What Causes Compressor Leads to Burn Off of Terminals?

[Ken Hall]

This thermostat cost $125 12 years ago. It uses a thermistor not a mercury switch. It has a cut-out timer in it such that if the signal to the a/c unit is lost for any reason there is a 4 minute delay before it will call for cooling again. Also, there is a similar, redundant, cut-out timer in the condenser unit that won't let the compressor start again after a power dropout for about 3 minutes. I never see this one in action because the delay in the thermostat is longer.

This lead is the Term-Loc lead that was installed about 6 weeks ago. They only burn back about 3-4 inches from the compressor terminals. I cut this off when I redo them.

No.

Thanks for the warning.

-- Ken

[Noon-Air]

Subcooling *maybe* with a TXV but not superheat.

Part of your problem is that the system is overcharged and the compressor is sweating and most probably causing the terminals to be wet all the time causing high resistance connections. With a 67 PSI SP, I would look for an SST of approximately 58 degrees with a fixed oriface(piston) metering device. Recover the refrigerant overcharge, and try again.

[Ken Hall]

You're wrong. I have the pamphlet that came with the unit in front of me.

-- Ken

[Ken Hall]

I should have added, you're right that the suction line sweats all the way to the compressor. I've attributed that to the fact that it's Houston and Houston has high humidity.

-- Ken

[udarrell]

Noonair made some good observations, do not flat out tell him he is wrong! If the compressor is sweating too much it can create problems with the terminals. Superheat does not mean anything if the airflow is too low or there is an insufficient heatload going through the evaporator coil.

It could be overcharged, -read the linked page!

I have not read all the posts so don't have enough info to make any meaningful assessments! - udarrell

[Ken Hall]

If I'm reading the chart wrong, please explain. Here it is:

-- Ken

[Mo Hoaner]

If you didn't do the hacking, who mangled the cap mount, and what exactly keeps the cap and hard start pack from going exactly where they want. Also, what's the evaporated metal on the right hand side of the hard start? Did you or someone else replace the condenser fan motor at some point, or did you replace the start cap with a dual cap because that's all you could scrounge? While we're looking at the cap.... is that the remnants of a flashover on the right hand terminal? And, is the red wire on the center terminal another piece of your handiwork?

[Stormin Mormon]

Sounds too hot.

[Jake]

Ken,

I've read all this back and forth and can't really answer your question... except to give you another avenue to look at...

I'm an electrician and NOT a HVAC guy, so take it for what it's worth.

What you describe are classic symptoms of a low voltage condition on startup.

Look at the side of your condensing unit and see what the required current is.... and then compare it to the wire size you have going out there.

Check all of the connections from the breaker, to the disco, to the unit. Clean and re-tighten all of them (with the breaker off, of course). Open/close the disconnect.. and while open inspect the thing.

Does your home have a adequate (in these days meaning at least 200 amp) service?

Did the contractor make the aluminum/copper wire transitions correctly (if applicable)?

Starting current is one heck of a lot than what it takes to run the thing... and I'd surmise that's where the problem is... a low voltage condition on start due to bad feed capacity or poor connections somewhere.

Just my 2 cents worth.

Jake

[Noon-Air]

What kind of metering device do you have?? What is your LLP and LLT??

[Ken Hall]

The people who installed and maintained the unit for 10 years did all of those things.

I don't see anything that looks like burns on the capacitor.

-- Ken

[Ken Hall]

I said he was wrong about the superheat of 7 not being correct. In effect I said he was wrong in saying *I* was wrong about the superheat. Maybe you want to tell me how I misread the superheat chart I linked to.

I didn't say he was wrong about that.

I don't disagree with that. Some *other* problem making the factory specified superheat meaningless was not the issue. Other problems can cause all kinds of difficulties. The issue was whether the superheat I quoted is what the manufacturer specified, and it is.

Thanks for the link. It seems to deal with systems that are performing below rated capacity. I don't have that complaint.

-- Ken

[Ken Hall]

capillary tube

-- Ken

[Al Moran]

lmao. he's an expert with a set of gauges!

[Al Moran]

Ok genius, what's the wet bulb, dry bulb, cfm, return duct size, filter size and tonnage of the system? Yep, thought so.

[Al Moran]

DOH!

[Noon-Air]

Leave it the way it is and you will...the flashover burns are all over the contactor.

Unless I am gone totally blind, on the capacitor, you have the red wire going to the common terminal, as well as *BOTH* hard start wires, and the compressor wire to the *FAN* terminal. DUHHHHH Gee, I wonder why its not working.

Call somebody that knows what their doing, before you end up as a Darwin Award nominee..... on second thought........

[Mo Hoaner]

You've not blind - I thought that too, but I enlarged, and looked really closely at the pic, and you can see the right spade on the left terminal has nothing on it. The 14 or so guage red wire is on the left spade of the center terminal, one of the wires from the HS is on the right spade of the center terminal, the other is on the left spade of the right terminal, and the white comp wire is on right spade of the right terminal. As to what this cap really is, who knows. The marking near the left terminal looks to be H R2, and the marking near the right terminal can't be made out, but does kinda look like FAN. Just think... the hard start is doing all the work ; ).

Anyway, look at the right terminal at about the 1 o'clock position, and you can see what appears to be the remnants of a flashover, all the way up to the crimp on the can (BTW: I didn't say burn). He's got major nicks on the insulation of several of the wires that we can see, and the ring terminal on the red wire for the comp on the left side of the contactor looks like it's been hot as well. For a good laugh, look closely at the strand or so of wire going in to the spade terminal on the L2 terminal on the hot side of the contactor. (just above the chunk of missing insulation on the black wire).

Come on Ken, tell us the truth.... this picture is of something that you found out for the garbage someplace.

[Ken Hall]

So, is this causing the leads to burn off the compressor terminals?

-- Ken

[-zero]

Superheat is not a fixed number in a cap tube system. (FWIW, maybe you would be better off not telling those who ARE trying to help you, that they're wrong when you yourself are still not sure what is what.)

The wiring looks awful.

Ken, there is a metal plate tack welded onto the compressor that has numbers stamped into it. If you would post all the info on that tag. As a WAG, this may be a butchered unit from the start and not have the proper start/run components.

-zero