2 story home + basement furnace/AC questions

[Linflas]

Our current AC compressor needs to be replaced and the whole system is 24 years old so we are going to replace the furnace as well. My next door neighbor is a heating/AC guy and lives in the identical house to ours and I was discussing with him the options since he deals with the same issue we do, the upstairs is hard to keep cool in summers and I cannot let it raise the temperature when we are at work as the system runs nonstop through most of the night to get it back to our preferred temperature. What he did was split his system so he added a furnace/AC for the upstairs in the attic and the existing (which was replaced right before he bought the house) for the main and basement.

The systems that came with the houses are semi zoned in that we have separate duct work supplying the main floor and basement and another supplying the top level with manual dampers to allow a bit of zoning. he is of the opinion that electric zoning would not work well which is why he went with the additional system. Anyone here have a house with this type of system? I see a lot of new construction in our area that I assume is like this as they have 2 compressors outside the house and I am willing to make the switch if is is effective. Also I am curious if this can all be controlled with 1 smart thermostat or are 2 separate ones needed?

 

[bbhaag]

Last fall my wife and I purchased a 2 story home with dual HVAC systems. One in the basement for the main floor and basement and a second system upstairs for the second story. I can't comment on the AC side because we moved in late fall and AC was not needed just heat. We love the fact that we can keep the upstairs at a separate temperature than the main floor and it does seem to do a better job at keeping the upstairs at a steady temperature compared to our last home which was a 1.5 story with a single HVAC system.
In our old house the upstairs was always cold in the winter and hot in the summer in the new house with the duel systems the upstairs is always nice and warm and hopefully cool this summer once I flip over to AC.

Each system has its own smart thermostat that I installed. A Nest on the main floor and a Honeywell for the second floor. I like it this way because it gives me a little more control but I suppose if you wanted just one thermostat for both systems it would be doable. You might run into the same issues you are already having though if just one thermostat is controlling both systems. If the main level of your house stays warmer/cooler then the thermo will kick off the system for the upstairs before it is comfortable. With a second thermo located upstairs that won't be an issue.

 

[Linflas]

Are the furnaces side by side in the basement/utility room? I don't like the idea of the furnace in the attic, since the existing duct work actually could be supplied by 2 different units from the same location I am going to ask him if there is a compelling reason not to do it that way.

 

[herm0016]

do it. you should have 2 thermostats, one each in the area the unit is supplying. the problem with the current system may be that there is too much pressure drop / the duct from the basement is not large enough to supply the 2nd floor.

 

[snoopy7548]

How's your insulation in the attic? You might find that properly insulating solves most of the problem. I have a single-zone system in the basement and the upstairs is only maybe 1-2F warmer than the downstairs during the summer, and 1-2F colder in the winter.

 

[bbhaag]

Are the furnaces side by side in the basement/utility room? I don't like the idea of the furnace in the attic, since the existing duct work actually could be supplied by 2 different units from the same location I am going to ask him if there is a compelling reason not to do it that way.

No it's in it's own furnace room located on the second floor off the family room and the main floor system is located in the basement.

 

[highland145]

Just dropped the price of new Corolla on ours. The old system/duct/design was effed/pieced together. I was told a damper system won't work right unless the 2 floors are about the same size. Our 1st is 1400 and the 2nd is 500. We had 2 thermostats trying to cover the a/c upstairs in the winter and the heat down in the winter....Short answer= cluster.

2 new Carrier units, all new duct under the house and in the attic. Gas pack for the 1st floor, all electric upstairs. That unit is in the attic. They spent 14 days. They weren't real fast but the crawl space is tight. Can't roll over unless you're between the joist. Nice professional job.

They pushed the Mitsubishis for the upstairs but we don't have the wall space for the units.

 

[Linflas]

How's your insulation in the attic? You might find that properly insulating solves most of the problem. I have a single-zone system in the basement and the upstairs is only maybe 1-2F warmer than the downstairs during the summer, and 1-2F colder in the winter.

The insulation up there is at least 2-3 feet deep but it gets hotter than Hades up there in the summer. I would be vary wary of installing equipment up there.

Just dropped the price of new Corolla on ours. The old system/duct/design was effed/pieced together. I was told a damper system won't work right unless the 2 floors are about the same size. Our 1st is 1400 and the 2nd is 500. We had 2 thermostats trying to cover the a/c upstairs in the winter and the heat down in the winter....Short answer= cluster.

2 new Carrier units, all new duct under the house and in the attic. Gas pack for the 1st floor, all electric upstairs. That unit is in the attic. They spent 14 days. They weren't real fast but the crawl space is tight. Can't roll over unless you're between the joist. Nice professional job.

They pushed the Mitsubishis for the upstairs but we don't have the wall space for the units.

