Carrier Infinity 96 Problem
I have an Infinity 96 furnace that is three years old with the DC fan motor. I also have the Infinity thermostat.
This winter the fan has been speeding up and slowing down during heating cycles. By that, I mean the furnance turns on, runs at low heat for a while, then the fan speeds up to high for about five seconds then slows down, then it speeds up and slows down again a few minutes later. This process is replicated until the firnace shuts off. The furnace does not do this all the time but it does seem to happen several times over a 24 hour period. Often, the furnace will just run at low with no reving up and slowing down.
The service tech gas failed to diagnose the problem.
We gave bo ice build up on either the intake exhaust pipes.
The filter is regularly changed and was repaced yesterday.
We keep the heat at 20 celsius through the day and evening and 19 celsius during sleeping hours so we don't have significant temperature changes.
I am not looking fir advice on how to fix the prpblem, just your thoughts concerning why this reving up and slowing down might be happening so I cabn present these qustions to the tach.
They found no error codes? Off hand, It seems like its going to high stage but the pressure switch is not closing, so it goes back to low stage.
Did it just started doing this?
I have to say, it sounds like it's a little oversized if low stage will maintain temp all winter long.
The techs said it's operation was normal?
It is a 60000 BTU furnace and they found no error codes. The house is very well insulated: R50 attic; R12 fiberglass exterior walls with R5 styrofoam on the outside and all new low e argon windows.
The tech played around with the thermostat and changed some of the settings and that helped a bit but did not solve the problem. Since install, the fan would come on for 5 or 10 second bursts at high speed when the furnace was not on. After he played around with the thermostat it stopped doing this but the random speeding up continues.
I never noticed the speeding up in previous winters so I think it is a new problem.
Thanks for your reply!
When you say the fan speeds up then down again are you refering to the blower motor or the inducer motor?
My question exactly. It would be helpful to know if it's the inducer motor (the combustion fan) or the air handler blower (the one that blows the air out of the supply registers).
Originally Posted by castillo7411
If YOU want change, YOU have to first change.
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this is a known problem that occurred a few years back, carrier put out a service bulletin on the subject. usually comes with a code 25, but sometimes no code at all. blower pulses high low. solved by replacing furnace control.
Thanks for the responses!
I think it is the air handler blower (I didn't know more then one existed!) because when it happens the air comes out of the registers with more force.
Would you happen to know the date or # of the service bulletin so I can direct the tech to it. I would have thought his shop would be aware of it because they are Carrier dealers but not everyone stays on top of their work.
Thanks again for the help!
referrob, Exactly, the furnace I was servicing was doing something very similar, when the blower would run on low stage, the motor was reving up for less than a second it was noticed by the homeowner because he would literaly sit in front of the furnace otherwise there was no way to tell. When I went out there there was no history in the Infinity control of any problems. It would occur so quickly that the rpm readout at the control would not see it I replaced the motherboard on the recommendation by carrier tech support and MAGICALLY it went away. Would that service bulletin be throu carriers hvacpartners.com site?
The tech just left my home and he failed to diagnose the problem. He called carrier and they told him they have no record of a similar problem in their files and no service bulletin for this issue exists. They did not allow him to change the motherboard. The tech couldn't replicate the revving up of the fan. He did notice a clicking noise that he said sounded like a pressure switch. He said the noise was unusual but that when he took the furnace cover off and powered the unit back up it would not replicate it.
If anyone can direct me to that service bulletin I would appreciate the help!
Just keep in mind that intermittent problems can rattle the most experienced tech sometimes. On another note I don't like to dog on my fellow techs out there but a Carrier dealer should be able to get any information on any service bulletin, it sounds like something is "off" here. Not "allowing" him to change parts doesn't make sense. As a Bryant dealer I know exactly what it is, not going to be posted here. Get A different Carrier or Bryant dealer to fix it. As for the service bulletin, it wouldn't benefit you and that kind of info is for the dealers only.
I only want the service bulletin so I can direct the tech to it so it can assist him. He asked Carrier if a service bulletin for this issue existed and he was told no. He was also told that Carrier had no record of this problem having ever occurred in any of its furnaces.
As for getting another dealer I can't do that. I bought the furnace from this dealer and although it has a 10 year parts and labour warranty, the warranty stipulates I have to use the dealer that I bought the furnace from to for the warranty work. I'll look into this further but I'm not hopeful.
If you can't use another dealer, call Carrier Corp direct (800-227-7437) so they can get some tech support to your installer.
Your can transfer your warranty to any Carrier dealer. Where are you located?