Carrier 58mca080

Jimmy2

Hi,

Just wondering if anyone could help me. I had a service call today with a carrier, it will light and run (with a noisy, pressured flame) when the combustion air piping is cut, if I put it together it will not. Checked pressure switch. I believe it's a plugged heat exchanger, anyone else have any ideas?

Tim McElwain

The fact that

it will run with the air intake disconnected and will not run with it connect Duh I think the air intake may be plugged or restricted in some way.

Jimmy2

Oh

That's good. Oh well thanks for your very intellectual feed back. I probably didn't already check that. Obviously you know what your talking about.

Anyways yeah checked that. Oh and also if there was a plug the pressure switch may not work and it was so thanks for your very wise reply.

mars_6

Are there small children in the house

And is the furnace side wall vented. I have had many occasions that if the kids can get to the comb air inlet and they are in the age range of 3 to 6 years old they will drop small stones used for landscaping down the comb air and it has caused problems like this in the past for me. Just a thought Matt

Jimmy2

thanks Matt

Thanks Matt, that is a good thought, but I did take apart the concentric vent kit as well as the complete venting system to check for blockages. Everything seems clear in that aspect. I believe it is the secondary heat exchanger because when intake is connected it won't light and the gas is pulled completely through the condensate as well as sent outside. I know as a plumbing and heating contractor, that carrier was having problems and don't have a very good name right now. I just haven't encountered one yet and not sure of the symptoms.

Thanks

Ironman

Blockage

A blockage in the heat exchanger would be evidenced by a high vacuum on the suction side of the inducer. Check it with a good manometer.

Gary_17

Carrier service bulletin

I don't the model #s, but saw a service bulletin on how to inspect the secondary heat ex. and also something about extending the warr. on them.

World Plumber

burner box temp

Is the burner box getting real hot? Is the delta T low. I just had a block secondary heat exchanger. The flames were orangeish and labored, the burner box was getting hot and transferring the heat to the flame rollout switch and shutting it down. Only had a delta T of 22 degrees. Once I cleaned the heat exchanger the delta T jumped up to 45 degrees.

    It is strange that it would burn with the intake pipe disconnect, but not when you reconnected it. Did you blow through the pipe to be sure there wasn't something like a dead squirrel, bat, bird of leaves stuck inside it? I have seen them all.

   Oh how long is your pipe? What size is the pipe? How many BTU furnace? I'm thinkung you had 80 in the model. They told me anything over 75 K to use 3 inch pipe, even though the manuel say you can use up to ten feet of 2 inch on a 100K. Also remember each elbow counts as 5 feet.

World Plumber

Baffel / New Install

    Oh carrier used to have baffles to put in the connection at the furnace to prevent noise. Check to be sure there isn't one that got blocked or should not have been put in.

     Is this a new install? Some of the ICP brands are having a problem on start up. The grease they used in manufacturing is blocking the heat exchanger there is a bulletin that tells how to remedy it. 

Jimmy2

intake

I did have .65" WC on the suction side of the intake fan when the intake pipe is connected, when it's not I have about .45" WC

Jimmy2

Venting

Well there isn't a big delta T maybe 30F, the one thing I did consider was certainly venting size. I seen in the manual that you could go 25 feet with 3 90's and a concentric. now I only have about 12 feet of pipe for each and 3 90's in each. I really am considering changing the venting to 3" but the manual does say that it is acceptable as well as the gas inspector approved it (doesn't mean too much!!) I didn't do the original install, the furnace is 07/01, it was installed I believe by sears and not a very professional install if I say so myself, gasline was undersized etc. We had fixed that all up. The funny thing is, is if you keep the intake apart and let the furnace light, you can then attach the intake completely and it will run no problem. I don't get it. Maybe what I should do is upgrade the venting to 3" and try that, I just don't want to be the "part swapper" haven't had anything like this.

thanks for all the suggestions and such, now I'm wondering if it is really the heat exchanger.

Jimmy2

baffle

Thanks, that is a very good tip, but I did check the baffles inside and they are clean.

World Plumber

baffle

You might want to take the baffle out. I can only remember using them in one application, generally use them as a screen outside. Then remove  them if there is operational problems.

Jimmy2

baffle

I did remove them, there is none outside, and I took the one out of the inducer fan as well.

Thanks

Tim McElwain

Some Carrier units

have vent restricter installed in the exhaust side of the venting system I believe the idea was to overcome to high a combustion air blower affect on the burner flame.

Jimmy2

baffle

Perfect. I will take a look at that as well. Thanks