I plan on going with Carrier too, the current system is Trane and the furnace was pretty problem free until the fan motor went out a couple summers ago. The replacement fan is louder than the original. The AC compressor developed a coil leak when it was 5 years old and we had it replaced with an identical one which has lasted 19 years now.

 

[herm0016]

hows the attic venting? more venting or a power vent on a thermostat could solve your problem

 

[highland145]

The AC compressor developed a coil leak

The 8 y.o. one I just replaced had a leak from the factory. Long story but the guy was out probably 5 times filling it. Found out why when they disassembled it to move it. It was a Friday afternoon unit. The factory nicked a line with a housing screw.

 

[bbhaag]

The insulation up there is at least 2-3 feet deep but it gets hotter than Hades up there in the summer. I would be vary wary of installing equipment up there.



I plan on going with Carrier too, the current system is Trane and the furnace was pretty problem free until the fan motor went out a couple summers ago. The replacement fan is louder than the original. The AC compressor developed a coil leak when it was 5 years old and we had it replaced with an identical one which has lasted 19 years now.

2-3 feet??? Are you sure that it is that deep because you might need to check the ventilation in your attic is adequate for that much insulation.

 

[Linflas]

2-3 feet??? Are you sure that it is that deep because you might need to check the ventilation in your attic is adequate for that much insulation.

I probably over estimated, it is likely 12"-15" which would be the norm for Northern Virginia. The venting is a single ridge vent running the length of the roof.

 

[herm0016]

no venting on the eves?

 

[Mr.IncrediblyBored]

no venting on the eves?

And to piggyback of this question, make sure the eves aren't blocked with insulation.

 

[Linflas]

Update: Ended up just having the original system replaced with Carrier Infinity series 96% efficiency furnace and a Carrier Infinity 4 ton 17 SEER AC. They did a much more professional looking install than the original builder installed system including a replacement AprilAire 700 whole house humidifier which replaced the one that came with the house and never really did much when it was working. Next up is getting the basement finished.

 

[herm0016]

did you address the venting? proper venting will:

1. make your singles last longer
2. prevent ice dams the winter
3. reduce energy cost
4. make the house temperature more even

i'm sure i am missing some benefits.

 

[Linflas]

There is a ridge vent and venting in the soffits. The insulation is not blocking the soffit venting.

 

[bbhaag]

Update: Ended up just having the original system replaced with Carrier Infinity series 96% efficiency furnace and a Carrier Infinity 4 ton 17 SEER AC. They did a much more professional looking install than the original builder installed system including a replacement AprilAire 700 whole house humidifier which replaced the one that came with the house and never really did much when it was working. Next up is getting the basement finished.

Nice upgrade. Those Carrier Infinities are hefty units. Does it cool the upstairs any better than the last unit or is still to early to tell? Not sure about Northern Virginia but around here it is still to cold to turn the AC on and have it function properly(central Illinois).

Just a heads up but keep an eye on that humidifier. We have one that the previous owner install but we had to turn it off. It was causing condensation to form on the inside of the windows and when the condensation dripped down on the bottom of the window frames it was creating a mold/rot issue. Not sure when your home was built but it could be an issue with newer construction homes especially those built with 2x6's like ours.

 

[cardiac]

Our home was built in 1874. 2 story 2,300 sq. ft farmhouse. Seperate furnaces/AC for downstairs and upstairs. This was origianlly done because of no chases to run ductwork due to the age of the house. We absolutely love it. I have 2 Honeywell programmable thermostats and our utility bills are quite manageable. Coupled with a whole house fan, and a well-ventilated attic, it is very comfortable. I think you will be happy....

 

[Linflas]

Nice upgrade. Those Carrier Infinities are hefty units. Does it cool the upstairs any better than the last unit or is still to early to tell? Not sure about Northern Virginia but around here it is still to cold to turn the AC on and have it function properly(central Illinois).

Just a heads up but keep an eye on that humidifier. We have one that the previous owner install but we had to turn it off. It was causing condensation to form on the inside of the windows and when the condensation dripped down on the bottom of the window frames it was creating a mold/rot issue. Not sure when your home was built but it could be an issue with newer construction homes especially those built with 2x6's like ours.

Sounds like the humidifier wasn't being controlled by a humidistat. The one we have is actually integrated into the thermostat control and you set the level of humidity you want it to maintain. So far the system seems to be doing a great job of keeping the house at our desired temperature but it hasn't really gotten hot enough to stress test it in any way so far although I expect it should do well since the older system worked ok for the most part until it began to age. I still have the option to zone it if I want greater control over the balance in different rooms as the duct work for the top level is accessible through the attic and the main level is accessible from the basement but I think I can probably achieve what I need to with the current manual baffles.

 

[Red Squirrel]

It would be better, but obviously much more expensive. What I would maybe do is setup a minisplit upstairs. Or if it's just the bedrooms that really matter, maybe through the wall units in each one. But if you are ready to spend the cash then two full units is the way to go especially if the ductwork is already all there.