Voltage requirement for residential refrigerated system

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Old 07-09-20, 04:13 PM
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Voltage requirement for residential refrigerated system

I have a simple question that I can't find the answer to:

For a residential refrigerated air unit, is there a system (compressor, blower, etc.) that can be run on 115VAC (20A)?

Or it this unheard of and all such systems MUST run on 220V?

Any good answer is appreciated.
 
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Old 07-09-20, 04:38 PM
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Only small window units and minisplits will be 120V.
No central air conditioner will run on a circuit like that.
 
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Old 07-10-20, 07:31 AM
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Thanks Roughneck. I guess I'll take your word for it. I had a feeling that was gonna be the case. (frown)
I was hoping to effect a retrofit with an available (vacant) 115V circuit.
 
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Old 07-10-20, 08:14 AM
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What size wire and how many conductors do you have?
If the wire size is correct, it wouldn’t be much to change to a 208/230V circuit.
 
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Old 07-10-20, 08:49 AM
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For a residential refrigerated air unit, is there a system (compressor, blower, etc.) that can be run on 115VAC (20A)?
I'm sure you could find a small mini split system.

The reason for using 240v on larger systems is because it balances the load connected to the power company and the wiring can be smaller.
 
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Old 07-10-20, 03:09 PM
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My thoughts exactly. I'm thinking 12-2 w/ ground. I may be able to convert the empty circuit to 220V w/ proper breaker. I will check.
 
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Old 07-11-20, 02:38 PM
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OK ... when all said and done, I found a vacant 220V slot in my service panel which I coudl tap for power.

I now pivot and pose a different question. For my 2000 ft^2 house in the SW, I believe I need a 3.5T system (42,000BTU).

I currently have a roof-mounted evaporative cooler. I'd like to replace this unit with a blower housing that would contain the evaporator coil and place the compressor/condenser on the ground down below.

Does anyone know of such a roof-mounted blower housing on the market? In some perusal, I have found separate compressor/condenser units (not the problem) but the blower housings are to be placed in an inside closet within the house somewhere. That's my dilemma..
 
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Old 07-11-20, 02:58 PM
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Packaged unit would be easiest if the roof is structured for it. Or tap into the duct in the attic and put an air handler up there.
Is your duct big enough for a central cooling system?
Equipment isnít sized via square footage. So you probably donít need 3.5 tons.
Youíll also need to run return air duct for the system, as youíll no longer be using outdoor air like the old evaporative cooler did.
 
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Old 07-11-20, 03:28 PM
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A packaged unit on the roof is probably do-able but you'll need a crane to get it up there.
You're basically starting from scratch installing A/C..... no ductwork.

Have you considered leaving the evap cooler and adding spot A/C in certain areas ?
Maybe a multihead split unit. That wouldn't require ductwork.
 
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Old 07-12-20, 06:57 AM
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As I said, I'd like to have only an air handler on the roof, not a "packaged" system that includes compressor/condenser. Virtally all equipment I see via Google presumes a packaged system (which I find strange). I don't see any free-standing air handlers that can be coupled with the ground unit.

I have radiant heat in the floor, so this is only AC. The evap. system I have uses a duct system to distribute cooling.

Roughneck makes a good point I hadn't thought of, which may be a show stopper: return ducting ! I hadn't thought of this. Uggghh !! Actually, I may be able to cut a hole in the hallway for this - a single return vent.

I really just need to find a roof-mounted air handler on the market. I'd like to at least see one. Any links to such are appreciated. Thanks for all help here !!
 
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Old 07-12-20, 07:03 AM
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I donít know if any such air handler available on the market. Outdoor air handlers are common for commercial but mostly unnecessary for residential use.
You need enough space for a return air duct large enough for the system your installing.
And you still donít know what size system you need.
The existing supply duct is likely not large enough for a central air conditioning system.
You mentioned this circuit you plan on changing is run with 12 gauge wire? You will have to rerun that in larger gauge wire for central air conditioning. Exactly how large depends on the requirements and specs of the condenser. But 12g isnít large enough.
Have you considered minisplits?
 

Last edited by roughneck77; 07-12-20 at 07:18 AM.
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Old 07-12-20, 10:29 AM
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I picked 3 ton as a starting point. I don't see any rooftop air handlers close to this size.
It looks like they start at roughly 10 ton. That would be immense on your roof.
 
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Old 07-12-20, 08:49 PM
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Thanks PJmax & Roughneck.

Firstly, I appreciate knowing that there may not be a residential air handler for what I need. All such handlers I have seen are either in a closet or attic space. I do not have an attic (Pueblo style house).

I could have an adequate return in the hallway ceiling.
He existing duct work accommodate a 5000 CFM blower, which theoretically I could match with the right air handler.

The 12-gauge wiring consideration was for a line I might have been able to tap. But as I said:
"OK ... when all said and done, I found a vacant 220V slot in my service panel which I could tap for power." By that I meant that I'd run new wire (of adequate gauge) out to the loads.

In the final analysis, my biggest obstacle is the roof-mounted air handler. I will check with a local mechanical guy to see if any are available here, understanding that the answer may be NO.

Finally, could either of you confirm that my wiring concept is basically right. (See image.)


 
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Old 07-12-20, 09:17 PM
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The transformer and low voltage connections will be in the air handler.
 
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Old 07-12-20, 10:08 PM
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Yes.... your wiring diagram is correct.
 
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Old 07-13-20, 06:32 AM
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Thanks for the quick confirmation of my sketch PJmax.

Besides the weight-on-the-roof issue, my main interest n having a split system was maintenance. It seems like having at least the compressor/condenser on the ground would facilitate that

A neighbor of mine - with similar flat-roof house - had a conversion to refrigerated air about a year ago. I saw a crane lifting the unit to the top. Given what I've learned on this thread, I strongly suspect it was an integrated (self-contained) system. I will visit them soon and soon and see exactly what they had installed. That may help inform my approach going forward.

Thanks again for advice and thoughts from you and Roughneck. I really appreciate your time.
 
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