annoying compressor problem

[zuke19]

the pressure control is the tstat, neutral leg is wired to the top of the relay which goes to the start cap as well and so does the other terminal on the relay-it is wired just like tecumseh shows, how would a pressure control not be able to handle the amp draw, its one of your cut in and cut out deals, i have it set for like 35 and out at 15 or so for r-401a
what would you do if you were in my position? can't change the compressor for the 3rd time

Little confused here. Are you using pressure control for temperature control or you using a T-stat? Possibly the pressure control switch cannot properly handle the current flow.

Shouldn't your neutral leg of the 115vac be wired to the Run on the relay? You have it on the Start.

[zuke19]

tried that on the first one before i changed it because it was tripping so fast

it worked but the next day the run winding was open on the compressor

[Capz]

A switch can work correctly and pass a ohm or continuity test but once asked to pass a full load, it can fail open or in your case, partial failure. Just throwing it out there, something for you to check. Jump out the switch, jump out the overload, see what happens. You can also have a loose connection at the overload terminal with that tiny screw connector. ( that is probably the issue ) Remove each jumper one at a time, see what happens. . Be careful.

Also, Make sure you are 115 wiring to the Run terminal on the relay, not to the Start.

[2sac]

So far, the only thing that has changed is the refrigerant. Prior to the retrofit there were no issues correct?

[MicahWes]

What is the head pressure?

[zuke19]

Reclaimed the gas out of the unit, pulled the txv screen and that was black, blew out the lines with nitrogen, cleaned the scrren with some flush,put the screen back in, vacuumed down unit and weighed in some charge, started comp and it was drawing 8.4 amps, tecumseh says it should draw 6.8, this was total system amps so it isn't too high, sight glass was bubbling, suction was at 2 and head was at 80 so I was putting more gas in, head pressure and suction started climbing and i was almost at full charge when all of a sudden my amp meter read 16 amps right out of the blue, the pressure was 17 and 120 at the time, than it kicked on overload, reset and tried to restart, drawing locked rotor amps each time trying to start, top of compressor not feeling hot, shut it off and waited and still drawing locked rotor amps, I have never seen a compressor in mid running all of a sudden draw twice the amperage, it almost seems like there is a restriction or more of that black crap floating around in the system but that doesn't explain the high amperage out of the blue.Thoughts!

[zuke19]

it worked great for several years witht he same refrigerant but i had issues left and right awhile back, ended up changing and adjusting txv and got it to work good, than out of the blue this starts happening

So far, the only thing that has changed is the refrigerant. Prior to the retrofit there were no issues correct?

[zuke19]

jumped it out already, still doesn't work, that connection is tight and new

A switch can work correctly and pass a ohm or continuity test but once asked to pass a full load, it can fail open or in your case, partial failure. Just throwing it out there, something for you to check. Jump out the switch, jump out the overload, see what happens. You can also have a loose connection at the overload terminal with that tiny screw connector. ( that is probably the issue ) Remove each jumper one at a time, see what happens. . Be careful.

Also, Make sure you are 115 wiring to the Run terminal on the relay, not to the Start.

[MicahWes]

I have seen small, critically charged systems do that when they are overcharged. The condenser gets full and boom, head pressure shoots up very quickly. It doesn't sound like your system is that small though, so this is probably not an issue. I will say that the unit should run even if there is a full restriction. There should be plenty of room for the refrigerant to stack in the receiver and/or condenser. The head should drop and the suction might go into vacuum. The amperage should drop since no work is being done by the compressor.

[2sac]

If you are positive it is not an incoming voltage issue, I'm still leaning towards a capacity or sizing problem. I have gone thru this before

[Capz]

Ohm the terminals on the compressor. Compare to the Tecumseh handbook. Barring any other incoming power and/or electrical wiring and components, must be a faulty motor in the pump. It's gets hot, windings could be losing resistance, amps increase.

I have the book out in the truck if you need factory numbers. Check with me tomorrow.

One otheR thought, this is the originally sized compressor for the condensing skid, right? I use the same compressor for my old R12 McCall pizza retarders. I've seen guys install smaller skids with smaller condensers or units without receivers. Something I need to watch for when i troubleshoot my units.

[trippintl0]

Do you have the condensing unit model #? Is there a brand or model of the unit, too?

Black stuff in the TXV sounds like the compressors have been overheating and putting trash in the system. (possibly oil sludge, etc.)

I'm just throwing this out there, but a couple of times I have seen issues where I'm checking pressure at one point in the system, but pressures are different elsewhere.
You check head pressure at the receiver outlet, and it is low. But it turns out there is a service valve on the discharge line or part of the condenser that is restricted (seen this once on an old Delfield). So you are reading 80#, but the compressor is seeing 200#.

I know you said can't change the compressor again, but it sounds to me like its time to have a talk with the owner and just explain the bad news... its time to spend money. I'd recommend what 2sac said, a new 1/2HP condensing unit. Clean all that trash out of the system. Make sure you don't have lots of oil-logged components from all the multiple compressor replacements. Make sure you aren't dropping voltage when system trying to start. Replace any controls and wiring needed. Just explain, you have the ability to make it work, but you need a bigger budget. (I know, easier said than done..)

*edit* also side note, I wouldn't jump out the overload, if you do, and compressor doesn't start, the compressor can explode! its ugly when the explode and blow the pins out the compressor be careful. better to just replace the overload. */edit*

[evilsanta]

I'm curious to the make.