My cheap idea for fixing uneven air temps in different rooms

[BrettS]

I just moved into a new house and I'm having two similar problems and I think I have a very inexpensive way to solve them, but I was looking for a bit of advice. The house I bought is a three story townhouse with living space on the first and second floors on one heat pump and the bedrooms on the third floor on a second heat pump. What I've discovered, after living here for a few weeks, is that two of the bedrooms face the east, so in the morning when the sun rises the temperature in those rooms also rises and those rooms can be several degrees warmer than the rest of the bedrooms. Also, along the same lines, during the day the second floor tends to get somewhat warmer than the first floor.

Now that I've automated the thermostats (I installed two TZ16's) I was wondering if I could solve my problems either by having HomeSeer run the just the fan without turning on the AC for a few minutes every hour (given the current outside temperatures the AC can be off for several hours, especially durning the night). Or, maybe even better, get something to monitor the temps in the rooms where I'm having problems and use HomeSeer to compare those temps to the temp at the thermostat, and if they're far enough off, have HomeSeer turn the fan on until they even out.

Do you guys think that might help? I don't really want to go through the labor or expense to install a zoned system and I'm thinking that just running the fan alone will help distribute the air and even out the temps.

Also, along a completely different line, the thermostats I replaced had an interesting feature. After an AC call had been satisfied they would shut off the compressor, but continue to run the fan for a few minutes. The theory, from what I've been told, is that the evaporator coils are still cold immediately after the compressor shuts off, so you may as well run the fan a bit longer to make sure you get as much cooling as possible for the energy spent to run the compressor. This makes sense to me, and I've set up a couple of rules in HomeSeer to emulate this behavior with my new thermostats, but I wasn't sure how long to run the fans after the compressor is shut off. Unfortunately I didn't pay close enough attention to see how long the fan ran after an AC call with my old thermostats and I can't seem to find much info online about it. Does anyone have any suggestions about this?

Thanks much,
Brett

 

[hucker]

I do this in a two floor house, bedrooms upstairs, living downstairs. During the day I run the fan to pull the heat from upstairs to downstairs and at night I let the system heat normally (thus making the upstairs warmer than the downstairs). In theory this should all work just peachy. I have temp sensors throughout the house and I find it difficult to see a measurable effect. I *think* I see a 1°F change in my favor. It seems that I should have gotten a 3°F change...

I'm not done yet but I haven't been impressed thus far...

I also have a house fan that I can use in the summer to suck heat out of the house but I haven't been here in the summer yet!

 

[beelzerob]

I also have a house fan that I can use in the summer to suck heat out of the house but I haven't been here in the summer yet!

Same here. I'm very pleased with it! I turned it on just to test it, and geez...stay away from any partially open doors, this sucker...well...sucks! Crack open a window and the air comes pouring in. Both our last houses suffered greatly from being hot inside while it was cold outside, and no amount of fans in the windows seemed to be able to overcome this. So I'm happy with this new solution, though as you say, I've not actually been able to test it in real living conditions.

Brett, what you describe is what we have planned also. I have a controllable thermostat, and temp sensors throughout the house and in the duct @ the fan. Our great room has a fireplace, so my plan is to just run the fan in winter to move that hot air throughout the house and mix it up. I'm interested to see the difference it makes. I can log the temp data, as well as when the fan comes on and off, so I plan to graph this stuff and see if I can actually see the temps start to converge. Not a whole lot of expense has gone into this, so I'll be extra pleased if it all works like it should. I'll let you know in another 8 monthes....

 

[drozwood90]

I do this in a two floor house, bedrooms upstairs, living downstairs. During the day I run the fan to pull the heat from upstairs to downstairs and at night I let the system heat normally (thus making the upstairs warmer than the downstairs). In theory this should all work just peachy. I have temp sensors throughout the house and I find it difficult to see a measurable effect. I *think* I see a 1°F change in my favor. It seems that I should have gotten a 3°F change...

I'm not done yet but I haven't been impressed thus far...

