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-   -   Furnace never goes into high fire, why? (http://www.diychatroom.com/f17/furnace-never-goes-into-high-fire-why-168741/)

tfunk 01-09-2013 11:05 PM

Furnace never goes into high fire, why?
 
Hi all!

My furnace never goes into high fire. It's a mid efficiency two stage furnace. It'll go on low fire for a given amount of time then the gas fire goes out and the blower goes on higher/louder for about a minute and then it switches off and restarts the process on low fire of course.

We are just north of the perimeter in Winnipeg.

Cheers,
Tyler

Missouri Bound 01-09-2013 11:13 PM

Model numbers would be nice, mfg. as well. Just start happening...always like this, new thermostat, any other problems......all answers are based on what you provide, the more the merrier.:laughing:

tfunk 01-09-2013 11:26 PM

Model: Rgpk-10eamer
Serial: Fq5d302f320401669
Manuf Date: 8/2004

We moved in oct 1 and it needed a new pressure switch. High fire never worked. The tech who replaced the switch noticed high fire never activated we tried some things nothing worked. One of the wires from the thermostat used to go to the furnace now it's going to the air conditioner (installed after the furnace apparently). I believe it's the wire that tells the furnace to recirculate air (my guess is the lazy air conditioner did this assuming no one uses this function). On the board itself we were putting this one wire (may have been black) into a constant "on" position (at least that's what the tech told me he was doing) to see if high fire would initiate. We were also trying to make it skip low fire and go into always high fire. We were also trying to hardcode the other wire to have the furnace always in recirculation mode. No dice!

Is this an ok start? I think that's all I can think about it.

Doc Holliday 01-10-2013 12:08 AM

do you have a w2 terminal on the stat that's connected to w2 in the furnace?

tfunk 01-10-2013 12:40 AM

No, just W, Y, RC and RH. RC/RH are on the same signal. Is W2 related to high heat?

tfunk 01-10-2013 01:01 AM

According to the manual, W2 is needed for high heat.... Is there a way to hardcode the terminal on the board somehow?

tfunk 01-10-2013 01:04 AM

hmmmm, seems to be a single stage thermostat option on middle column of page 3:
http://www.rheem.com/documents/rgpk-...e-instructions

It appears high fire is possible without W2 connect? I'm lost ....

tfunk 01-10-2013 01:23 AM

My stat appears to be 2 stage capable but is operating in single stage mode. So probably jumpers on the board are preventing the jump to high heat. Is high fire really less efficient than low fire? That's what the thermostat manual tells me. Set the differential (when high fire shuts off) to a higher degree saves energy.

beenthere 01-10-2013 05:37 AM

Furnace is probably set to control second stage off of its timer. Is it maintaining temp the way it runs now? How long is its burner on time?

tfunk 01-10-2013 09:41 AM

It maintains temp, but going up 4 degrees can take about an hour or more.

tfunk 01-10-2013 09:48 AM

Also, if that's true, why does it have to recycle? Why doesn't it just stay on in low fire?

yuri 01-10-2013 12:11 PM

After 12 minutes the timer on the board will kick it to high fire. You need a wire from G on the tstat to the board G to run the fan continuos but I don't recommend it as it is drafty and can cost up to 1$/day to run the fan. Some newer units have high efficiency NRG saving motors but yours doesn't unless it has a 16 wire cable going to the motor. High fire should work as we get to -40C/F here and it is pretty hard to be comfortable with just low fire.

yuri 01-10-2013 12:16 PM

Quote:

Originally Posted by tfunk (Post 1090366)
Also, if that's true, why does it have to recycle? Why doesn't it just stay on in low fire?


There is a heat anticipator/length of cycle feature in the tstat and it is maxing out due to it being on low 2 long and will start cycling the burner/itself irregardless of house temp.

tfunk 01-10-2013 12:39 PM

Interesting. Is there a way to have te board go into high fire on it's own? Or would you more or less say my setup is sufficient/good enough?

tfunk 01-10-2013 12:51 PM

Quote:

Originally Posted by yuri (Post 1090460)
After 12 minutes the timer on the board will kick it to high fire. You need a wire from G on the tstat to the board G to run the fan continuos but I don't recommend it as it is drafty and can cost up to 1$/day to run the fan. Some newer units have high efficiency NRG saving motors but yours doesn't unless it has a 16 wire cable going to the motor. High fire should work as we get to -40C/F here and it is pretty hard to be comfortable with just low fire.

So your take is that the board is already wired for high fire the furnace is just choosing not to do it currently? Or is randomly doing it when I'm not looking? :)


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