New compressor over heat??

[segjag]

Replaced blown 1/4hp compressor and filter dryer on a holding plate.. cap tube system ...evacuated overnight... am trying to vapor charge on the low side pressures keep on rising 45psi low side 65psi high side and compressor heats and cycles off .......What am i doing wrong or should i keep trying to get enough gas in to cool the compressor didnt seem like the pressure difference was correct...

[expat]

Being as it's a cap tube the system will need a precise charge. Didn't you you see any stickers on the equipment stating the charge?

You haven't given much information but I would suggest you check the amp draw of your comp against the spec on the comp plate.

Remember that putting more gas in will raise both the LP and the HP simultaneously.

[segjag]

This is a home built system in an alaskan truck motorhome. The system was built/designed so that freezer only ran once a day to refreeze the plates with a genset. Compressor finally failed so i put in a match but no weight of refrigerant is possible. I notice the compressor will draw to -30 psi on startup but if i add gas there never seems to be a pressure differential of greater than 30 psi. It will run 60hi/40lo psi and the compressor gets hot so i shut it down. It sounds ok and doesnt whack the genset like its drawing too many amps on startup (as the other one did prior to its failure). Should i get a greater pressure differential ? and thankyou for you time and help <s>

[expat]

What are the details (numbers) on the name plate of the compressor?

What is the refrigerant, and how much have you put in?

How long did the old compressor last?

[tonyelian]

hi segjag
it seems that u have a bad compressor i suggest a compression test i guess it has bad valves check ur cap-tube if it is blocked it can damage the compressor

[Electrocoolman]

When you replaced the compressor did you fit new electrical components at the same time - overload, relay (and capacitor)?

[segjag]

Compressor says Americold P/N 2859... Old one was a tecumseh 1/4 low temp r12 high start torque. I went to low start capacitor because i thought the low would be easier on the genset. The old compressor was used when i got it and lasted 20 yrs and we live in this truck 6mo /yr. I manually run it about 3-4 hrs a day ..so lasted real well I think. I went to r134a evacuated and had some leaks (didnt know the silver solder trick) re-evacuated and my plan was to put in vapor on the low side until the dig temp on the suction tube started to drop ...but no cooling at all the compressor would go -20 psi//40psi on the discharge side with no drop in temp ...so i added more until the low side pressure came up to +10 no cooling after a long time (2hrs+) so then added untill the high side was 75-80psi and the low side was 40-50 psi (had to warm the can) compressor started jumping up and down and cycled off so un plugged it and let some gas out ...runs smooth until low side pressure gets back up towards 40psi or so then starts vibrating like its flooding anyway no cooling at all. Started over again this am (purged, evacuated ran for an hour this am added gas untill the suction pressure started to rise to 0 hi side was 50 psi no cooling compressor just kept grtting warmer and warmer, sounded and felt smooth after a 2-3 hours got too hot to keep hand on for long (ambient temp in the 50's so shut it off. This am before start up i hooked the gas r134 container to the highside after i let the pressure out and put the valve open and checked the shaeder on the low side gas came thru not in big way but the system was open unless it came back thru the compressor .. The new compressor came with all the electrical components and it runs vibration free untill the low side pressure get up to the 40+ range the it bounces terrible and i have shut it down. Really appreciate you guys your interest and help, And thank you <s>

[nike123]

When you change compressor from original to replacement you need to fit compressor with same displacement and same motor power.
Second, when you change from one refrigerant to another you need to adjust capillary tube length. For R134A it should be longer.
Did you done that?
What is "genset"?

[Electrocoolman]

Hi Nike,
Genset = Generator Set i.e. electrical generator driven by petrol or diesel engine

ECM

[nike123]

Hi Nike,
Genset = Generator Set i.e. electrical generator driven by petrol or diesel engine

ECM

Thanks! .....

[jsimon]

how is the heat rejected ?
is there a fan is it working is the coil clean ... blow it through any way

[FEISTY]

If R12 compressor had mineral oil and now 134 being used, where did the POE il changeout occur ? Cap tube most likely not correct ID along with wrong length. Sounds like still missing information.

[damis]

both presures are too hi for R12 and R134A. the lo press difference is cause by the cappilary is short or to big the diameter.

[Gary]

Remove refrigerant until the low side pressure is about 0-5 psi, then leave it alone for a day or so.

Let us know what the pressures are then.

[Gary]

... my plan was to put in vapor on the low side until the dig temp on the suction tube started to drop ...

Bad plan. The suction line temp isn't going to drop until the plate is frozen... and that will take a very long time.