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Message
How to size HVAC for home addition. Is my current model big enough?
Posted on 4/30/21 at 11:18 am
Posted on 4/30/21 at 11:18 am
Looking for some help from any resident HVAC experts. We are working on closing in our garage to add heated sqft. I pulled model number on our unit and its a 14 SEER/48,000 BTU (4 ton) Goodman Heat Pump. That unit is cooling our downstairs area which is ~2,500sqft. With the addition it will be cooling closer to ~3,100sqft. Avg. ceiling height is probably 9ft.
Can anyone tell me if the unit be able to handle the additional space? I tried to do a Manual J calculation but it got way too complicated for me. Would adding a portable AC in the added room help at all with reducing the load or is that just drops in the bucket? We already have a mini-split cooling the bonus room upstairs. Would it just be easier to add another one to the bonus room?
Any help would be much appreciated
.
Can anyone tell me if the unit be able to handle the additional space? I tried to do a Manual J calculation but it got way too complicated for me. Would adding a portable AC in the added room help at all with reducing the load or is that just drops in the bucket? We already have a mini-split cooling the bonus room upstairs. Would it just be easier to add another one to the bonus room?
Any help would be much appreciated
.
8
Posted on 4/30/21 at 1:16 pm to Drunken Crawfish
You need an in home visit from an A/C professional to tell you that, but 4 tons seems pretty small for that size space.
Posted on 4/30/21 at 1:19 pm to Drunken Crawfish
4 tons sounds small for 2,500 sq ft.
How does it cool now?
4 tons probably will not cool 3,100 sq ft.
How does it cool now?
4 tons probably will not cool 3,100 sq ft.
Posted on 4/30/21 at 1:23 pm to Drunken Crawfish
(2500ft²*9ft)/1600cfm = 14.0625 minutes
60/14.0625 = 4.267 cycles per hour
(3100ft²*9ft)/1600cfm = 17.4375 minutes
60/17.4375 = 3.441 cycles per hour
4 is typically considered minimum.
60/14.0625 = 4.267 cycles per hour
(3100ft²*9ft)/1600cfm = 17.4375 minutes
60/17.4375 = 3.441 cycles per hour
4 is typically considered minimum.
Posted on 4/30/21 at 1:27 pm to Drunken Crawfish
I had a 2600 sf area once and it had a 5 ton
Posted on 4/30/21 at 1:29 pm to Drunken Crawfish
I have 2550sf and variable speed 5 ton.
Posted on 4/30/21 at 1:46 pm to footballdude
quote:
4 tons sounds small for 2,500 sq ft.
How does it cool now?
4 tons probably will not cool 3,100 sq ft.
It works great now. I guess back up option may be to just get a second mini-split for the new room.
Posted on 4/30/21 at 2:10 pm to Drunken Crawfish
Is this a basement garage, or is it on the main level and exposed more to outside walls? We have a 4 ton new unit we had installed last fall, similar size house but with 8 foot ceilings. There are a couple of vents in the ductwork in the basement/garage, but it typically stays much cooler than the house in the summer and warmer in the winter due to more than half of it being underground. You might be fine with some fans and adding a vent or two if yours is similar. The only time ours really gets hot down there is if we have the garage doors open in the summer time.
Posted on 4/30/21 at 2:24 pm to TU Rob
No, its on the main house. Currently 2 of the 3 walls are insulated and we will be adding a 3rd insulated wall. The 4th one faces west and is uninsulated so that's what I am worried about.
Posted on 4/30/21 at 3:28 pm to Drunken Crawfish
Glad you tried to do the Manual J - did you use the free loadcalc.net site to do that? I know it can be a little confusing initially but I’m sure you can follow through with it. But with that said,
1. Ideally your 4 ton should have been sized properly for the 2500 sq ft and should not have extra capacity for additional 600 sq ft. Does your HVAC short cycle frequently during the warmest days of summer? If not, you likely don’t have extra capacity.
For comparison if this helps, my house, slab on grade, single story, 1993 construction, R-13 walls, R-30 attic, NE-SW orientation, porches front and rear, and a fair amount of windows on the southern exposure, 9.5 ft avg height, is right at 2,500 sq ft conditioned area, with a 4 ton HVAC. On-line manual J says 3.5 ton should be sufficient for my house, and I believe it, but it never short cycles during the hottest days of summer at design temperatures. I know a 600 sq ft addition to my house could not be cooled by the “extra 1/2 ton capacity” of my 4 ton unit.
2. Though you need the advice of a professional, I think in the long run you’ll likely be served best with an appropriately sized mini split cooling for that new addition - assuming a manual J demonstrates that the 4-ton unit is properly sized for the current 2500 sq ft.
1. Ideally your 4 ton should have been sized properly for the 2500 sq ft and should not have extra capacity for additional 600 sq ft. Does your HVAC short cycle frequently during the warmest days of summer? If not, you likely don’t have extra capacity.
For comparison if this helps, my house, slab on grade, single story, 1993 construction, R-13 walls, R-30 attic, NE-SW orientation, porches front and rear, and a fair amount of windows on the southern exposure, 9.5 ft avg height, is right at 2,500 sq ft conditioned area, with a 4 ton HVAC. On-line manual J says 3.5 ton should be sufficient for my house, and I believe it, but it never short cycles during the hottest days of summer at design temperatures. I know a 600 sq ft addition to my house could not be cooled by the “extra 1/2 ton capacity” of my 4 ton unit.
2. Though you need the advice of a professional, I think in the long run you’ll likely be served best with an appropriately sized mini split cooling for that new addition - assuming a manual J demonstrates that the 4-ton unit is properly sized for the current 2500 sq ft.
This post was edited on 5/1/21 at 6:48 am
Posted on 4/30/21 at 5:08 pm to CrawDude
quote:
Glad you tried to do the Manual J - did you use the free loadcalc.net site to do that? I know it can be a little confusing initially but I’m sure you can follow through with it
Yes, and my brain almost exploded. I am not sure the R-factors of a lot of my building materials. When I ran the simple Manual J (sqft/ceiling height/windows/doors/occupants) total load came out to ~45,000btu.
quote:
Does your HVAC short cycle frequently during the warmest days of summer? If not, you likely don’t have extra capacity.
It does not. Unit has performed well.
quote:
I think in the long run you’ll likely be served best with a an appropriately sized mini split cooling that new addition
This is what I am thinking. I may also look at getting a portable unit to supplement it as well and to use for hurricanes/power outages.
Thanks CrawDude. You are a champion on the H&G board!
Posted on 5/1/21 at 6:43 am to Drunken Crawfish
You have a Goodman lol
Posted on 5/1/21 at 7:56 am to LEASTBAY
How do you like the variable speed??
Posted on 5/1/21 at 7:09 pm to Drunken Crawfish
Generally it’s one ton per 500 sq ft. But a lot factors play into this
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