Is 2 ton for 2000 sqft 1.5 story too small?

[bearrock]

I'm buying a house and the hvac system is really old (the handler is 20+ years and the heat pump is about 16 years old). I'm in the process of getting multiple estimates, but the first contractor gave me a recommendation of 2 ton heat pump. He did take measurements around the house, but I'm not sure if he did a manual J. The current system is a 2 ton, but based on some of the information I've found, 2 ton seems undersized for the house in our area (I'm in Northern Virginia).

So, can 2 ton be appropriate for a 2000 sqft in some circumstances or is it possible that the contractor underestimating the air conditioning/heating needs based on the current size of the system? Any help is greatly appreciated. Thank you.

[BaldLoonie]

Only the Manual J will tell. Odds are if it has been there all these years, it does the job. If someone suggests going bigger, they better be planning on adding to the duct system too!

[Airmechanical]

So, can 2 ton be appropriate for a 2000 sqft in some circumstances or is it possible that the contractor underestimating the air conditioning/heating needs based on the current size of the system? Any help is greatly appreciated. Thank you.

the person who has a 2 ton system in a 2000 square foot house could mean a few different things;

1. possible undersized by 2 tons
2. the owners design temps were very conservative
3. the house is super sealed and sized properly

if it's #3 make sure the house has fresh air injection or you may be getting sick often



.

[bearrock]

Only the Manual J will tell. Odds are if it has been there all these years, it does the job. If someone suggests going bigger, they better be planning on adding to the duct system too!

I asked the contractor whether the duct system would need upgrading and he said that because ducts in the walls are pretty much a part of the house, it really couldn't be changed (although he did say the exposed duct around the air handler would be changed). Seemed kind of contrary to other things I've read (people do seem to mention upgrading the duct (or people mean just the duct around the handler?).

[bearrock]

the person who has a 2 ton system in a 2000 square foot house could mean a few different things;

1. possible undersized by 2 tons
2. the owners design temps were very conservative
3. the house is super sealed and sized properly

if it's #3 make sure the house has fresh air injection or you may be getting sick often



.

As the house is about 30 years old, I doubt the house is super sealed. How would I go about getting fresh air injection into house? Is it as simple as opening the window every once in a while or is there a device I need to get?

[SBKold]

No need to worry about this unless you have spent lots of $ on Windows, spray foam, etc.

Where are you in the country? What is your climate like?

[BaldLoonie]

Our experience says most duct systems are marginal or undersized for what you have. You go 33% bigger on existing without adding 33% capacity (and I know, it is murder once the house is done) and you won't get the comfort, efficiency or reliability you expect. Seems funny the house has had 2 ton all these years and suddenly needs much larger.

BUT, since no mention of a load calc has been done.....

[bearrock]

No need to worry about this unless you have spent lots of $ on Windows, spray foam, etc.

Where are you in the country? What is your climate like?

I'm in Northern Virginia. It can get pretty hot in the summer (90's to 100's, but humidity is the bigger concern) and cold in the winter can get as low as teens and single digits. Below 0 is pretty rare if I remember correctly. (When the weather gets really cold, I think we need to crank out the space heater because we are relying on just the heat pump).

[bearrock]

Our experience says most duct systems are marginal or undersized for what you have. You go 33% bigger on existing without adding 33% capacity (and I know, it is murder once the house is done) and you won't get the comfort, efficiency or reliability you expect. Seems funny the house has had 2 ton all these years and suddenly needs much larger.

BUT, since no mention of a load calc has been done.....

To be fair, the first contractor is recommending staying with the current 2 ton set up. I just thought the size might be too small because I don't think the contractor did a heat load calc. (I have another contractor coming on Monday who will do a manual J).

I suppose the house may be fine with a 2 ton if that was the set up all these years. I just thought 2.5 to 3 ton may be more typical for a 2000 sqft house. Is there a huge price difference between a 2 ton and 2.5 to 3 ton system? I heard that contractors tend to oversize systems rather than undersize them.

Also, the first contractor is NATE and ACCA certified and has been in the business a long time, so he does seem to know what he is doing. Kind of surprised that he didn't seem to do a manual J (although he did take measurements of the outside dimensions)

[BaldLoonie]

Only reason to take outside dimensions is for a load calc. Quick measurement of windows and sit down to the spreadsheet or computer. On a simple house I could do one in a short time on my laptop.

Size of house has only partial bearing on size needed. Construction, windows, direction they face, how much shade... We have a house bigger than that cooling on 2 ton. Faces south with minimal east-west glass and so many trees the sun couldn't begin to heat it. Take the same house, face it west with no trees and it would take 3 ton.

[bearrock]

Only reason to take outside dimensions is for a load calc. Quick measurement of windows and sit down to the spreadsheet or computer. On a simple house I could do one in a short time on my laptop.

Size of house has only partial bearing on size needed. Construction, windows, direction they face, how much shade... We have a house bigger than that cooling on 2 ton. Faces south with minimal east-west glass and so many trees the sun couldn't begin to heat it. Take the same house, face it west with no trees and it would take 3 ton.

Then I guess he might have done a heat load. We have west facing with windows on east, west, and north, but because there are so many huge trees around the houses in the neighborhood, I doubt the house would get very hot during the summer. Do you only take cooling into accounting for the heat pump size? If the house is shaded during the summer wouldn't the house also be colder during the winter, perhaps needing a bigger unit to heat? Thanks to everyone for the wealth of information by the way.

[Beaver Bob]

I may have missed it but do you know the R rating of the insulation
What type of windows and doors do you have as well, all this is taken into consideration during the sizing of the unit, if it has been there that long and a contractor installed it unless they were shoddy you should most likely be fine.

Going to a bigger unit just for the sake of doing it would be quite costly and is probably best to avoid if you can.

[BaldLoonie]

The proper way to size a heat pump is to the cooling needs. In a cold climate, can't get it big enough to handle the coldest day alone. Some say oversize the heat pump to save on heating costs. But if you graph it, going 1/2 to 1 ton bigger does little to raise the balance point which is the outdoor temp at which the heat pump alone can't do it.

Backup heat should be sized to the heating needs. If you can't heat the house in cold weather, you may have elements out or insufficient amount of backup installed. Or duct issues causing the elements to cycle on overheat protection.

http://www.proctoreng.com/articles/bigger.html