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OT - A/C systems

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Posted by on October 14, 2003, 12:44 am
Anyone here have a dual compressor central air unit? I'm trying to find out
if both compressors are used when the demand is great enough. I believe both
Trane and American Standard use dual compressors for their top of the line
models. All I know is one compressor is rated more powerful than the other.
Are they both used at the same time or does the system switch from one to
the other?
Thanks, and sorry for the OT post.

Posted by Dale Farmer on October 14, 2003, 3:02 am

"mark_digital©" wrote:

    For that sort of unit, the controller will select which compressor will give
the most efficient operation.  Some models will be able to run both of them at
the same time, others will not.   Your best bet is probably to go look at the
manufacturer's web site and ask them.


Posted by Zathera on October 14, 2003, 3:46 pm

I do not have one but a buddy does. One compressor runs pretty much all of
the time. The other kicks in when the first one can not handle the load.
Neet setup, I wished that it was available when I bought my a/c.

By the way, Trane and American Standard are the same company, Trane.
American Standard is the residential stuff. The Trane name used to be used
on the commercial stuff, bigger units. I bought an AS when I was looking, 5
ton  12 seer. Never regretted the decision. AS did not make anything better
when I purchased the equipment. Check out their extended warrantees. I
bought one never used it. The only problem I have had is with the vfd motor.
It died after 7 years. I called the supplier and they said replace this cap
and all will be fine. They admitted that the original ones were weak. Cost
70 bucks and a half day to R&R.  I am CFC certified but do not like working
with sheet metal. A/C work is not my chosen profession. I got certified
because the mechanics at work did not like working on the 5kv supply lines
when the chillers needed work.  We have 5 Trane's, 3-2500 ton and 2-3000
ton. Got a couple of York's as well.

Posted by on October 14, 2003, 9:25 pm


Thank you!
My wife now has a question. She wants to know if A/C units and their air
handlers need or should be surge protected at the breaker panel. Do you
Again, thanks.

Posted by Zathera on October 15, 2003, 3:30 am


If your in an area that gets a lot of lightning  or over head lines then I
would protect the service and again where ever your sensitive electronic
equipment is located. You know the plug strips with MOV's ( metal oxide
varistors the active part of most plug strips. I live in Tempe AZ with a cap
bank for the grocery store in my back yard on a pole. It switches a couple
of times a day to keep the voltage stable. I have a whole house unit on my
service, and again every where I have sensitive equipment.  Yes on my air
handler, the vfd and it is 120 volt. No on the compressor. I figure the
whole house unit will bring down the surge enough to protect my compressor.
If your not getting a vfd on the air handler I would not worry about
protecting it. It never hurts to protect your whole house.  My unit is made
by Cutler-Hammer. I am sure there are others out there. Mine was a gift from
CH when they published some of my field reports when I worked for them.
Surges can come from more than lightning. We get a fair amount of storms in
the monsoon season. None of my neighbors have them.  Check the voltage
requirements on the equipment. Call up and ask their help desk. If the unit
has a lot of electronics then I would think about protection of some sort.

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