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Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
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Dave Taylor
I need to put an air handler/evaporator unit into the attic of this old house I'm renovating.
The attic opening is about 2'x1', obviously not big enough so I need to make it bigger.

But, how much bigger? The joists are 18" apart, I could go two, and end up with somewhere south of 3'x......?

So, how big is the typical unit for a 2500sqft house?
Can I assume these are standardized?

Haven't been able to get an hvac contractor to come out.

Also need to keep in mind, the rafters are close to the opening. Probably start at 30" and go up, being higher on the other end of the existing opening.
 
So, like, a lot of stuff is going to have to go up there - evaporator, blower, duct work, etc. Do you have a gable end that you could cut into - less structure involved that way. plus you don't have someone hauling all that stuff through the house.

Aluminum and/or vinyl siding isn't that hard to "unzip" and remove...
 
-nope no gables.
-have good access through this hole...real close to the exit door and driveway.
 
If you need to make the opening bigger, can't you just make it longer so you are not cutting into any joists? It's hard to say without seeing the setup, but the joists could be in tension holding the walls together (rafter load trying to push walls apart).

Can you post a sketch?

Here is a good place to do some research on unit sizes:

http://www.alpinehomeair.com/

Also, it may be possible to partially disassemble and reassemble the unit.
 
fwiw - If I found myself in such a situation, I'd get the building contractor I know
to expand the access to the attic by cutting into one of the joists, with the appropriate
doubling/reinforcing. In the long run I'm happier when I do the job right. Even
if you aren't going into the attic a lot, it's just easier for everyone if there is
good access.

Of course, whether or not there is immediate need to widen the opening will depend
on whether or not the HVAC contractor has a way to get stuff up there through the
existing opening.

Good luck with the project.
 
I've never spent any time contemplating air handler dimensions but my impression is there's no standard. There are practical constraints (it has to fit through a door). FWIW the air handler in my basement is 17.5 x 22 x 44 inches. It looks to come apart in several pieces along its length, so the 17.5 x 22 would be the controlling dimension getting it through a hole. This is not an especially big unit as it was only designed to heat 3 rooms.
 
Is it for A/C only, or a heat pump? When my attic A/C air handler needs replacement, I'm going to go to mini-split units. A lot more efficient.
 
Or do what I did. Place the unit downstairs and run the duct up between the joists and reconnect to the ductwork. A lot easier to work on if it ever gives a problem, and actually a lot quieter because it is not vibrating the ceiling every time it runs. I still have access to the attic through the access door if I should need to. The old unit disassembled enough to come down through the hole, and I would assume most of the units designed to install in the attic are capable of the same type of dis-assembly.
 
Let'sgoflying! said:
I need to put an air handler/evaporator unit into the attic of this old house I'm renovating.
The attic opening is about 2'x1', obviously not big enough so I need to make it bigger.

But, how much bigger? The joists are 18" apart, I could go two, and end up with somewhere south of 3'x......?

So, how big is the typical unit for a 2500sqft house?
Can I assume these are standardized?

Haven't been able to get an hvac contractor to come out.

Also need to keep in mind, the rafters are close to the opening. Probably start at 30" and go up, being higher on the other end of the existing opening.
Click to expand...

If it were me, I'd try to find another location for the unit. If you do put it in the attic, you're also going to need to run the line set for the evaporator, power for the blower & controls and also find a way to drain the condensate. The harder the unit is to access, the less likely it is that the filters will get changed regularly, too. And if the space is tight as you mention, getting efficient ductwork installed is going to be a real challenge.

Since you have 2,500 SF to work with, it might be better to build a utility room on the main level (I'm assuming you don't have a basement since you're in Texas).


Trapper John
 
Dave, they put our big Trane unit in the attic through a standard pull-down attic stairway. The stairs have the 22.5" inside opening to handle the standard 22" wide units that Joe B mentioned above. They're designed to go on 24" center studs, though, so your 18" center rafters will pose a challenge. I agree with jhausch, I'd not go cutting rafter beams until I had an engineer look at it and ensure they're not load-bearing or load-supporting.

If you have a 22" wide unit, you may need to go get a 17.5" unit--they make those, too, specifically to deal with the 18" on-center studs:

http://www.gohvacrsupply.com/store.php?cid=80

This info might help, too, if you do decide to install pull down stairs, it discusses how to change the framing to redirect loads from the cut joists:

http://www.thisoldhouse.com/toh/asktoh/question/0,,20054778,00.html
 
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I really need to get an hvac guy over to make some suggestions. If I can find one.

I want to retrofit the house with a/c. I was thinking heat pump as that is what works well in the house & the bidness.
Right now there is a gas burner downstairs in a 3x3 closet, no remaining space.

I had hoped to plumb in a heat pump atop the heater (ie in the attic) and continue to use the existing gas heater.

Depending on the condition of the heater, and how pricey to replumb the ductwork....and if the hvac contractor said if this was even possible.
Might be better to pull the heater and replace it with the heat pump evap coils plus a new gas heater, if that can be done.
 
He's either going to drop a cased evaporator coil on top of the existing gas furnace (if it remains serviceable), or put in a new furnace and evap coil, if the existing furnace is too old (especially, heat exchanger condition). Either way, existing ductwork remains in service.

I'm just sayin'...
 
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