Subject: Re: Help me diagnose?

From: [email-masked] (Woody Delp)
Date: 31 May 1995 20:08:47 GMT

A service tech. can install a "hard-start kit"
which is a relay/capacitor combo to give the compress.
an added "kick" during start-up....might do the trick
MUCH cheaper than a new compress.
-- 
Woody Delp

"Question authority....and the Authorities will question you"

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From: [email-masked] (Doug S. Caprette)
Date: 1 Jun 1995 13:38:50 GMT

In article <[email-masked]> [email-masked] (John Allds) writes:
>[email-masked] (Carl Oppedahl) wrote:
>
>>	
>>So the air conditioner, a York 3-ton package unit, has stopped working.  The 
                                 ^^^^^

Within the context of AC, what does this mean?  I.e. what is the defintionof a 
'ton' of cooling?

--
[email-masked]  
 |  Regards,         |   Hughes STX                |    Code 926.9 GSFC        |
 |  Doug Caprette    |   Lanham, Maryland          |    Greenbelt, MD  20771   |
 -------------------------------------------------------------------------------
"Gort, klaatu barrada nikto." -- Klaatu in "The Day The Earth Stood Still"

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From: [email-masked] (Scott Sehlhorst)
Date: Wed, 31 May 1995 17:23:53

In article <[email-masked]> [email-masked] (Carl Oppedahl) writes:
>blower and fan both work fine, but no cooling.  The compressor, obviously, or 
>loss of coolant, or something like that, is to blame.  It's not the compressor 
>relay, because that same relay turns on the condenser fan, and it spins fine.

>Putting an ammeter and voltmeter on the compressor, what I get is this.  
>Whenever the relay turns on, the compressor gets about 215 volts.  For a brief 
>moment (about 1.5 seconds), I get about 70 amps on the ammeter.  Then it drops 
>to zero.  If I sit and watch for a couple of minutes, I see a continued zero, 
>then the current jumps back to 70 amps, then after 1.5 seconds it drops to 
>zero.

>With normal operation I would expect the current to drop to about 18 amps, not 
>zero.

>I assume that a thermal limit switch is tripping inside the compressor, which 
>would explain the drop to zero current.  The limit switch cycles, hence the 
>brief instants of 70-amp draw.

It certainly sounds like the motor protector is tripping.  I'm surprised it 
takes over 1 second to trip.  The motor protector is probably in series with
the compressor starter coil, and is self heating from the current.  It could
be a thermal safety control, but then I would be surprised that you can get it
to trip in under 2 seconds.  The time constant for thermal controls is usually
much longer than that, and the trip point would be high enough to prevent 
nuisance trips, so I'd put my money on a current limiter.

It could also be a high pressure limit control, but the compressor would have
to start for that to happen, and it should require more than 2 seconds to 
reach trip pressures (probably 375-450 psi) on the discharge line of the
compressor, so we should be able to rule that out too.

If you had a loss of coolant, you would cause the loss of charge pressure
switch to open the circuit to the compressor.  We can rule that out from
your data.  If the charge was partially lost (hypothetically, 10 psi on the
suction line prior to compressor start), then when the compressor kicked in
it would draw down (tripping a hypothetical 7 psi loss of charge limit) and
open the circuit.  Again, we can rule this out because the compressor didn't
start.  

The pressure switches would be controlling contactors for the current levels
shown, not direct line break (70A220VAC is a lot of power for a pressure
switch), so check those contactors for any faults, although they would tend
to fail either open circuit or by tack weld, which doesn't fit your 
description.

It sounds like you might have a locked rotor on your compressor.  Maybe one
of the service experts can tell if rotating it manually and then restarting
will work (like a car alternator) for now.  Maybe there's a dead spot in the
coil, or possibly the starter coil.  The unit could be a capacative start,
and maybe there's a short in the capacitor, causing 70A to flow right past
the windings, until the motor protector opens the circuit.  There are several
different motor schemes, and I don't know which one drives your compressor,
but don't immediately assume it needs to be replaced.  Give the experts on 
this list a chance to respond, they've always impressed me!

>I suppose I have to hire somebody to take out the compressor and put in a new 
>one, right?

>Carl Oppedahl
>Oppedahl & Larson, patent law firm
>[email-masked]
>watch this space for a web server with frequently asked patent questions and answers

Scott Sehlhorst
Design Engineer
Texas Instruments
Commercial Sensors and Controls
[email-masked]
speaking of course for myself only and not TI

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From: [email-masked] (Mike Waller)
Date: 31 May 1995 22:50:58 GMT

Carl Oppedahl ([email-masked]) wrote:

: Putting an ammeter and voltmeter on the compressor, what I get is this.  
: Whenever the relay turns on, the compressor gets about 215 volts.  For a brief 
: moment (about 1.5 seconds), I get about 70 amps on the ammeter.  Then it drops 
: to zero.  If I sit and watch for a couple of minutes, I see a continued zero, 
: then the current jumps back to 70 amps, then after 1.5 seconds it drops to 
: zero.

