Big problems (temperature differences) with new furnace-- what to do?
February 14, 2016 6:26 PM Subscribe
We just got a new furnace installed a few days ago, and we're not happy with it, especially the major temperature variations between rooms. (Maybe because of being oversized?) What can we do? What is reasonable to ask the installers to do?
Our furnace died last week, and with a 3 month old in the house and temperatures falling, it was pretty urgent to get it replaced quickly. We got 3 fairly well-reviewed companies out who could provide estimates and install within a couple days, and I tried to quickly educate myself about furnaces, but with the time crunch and the baby, I only was able to figure out a limited amount, and had to make some quick decisions. (We're new homeowners and I knew almost nothing about furnaces before last week.)
So the furnace (a Lennox ML195) went in Thursday, and on the first floor alone, we have some rooms measuring at 65-67 and some rooms at 72-74 with the thermostat set at 69. (Some spots in the rooms can go as low as 63 or as high as 78 at times; we've had to rearrange furniture to avoid the cold/hot spots.) The old furnace also had inconsistencies, but this seems worse. It's kind of a big deal because keeping the baby's room the right temperature for her (which is obviously non-negotiable) makes my room so warm it keeps waking me up at night. I've had to resort to closing the vents to my room, which then gets very cold but blankets and layers help adjust for that. It seems like things shouldn't be this hard with a brand new furnace, though. (Also worried about the implications for our pipes, which are weirdly placed and froze last winter; I don't know if we can get the air around them warm enough without other places in the house feeling way too warm.)
Also, according to some Internet searching, this could maybe be because of the furnace being oversized? (It seems to be turning on and off a lot too.) The company says they just went with the same size as our old furnace, and that it would have been too hard to do a load calculation (which I thought they'd done when they came out for the estimate) because they'd have to know stuff about insulation and windows and soil and such, and that 20,000 BTU doesn't make much difference. (The new furnace is 90,000 BTU in a 1400 square foot house, by the way; the other companies and the Internet calculators suggest we need 70,000. We live in DC, in a 1951 1.5 story Cape Cod without a basement.) Is that true? I've also read that an oversized furnace that does a lot of short cycling will wear out a lot quicker.
The company also says this is to be expected because we didn't choose the two-stage furnace. For the record, they didn't really explain anything about the differences between the options they proposed; I tried to quickly research the differences between single and two-stage furnaces myself, and when I asked them about doing a two-stage lower efficiency furnace (to match a cheaper proposal from another company; their proposal was all 93%-96% efficiency, with the two-stage furnaces a bunch more expensive than single-stage), they said that higher efficiency was more important than a two-stage furnace, so we ended up going with a high-efficiency single-stage.
What can we do? How normal are temperature variations like this? How much of this is my responsibility for not researching well enough and deciding against the two-stage furnace in order to save money? Is there an expectation that even their lower cost recommendations should work better than this is? They've offered to adjust the fan speed to help deal with this, and it seems like there's no harm in trying that, but if it doesn't help much, what next? Part of me wants to demand that they switch it out for a properly-sized/better furnace (is that totally unreasonable to ask, though?), and part of me thinks this is all my own dumb fault for not researching things enough and we should just suck it up for the next 20(!) years of furnace life. Please give me a reality check and some advice about next steps!
Our furnace died last week, and with a 3 month old in the house and temperatures falling, it was pretty urgent to get it replaced quickly. We got 3 fairly well-reviewed companies out who could provide estimates and install within a couple days, and I tried to quickly educate myself about furnaces, but with the time crunch and the baby, I only was able to figure out a limited amount, and had to make some quick decisions. (We're new homeowners and I knew almost nothing about furnaces before last week.)
So the furnace (a Lennox ML195) went in Thursday, and on the first floor alone, we have some rooms measuring at 65-67 and some rooms at 72-74 with the thermostat set at 69. (Some spots in the rooms can go as low as 63 or as high as 78 at times; we've had to rearrange furniture to avoid the cold/hot spots.) The old furnace also had inconsistencies, but this seems worse. It's kind of a big deal because keeping the baby's room the right temperature for her (which is obviously non-negotiable) makes my room so warm it keeps waking me up at night. I've had to resort to closing the vents to my room, which then gets very cold but blankets and layers help adjust for that. It seems like things shouldn't be this hard with a brand new furnace, though. (Also worried about the implications for our pipes, which are weirdly placed and froze last winter; I don't know if we can get the air around them warm enough without other places in the house feeling way too warm.)
