking figure. Long story short...after ripping it down to nothing but the HSI control still in place, and starting over, there was nothing wrong with it other than some really, really reeeeeealy dumb wiring done by a tech from another company, that didnt have a clue. Funny part was, it was proof positive that if the fan starts at the same time as the inducer, the heat exchanger will never get to temp....the sounds of commotion from the owner when she thought the house was on fire..LOL..from the crap burning off the HE was priceless. Point is, you and I both know that too many people think an extra relay to make things work fixes the problem...

I thought of him...I really honestly did... I have even thought of printing up a sign, and when I run into a REALLY hacked one like that, taping it to it and snapping a pic for the website..:) Sign might say...SM was here....or...Stormy...is this your work?

[CBHVAC]

Define alot..:)

90%+ units are condensing. They make tons in some cases of condensate. IF and thats IF everything is working like its supposed to, thats remvoed and no water will build up in the unit. The PVC exhaust normally will have a drain, and so will the heat exchangers. They normally run into a common drain to the unit, and the condensates removed from the area. IF the units installed at the wrong angle (very common) or the drains are not installed at the right location, the secondary in particular will actually fill with water. I myself have vac'd out a couple that were wrong. They work fine, till the water either clogs the tube, or the inducer cant pull a vac due to water, and the 24VAC system is shut down.

[Rob Lewis]

replying to Roy Zimmerman, Rob Lewis wrote: Thank you very much. I cleaned mine with a wire bread tie. Rob

[Rob Lewis]

replying to Roy Zimmerman, Rob Lewis wrote: Thank you very much. I cleaned mine with a wire bread tie. Rob

[Refral]

replying to Roy Zimmerman, Refral wrote: Thank you Roy for posting this article. You, this article, probably saved me hundreds of dollars. I have often said, it is the simple things that may get you out of a jam, if you seek the right knowledge. Especially if ask for Devine guidance. Peace, Reginald It will be a comfortable winter in my home with coffee, rolls, and glazing out the windows.

[mmm75821455]

The vacuum pressure switch ensures that the induction motor fan is properly working, because it's job is to push the poisonous exhaust gasses up the chimney. If there's no suction on the switch because of a clogged line the furnace shuts down due to safety precautions.