: I assume that a thermal limit switch is tripping inside the compressor, which 
: would explain the drop to zero current.  The limit switch cycles, hence the 
: brief instants of 70-amp draw.

Your compreesor is trying to start, but the internal overload is tripping on
the current draw of the start windings.  You might want to check the capacitor
with your ohmmeter, if you have one that goes up in scale to 10K.  If the
needle swings up and slowly swings back down it is good.  But I basically have
them on hand and just change it out to see if that is the problem.  There is
also a hard start kit that you can buy to hook onto the capacitor terminals.
I have used them with success.  They look like minature flashlights.

The other problem could be a "lockup". But getting it to unlock with a Little
Annie just postpones the problem until it locks up again.

Hopefully it is just the capacitor, simple and cheap.

D
D
C
A
Hopefully the capacitor is your answer.

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From: [email-masked] (John Allds)
Date: Thu, 01 Jun 1995 02:31:34 GMT

>I suppose I have to hire somebody to take out the compressor and put in a new 

============================
 
The Compressor is definetly trying to start,.....have you tried ohming
out the compressor??..........if not, then kill the power to the unit,
Unhook the three wires to the compressor e.g. the Common Start
and the Run wire's, (make sure you put them back on the correct
terminal's when your done!!) Now take a ohm meter or continuity 
tester and check from (C) Common to (R) Run and then (C) Common to
(S) Start and then (S) Start to (R) Run.  If you  find an open  circut
on any of the above combination, then the I.P. is Tripped or the
windings have opened and are NO GOOD. If it's the I.P. and it's
internal, and it won't re-set, then the compressor is Trashed. If the
I.P. is external, replace it.  If you get a closed circut on the above

combination, then the winding's are OK, and the Motor itself is Froze
up and not spinning.......on last thing you can try is to put on a
Hard Start Kit, and see if that will kick it in.
 
Good Luck.

     _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
          -----John & Dia Allds-----  
        [email-masked] 
    ---- [email-masked]
   _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/

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From: [email-masked] (David Oller)
Date: 2 Jun 1995 05:54:40 GMT

>I suppose I have to hire somebody to take out the compressor and put in 
a new 

Carl,

I'm afraid you are getting some bad advice here. I am not going to say 
>from  whom, but I do suggest you get a qualified tech to check out your 
system. It could be several things--some of which has been mentioned. It 
could also be a txv system without a start kit, or with a bad SAK--there 
are several possibilities. One thing for sure, and here is where you have 
gotten bad advice--you are obviously not qualified to trouble shoot this 
problem, and you could get hurt. Get a pro, please.

Note to all readers: We didn't cover this in the FAQ, but I really hope 
that this is not going to turn into a "Help the Do It Your-Selfer" 
Newsgroup.

David O.

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From: [email-masked] (David Oller)
Date: 2 Jun 1995 14:13:11 GMT

I want to correct my error here.

My use of the wording "Bad Advice" is not correct, because I didn't see 
any incorrect opinions in *any* of the posts.

What I should have said is: "The best advice---which you have not been 
given is to call an expert."

Short Story:

I had a friend who was a HVAC contractor. Told a homeowner how to clean 
his condenser coil on the phone. The homeowner was electrocuted. Home 
owners dead, the friend lost everything he had, and many people (mainly 
the owners children) were hurt.

Technically I did not see anyone who gave a wrong or bad answer.

David

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From: [email-masked] (Thomas H Miller)
Date: 2 Jun 1995 14:05:48 -0400

David Oller ([email-masked]) wrote:
: I want to correct my error here.

: My use of the wording "Bad Advice" is not correct, because I didn't see 
: any incorrect opinions in *any* of the posts.

: What I should have said is: "The best advice---which you have not been 
: given is to call an expert."

: Short Story:

: I had a friend who was a HVAC contractor. Told a homeowner how to clean 
: his condenser coil on the phone. The homeowner was electrocuted. Home 
: owners dead, the friend lost everything he had, and many people (mainly 
: the owners children) were hurt.

: Technically I did not see anyone who gave a wrong or bad answer.

: David

What are you, a lawyer or something?  :)) :)

Anyway, you are most correct. If you do not know how to do a job, call an 
expert.  It will usually save you money in the long run.