How to run the forced air gas furnace fan without heat

OK guys. I know this can be done without hiring a HVAC tech. We would like to run the furnace fan without heat to move the heated air from the woodstove around the house. This would only be for short time periods. We have a relativly new forced air gas furnace that was wired to the existing 2 wire thermostat meaing that we cannot run "fan only". Question is can a simple switch be installed to make the fan run be itself or am I asking for trouble?

 

Probably a bit out of my range of knowledge on this but is it possible to upgrade your thermostat? I was in the same boat few years back, wanted to run fan only but my thermo didn't have it, I upgraded it and was able to achieve running fan only. However just my experience and 0.02 cents it didn't achieve what I anticipated it doing by sucking that hot air and circulating it through the house. The air quickly got cooled going through hvac vents and came out to cold. And one of my return vents is just above and to the right of the stove. I am sure there are many other factors and each house is different.

 

Others have warned me that this would happen. Still would like to give it a try since we have a small ranch on a crawl. Yes I could upgrade the thermostat, but would laso have to rewire.

 

Gotcha!!! That's what I wasn't sure about the wiring and thermos.

 

Trust me small ranch house or not, it won't work. Your cold air returns for the furnace are floor level where cold air lives. So, you will be pushing cold air thru your ducts. The faster you push it without adding the furnace heat, the colder the moving air will be. Been there, done that and have the tee shirt.

 

hmmm! My heat registers are on the floor and cold air returns are on the walls about 7' up.
also the furnace is a downflow. Does this change things?

 

Don't know. First time I ever heard of C/A returns mounted up 7' off the floor. Not sure how that works as hot air always rises. Either way, the faster you move ANY air the quicker it cools down. That's why often times long runs of duct work dispel much cooler air than short runs. I tried the fan only thing on my furnace and didn't gain anything. Sounds like you better try it yourself and see if the results work for you.

 

My forced hot air oil furnace has a switch on the furnace itself that will turn on the fan without the burner running. I have tried it a couple times and was unimpressed. The air coming out was not warm.
I have a vent cut in the ceiling about 10 feet in front of the wood stove which comes out in the master bedroom. This results in warm air getting upstairs and the cold air its replacing pours down the stairway into the pantry/laundry room where nobody is sleeping or sitting. We also have a small fan on the floor of the living room pushing cold air to the wood stove in the dining room. That air is replaced with warm air from the dining room.
These 2 things adequately move air in our house with much better results than using the furnace fan.

 

Description of your fan setup reminds me of a post from Backwoods Savage. I intend to try this soon. For the furnace "fan on" idea, it is starting to look like a "non idea".

 

My furnace only runs two wires: Red/White from the furnace to the thermostat. Should be no reason to rewire anything. I have never seen a t-stat that doesn’t have a fan only setting.

 

You need a thermostat with a fan switch and the wire needs to have four conductors (technically for heat and fan only three). Connections would be R W & G terminals at the stat and furnace. Turn the power off to the furnace before working on it.

 

So honestly after a negative post, I gave up reading! I feel you shouldn’t give advice saying no way it’ll work if you don’t know for a fact it won’t.
For 10 years I did this very thing with my forced hot air oil furnace and it worked great. I removed the blower motor/squirrel cage access door and taped a filter in its place. Then I just turned my fan “on” manually from my thermostat. My wood stove was placed beside that side of the furnace. I propped open my basement door to supply air and it pulled from across the ceiling, where hot air was, and up through the ducts.
So I say don’t give up on the idea.

 

I would look at the control board on the furnace to see if it even has a fan only capability before buying new thermostats or running new multiconductor wire. Usually if it does there is a terminal marked 'G' at the thermostat terminal strip.
I've had a nat gas forced hot air heat before and I really wouldn't want to listen to that fan rumbling 24/7. Especially at night.
This was a few years ago. I'd hope newer ones are (a lot) quieter.

 

My last home was a single story with walkout finished lower. Woodstove was in the finished lower and kept both floors warm on that end of the house. The bedrooms with unfinished basement under were furthest from the stove and would get chilly without running the fan continuous. Worked that way for 20 years. You don't loose heat out of the building, it just gets redistributed. Warm spots will be slightly less warm and cool spots will gain some of that warmth.

 

Some furnaces can have a different(lower) fan speed for fan only use.

 

house on crawl space furnace fan if the ducts run through crawl space you need to insulate them ( same as a regular basement) otherwise you are losing all the heat to basement along those runs.
I had a home many years ago, apx 1000sq ft ranch full basement, the return registers were at the top of the wall , seemed to work ok that way. never understood why at the time. Maybe pulling the hot air off the ceiling and redistributing it aided in less fuel needed on the ng furnace. I have registers in the kitchen and both bathes that high on wall they are tied into the air exchange system. that air is used to preheat or cool incoming fresh air which is fed into the main cold air return.

 

That too.

A/C ?

 

Perhaps a picture of the thermostat would be helpful.

 

I've read threads like this a hundred times over the years...and for everyone that said it worked for them, there is 20 that said it did not...which is the group I'm in...didn't work, not even a little bit.
But if OP wants to try, look at the control board on the furnace...they often have a "fan run" setting.

 

I agree on the results of running the furnace fan trying to redistribute heat from a wood stove.

In isolated cases where the proximity of the wood stove is close enough to the intake for the furnace blower motor, yeah, maybe some of a gain. But remember, this is why ductwork was designed....to distribute the heat more evenly throughout the conditioned spaces.

As far as wiring the T-stat to run fan only, if it is only a two wire to the stat, you're going to need at the very least a "add a wire kit". Why not just run a new T-stat wire to the stat and be done? 18-5 will serve you completely in the event if you ever add AC or use a t-stat that requires a ground wire.

Before you do any of this re-wiring though, make sure to see if the furnace has a terminal board with the required terminals. R W Y G C would be the most common with variances of those sometimes showing. If you don't see these terminal designations, it may be easier for you to call local HVAC company and have them wire it for you.

edit: One more thing. Just as brenndatomu stated, it did not work here either.