Also, according to some Internet searching, this could maybe be because of the furnace being oversized? (It seems to be turning on and off a lot too.) The company says they just went with the same size as our old furnace, and that it would have been too hard to do a load calculation (which I thought they'd done when they came out for the estimate) because they'd have to know stuff about insulation and windows and soil and such, and that 20,000 BTU doesn't make much difference. (The new furnace is 90,000 BTU in a 1400 square foot house, by the way; the other companies and the Internet calculators suggest we need 70,000. We live in DC, in a 1951 1.5 story Cape Cod without a basement.) Is that true? I've also read that an oversized furnace that does a lot of short cycling will wear out a lot quicker.
The company also says this is to be expected because we didn't choose the two-stage furnace. For the record, they didn't really explain anything about the differences between the options they proposed; I tried to quickly research the differences between single and two-stage furnaces myself, and when I asked them about doing a two-stage lower efficiency furnace (to match a cheaper proposal from another company; their proposal was all 93%-96% efficiency, with the two-stage furnaces a bunch more expensive than single-stage), they said that higher efficiency was more important than a two-stage furnace, so we ended up going with a high-efficiency single-stage.
What can we do? How normal are temperature variations like this? How much of this is my responsibility for not researching well enough and deciding against the two-stage furnace in order to save money? Is there an expectation that even their lower cost recommendations should work better than this is? They've offered to adjust the fan speed to help deal with this, and it seems like there's no harm in trying that, but if it doesn't help much, what next? Part of me wants to demand that they switch it out for a properly-sized/better furnace (is that totally unreasonable to ask, though?), and part of me thinks this is all my own dumb fault for not researching things enough and we should just suck it up for the next 20(!) years of furnace life. Please give me a reality check and some advice about next steps!
You said "vents", so I am assuming forced air. Your newly efficient furnace may be highlighting design failures of your original ductwork. You should ask about having your system balanced, which generally involves adjusting duct dampers so that each room receives the proper CFM of air for its size and distance from the furnace.
posted by misterbrandt at 7:12 PM on February 14, 2016 [11 favorites]
posted by misterbrandt at 7:12 PM on February 14, 2016 [11 favorites]
Yes, balancing the system is a normal re-adjustment with a new furnace. There are baffles and dampers that all need to be adjusted to minimize the hot and cold rooms. It's not at all an unusual request to have it done after a new installation.
posted by raisingsand at 7:18 PM on February 14, 2016 [1 favorite]
posted by raisingsand at 7:18 PM on February 14, 2016 [1 favorite]
There should be several dampers (look like large handles) on the duct work near the furnace. They may or may not be labeled. Try messing around with them to adjust the airflow into the rooms, or have the HVAC company do it. Put somebody in the too hot room on a cell phone and adjust one at a time until you find the one the reduces air flow into that room. Then label the handles with a Sharpie so you know which one controls which rooms, as you may need to readjust when it gets warm.
posted by COD at 7:27 PM on February 14, 2016 [1 favorite]
posted by COD at 7:27 PM on February 14, 2016 [1 favorite]
Response by poster: Yes, forced air (although it will give you an idea of my level of knowledge that I had no idea the answer to your question until I researched it a bit just now.)
What amount of variation between rooms is normal? Does this situation seem like a problem with the furnace choice itself or not? Are we within our rights to keep pushing the company to make changes at no charge until it reaches a certain degree of consistency, or do we need to pay them to do this balancing and whatever else?
posted by EmilyClimbs at 7:36 PM on February 14, 2016
What amount of variation between rooms is normal? Does this situation seem like a problem with the furnace choice itself or not? Are we within our rights to keep pushing the company to make changes at no charge until it reaches a certain degree of consistency, or do we need to pay them to do this balancing and whatever else?
posted by EmilyClimbs at 7:36 PM on February 14, 2016
I think a few degrees is pretty normal. 8 degrees, not so much. Our family room faces west with a large windows, in the summer it is noticeably warmer in that room with the setting sun beating down on the west side of the house. The thermostat is in the dining room, so it doesn't know its heating up in the family room. In a budget set up where you don't multi zone the house it's just a trade off you deal with. Yours sounds extreme though, they ought to be able to get it within 3 or 4 degrees at worst.
posted by COD at 7:42 PM on February 14, 2016
posted by COD at 7:42 PM on February 14, 2016
Yes, you should have your dampers adjusted and that may well solve the problem. Fan speed may also help. However, if you had an older furnace and replace with the same BTU rating in a efficient model, you are actually increasing your heating capacity significantly.
