Two Stage AC Question

Posted by on October 21, 2006, 12:14 pm

I worked on a 2 stage carrier package yesterday (single compressor,
double pole contactor, 208v) that would open the contactor every time
the 2d stage kicked on. I suspect something is wrong with the windings
or internal overload of the compressor but if that were the case I
don't understand why it would run fine in first stage and then die
immediately when second stage is energized. It loses the low voltage
at the contactor and if I push the contactor in when it happens it
runs. also, there are low and high pressure cutouts in it, when I
checked the pressure in 1st stage they were 210/68 at 80 degrees oat.
The second stage cuts out so fast I could not get a pressure or amp
reading. The fla is 19 and it draws 12a in 1st stage.

Posted by Stormin Mormon on October 21, 2006, 2:28 pm

Your diagnostic skills have ruled out a bad compressor, or bad
contactor.

The resi systems I've worked on, there is a separate YH and YL for the
stages. Sounds like you might have a fault in the YH wire, some where.
Might want to see if YH is used on this system, and if it's atached to
the same wire at both ends of the run. Like brown at the thermostat,
and purple at the board....

Second thing comes to mind, to ohm out the wire and see if there is a
break in the YH wire, along the way. As you're an experienced tech, I
won't bore you with details how to do this. Nor will I write how to
pull the thermostat off the base, and force the unit into YH to see if
it's a bad thermostat, or a bad wire.

As a new tech, enough things get me wondering. I do wish you the best,
and please let us know how things resolve. Maybe there is a set of
panties wrapped around the contator (grin here).

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
.

<Al Moran> wrote in message

Posted by Noon-Air on October 21, 2006, 6:26 pm

> <Al Moran> wrote in message
> I worked on a 2 stage carrier package yesterday (single compressor,
> double pole contactor, 208v) that would open the contactor every time
> the 2d stage kicked on. I suspect something is wrong with the windings
> or internal overload of the compressor but if that were the case I
> don't understand why it would run fine in first stage and then die
> immediately when second stage is energized. It loses the low voltage
> at the contactor and if I push the contactor in when it happens it
> runs. also, there are low and high pressure cutouts in it, when I
> checked the pressure in 1st stage they were 210/68 at 80 degrees oat.
> The second stage cuts out so fast I could not get a pressure or amp
> reading. The fla is 19 and it draws 12a in 1st stage.

For some reason I seem to have Al Moron in the killfile.....

First thing is... Is it a straight A/C?? or is a heat pump?? If a heat
pump.... what mode was it in??
Did you try jumping out the individual pressure cut-outs to see if you have
a bad one??

Posted by AKS on October 21, 2006, 5:34 pm

I don't believe what I am reading what a mechanics
Dido

<Al Moran> wrote in message
> I worked on a 2 stage carrier package yesterday (single compressor,
> double pole contactor, 208v) that would open the contactor every time
> the 2d stage kicked on. I suspect something is wrong with the windings
> or internal overload of the compressor but if that were the case I
> don't understand why it would run fine in first stage and then die
> immediately when second stage is energized. It loses the low voltage
> at the contactor and if I push the contactor in when it happens it
> runs. also, there are low and high pressure cutouts in it, when I
> checked the pressure in 1st stage they were 210/68 at 80 degrees oat.
> The second stage cuts out so fast I could not get a pressure or amp
> reading. The fla is 19 and it draws 12a in 1st stage.

Posted by Bob_Loblaw on October 22, 2006, 12:25 am

> I don't believe what I am reading
> Dido

More like you don't UNDERSTAND what you are reading....
--
Respectfully, Bob

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