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We have spray foam installation and Anderson windows. We have one unit for the ground floor, and a unit that splits the second and third floor. There's a ducted mini split for the FROG. Every new home must have a load calculation done during construction to find what is the correct size units for the house. This was a change Obama put in place so HVAC companies aren't "guessing" anymore. When we completed the house they did a leak test not only for the units, but for the house itself.
In the summer we can keep the house at 78, but the AC runs most of the day. Maybe that's the point of the new methodology is they feel it's more efficient for a smaller unit to run all the time than a larger unit running for a short time and shutting off. Maybe they target 78 as a good temperature in the summer.
We had a different HVAC company come out and do a survey when the units were running all the time. They pretty much told us the units were sized correctly.
We're comfortable in the house and that's what matters I suppose. Of course they shut off at night.
It could just be that they made the wrong assumptions in their load calc. An oversized unit is one that cools so quickly it never a removes any humidity. An undersized unit is one that runs all the time without getting to the temp you want. Cooling to 75 degrees on a 98 degree day isn't an unreasonable expectation.
I don't think they made the wrong assumption as it was bid by three HVAC companies each recommending roughly the same size units, just different vendors. We even looked at a thermal heat pump solution. But a lot has to do with the size of the home. It's much easier to cool a 1200 sq foot apartment than a 4500 sq foot single family home.
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If the HVAC folks now what they are doing, it shouldn't be harder, just more expensive. I had an undersized unit in a 2600 SF house. It would run all day in the summer. Upgraded and cut our bill in half.
I don't think they made the wrong assumption as it was bid by three HVAC companies each recommending roughly the same size units, just different vendors. We even looked at a thermal heat pump solution. But a lot has to do with the size of the home. It's much easier to cool a 1200 sq foot apartment than a 4500 sq foot single family home.
Not likely that 3 different companies made a mistake but it also doesnt' seem right that you can't cool your house down more on a hot day. If you have a heap pump, it would likely run a lot in July but it should still be able to bring the temp down I wonder if a piece of ductwork is damaged somewhere and blowing air into the attic or drawing air from the attic.
I bought a duplex recently and during inspection I found that the front unit's cold air return had been knocked apart and they were drawing their air directly from under the house instead of recirculating it. Who knows how long it had been like that.
We don't have an attic. What would be an attic is fully HVAC living space due to a sealed design and foam installation. It basically became our third floor.
We don't have an attic. What would be an attic is fully HVAC living space due to a sealed design and foam installation. It basically became our third floor.
You probably have attic space over by the eaves of the house with duct work in it. Where are the vents in the rooms on the 2nd and 3rd floors?
Vents for the 2nd floor are in the space between the 2nd and 3rd. floor. We have open web trusses between floors. The ducting for the 3rd floor vents are in smaller spaces between the drywall and the peak of the roof line, accessible for inspection via small doors in the knee walls. Think of a triangle then drawing a box on the inside. The whole triangle is sealed, but the vents attach to the "box" inside the triangle.
The second HVAC company we had come out after noticing the AC ran often did a flow test of each vent, and a temperature output test off each vent.
You have a 4500 sqft house with 1 unit for the second and third floor?
No it's not 4500.. a little smaller ~4200. The 800 sq foot FROG is handled by it's own ducted mini split.
The main house is ~3400 sq feet has a single unit that handles the first floor and a larger unit that handles both the second and third floor. The third floor probably has 800 sq feet of cooled space.
Vents for the 2nd floor are in the space between the 2nd and 3rd. floor. We have open web trusses between floors. The ducting for the 3rd floor vents are in smaller spaces between the drywall and the peak of the roof line, accessible for inspection via small doors in the knee walls. Think of a triangle then drawing a box on the inside. The whole triangle is sealed, but the vents attach to the "box" inside the triangle.
The second HVAC company we had come out after noticing the AC ran often did a flow test of each vent, and a temperature output test off each vent.
Yes, The spaces behind the knee walls and at the peak would be considered "attic" spaces. Flow test should show any duct problems. I don't know... Does the hvac contractor say it's normal that you can't get the house below 78 on a hot day?
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