The BTU rating is the input capacity of the furnace (the amount of gas flowing in). So if you replace an older 90,000 BTU furnace it may actually put out about 63,000 BTU of heat, while your new 90,000 BTU furnace puts out 85,500 BTU. In reality an efficient 70,000 BTU furnace puts out about the same amount of heat as an older 90,000 BTU furnace. Good luck convincing the furnace company to do anything about this though.
posted by ssg at 7:50 PM on February 14, 2016 [4 favorites]
The BTU rating is the input capacity of the furnace (the amount of gas flowing in). So if you replace an older 90,000 BTU furnace it may actually put out about 63,000 BTU of heat, while your new 90,000 BTU furnace puts out 85,500 BTU. In reality an efficient 70,000 BTU furnace puts out about the same amount of heat as an older 90,000 BTU furnace. Good luck convincing the furnace company to do anything about this though.
posted by ssg at 7:50 PM on February 14, 2016 [4 favorites]
I've never seen adjustable dampers on a hot-air furnace, and I've examined a few dozen different systems. But I got a 10-minute workaround for you. For every bit of air that comes out a vent, the same(ish) amount of air needs to enter the furnace, so each room should have a hot-air and return vent (if it doesn't, opening a door will make the room warmer). Anyway, tape a piece of paper over some or all of the return vent in the rooms that are too warm. It isn't pretty but it should start working right away.
Also, you can insulate the cold rooms better to warm them up; use those plastic window cover kits over the window in the baby's room and make sure they aren't any other air leaks to outside.
posted by flimflam at 8:06 PM on February 14, 2016 [2 favorites]
Also, you can insulate the cold rooms better to warm them up; use those plastic window cover kits over the window in the baby's room and make sure they aren't any other air leaks to outside.
posted by flimflam at 8:06 PM on February 14, 2016 [2 favorites]
Given that you did not drop down in size and that the air your furnace produces is warm, this is likely due to issues with your air ducts, not the furnace itself. Because you changed the amount of power for your furnace, your ducts will need to be adjusted as well.
Additionally, you probably have some crappy insulation issues contributing to this. Before your next heating/cooling upgrade, I strongly recommend you invest in insulation first. It will allow you to get the most value out of your HVAC system, since your home's walls and attic will do a better job of keeping your treated air in.
posted by samthemander at 8:28 PM on February 14, 2016 [2 favorites]
Additionally, you probably have some crappy insulation issues contributing to this. Before your next heating/cooling upgrade, I strongly recommend you invest in insulation first. It will allow you to get the most value out of your HVAC system, since your home's walls and attic will do a better job of keeping your treated air in.
posted by samthemander at 8:28 PM on February 14, 2016 [2 favorites]
Hot air systems are notoriuos for uneven heat, even in modern office buildings.
If you can, set the system so the circulating fans run part of the time that the furnace is not running to help mix the air.
posted by SemiSalt at 4:59 AM on February 15, 2016 [1 favorite]
If you can, set the system so the circulating fans run part of the time that the furnace is not running to help mix the air.
posted by SemiSalt at 4:59 AM on February 15, 2016 [1 favorite]
Have a look at your overall air system. Here is a semi-coherent very basic primer. Yes, you can improve this situation.
As an extreme example, I investigated my mother's ducts when she was like "these rooms are cold" and found that there were DIRTY ROTTEN MOLDY TOWELS STUFFED INSIDE THEM from a previous owner to block the air output. Ugh it was so gross. (To be fair, I have had to block HVAC output vents in some rooms in other houses because they were at the end of the system and would just dump out their air, not servicing rooms en route.)
But get to know the returns and outputs in your system. It might take a little finagling but you can definitely make things better.
posted by RJ Reynolds at 6:37 AM on February 15, 2016 [1 favorite]
As an extreme example, I investigated my mother's ducts when she was like "these rooms are cold" and found that there were DIRTY ROTTEN MOLDY TOWELS STUFFED INSIDE THEM from a previous owner to block the air output. Ugh it was so gross. (To be fair, I have had to block HVAC output vents in some rooms in other houses because they were at the end of the system and would just dump out their air, not servicing rooms en route.)
But get to know the returns and outputs in your system. It might take a little finagling but you can definitely make things better.
posted by RJ Reynolds at 6:37 AM on February 15, 2016 [1 favorite]
This thread is closed to new comments.
posted by SemiSalt at 6:28 PM on February 14, 2016