Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 06-08-2008, 08:19 PM   #16
Ouch!That'll leave a mark
 
Join Date: Jun 2008
Location: Ridgeville SC near Charleston
Posts: 49
Rewards Points: 25
Default

Bad compressor, and coil question...


quote "all I want to do is get it to stop tripping the breaker "

This is not in your previous posts. Think like a service tech. does the breaker trip as soon as it is reset? Is the t-stat calling for cooling? If it is. Can I turn t-stat off and breaker stays on? (Remove the compressor wires from the contactor and try the breaker. With no power going to the comp. this will eliminate or confirm the Comp.) Can I isolate the low voltage wires going to comp. contactor and breaker stays on? Basicly anything in this cond. is subject to trip a breaker. of course the compressor. or the contactor the cond. fan motor, the reversing valve the compressor heater element. You will have to test all componets that run on 240v just like the compressor to find the culprit. I am not going to get into the air handler could be on the same circuit. Make sure this is not the case. There are lots of componets there too. Good Luck, Mike

ridgevilleac is offline   Reply With Quote
Old 06-08-2008, 08:37 PM   #17
Ouch!That'll leave a mark
 
Join Date: Jun 2008
Location: Ridgeville SC near Charleston
Posts: 49
Rewards Points: 25
Default

Bad compressor, and coil question...


Quote:
Originally Posted by Undepelo View Post
What I did was measure the resistance across pairs of all three, ie red and brown, then red and black, then black and brown. The black and brown gave me the low ohm reading I though would indicate a shorted compressor. I read it's good if it's zero and bad if there was low resistance between them. I did remove the red/black from the switch block and the brown from the capacitor. BTW the system has been switched off for a while, and I know capacitors discharge eventually, but I read no voltage across the terminals of the capacitor. Is this normal?

Yes this is normal. The cap will lose its charge over time. If the breaker is tripped there will be no voltage to measure for the simple fact as soon as the breaker trips it discharges the caps because of a dead short.

You are measuring resistance across the terminals. This is wrong. You will have to follow my prev. thread about testing. The res. you are telling me indicates in my experience the comp. is good. unless shorted to ground.

Zero or infinite ohms is when the needle goes all the way to the right of the meter that is zero. on an anolog. if the 0 appears in the led display... this is 0 or infinite. Infinite meaning non ending, the meter goes to zero Hope this clarifies. Mike
ridgevilleac is offline   Reply With Quote
Old 06-08-2008, 10:34 PM   #18
Newbie
 
Join Date: Jun 2008
Posts: 12
Rewards Points: 10
Default

Bad compressor, and coil question...


Quote:
Originally Posted by ridgevilleac View Post
quote "all I want to do is get it to stop tripping the breaker "

This is not in your previous posts. Think like a service tech. does the breaker trip as soon as it is reset? Is the t-stat calling for cooling? If it is. Can I turn t-stat off and breaker stays on? (Remove the compressor wires from the contactor and try the breaker. With no power going to the comp. this will eliminate or confirm the Comp.) Can I isolate the low voltage wires going to comp. contactor and breaker stays on? Basicly anything in this cond. is subject to trip a breaker. of course the compressor. or the contactor the cond. fan motor, the reversing valve the compressor heater element. You will have to test all componets that run on 240v just like the compressor to find the culprit. I am not going to get into the air handler could be on the same circuit. Make sure this is not the case. There are lots of componets there too. Good Luck, Mike
Mike, thanks for your help and patience. I'm not familiar with the components in the system so its taking some time for things to register. The reason I say I want the breaker to stop resetting is because I'm guessing that once I determine what was making it trip, I'll know what's broken. The system was working during winter, there was some time of inactivity during spring and when I placed the thermostat to the cool setting, ambient air was all that came out the of vents. The breaker trips as soon as the thermostat calls for cooling. The handler blower runs with no issues besides a faint humming thats constant even when off. I exposed the electronics of the handler and saw no obvious signs of damage. The handler has it's own breaker switches in the main box so that tells me it's on its own circuit. I'll search the net for a basic diagram of components and with your tips I'll try some more troubleshooting. My fear of tripping the breaker too much was a possible short in the house that could trigger a fire.
Undepelo is offline   Reply With Quote
Old 06-08-2008, 10:35 PM   #19
Newbie
 
Join Date: Jun 2008
Posts: 12
Rewards Points: 10
Default

Bad compressor, and coil question...


