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Douglas, HVAC Technician
Category: HVAC
Satisfied Customers: 3089
Experience:  Manufacture Rep for Major Brand, Technical Trainer, NATE
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problem 90I series will not stay running with condensate trap

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problem 90I series will not stay running with condensate trap installed on unit. Can't figure this one out. past problem (4 years ago) unit will not go into high heat mode. not sure what the problem was told son-in -law to call a service tech with more experiance on these bryant units . problem was solved with condesate drain trap being removed and cleaned. Same problem happening again but after removing trap and cleaning the unit still will not continue to run and shuts down after second stage heat process is started. removed trap, ran condensate drain to bucket, unit working fine . trap appears fine but the unit would not stay running with trap installed. After the third removal of the trap I plan on replacing the trap, with the hopes I don't have to pull the draft inducer assy. I also didn't have a mag gauge with me to check my inlet and discharge pressures of the induced draft fan. any ideas ??? thanks Joe HVAC service tech 30 yrs
Where the drain line exits the side of the furnace, install a T in place of the elbow as a vent. This will act like a plumbing vent on your sink and will allow it to drain better.
Customer: replied 6 years ago.
Tried that , unit still tripped out , after all the condensate (which was in the second heat exchanger) drained out when I turned off the unit . I hooked the trap back up and the unit wouldn't even stay running through the first stage heat. I can't figure out how a drain trap could cause the pressure switches to trip. again I've been working on systems a long time. I understand how systems should work, I refered to my HVAC text on two stage sequence of operations and I still not sure how the fuction of this trap could cause this problem.
I'm with you in that taking the trap out should prevent it from draining and sooner or later it will trip and drain.

One thing I found in those old secondary's was the lining which is a silicone like coating can be peeled and when the inducer comes on, the peelings flip up and obstruct the tubes and there is not enough flue passage through the secondary to keep the pressure switch closed or to close it in the first place. With the trap removed, air pulling into the secondary via the drain can support the flow to the inducer and allow the pressure switch to make.

It played havoc on the old SXB's with the variable speed inducers because they would just keep ramping up to overcome the blockage and eventually fault on inducer overspeed. On this model with a PSC inducer, it just tanks.

Those secondary's are not too hard to replace and I think recently when Carrier got sued by some lawyer in Canada, they now pay labor to change the secondary's. Of course the lifetime was to the original owner. beyond that it went to 20 and your probably within that. I don't know the serial number you have but those were 91-94 era if I recall.
Customer: replied 6 years ago.
HI Doug, now that makes since, the unit is a 91, am I to believe that the drain trap is OK if I can blow through all the ports both inlets are clear to the drain port? If the silcone flap is causing the problem is it something that can just be cut away or resilconed or as you say if it's not to labor intense change out the secondary heat exchanger? thanks again for your help it was driving this old tech crazy your explanation is right on......Thanks Joe
No those tubes are like between a 1/4" and 3/8 inch and you cant get back into them easily. The whole secondary slides out easy enough although for the life of me I don't remember if you get a new collector box. If you don't get one, get one.

91?... If it were me, I would see if I could get credit on the secondary toward a new furnace but it would be up to the warranty folks and it would have to be replaced with another Bryant (maybe Carrier).

Changing the secondary isn't that hard, it takes about 2 hours. One little tip. If you pull the collector box off, peel all the old rtv silicone off and spray the secondary face with Pam and put the silicone on the collector box. That way if you ever take it off again it will come off easier. If it's a 91... it may be a plastic collector box or may be metal..
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