I have a bright idea I’d appreciate some input on.
Our house has a fully finished basement – they call it a bi-level. We have an issue with the downstairs being uncomfortably cool in the winter. Yes, the airflow could be better, but warm air rises, and the thermostat is upstairs.
My bright idea is that if I had a secondary thermostat downstairs, that only triggered the furnace fan to run when it was too cold down there, it would help equalize the up and down temps. Then, if that made the upstairs cool (as it might), the heat would kick in normally, like it always does. They say we could just set the fan to run 24/7 in winter, but that seems like a waste of electricity. Not to mention it would bug my wife.
An possible alternative might be to configure the furnace to just run the fan longer on the normal heating cycle. I have no idea how one would do that, and it doesn’t seem like it would be as effective, but might be simpler to do, if it’s possible.
The furnace is a Trane XV-95 high efficiency two stage unit, with central air added last year, if that matters. I haven’t actually looked into how things could be done, or if they are even possible; so far, I’m just thinking conceptually.
I don’t think your idea is going to work very well.
Does the basement have any heating air ducts in it or is it relying on the radiant heat from the furnace?
Assuming you’ve got ducts/vents in the basement, the way you regulate the heat between floors is to partially close the vents on the upper floors. This will force more of the warm air into the basement, heating your basement more than it heats the upper floors and equalizing out the temperatures.
If you don’t have ducts/vents in the basement, electric space heaters may be your cheapest and easiest solution.
Yes, the basement does have ducts (this is a totally forced air heating system), albeit not as many or as well placed as we would like. And there’s a big central cold air return duct near the floor, right by the furnace.
We’re aware of that vent balancing approach. But when the furnace fan isn’t running, the vents do nothing, cold air still settles downstairs, and the main thermostat upstairs doesn’t detect that.
I don’t like the electrical heating approach. Our furnace runs on natural gas, which is cheap. The amount of electrical power it would take to heat the downstairs would be prohibitive for a large area, more expensive than running the fan 24/7. Especially when it’s really cold out. And the hot air would still rise upstairs.
Why don’t you just run the fan all the time?
Our system (heat pump) has a setting that switches the fan to a very low, almost silent mode when not actively heating or cooling.
We have a variable-speed air handler, so it’s a feature.
The thermostat just needs to be able to set the fan from Auto to ON. The air handler automatically does the speed control.
An idea used in an older home nearby with similar problem (though mostly with air conditioning) was to add a ventilation duct (actually a large plastic drain pipe) from the upstairs level down to the basement, near the furnace intake. There was a fan installed in this, which would suck air from the upstairs and release it down at the furnace level. (It could also blow air up from the basement to the upstairs level, but this was seldom needed.)
The recirculation of air that this provided helped greatly in keeping all levels of the house comfortable. And using small blower fan was much cheaper than running the furnace heating/AC system.
can you get to the ducting?
Because it sounds like perhaps setting up zones might help.
When basement is too cool, furnace comes on and basement ducts only open, if upstairs needs heat it kicks on and opens upstairs ducting.
If one cools while the other is heating, the ducts just open
A cheap solution may be to move thermostat in basement, at least the winter thermostat, and close down upper floor ducts until you achieve a kind of balance
From my own experience I think the OP’s idea would work fine, though might be overkill. We have two ceiling vents in our basement. I do not heat the basement all the time but when I want to warm it up I open the vents and then turn the fan to ON (we also have a variable-speed system about 3 years old). It circulates the air throughout the house making temperatures more even, including warming the basement. The basement has more heat loss (at certain outside temperatures) so waiting for the the family room, where the thermostat is, to cool enough to turn on the furnace doesn’t do the basement any good.
I just leave the fan On all the time, but it seems like running the fan only when the basement fell below a threshold temperature would work, at least in a house like mine.
We have three ducts with dampers. I have tried endlessly to jockey the dampers around but they are not planned well. The duct that feeds the basement also feeds certain parts of the ground floor. Another duct feeds the upper and ground floors of the east side of the house, the the third duct feeds the other bedrooms on the top floor. It would be easier to manage if each duct fed a single floor.
It would take endless experimentation to management the basement temperature by closing vents around the house, given the way the ductwork is set up. We’ve got 23 vents in our house (I have mapped them all back to the ducts).
Beowulff is correct. Those fans are designed to run 24/7 so leaving your fan on is the best first option. If that doesn’t fully solve the problem, the solution is to address both supply AND return. I suspect it’s not so much of a supply issue as much as return. Keep in mind, air (whether supply or return) will take the path of least resistance. Turn on the fan first. From there, ‘air balance’ is needed.
Another reason your idea of running the fan to circulate the warm upper air with the cool lower air may not work well is the placement of the return air vents. In my and a lot of other houses the intake vents in the basement are in the ceiling and along the main level floor; they are basically 16 inches apart vertically… so you’re pulling the warmest basement air and the coolest main floor air and mixing them together, which doesn’t give you as much heat exchange as you’d hope. It might be preferably to pull warm air from near the ceiling upstairs and cold air from the basement floor, but that’s not the way most HVAC ducting systems are configured.
I’d suggest simply shutting most or all the upper floor vents and forcing most of the warm air down to the basement. The vents aren’t air tight so the upper floor will still warm up, only the furnace will run longer to get it there and with basement vents open and upper closed will be pumping more warm air downstairs before the thermostat switches off.
