3 ton A/C compressor ohm readings
#1
09-07-19, 02:25 PM
Join Date: Sep 2019
Posts: 8
Upvotes: 0
Received 0 Upvotes
on
0 Posts
3 ton A/C compressor ohm readings
Have a single phase 230v compressor in outdoor condenser unit. Breakers tripping fuses blowing, no start condition. No humming. Isolated to compressor. New Contactor and capacitor. Taking ohm readings on compressor terminals I’m getting 0.8, 20, 20.8. The values add up correctly but the C-S seem quite high. Can someone help me diagnose based on these values? Would this indicate a short in the windings? Is the high resistance an indication that the compressor is shot or should i be looking elsewhere? Thank you!
#2
09-07-19, 02:30 PM
Group Moderator
Welcome to the forums.
In addition to your measurements posted..... did you check from all three wires to ground ?
The .8 is basically a short.
What does your meter register when you short the two leads ? Probably close to .8 ohms.
In addition to your measurements posted..... did you check from all three wires to ground ?
The .8 is basically a short.
What does your meter register when you short the two leads ? Probably close to .8 ohms.
#4
09-07-19, 08:51 PM
Join Date: Sep 2019
Posts: 8
Upvotes: 0
Received 0 Upvotes
on
0 Posts
Yes two leads read .8 dropping to 0. I’m going to take another reading just in case but i did do two already. No short to ground. Any options besides new compressor? Are the coils serviceable? Thank you for the welcome!
#5
09-07-19, 08:58 PM
Member
No, not serviceable.
To get to the internals the refrigerant must be reclaimed, the compressor removed and the shell must be physically cut open.
They are referred to as hermetic, or a non-serviceable style of compressor.
To get to the internals the refrigerant must be reclaimed, the compressor removed and the shell must be physically cut open.
They are referred to as hermetic, or a non-serviceable style of compressor.
#6
09-07-19, 10:25 PM
Group Moderator
It would appear the start windings are burned but not shorted to ground. When the resistance gets that low there is no recovery other than replacing the compressor.
Based on system age you need to weigh the cost of replacement of the compressor against replacing the entire condenser.
Based on system age you need to weigh the cost of replacement of the compressor against replacing the entire condenser.
#7
09-08-19, 05:14 AM
Join Date: Sep 2019
Posts: 8
Upvotes: 0
Received 0 Upvotes
on
0 Posts
The system is an old R22 Comfortmaker setup. Eight years ago, I was told it was shot and that I needed a new system. Back then i did my first HVAC DIY and only had to replace the fan motor. It’s been fine until now. I just cross referenced the Bristol (Benchmark) compressor number and found a replacement for about $500.00. Not sure how much a charge of R22 would cost. New condenser I suppose i would have to find an r22 to match up with my air handler? Otherwise a whole new system which I’m not looking forward too. Thank you for your assistance; much appreciated.
#8
09-08-19, 05:34 AM
Member
Hi, does the unit have a crankcase heater, any readings from the compressor terminals to ground?
Geo
Geo
#9
09-08-19, 08:03 AM
Member
Bristol is out of business.
You’ll have to reclaim the existing charge. It can be tested for acid to see if reuse is an option. If not the refrigerant will have to be recycled.
You’ll need a torch. And vacuum pump.
Refrigerant prices vary. But there are alternatives to R22.
You’ll have to reclaim the existing charge. It can be tested for acid to see if reuse is an option. If not the refrigerant will have to be recycled.
You’ll need a torch. And vacuum pump.
Refrigerant prices vary. But there are alternatives to R22.
#10
09-08-19, 02:05 PM
Group Moderator
At this point...... you are beyond a DIY repair. Special equipment is needed to capture the refrigerant.
#11
09-08-19, 05:38 PM
Join Date: Sep 2019
Posts: 8
Upvotes: 0
Received 0 Upvotes
on
0 Posts
No crankcase heater or short to ground. I can buy a recovery tank and manifold for $100.00 so I’m thinking I’m still in diy zone. I think with a new compressor, recovery tank and manifold, and gas, i would be in around $800.00 or perhaps a bit less. Can possibly buy used r22 condenser for less.
#12
09-08-19, 05:52 PM
Member
You’d still need a reclaim machine, vacuum pump, nitrogen, micron gauge.
The refrigerant may not be reusable which you’d have to find somewhere to turn in the bottle to.
New R407C condensers are available. But may not work well with old evaporators.
I’d not suggest used equipment. I’ve seen many get burned doing such a thing.
The refrigerant may not be reusable which you’d have to find somewhere to turn in the bottle to.
New R407C condensers are available. But may not work well with old evaporators.
I’d not suggest used equipment. I’ve seen many get burned doing such a thing.
#14
09-08-19, 06:36 PM
Member
Refrigerant isn’t going on the reclaim tank by itself, it needs to be pumped in.
The tank needs a vacuum pulled in it to remove noncondensables.
Used tanks sold via eBay and such tend to be heavily contaminated and shouldn’t be used for anything other then refrigerant headed to the recycling center. If you use one you’ll risk contaminating your system which causes all sorts of major problems.
Once completed the system should be pressure tested and needs to have a vacuum pulled below 500 microns.
If you recycle the refrigerant you’ll have to show your epa certification card.
The tank needs a vacuum pulled in it to remove noncondensables.
Used tanks sold via eBay and such tend to be heavily contaminated and shouldn’t be used for anything other then refrigerant headed to the recycling center. If you use one you’ll risk contaminating your system which causes all sorts of major problems.
Once completed the system should be pressure tested and needs to have a vacuum pulled below 500 microns.
If you recycle the refrigerant you’ll have to show your epa certification card.
