# Carrier furnace flame rollout keeps tripping - why?



## Billyv (Oct 8, 2011)

Carrier Furnace model 58MVP080
flame rollout on side keeps tripping. Replaced filter, opened all vents, returns not blocked, checked combustion air intake and exhaust and they are not blocked. Inspected burner nozzles and they look good( they are only 3 yrs old from when furnace was converted to propane)
Only thing I can see is that there is a bit of residual flame around the ends of the tubes that feed the heat exchanger. (the jet of flame does not completely shoot into the heat exchanger)
The box containing the propane nozzles and flame tubes and the rollout switch gets very hot to touch - is this normal?
Also, The 2-speed large blower never switches into high speed like it used to. 
Are these things related and if so which is causing which?
Since this is at the cottage and hard to get contractors would love to get this fixed quickly myself.


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## hvactech126 (Nov 11, 2010)

need to have the heat exchanger checked by a pro, sounds partially blocked or possibly even cracked.


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## Billyv (Oct 8, 2011)

Thank you hvactech126
Is this normal in a 11 year old furnace even though it ran normally all season last year? Is there anything else I can check to be sure before calling for a very expensive repair/replacement?


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## beenthere (Oct 11, 2008)

Heat exchanger could be bad. or if it wasn't set up right when converted to propane, the heat exchanger could be clogged with soot.


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## hvactech126 (Nov 11, 2010)

As beenthere and I both suggested it may be partially clogged with soot. Not something you can really yourself. Most likely if it is a sooting issue then the secondary passages are blocked. This would be due to improper setup/ combustion. You didn't run your propane rank empty while your furnace was running did you? Under normal circumstances it would not matter but if the installing contractor did not install a low gas pressure switch then this might have sooted the heat exchanger.


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## Billyv (Oct 8, 2011)

It has never run empty to my knowledge but since it is a cottage we are not up here most of the winter. The propane company comes very often thoughts evidenced by the frequent billing for a modern ultra-insulated building. Attached are photos of the tank regulators and inside of furnace in case you can see anything unusual. The contractor who installed this is pretty reputable but I guess you never know if you got a junior tech or something.


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## beenthere (Oct 11, 2008)

They did install a low gas pressure switch.


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## Billyv (Oct 8, 2011)

I should also add that I bought this furnace used three years ago(it is a 2000 model year) and the heat exchanger was checked by a heating contractor and it looked good in 2008 when I bought it.


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## hvactech126 (Nov 11, 2010)

Used.....LOL!


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## Master of Cold (Aug 7, 2011)

Was this furnace converted to use propane?


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## Billyv (Oct 8, 2011)

Yes it was converted by a local contractor to use propane.


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## Billyv (Oct 8, 2011)

It has run perfectly for 3 winters but when starting it up for this season I have encountered this problem.


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## biggles (Jan 1, 2008)

eye ball the flame right as the fan comes on see if you see a waving of that flame indicating possible heat x crack or holes.do you have colling there and if yes did you have condensation problems as if water dripped onto the heat ex in the summer


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## Billyv (Oct 8, 2011)

So if the low pressure switch was installed, then would we not suspect soot partially clogging the heat exchanger and thus it must be a cracked heat exchanger? Could it be anything else?


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## Billyv (Oct 8, 2011)

Thanks biggles. Will check flame when fan comes on. We do not have cooling installed so I don't suspect condensation.


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## biggles (Jan 1, 2008)

remove the flue pipe nearest the heat x and run your finger inide it look down into the exchanger


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## Billyv (Oct 8, 2011)

The flames not not seem to waver when the fan comes on but at least one flame jet seems almost mis-aligned so that not all of the flame is getting into the heat ex. There is some rust on the ports where the flame comes out and perhaps flame is leaking out there? I'm talking about the metal tubes, not the brass nozzles.


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## Billyv (Oct 8, 2011)

Biggles:
Sorry do not understand. What do you mean by flue pipe nearest the heat exchanger? Thanks for your help


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## Billyv (Oct 8, 2011)

This is what the flames look like whether the fan is blowing or not.


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## biggles (Jan 1, 2008)

anything yellow is starving for air check those air adjuster if you have them where the nozzle is...that yellow one is producng soot.that flue is where the burnt gases rise up and out should be on top and a ducted 4" or so pipe going out even down the line from the burner...just want to see if you have soot tripping down the pipe..like on your car exhaust:wink:


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## Billyv (Oct 8, 2011)

Disconnected the exhaust pipe and there was a bit of water and it is a bit dirty(sooty?). there is no adjustment for the air/propane jets they are just wide open flutes. Any other way to improve combustion so that all 4 ports are blue flames?


