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suthrnreject 01-19-2009 03:00 PM

Is there such a thing as a dirty heat exchanger?
My American Standard furnace (13-14 years old) has been acting up lately, not wanting to start for a while, especially in the mornings. It can take around 5- 10 minutes to finally get started, but once started, runs just fine.

We thought this was a thermostat issue, but after one conctractor spent two hours in the basement checking things out, he said the pressure reading was low, which was causing it to cut out early or take a while to start up. He attributed this to a dirty heat exchanger (i.e., the caked on dirt was causing a blockage and thus bad pressure readings), which he could clean for only $1000!!!!. However, if this turned out not to be the source of the problem, then I would need to replace the furnace for the low, low price of only $6000. This just didn't seem right to me.

I called another contractor this morning, and he felt it was the pressure switch itself if it was indeed not reading properly, or something to do with the blower. He never heard of cleaning the heat exchanger, although he said he could probably do it by simply vacuuming out the soot if that's what I wanted. The other guy made it sound like it was more than soot caking the exchanger, like it was hard stuff that would need to be scraped off (I have no idea what this would be).

Absent a dirty exchanger, it might be due to cracks in the exchanger causing pressure problems. He seemed eager to clean the exchanger and charge me a boatload for it, but couldn't tell me if there were cracks in the exchanger. We would know this, according to him, if the cleaning didn't do the trick.

In any event, should I first try to get the exchanger cleaned (by the second contractor, and not for $1000), and if that does't work, and if it's not the pressure switch, can I simply replace the heat exchanger rather than purchase a new furnace? I can't afford a new furnace right now.

Something about the first guy, even though he spent two hours of his time and didn't charge me for it, still doesn't sound right. He did lower the price of the cleaning to $875, and then said that if it turned out not to be the problem, and I bought a new furnace, they would only charge me $125 for the cleaning, and apply the remaining cost to the new furnace. Reading other people's posts, it sounds like he could have easily determined whether the heat exchanger was cracked or not, rather than putting me through an expensive cleaning that may not be the issue after all.

Is this a scam?

Any and all help and suggestions are appreciated.

JohnH1 01-19-2009 03:03 PM

Something dosent soud right. A $1,000.00 cleaning on a furnace Holy s**** Batman

Bondo 01-19-2009 03:42 PM


can I simply replace the heat exchanger rather than purchase a new furnace? I can't afford a new furnace right now.
Ayuh,... Donno where you are or the going rates,...
But from Here,.. It sounds like those prices are alittle High....

A simple furnce Cleaning, I would think, should be pretty well covered by the $125.00 you mention in the end...

As far as changing Just the heat exchanger,... You might as well buy a New Furnace....
The Heat Exchanger pretty much "Is" the furnace...

At the rates you're being quoted,...
The labor bill for changing the heat exchanger would be about Twice the cost of a New Furnace...

biggles 01-19-2009 03:45 PM

the only money you should spend is on some thick 1"-2" brushes used to clean HX out.....remove the burners tubes( push foward-lift up-pull out)leave the header.your running an Induced Draft for the furnace itself and that is a cleaner just with the air being forced thru the heat exchanger.ever run your finger on the inside of the tailpipe of your car...soot to a minimum......:thumbsup: right sould be the same on that exchanger.if your burning a blue flame when the gas is running that is considered clean.that pressure switch is totally dedicated to the proof to the main gas valve that the ID is running(might need an adjustment)...CCW the adjuster out a 1/4 turn for now .IMPORTAANT the only pressure the switch looks at and senses is the ID motor draft where it(tube) connects.check the tube make sure it isn't cracked or has water in it.if the burner is running and you pull the tube on the controller the main burner will shut down thru the pressure switch......put it back on and the cycle will relight.BACK TO THE CLEANING OF THE HEAT X after you remove the burner tubes you run the brushes up and down the heat exchanger front to back. see what comes down if it is light black soot "if that" like the tail pipe test your safe.quick test on a cracked heat exchanger with everthing back together restart the furnace just when the burner lights off you want to eyeball the flames and just as the fan comes on you shouldn't see any wavey action on the flames right after the fan comes on.if you see any movements you need to get a tech in to check it visually and with test instruments.over heating can crack them,condensate dripping off the AC coil rust them out during the summer

suthrnreject 01-19-2009 05:39 PM

Ugh! I guess I'll have the second contractor come by and present him with all my newfound knowledge, thanks to you guys.

Good news on the second contractor - his business is rated A+ with the BBB. The first contractor isn't even listed with them. Bad news is that the second's technician won't be available for a couple of weeks - out of town due to family illness or something.

We've been running like this for a while - assuming we're safe to keep going for the next couple of weeks??? We live in Colorado, but the days have been in the 60's the past week, and we drop the furnace down to 58 at night, so not been running much of late. Could change at a moment's notice though, although we haven't been getting much of a winter lately. Very strange for this area.

sgthvac 01-19-2009 05:58 PM

Yes, I've cleaned heat exchangers in the past, but with the advent of high effiencies and the way heat exchangers are designed any more it is difficult to impossible. If it's plugged we usually relace the heat exchanger if still under wnty or replace the furnace. As far as pricing, it depends on the area and what has to be done. That being said, it does seem high.

The question I have is did any of your techs use a magnahelic to test what the pressure switch is seeing. Is the flue, drain, or intake plugged up? Is the port where the pressure sw. hose attaches the furnace blocked..etc. I've seen alot of pressure switches replaced that were not bad.

Dr Heat 01-19-2009 06:29 PM

Ok is this a natural gas propane or oil furnace (if I missed that in your post sorry )


2 We clean them regularly Last Friday I had a tech take a shoe box full of soot out of a gas furnace. The Flue was run incorrectly causing an incorrect fuel to gas mix. Once I cleaned a 70% that was setup lp and was running on Na it was plugged solid.

3 If it is a bad heat exchanger American Standard has a good warranty it should cost no more than $150 handling on a warrantied HE and we charge $100 an hour to install should not take more than 4 hours for one man

Dr Heat 01-19-2009 06:38 PM

In rereading your post something came to mind you really did not describe what the problem was only a diagnosis by some one you do not trust.


Does the furnace light and not stay lit

How long does it stay lit

Walk us through the sequence 1venter motor starts 2 glow bar glows 3 burners ignite and so forth

Give us as much detail as possible

SKIP4661 01-19-2009 08:23 PM

If that heat exchanger is cracked, it may still be under warranty. If you could post a model and serial number someone could let you know for sure. As far as cleaning the furnace, if it's an 80%er you may be able to clean it with a brush. If it's a 90+ it will have a secondary htx that will also need to be cleaned. This may require the secondary be removed and washed out. If a vacuum is used make sure the filtration is adequate to handle soot. It could blow straight through a shop vac and really make a mess of a house.

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