Pay to have a load calculation done to see what size you need then take it from there.

 

So is the house 2400 or 3800 sqft?

I looked up the zip and you look about the same latitude as me. I have a 3200 sqft ranch with a 3 ton. Set my unit to 75 and we have never had a problem. My design temp is 89. When we had two back to back days of 96 my 3 ton did fine. If I could get a 2 stage 2.5 ton I would have.

My unit runs in low stage 90% of the time in dehumidify mode.


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jbhenergy - the home is 2400 SF.

 

So from where I’m sitting I would say 2.5.

But I also don’t know what type and how many windows. Color roof. Which direction your house sits etc etc etc.

But again my swag is 2.5.


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Sounds like a pickle - you said the 4 ton guy measured the rooms, so he did a load calculation? Ask him about the ductwork sizing and ask if you need to add runs or return air.

The 3 ton guy told you that was all he'd put in with your existing ducts, but did you ask him about adding more ductwork? Seems odd to put an undersized unit in because the ducts are limited.

Also, is this being connected to a furnace? Existing? Does it have a drive large enough to handle 4 tons?

 

In HVAC, bigger is not necessarily better. Too large of a unit will short cycle and won't dehumidify as well as it should. What you need is just the right size.

The only correct way to determine that is to have a proper load calculation done on it, typically called "running a Manual J".

Find out if either company ran a full load calc. And I mean a proper one, not a short cut. Square footage is certainly one of the factors, but the type of construction, windows and roof you have, amount of insulation, even the direction your home faces all factor in to a proper load calc.

A 62 year old home was likely not built to be energy efficient, so that is a consideration, especially if the home has not been upgraded with additional insulation, windows, etc. If it hasn't, you might want to put some of your money into doing that instead of toward a bigger A/C unit.

Sounds to me like you need a complete energy audit before you buy an HVAC system. Make the home as efficient as is feasible before determining what size A/C you need. It will save you money in the long run.

 

- Bazooka - thank you for mentioning the load calculation - something else I'm unfamiliar with. Will look into it. (Great looking bike BTW. Almost bought a 750 Commander a couple of years ago, and decided at my age then - early 70's- didn't have enough time left to both wrench & ride. Opted for the 900 Triumph Thunderbird).
- jbh - thank you. per above, planning to look into the load calculation.
- doug - great Q's, which I wouldn't even know to ask. And yes - a furnace is also going in. Both units are 15 years old, we are in our 70's and don't know how much longer before we downsize, so want to replace both.
- SpecialK - definitely looking into the load calculation - thanks for the more in-depth explanation. Also appreciate the energy audit suggestion.

Man! This has really been an enlightening experience!! Greatly appreciate everybody's interest!

 

Thank you all for bringing the J manual load calculation to my attention. Had one done this AM by a very highly rated 2nd generation local contractor. The result - recommendation for a 3.5 ton unit - splitting the difference between the 4 and 3 ton proposals. Greatly appreciate the advice received here - this site is an incredibly educational resource.

 

What is the model number of the unit in there now. Is it a 3 ton now?


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JBH - yes - it is a 3 ton. I’m away so can’t give you the model #. It’s a Lennox.

 

How well does it do with the load currently. Or before is was broke…


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We were w/o AC for the first 17 years so we were initially impressed. Over the next 15 years as we became more accustomed to it, realized that in our 62 year old split level home it wasn’t as effective on the 2nd floor (bedrooms) as it was on the ground level (family room - most effective) and the first floor (LR, DR, K - 2nd most effective). The 3rd floor ( BR, office) was nonexistent.

 

That’s ductwork not ac size


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