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## JJboy (Oct 12, 2010)

If the flames is shaking check for heat exchanger leak


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## hvac benny (Dec 29, 2009)

This furnace has a problem with the secondary heat exchanger failing and I have worked on many of them. Although the heat exchanger suffers from a manufacturer's defect, the real problem is improper commissioning (or lack of commissioning). There are three simple things you can do:

1)Feel the top of the furnace when it's running. It should be warm, but not hot. 

2)Remove the hoses from the trap. There should only be clear "water". If there is brown sludge, then the secondary heat exchanger is probably plugged. Also, the hoses should should feel firm, not flimsy and soft. This is also a good indicator that the heat exchanger is plugged. 

3)Pull the blower (5/16 hex head screws) and inspect the secondary heat exchanger. You should only see smooth metal. If it's plugged, and corroded through, you will see small brownish red balls or globs on the outside of the fins. 

If you observe any of this, I can advise you further on what to expect from a repair. There are certain things which usually need to be replaced with the heat exchanger, so if the company has to travel far to get to your cottage, then it would be best if they brought them with, to avoid having to go back.


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## beenthere (Oct 11, 2008)

Its probably one of the Carriers with the defective secondary heat exchanger. Carrier got sued over it. Not sure your covered under the suit, since you bought it used, and moved it from its original installation location.


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## JJboy (Oct 12, 2010)

beenthere said:


> Its probably one of the Carriers with the defective secondary heat exchanger. Carrier got sued over it. Not sure your covered under the suit, since you bought it used, and moved it from its original installation location.


SO what is the problem with Carrier secondary heat exchanger?


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## beenthere (Oct 11, 2008)

http://www.omaha-home-inspection.com/carrier-settlement-on-high-efficiency-furnaces.pdf


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## hvac benny (Dec 29, 2009)

While the material that Carrier used was poor, the real problem is poor installs. It's sad to say, but the majority of furnaces being put in today are simple hooked up to ducts, gas, electric and thermostat, then simply fire up while the contractor collects his payment and loads his tools into the truck. Of the 100 or so Carrier heat exchangers that I've replaced, ALL were the result of the installer not commissioning the furnace upon start-up/ poor installation. I've run into countless numbers of techs who think that simply checking the manifold pressure is enough. Hell, I've had to teach techs with 20+ years how to clock an appliance. The worst example that I've come across was a 100 MBTUH three stage Carrier furnace that was over firing by 20,000 in each stage! The company that installed it kept replacing the roll-out switch, without looking for the cause of the failure. By the time I got called to look at it both heat exchangers were toast, as well as about $500 in other components. There are far too many people doing work without gas tickets, as well as too many people with gas tickets who shouldn't have them in the first place.


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## Billyv (Oct 8, 2011)

Finally back at cottage. Thank you hvacbenny. The top of the furnace does get too hot to touch after running for a while. I removed the blower and attached is a picture of the fins. They look pretty clean. Do they look normal to you? The second photo is of the very back of the furnace and looks like water has been dripping from the very back. Does that mean cracked heat exchanger? You mentioned you might be able to tell me what else to look for or what other parts to have the contractor bring?


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## hvac benny (Dec 29, 2009)

It's hard to tell from your pics, but from the lower pic, the fins on the left look like the may be corroded through. Water leaking from the back is also common with plugged secondary heat exchangers, as the coupling box rots through. Since your furnace is in a cottage, I'd assume that it's probably not in as bad of shape as a similarly aged furnace with the same problem. If I were the service company, and had to travel quite some distance to you, I'd, at the very least, bring a coupling box kit (coupling box and cold spot baffle) as well as some extra hoses for the pressure switches along with a new secondary heat exchanger. How did the trap look?


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## Billyv (Oct 8, 2011)

Well thanks everyone for your help! I was able to troubleshoot and eliminate a number of items. In the end, the secondary heat ex was quite restricted with gunk and had minor perforations and leaks. With the help of a contractor we pulled the whole thing out and verified this. So I am awaiting a quote for a new heat exchanger and a new furnace and suspect I will choose the new furnace. I am looking for a good quality unit that will not get used a whole lot but I want it to last a long time. What is a brand that will deliver good service at a good price? - don't need bells and whistles, just need to keep the pipes from freezing and provide basic heat when I turn it on the couple of times we go up in the winter.


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