I also have a house fan that I can use in the summer to suck heat out of the house but I haven't been here in the summer yet!

You would only get the 3 deg or greater change IF you set back the lower thermostats, as they will continue to pump heat into their zone until they reach equilibrium. Basically, what you have done, is made your lower floors heat the upper floors. I would think if you monitored WHEN they went off, the upper floor does not go off as much as it did without the fans.

I had noticed something similar in my 4 zone 4 floor house.

my $0.02

--Dan

 

[hucker]

I do this in a two floor house, bedrooms upstairs, living downstairs. During the day I run the fan to pull the heat from upstairs to downstairs and at night I let the system heat normally (thus making the upstairs warmer than the downstairs). In theory this should all work just peachy. I have temp sensors throughout the house and I find it difficult to see a measurable effect. I *think* I see a 1°F change in my favor. It seems that I should have gotten a 3°F change...

I'm not done yet but I haven't been impressed thus far...

I also have a house fan that I can use in the summer to suck heat out of the house but I haven't been here in the summer yet!

You would only get the 3 deg or greater change IF you set back the lower thermostats, as they will continue to pump heat into their zone until they reach equilibrium. Basically, what you have done, is made your lower floors heat the upper floors. I would think if you monitored WHEN they went off, the upper floor does not go off as much as it did without the fans.

I had noticed something similar in my 4 zone 4 floor house.

my $0.02

--Dan

Dan:

I do not have multiple zones. I have a single stat in the house.

I'm looking at the delta between upstairs and down stairs not absolutes. The normal system shows that the upstairs is usually about 3F warmer than the downstairs. If I turn on the fan only to mix things up I see that the upstairs is MAYBE two degrees warmer than the down stairs thus a single degree 'gain'. I might say that since the downstairs is 150% the square footage of the upstairs that perhaps I really am getting more than I say... I am not ready to stand by this as I need some more sensors downstairs but my preliminary results indicate that mixing the house up with the furnace fan does not do much to equalize the temperatures. I'll be looking at this in more detail over the next few months.

Beelzebob:

Did you get a quiet cool fan? Those things rock 1500CFM and quiet enough to have in your bedroom!

 

[beelzerob]

Beelzebob:

Did you get a quiet cool fan? Those things rock 1500CFM and quiet enough to have in your bedroom!

No...I wouldn't call it quiet. I'd put the sound close to a clothes dryer. But then again...it's 7600 CFM.

This is something you turn on for like 2 or 3 minutes at a time, I'm guessing. Open the right windows, and you'll swap out your entire house in short order.

 

[ckindt]

Beelzebob:

Did you get a quiet cool fan? Those things rock 1500CFM and quiet enough to have in your bedroom!

No...I wouldn't call it quiet. I'd put the sound close to a clothes dryer. But then again...it's 7600 CFM.

This is something you turn on for like 2 or 3 minutes at a time, I'm guessing. Open the right windows, and you'll swap out your entire house in short order.

I installed one a few years ago They're very effective at sucking all the smoke out of the house when the wife burns the dinner too.

 

[beelzerob]

I installed one a few years ago They're very effective at sucking all the smoke out of the house when the wife burns the dinner too.

Hehe...it does raise a question that I've had, though. Once I hook all this stuff up...what do you think about setting this house exhaust fan to come on in case the smoke alarms go off? (Not to get too far off topic....).

On the one hand, it seems like it might do a good job of clearing out the smoke, but I also wonder if it might feed air to a fire.

 

[upstatemike]

I installed one a few years ago They're very effective at sucking all the smoke out of the house when the wife burns the dinner too.

Hehe...it does raise a question that I've had, though. Once I hook all this stuff up...what do you think about setting this house exhaust fan to come on in case the smoke alarms go off? (Not to get too far off topic....).

On the one hand, it seems like it might do a good job of clearing out the smoke, but I also wonder if it might feed air to a fire.

It would absolutely feed the fire. A fire alarm should shut down all fans and air handlers when triggered.

