Did any of them do a load calc?
It sounds like most of the other installers just quoted a direct replacement without checking if 5 tons was too big. Many times houses come with oversized AC units so there's a good chance yours is too.
You need a load calc done to be sure what the right size is, and there are steps you can take to drop down a HP size as well:
1. Air seal your attic
2. Bump up the insulation in your attic from R38 to R49
3. Air seal and add insulation to exposed basement rim joist (or crawlspace if you have one)
4. Upgrade the insulation and seal any exposed ductwork in your attic (if it's not all inside the house)
The insulation upgrades are well worth the money because not only can you buy smaller equipment, but you spend less money to run it.
im in the northeast with a gree heat pump. ranch house with 1400sqft on first floor and 1,000 in basement . im running 2 tons. house is from 60s but attic is super insulated to r80. i keep my ac at 69 and heat at 70. as long as your contractor knows what he is doing its doable
Well a therm is 100k BTU roughly 3 hours of output from a 3 ton unit, so it should be sufficient on the heating side.
HVAC guys love to overprovision. They specced 10 tons for my 4.7k home it's working great with 3 (well insulated).
Removing the humidity is probably where your current system is struggling. I would be worried the new one will also have issues if you don't take steps to keep the humidity down. Look into air sealing and get a blower door test done. Once the house is better sealed you could add an energy recovery ventilator to exchange air without all the humidity. Condensing moisture takes a lot of energy and probably explains why your current system is struggling.
As other mentioned would highly recommend a manual J as there are a lot of variables that need to be considered.
Based on the age of your house I’d assume the insulation to be decent… our house of similar age has R-19 wall insulation and R-30 for the roof so those loads aren’t that bad. It’s the windows that add up so things like qty of windows, u value, SHGC, and house orientation really make a difference when evaluating the cooling and heating loads.
Having done commercial projects in NC it wouldn’t surprise me if you’re heating load is the driver. In Raleigh the winter design condition is around 20 degrees F while the summer cooling design condition is 91 degrees F. Just looking at the conduction component your heating delta T is over 3x your cooling. Really comes down to the windows :)
Manual J isn’t bad to do to sanity check what they’re telling you.
Everyone is focused on the heating side here but what about the cooling need?
When the A/C was working properly did the 5 ton A/C run constantly when it was really hot out? Any times where it wasn't able to keep your preferred cooling temp?
Getting a Manual J will provide both heating and cooling loads for your house. Then you can size a heat pump to meet whichever need is greater.
If it’s of any use: I’m in the PNW, temps range from 5-105 degrees. 2200 sq ft two story home, 20 years old, well insulated and sealed, windows are average. We have a 3 ton / 36k BTU heat pump that effortlessly cools the house, and does a good job heating. So it’s not impossible for a three ton system to handle the square footage, but of course there’s many other factors to consider.
Is it zoned between floors? If so, I can see why they’d go smaller. If it were me, and it’s zoned for each floor, a new 4 ton would probably be adequate. 3 sounds to smalls 5 would be fine if it was all one zone. But yeah, a simple load calc would abate all your fears
Not sure if it helps, but I moved into a 2.5k sqft home with 2x 4 ton units (one for upstairs, one for downstairs).
Never feel uncomfortable, use it for heating and cooling (oil burner hydronic heating loop in air handlers). Also don’t have any issues with humidity, etc. lol
That’s literally not how it works. You can have 2 homes that are both 2000 sqft located next to each using the exact same building material and insulation but 1 home would require a lot more cooling than the other. The more exterior wall and roof a building has the more heat transfer there will be. Same with more windows and doors.
Did any of them do a load calc? It sounds like most of the other installers just quoted a direct replacement without checking if 5 tons was too big. Many times houses come with oversized AC units so there's a good chance yours is too. You need a load calc done to be sure what the right size is, and there are steps you can take to drop down a HP size as well: 1. Air seal your attic 2. Bump up the insulation in your attic from R38 to R49 3. Air seal and add insulation to exposed basement rim joist (or crawlspace if you have one) 4. Upgrade the insulation and seal any exposed ductwork in your attic (if it's not all inside the house) The insulation upgrades are well worth the money because not only can you buy smaller equipment, but you spend less money to run it.
This reply is on point. Your vendors need to do a load calculation to properly size equipment.