Shutting down upper level vents may not be practical if there’s only a few in the basement. To get any semblance of balance the vents in the basement would be roaring and the ones upstairs whistling from the pressure. That could even cause the furnace to hit its overtemperature limit control because of insufficient airflow. Also, even on relatively modern furnaces, the blower can be a huge power draw, like 1,000+ watts. That’s as much as a small air conditioner. So running the blower 24/7 can lead to a pretty big hit on the electricity bill. Electronically controlled variable speed blowers are much better in that regard, which this furnace does appear to have. At low speeds (when running fan-only in heating mode) it may be less than 200 watts which isn’t so bad: https://www.bayareaservice.com/wp-content/uploads/2011/12/XV95-Performance-Data.pdf
It seems to me the thing to do is get any basement returns as low to the floor as possible (supplies are probably impractical as they’re running across the ceiling anyway) and perhaps to cut in a few more supply registers. That way, you can close down more of the upper level registers and still have enough openings into the basement that you’re not choking the system. Of course do the opposite in the summer.
The typical blower running 24/7 is typically around 400 Watts. I don’t believe I’ve seen 1000 watt blower load in a long time. A variable speed ECM motor converts AC to DC and uses 70% less energy—-but that would involve a new furnace. About 5% of the people I would guess leave their blower on all the time. If a return grille is cut into the return plenum then that cooler will be distributed through the house; the stat will sense that and create a call for heat. However it will even the temp throughout the house. There is no free lunch: if you bring the cooler air upstairs it will need to be heated. But warmer indoor climate is what he needs.
Some good responses here guys, thanks! The upshot so far seems to be “maybe”.
Yes, there are duct issues – there are too few heat vents downstairs, but there is a very good floor-level return down there. The limitation is that, when the fan stops, hot air still rises and cold air still sinks. And the two areas are open to each other, so that happens freely.
So I think at this point I have two key questions:
Does this furnace even support the addition of a secondary, fan-only thermostat to address situations like this? I’m doubtful at this point: I don’t see it mentioned in the documentation. But I’m asking Trane support. Definitely not planning on modifying the controller.
How much power does the fan really draw if we set the thermostat to continuous fan mode? And does it vary, and is it adjustable? Also asking Trane about that. I might just have to try it and watch the power meter. Personally I like the fan thermostat idea better, because it would only run as needed, but… I suppose one could say it’s always needed, it’s just a question of to what degree. Hmm.
We have an Ecobee4 smart thermostat. I has a couple of features that might appeal to you:
it has wireless occupancy sensors that can read the temperature in rooms other than where the thermostat is located. If that room is occupied (as also determined by the sensor) the room’s temperature is factored in (averaged) with other occupied rooms to manage the furnace operation. (it will let unoccupied rooms run hotter or colder to manage the temperature in the occupied rooms at the requested temperature; it’s not the same as zoned heat.)
it can be configured to run the blower fan a minimum amount of time per hour regardless of whether the thermostat calls for heat.
If you don’t want Alexa integration, the Ecobee 3 can be paired with the remote sensors as well (and AFAIK will also run the blower separately from the furnace heat).
I had the same kind of problem and, when I got a new furnace, I got a deal on modifying the duct system. It has made all the difference in the world this winter. I really think that is the best approach.
Question: How are your windows in the basement? New, high efficiency insulated windows can make a stunning difference in how your residence retains heat if your present windows are old and drafty. Just wondering because that can save a lot of money in heating. They pay for themselves over time.
This is readily answered. Look for the power rating on the fan motor. There should be a metal plate on the motor housing with this information. Or it will be listed in the furnace documentation, if you have that. It could be expressed in Amps, Watts, or Horsepower.
I also fourth leaving the house fan on all the time. I’ve done this in every house I have lived in at least twenty years and have had no failures of any blower fans. The only time I ever turned them off was when I replaced the air filters.
Also, I doubt you need a new thermostat as I have seen very old ones with an Auto/On switch, as others have stated, move that to On and the blower will go all the time balancing out the house. I also do this as I live in the DC area and it gets humid from late winter to late fall and having the fan on has prevented undue humidity in the basement.
I would try the fan in the On position option first as it’s the easiest, cheapest, and you can see if in less than a day if this does the trick.
IMO, look for cold spots or drafty areas, as this will most certainly affect how evenly heated or cooled your house will be. And, solve that problem. Next thing would be to have an HVAC tech come out and test the system in cool/heat modes and adjust the dampers for summer/winter settings. After those two are done, you can move to more esoteric things like running plenum everywhere. :rolleyes:
I’m a 25 year HVAC contractor and tech. Several suggestions make sense but there is an easier way.
Whether supply or return air will take the path of least resistance. If you install a return grille in the return plenum near the air handler it will take more area from THAT AREA, than the upstairs returns because there is infinitely less resistance at that location than pulling return through the duct. As an example, if the door was off and you engaged the fan it would pull all the air that blower was rated at and needed from that specific location. (As an example; there are other reasons not to do that long term)
ANY stat that has a “fan on/ off” switch will do THE EXACT THING you’re proposing. A tech could wire new fan only stat in parellel but he’d be scratching his as to why.
A variable speed fan (called an ECM motor) comes with a set of controls indigenous to the furnace; so that means a new furnace. You simply don’t add an ECM blower to a PSC furnace.
I really think it’s becoming more complicated than it needs to be. Those blowers are DESIGNED to run 24/7. (I just came a factory trip and a lab tech told me “this blower has been running nonstop for 8 1/2 years.”
I think the solution is as easy as cutting in an appropriately sized return in the return plenum and turning your stat to continuous fan. Calling support lines and ecobee stats etc etc etc I really don’t think is necessary. And I do this for a living.