Quote:
Originally Posted by ridgevilleac View Post
Yes this is normal. The cap will lose its charge over time. If the breaker is tripped there will be no voltage to measure for the simple fact as soon as the breaker trips it discharges the caps because of a dead short.
Any simple ways o testing the cap?
Undepelo is offline   Reply With Quote
Old 06-09-2008, 07:13 AM   #20
Ouch!That'll leave a mark
 
Join Date: Jun 2008
Location: Ridgeville SC near Charleston
Posts: 49
Rewards Points: 25
Default

Bad compressor, and coil question...


Unless the cap is in pieceses. I would be willing to bet The cap is not your problem. Test everything to ground. You will find the culprit.
ridgevilleac is offline   Reply With Quote
Old 06-09-2008, 10:15 AM   #21
Member
 
Join Date: Mar 2008
Posts: 109
Rewards Points: 75
Default

Bad compressor, and coil question...


Quote:
Originally Posted by ridgevilleac View Post
A shorted compressor will show 0 or infinite ohms. The way to test for a short to ground is remove the compressor leads and and with your ohm meter test each spade c s r to a good ground. The readings you are coming up with seem normal for the compressor windings around 1.5
When reading the resistance of windings in a single phase compressor, R-C + S-C = R-S. A winding does not always short out to ground..it can short out to another winding and his readings seem to indicate this.
statman is offline   Reply With Quote
Old 06-09-2008, 05:48 PM   #22
Newbie
 
Join Date: Jun 2008
Posts: 12
Rewards Points: 10
Default

Bad compressor, and coil question...


Quote:
Originally Posted by statman View Post
When reading the resistance of windings in a single phase compressor, R-C + S-C = R-S. A winding does not always short out to ground..it can short out to another winding and his readings seem to indicate this.
Ok so I go from bad compressor, to good compressor, to bad compressor...
So the formula establishes how it should read if it's operating properly? I that is the case (RC+SC=RS) Then 1880Ω+2.3Ω=1882.3Ω which is about 1.88KΩ. So based on the formula, how can my readings indicate to you that there is a short?

Last edited by Undepelo; 06-09-2008 at 06:35 PM.
Undepelo is offline   Reply With Quote
Old 06-09-2008, 08:16 PM   #23
Member
 
Join Date: Mar 2008
Posts: 109
Rewards Points: 75
Default

Bad compressor, and coil question...


Sorry..missed the K in your equation.....Why?...Because there is no single phase AC compressor that I know of that has an 1880 ohm winding. Most are in the 3- 10 ohm range. Therefore I suggest you recheck your readings. You have the formula..if the windings do not match up,what does it matter...you have to replace it either way. And if you do, then ensure you replace the capacitor as well.
statman is offline   Reply With Quote
Old 06-09-2008, 08:35 PM   #24
Newbie
 
Join Date: Jun 2008
Posts: 12
Rewards Points: 10
Default

Bad compressor, and coil question...


Quote:
Originally Posted by statman View Post
Sorry..missed the K in your equation.....Why?...Because there is no single phase AC compressor that I know of that has an 1880 ohm winding. Most are in the 3- 10 ohm range. Therefore I suggest you recheck your readings. You have the formula..if the windings do not match up,what does it matter...you have to replace it either way. And if you do, then ensure you replace the capacitor as well.
I see. I wasn't aware that the resistance range was supposed to be so low. I guess at this point I'm going to try and find recommendations on good companies that can service the unit, although I have serious trust issues and won't be comfortable no matter who comes to do the work.
Thanks for all your advice and help.
Undepelo is offline   Reply With Quote
Old 06-13-2008, 01:28 AM   #25
Newbie
 
Join Date: Jun 2008
Posts: 1
Rewards Points: 10
Default

Bad compressor, and coil question...


Undepelo,
I think I have the same or similar problm.
I am working on a Coleman Mach EL 15k BTU rooftop unit. I violated my normal rule of not waiting a few hours to a day to power up after moving and tipping the unit. When I first turned on, blower and fan working fine. turn to cool and after a few seconds, got the buzz briefly, then only the fans running. I turned to fan only and waited 14 hours then tried again. Now a fuse blows. (wall fuse). Changed fuse, same thing.
After researching, symptoms pointed to the starter capacitor. Took my 3 caps to appliance parts dealer. He checked and confirmed. Will be installing caps later today so will report back my success hopefully.
On the winding resistance... If you think about it, it would have to be a very low resistance. After all, you are basically checking the resistance of a long piece of wire.

Don't give up doing it now! You are almost there. And if you have a bad starter cap, mine was only 8 dollars!

Good luck

Randy

randyt58 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.