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woodburner · Dec 5, 2009, 12:05 PM

How do I get my fan to run all the time on my 08 rheem prestige 90 plus gas furnace I have to modulating t stat? I turned it to run on the t stat and put dip switch 5 to the on position and still nothing?? What am I doing wrong?
Robert

hvac1000 · Dec 5, 2009, 12:53 PM

On that unit you should really have a tool to see what the air flow in the ducts is doing and then adjust the fan speed. If this is a variable speed unit it can be damaged by improper adjustment.

woodburner · Dec 5, 2009, 02:52 PM

it is a variable speed unit ECM2, in the manual it says that you can have to fan run all the time for better air circulation, and it has been calibrated and the air flow switch's are set, I am just trying to get better air flow in the house.

hvac1000 · Dec 5, 2009, 02:54 PM

Just turn the thermostat fan control from auto to on. That should cause the blower to run all the time. If not then you might try to jump the G/Green wire to force the issue.

woodburner · Dec 5, 2009, 02:58 PM

Thanks, I have it in the on mode, and nothing happens. Is it safe to jump it. I don't want to break it. Thanks for your help.

hvac1000 · Dec 5, 2009, 03:55 PM

The green wire controls the activation of the furnace blower. You should be able to have CAC or Constant Air Control with your unit BUT it will usually be at a slower/lower speed. Normally when you put the fan to on instead of automatic it activated the constant fan. NOW if you are trying to get the fan to run at high speed for circulation purposes all bets are OFF since I would have to see the operating/instruction manual for that particular furnace before I would just jump it out. The movement of the fan control from auto to ON should have brought on the fan motor to start with unless the installer or you changed something.

The variable speed drives are not prime candidates to do anything else but operate for the furnace they are attached to unless modifications are made. Trying to get a woodburners heat to circulate might work well with a standard furnace blower motor but the variable speed units have operational quarks that may prevent them from operating well under those circumstances. Your manual below says the fan runs all the time on low to circulate.

woodburner · Dec 5, 2009, 04:14 PM

OK, yes I am trying to circulate my wood stove heat through the furnace duct work from a return duct that's mounted close to the wood stove. Is this a bad idea? I have never been able to get the fan to come on by itself even before I put in the wood stove. Not really sure why, I haven't modified anything, I think the fan being on low would be OK. Just looking for air movement with the equipment I have and not buying those corner fans. Thanks for the help

hvac1000 · Dec 5, 2009, 04:18 PM

That blower should be running at low speed to circulate the air under normal circumstances. I am just wondering if the thermostat has been setup not to allow the unit to do that?

Do you have the exact brand and model of the thermostat you are using? I think it is made by White Rodgers.

hvac1000 · Dec 5, 2009, 04:18 PM

WOOPS the part number is on the doc.

hvac1000 · Dec 5, 2009, 04:22 PM

See page 13 on this doc. It says fan is adjustable.

http://www.kwikpro.com/Documents%5C9...%20Rev%202.pdf

hvac1000 · Dec 5, 2009, 04:29 PM

If you are knowledgeable enough you can get to the setup mode and setup the "special test mode for PWM (V). Now if you do not want to take the chance of making a mistake call in a on site professional so they can adjust it for you. In other words you want to stay away from the V (PWM) adjustment. I just added this to clairfy.

This furnace and thermostat are not real user friendly with out experience.

Here is a link to your thermostat installer menu.Easy does it.

http://www.hphaa.com/knowledge/therm...TST401MDMS.pdf

woodburner · Dec 5, 2009, 04:39 PM

Thanks that's the t stat I have, I have looked at the manual and the wiring a thousand times the green goes to the green on the furance and the t stat is on run for the fan and it is set up so the t stat turns on the fan(set for elec not gas) not sure what I am missing??

woodburner · Dec 5, 2009, 04:41 PM

Yes this furnace is very very very difficult to operate

hvac1000 · Dec 5, 2009, 04:53 PM

Actually the thermostat should be set up to use gas not electric. That also controls how the blower comes on.

woodburner · Dec 5, 2009, 06:17 PM

I switched it to gas and still nothing? Am missing something?

hvac1000 · Dec 5, 2009, 11:00 PM

If the thermostat is setup correctly the blower should run on low speed if turned to ON. There has to be something wrong so you might start with the low voltage wiring.

woodburner · Dec 6, 2009, 05:52 AM

Thank you for your help,I have checked and triple checked the wiring and still nothing when it calls for heat it works, the only thing in the book is on sw2 it only shows 5 switch's and I have 6?

KC13 · Dec 6, 2009, 06:32 AM

Is this system/thermostat also used for cooling? Is a "Rc-Rh" jumper present at the thermostat?

woodburner · Dec 6, 2009, 08:16 AM

No it is not used for cooling, is it possible that I have a bad tstat? I was reading on another forum that these rhc-tst401mdms tstat had has some issues? When modulating the draft inducer rocks between high fire and low fire and with a new tstat people have said it fixed the problem. Could this also be why my fan doesn't work when I press on on the tstat..?

woodburner · Dec 6, 2009, 08:17 AM

Sorry no jumper present