Cant get just my blower fan to come on... HELP!!

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DaneeP

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So I just installed a Pellet Burning Stove in my house and would like to be able to turn just the blower fan on on my furnace to circulate the hot air through my house and crawl space. My cold air return is in the same room as the stove so this will be perfect.. I have 4 wires going to my thermostat and furnace and a thermostat that has a Auto and On setting but it doesnt do anything?! The furnace is a Rheem Imperial 80 Plus. Any help would be greatly appreciated!!
 

DaneeP

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Also forgot to say that I did try connecting R to G with a jumper at the furnace. you can hear the relay close but the fan still doesnt come on
 

Jadnashua

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If you do not have the installation manual for that furnace, you may be able to find it online at the manufacturer's website. But, typically, inside of the access panel, there will be a system diagram. Check it to see if there is anything other than a relay to the fan. Not all furnaces offer a manual/auto fan function, and only turn on when the air temperature is within a certain range in the heat exchanger. If you determine that it should turn on, the relay could be bad (you could try turning up the furnace thermostat and see if it turns the fan on by itself).

If the fan doesn't come on with the furnace call for heat, then you have either a control issue (relay) or a fan issue (fan motor), or possibly, a high/low thermostat control issue for fan control. There may be other things, but that's all I can think of for the moment.

If you feel comfortable doing it, and you can't get the fan to turn on normally, you could test the relay for the proper voltage on the output terminals and to the motor. Well, one more thing...many of those motors have a starting capacitor...if the fan doesn't turn on, it could be that as well. All of that should show up on the diagram. Knowing how to read it is another thing!
 

Dana

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The heating efficiency of using the furnace air handler to recirculate tepid room air around the house is pretty lousy, and delivers more wind-chill to folks in the remote rooms than actual comfort. It's really not worth it unless you're moving air from a 110F (or hotter) room into a 68F room, so that the air coming out of the registers at the other end isn't much below human body temp.

The exception would be if you had a ECM drive air handler that could run at very low speed using very low power, but the amount of actual heat distribution per kwh of power use would still be quite low.

While it might intuitively seem like a good idea, do the math. A cubic foot of air has only about 0.018 BTU per degree-F difference. So if it's say, 75F in the room with the pellet stove and the remote rooms are 60F (not exactly warm), that's a delta-T of 15F. If the heat load of that room is a modest 1500 BTU/hr at that point in time (it'll vary with outdoor temp), which is 25 BTU/minute. At 0.018 BTU/cubic foot and a 15F delta you're looking at only 0.018 x 15F=0.27 BTU per cubic foot of air moved, and need about 25/0.27= 93 cfm just to keep it from losing ground and getting colder. In a 10 room house with a ~1000 cfm air handler, you'll barely break even at 60F at a 15000BTU/hr whole-house load. If you're trying to keep the remote rooms at 68F, that's about half the delta-T, and twice the cfm requirements for actually achieving that low of a temperature difference.

And in a 68F room air coming out of the registers at 75F (if you should be so lucky to have it that high) would seem AWFULLY cold, compared to the typical 110-130F register temps of a condensing hot air furnace.

You would be better off using small electric space heaters to stay comfortable in the other rooms (only when occupied) for the ~500Watts the air handler is using. If the ducts aren't perfectly balanced by design, perfectly sealed & insulated or if the house is leaky you'd also be driving a good fraction of the heat out of the house due to air-handler induced air infiltration.

Bottom line, it's only going to be worth moving heat via an air handler if the delta-Ts are 30F or greater. If you boost the temp in the pellet-stove room to a sauna-like 110F you might be able to heat the remote rooms to 68-70F, but unless you're willing to roast yourself out in that room fuggedaboudit.
 
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