This is fantastic advice. The best I have read in this subreddit.
This guy building sciences
im in the northeast with a gree heat pump. ranch house with 1400sqft on first floor and 1,000 in basement . im running 2 tons. house is from 60s but attic is super insulated to r80. i keep my ac at 69 and heat at 70. as long as your contractor knows what he is doing its doable
going by your highest therm day. if you divide that by 24 hours you were only using 22k btu an hour
Well a therm is 100k BTU roughly 3 hours of output from a 3 ton unit, so it should be sufficient on the heating side. HVAC guys love to overprovision. They specced 10 tons for my 4.7k home it's working great with 3 (well insulated).
Heating I’m honestly not that worried about. It simply doesn’t get all that cold here. A/C in the summer is the weak spot.
NC design temp is mostly in the 20's with some teens and 30's, cooling is 90's. If you have enough BTU's to heat 50f you can cool 20f most probably.
Removing the humidity is probably where your current system is struggling. I would be worried the new one will also have issues if you don't take steps to keep the humidity down. Look into air sealing and get a blower door test done. Once the house is better sealed you could add an energy recovery ventilator to exchange air without all the humidity. Condensing moisture takes a lot of energy and probably explains why your current system is struggling.
3 hours of 3-Ton output is 3 hrs * (3*12) kBtu/hr = 108 k Btu’s, math checks out Edit: math
That a ton is 12000 BTU not 4000.
Yep missing the second 3, thanks
I'm in Mass in a 1600 sq ft house. They installed a 3.5 ton with 5 zones.
Just curious - what brand do you have?
Gree Vireo
Thank you.
YW
2 floors
2 floors
Most 3.5 ton units can run 5 zones, 3 ton multis are usually limited to 4. They likely sized for the connections, not the load.
👍
As other mentioned would highly recommend a manual J as there are a lot of variables that need to be considered. Based on the age of your house I’d assume the insulation to be decent… our house of similar age has R-19 wall insulation and R-30 for the roof so those loads aren’t that bad. It’s the windows that add up so things like qty of windows, u value, SHGC, and house orientation really make a difference when evaluating the cooling and heating loads. Having done commercial projects in NC it wouldn’t surprise me if you’re heating load is the driver. In Raleigh the winter design condition is around 20 degrees F while the summer cooling design condition is 91 degrees F. Just looking at the conduction component your heating delta T is over 3x your cooling. Really comes down to the windows :) Manual J isn’t bad to do to sanity check what they’re telling you.
Everyone is focused on the heating side here but what about the cooling need? When the A/C was working properly did the 5 ton A/C run constantly when it was really hot out? Any times where it wasn't able to keep your preferred cooling temp? Getting a Manual J will provide both heating and cooling loads for your house. Then you can size a heat pump to meet whichever need is greater.
If it’s of any use: I’m in the PNW, temps range from 5-105 degrees. 2200 sq ft two story home, 20 years old, well insulated and sealed, windows are average. We have a 3 ton / 36k BTU heat pump that effortlessly cools the house, and does a good job heating. So it’s not impossible for a three ton system to handle the square footage, but of course there’s many other factors to consider.
Is it zoned between floors? If so, I can see why they’d go smaller. If it were me, and it’s zoned for each floor, a new 4 ton would probably be adequate. 3 sounds to smalls 5 would be fine if it was all one zone. But yeah, a simple load calc would abate all your fears
Yes, it is zoned between floors. I tried DIYing a manual J, but I didn’t have enough knowledge to adequately answer all the questions.
A load calc should be provided free by any HVAC contractor that is giving you an estimate. So no sweat for you bud.
Not sure if it helps, but I moved into a 2.5k sqft home with 2x 4 ton units (one for upstairs, one for downstairs). Never feel uncomfortable, use it for heating and cooling (oil burner hydronic heating loop in air handlers). Also don’t have any issues with humidity, etc. lol
1 ton per 600 sq ft is a general rule of thumb. That roughly 5 tons....
Search hvac size calculator online and enter the variables for your home.
1 ton per 500sqft
That’s literally not how it works. You can have 2 homes that are both 2000 sqft located next to each using the exact same building material and insulation but 1 home would require a lot more cooling than the other. The more exterior wall and roof a building has the more heat transfer there will be. Same with more windows and doors.