Carrier WA furnace servicers

Dale

We have been finding Carrier SX furnaces, not sure of the Bryant number, from the late 80's that have failed secondary heat exchangers. There is major corrosion damage at the inlet to the secondary cells where they connect to the upper collector box. Has any one else run into this? The symptom we see is very high CO ( we always test for exhaust CO) and often an open fusible link. The flame at the inshot burner looks lazy. The pressure switch doesn't cause any problem since this blockage is internal to the furnace. We guess that the problem stems from recirculation of the exhaust products and short cycling from oversizing but this is a guess. Carrier officially hasn't acknowledged the problem but no one seem surprised when dealers in our area request replacement heat exchangers, it's a "lifetime warranty" so the part is covered at least. Any one else have any of these you have found or ideas on what seems to be the root cause? Or specific model number runs that have falied more often.

rob

CAC/BDP WA

Are there any externally visible indications of this problem? Is it visible if the blower is pulled? Do I need to invest a CO detector and where do I test, the exhaust pipe or the SA plenum. Wasn't the SX the first condensing generation? Repaired a 58MVP yesterday, brand new, FC#42
ICM/IDB failure. Someday every installer will have to repair a furnace/boiler, that they have installed. No access to HSI/FSR, glued CA pipe, questionable gas piping,
duct work that makes me "cry". Maybe my standards are just too high. I do not understand why management condones this type of workmanship. Maybe I need to find another employer.
BTW, still snowing out there South Jersey.

Mark A. Custis

Most of the rotted secondary heat exchangers

I've seen leak water all over the place. I hope folks are looking for these guys before the flames get lazy and they start making CO.

Yes get trained and carry a CO detector or a combustion analizer.

Hook up with Jim Davis (see his post today on energy), he taught me and I think he is one of the best CO guys around.

Mark

ps. No offence ment to Rudy Leatherman, he's the best combustion guy I know.

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Wayco Wayne_2

Ive been having a problem

with an older Carrier condensing furnace. It turns off over night and re-sets when turned off and back on and works fine. I wonder if it is a similar problem?? WW

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Glenn Harrison

Seeing them here too.

Our company has had three rotted secondary heat exchangers this winter alone, and have been coming accross this for 3 years now. The first one this year another company was having trouble with the pressure switch making so they left the burner door off! All the ones we've had have rotted thru in the back on the turns. So much for the epoxy coating inside.

The worst part is when the Carrier/Bryant distributor tells you the Heat exchanger is made on an as needed basis in Syracuse, NY and will take 2 weeks to make and deliver. This is brilliant customer service and warranty satisfaction when people have 10 to 14 year old furnaces down and it is cold out. Needless to say we have sold new furnaces at three times the cost of labor for a new HX just so our customers can be warm.

Glenn Harrison, Residential Service Tech

Althoff Industries Inc. Mechanical and Electrical Contractors

Crystal Lake, Illinois

Althoff Industries website

Glenn Harrison

Things to check, Wayne

First, check ALL the drain hoses, fittings, and the drain trap. These furnaces are infamous for having a slimy substance grow in the secondary HX collector drain box and then work it's way into the drain hose and trap. Also be sure to check the exhaust pipe for proper pitch to insure proper condensate drainage.

Second, if this unit has the original three wire pilot assembly, change it. If not the original, clock the time it takes for the main burners to lite after the pilot is lit. This should be no more than 60 seconds.

Third, I have had problems with the lockout relay built into the igniton control not making or holding in. So you may have to replace the module also.

The key thing to remember is that the reason the furnace won't start is due to a timing sequence built into the ignition control. This does not neccesarilly mean the shut down is due to an ignition failure. Since it is only a timing sequence looking for the signal from the main valve burner circuit, the failure could be due to ignition, pressure switch, or inducer failure. I've even seen shut down of these units due to sticking pressure switches, intermitent gas meter/regulator problems, and the relay for the inducer board not always making contact. The three suggestions I have listed above are the most common reasons for a shutdown.

Hope this helps.

Glenn Harrison, Residential Service Tech

Althoff Industries Inc. Mechanical and Electrical Contractors

Crystal Lake, Illinois

Althoff Industries website