Run fan only on old gas furnace

[BillyPilgrim]

Hi

I just moved into our 2 story house of 1600 sqft near Vancouver BC and it has an older gas furnace, not sure how old the furnace is.
The problem I am having is that the ground level floor is very cold and the upper main living area is nice and warm. When the furnace runs the ground floor heats up fairly well but as soon as it stops all the heat travels upstairs and the ground floor is quite cold.

THe thermostat is on the second floor and only has two wires running to it so I can't run the fan only. I'm hoping someone can give me some advice on how to run the fan only on my furnace. Maybe on a switch or timer or run a new wire to thermostat. I'm hoping that running the fan will even out the heat in the house.

Pic of furnace here:https://plus.google.com/111042771435208504902/posts/XydQZj8X2ba

 

[BillyPilgrim]

Here is one more pic

 

[Sponsor]

 

[Jadnashua]

You'd need a new thermostat with an AUTO/ON switch for the fan, and to run at least a 3-wire cable so you can also make a connection to the 'G' terminal. When 28vac is connected to that terminal, it should turn on the fan motor. I can't read the wiring diagram as well as I'd like, but check for that 'G' terminal there to verify.

 

[BillyPilgrim]

Thanks for the response.

Just to clarify, the thermostat has the auto/on for a fan, but the install only has two wires. I'm not sure what you mean by the G terminal but I will have a closer look and see if I can figure it out.

 

[Dana]

Running the furnace without the burner just produces wind-chill drafts. With the burners on you're probably getting 50-60C air at the registers into a 20C room, a delta-T of 30C or better, but reciruclating 21C air into an 18-19C room is just a noisy draft inducer- it'll make you feel colder, even if it raises the temp a degree or so.

The heating efficiency of running a 500-1000 watt air handler to move air at a delta-T of 2-3C is also ridiculously low, and may even be actively blowing heat out of the house due to pressure differences created by supply/return duct flow imbalances on a room-by-room basis.

If it gets cold quickly in the first floor once it's off you may have unusually high outdoor air infiltration coming into the first floor, and hot air leaking out of the attic or second floor. It takes quite awhile for air to stratify between floors in a tight house, but barely any time at all for stack-effect draws to suck cold air into the first floor as the warmed air from the first floor gets drawn up to the second floor.

If you want to actually be COMFORTABLE, figure out where all the big air leaks are at the top & bottom of the house, and seal them. (Sometimes easier said than done.)

A really big leak often missed is the foundation sill & band joist in the basement, which is often several times all of the window & door crackage combined. A clothes dryer in the basement also needs a backdraft preventer. Anything that you can do to air-seal plumbing / electrical / flue chases etc between the basement & first floor also helps impede stack effect draws, and don't forget a door-sweep on the door to the basement.

Common leaks out of the top of the house are unsealed electrical penetrations into the attic, bath fans without backdraft preventers, older pot light fixtures that aren't air-tight that are not sealed at the edges at the ceiling gypsum.

The greater the elevation change between the lowest air leak and the highest, the greater the stack-effect drive. If you seal both the top and the bottom of the house it almost doesn't matter how leaky it is in-between (until the wind blows.) In general it's easier to seal the basement at the foundation walls, but do what you can at the basement ceiling too.

 

[BillyPilgrim]

Here is a pic of the wire diagram with no flash

 

[BillyPilgrim]

Thanks for the feedback on air sealing. I'm working on the air sealing as well, but there is only so much that I can reach. We have a full first floor gut in the plans but need to make it thru this winter and maybe another first. I'll look into sealing all the pot lights upstairs next. We have an open stairway between floors (no door) so I think that is a big part of why the heat goes up so fast

 

[Dana]

Open staircase or not, it takes time for air to stratify within a space, an order of magnitude more time that it takes for stack-effect infiltration to displace first-floor air with cool outdoor air.

When you gut the place you'll have opportunity to get serious about air sealing the walls, but it's still the top & bottom of the stack that are most critical.

 

[DonL]

Thanks for the response.

Just to clarify, the thermostat has the auto/on for a fan, but the install only has two wires. I'm not sure what you mean by the G terminal but I will have a closer look and see if I can figure it out.

Are you sure there are no other wire conductors in the wire ?

It looks like the spare conductors have been cut below the outer insulation.

As mentioned running the Fan may make it feel colder, Unless the return is upstairs.


Good Luck.

 

[Tom Sawyer]

Move the thermostat

 

[DonL]

Move the thermostat

That would work for downstairs, But upstairs may be toasting.

The upstairs vents may need to be closed some to balance the system.

The thermostat should be near the Air Return.

 

[Tom Sawyer]

Without zone dampers, it's ALWAYS going to be hotter upstairs.

 

[DonL]

It is strange how hot air rises. lol

Around here 2 story houses have separate heating and cooling systems.

Heat Pumps are the norm. So is $500,000 for a 2 story house on a postage stamp size property.

 

[Jadnashua]

My air handler has a variable 16-speed fan motor, and I generally do run it on the 'FAN' setting to move some air around and also cause it to be run through the filter (this causes it to be on the lowest speed unless the system is calling for heat or a/c). This is slow enough so it is not drafty. Your typical constant speed fan can be both noisy and inefficient. The temperature differential is typically in the order of 1-2 degrees for me between floors, but that is after some careful tweaking. A typical blower fan could easily be a 1/2Hp or bigger, so it will be noticed on your electric bill!

Your furnace connection panel shows a 'G' terminal...that needs to be connected to the 'G' terminal of your thermostat. If it is conforming to conventions, that would apply 28vac onto the 'G' terminal back to the furnace when you switch to 'FAN ON' at the thermostat, energizing the fan motor control, turning the fan on 'constantly'.

 

[BillyPilgrim]

Thanks for all the advice. I'm going to hook up the G terminal to the thermostat and see if that helps things along with some extra air sealing.

 

[DonL]

Thanks for all the advice. I'm going to hook up the G terminal to the thermostat and see if that helps things along with some extra air sealing.

Did you find a extra wire conductor in the wire you have, or do you need to run new wire ?

Good Luck on your project.

 

[BillyPilgrim]

There are two returns upstairs and none on the lower floor. I have sealed off the two strongest blowing vents upstairs with metal tape. What percentage of the upstairs vents is it ok to seal off, I have heard that you can damage the blower if you seal too many off. I know there are a lot of variable here but is there a general rule of thumb.
Sealing the vents on the upper floor has made some differnce, basically the basement gets a little hotter in each heating cycle. Not a real solution but maybe with some better air sealing I will get something that will be ok for a winter or two until I can gut basement.
I'm thinking of going with two ductless mini splits(one for each floor) in the renovation

 

[BillyPilgrim]

I will need to run a new wire

 

[DonL]

I will need to run a new wire

Maybe you can get lucky and use the old wire as a pull string for the new wire.


Good Luck.

 

[Tom Sawyer]

Or, you could just wire a switch inside the stairwell or wherever else you want it.