 

[beelzerob]

It would absolutely feed the fire. A fire alarm should shut down all fans and air handlers when triggered.

Ya, that's kinda what I was thinkin' too. Too big a risk to take.

 

[RobWalker]

No...I wouldn't call it quiet. I'd put the sound close to a clothes dryer. But then again...it's 7600 CFM.

I'm not sure I follow how this works ... where does the make up air come from? What if you turn it on when there are no windows open (that's a tricky function to automate!)? Is there a concern about combustion appliances?

I know the HRV I installed warned against exhausting from a room with a combustion appliance, and it doesn't hit anything even remotely like that capacity!

 

[beelzerob]

Ya, we've already figured out NOT to use it when we have a fire in the fireplace.

To answer your question, the air has to come from outside. The fan sucks air from the 2nd floor ceiling and pushes it up into the attic. The attic air then is blown out the ridge venting...so it does double duty of replacing the house and attic air, all in one.

I wired all of our windows, so I could put a rule in to block it from running unless a window is open somewhere. That wouldn't be hard to do.

I'm not concerned that it'd break a window if we turned it on with everything closed...but it wouldn't be a happy fan, and we'd probably get some air flowing through gaps it shouldn't be.

The thing has 2 speeds, the lower speed is 5000 CFM...still more than enough.

 

[BrettS]

I wired all of our windows, so I could put a rule in to block it from running unless a window is open somewhere. That wouldn't be hard to do.

I'm not concerned that it'd break a window if we turned it on with everything closed...but it wouldn't be a happy fan, and we'd probably get some air flowing through gaps it shouldn't be.

That seems like a very good idea. I had a whole house fan in my old house and we left it running one night when we had guests over. They didn't know about it and they shut most of the windows we had left open. We woke up at 2AM when the carbon monoxide detector started going off. It turned out that the fan was pulling air in through the water heater chimney, so the water heater was exhausting into our basement. It's a very good thing that we had that carbon monoxide detector, and it made us very careful to make sure we had windows open when we ran the fan.

Brett

 

[beelzerob]

Good input. I'll probably limit it to 2 windows open minimum before it runs. More than likely, I'll put it on a timer too. This thing really shouldn't have to be run more than 5 minutes to get the job done.

 

[drozwood90]

Ahh, sorry, I mis-understood. I read the thread's posts while eating lunch...

--Dan

I do this in a two floor house, bedrooms upstairs, living downstairs. During the day I run the fan to pull the heat from upstairs to downstairs and at night I let the system heat normally (thus making the upstairs warmer than the downstairs). In theory this should all work just peachy. I have temp sensors throughout the house and I find it difficult to see a measurable effect. I *think* I see a 1°F change in my favor. It seems that I should have gotten a 3°F change...

I'm not done yet but I haven't been impressed thus far...

I also have a house fan that I can use in the summer to suck heat out of the house but I haven't been here in the summer yet!

You would only get the 3 deg or greater change IF you set back the lower thermostats, as they will continue to pump heat into their zone until they reach equilibrium. Basically, what you have done, is made your lower floors heat the upper floors. I would think if you monitored WHEN they went off, the upper floor does not go off as much as it did without the fans.

I had noticed something similar in my 4 zone 4 floor house.

my $0.02

--Dan

Dan:

I do not have multiple zones. I have a single stat in the house.

I'm looking at the delta between upstairs and down stairs not absolutes. The normal system shows that the upstairs is usually about 3F warmer than the downstairs. If I turn on the fan only to mix things up I see that the upstairs is MAYBE two degrees warmer than the down stairs thus a single degree 'gain'. I might say that since the downstairs is 150% the square footage of the upstairs that perhaps I really am getting more than I say... I am not ready to stand by this as I need some more sensors downstairs but my preliminary results indicate that mixing the house up with the furnace fan does not do much to equalize the temperatures. I'll be looking at this in more detail over the next few months.

Beelzebob:

Did you get a quiet cool fan? Those things rock 1500CFM and quiet enough to have in your bedroom!