Start up.......why cycle on O/L ??

[northern-tech]

Replaced a small 1/4 hp compressor, on beverage cooler. Leak checked, evacuated, charged just enough refrigerant in the lines, to get pressure about 5 psi. Started compressor, and the overload cut out?? What the heck goes on here ?? Did this 2 or 3 times, then finally kicked in. This is what I have done on any change out, and this is the first time it has ever cut out, on OL, especially at such a low pressure. ( also checked voltage on start up, and no problems with voltage drop ). Its a Tecumseh compressor. Is there any chance of getting a dud ??Now, after 3 or 4 months, the amperage is starting to go up, and cycle much too frequently. This particular unit is giving me
many headaches. Any tips would be welcome, THX!

[Andy W]

I presume you mean the klixon overload on the compressor, is the compressor very hot to the touch as they will cut out on heat as well as current. Check the condensers clean and the machine has adequate ventillation all round, remove the gas charge, vacc out and weigh a fresh charge of gas in the system, also prior to changing the comp do you as a matter of routine cut the filter drier out and blow the system through with nitrogen to prove there are no restrictions.

What I have come across in the past is when someone replaces a filter drier they clog it up with solder so when they charge it with gas it is in a vaccum so they keep banging gas in until it is so full it cycles on overload, you can usually tell that something is wrong as the compressor changes tone.

[Abe]

Replaced a small 1/4 hp compressor, on beverage cooler. Leak checked, evacuated, charged just enough refrigerant in the lines, to get pressure about 5 psi. Started compressor, and the overload cut out?? What the heck goes on here ?? Did this 2 or 3 times, then finally kicked in. This is what I have done on any change out, and this is the first time it has ever cut out, on OL, especially at such a low pressure. ( also checked voltage on start up, and no problems with voltage drop ). Its a Tecumseh compressor. Is there any chance of getting a dud ??Now, after 3 or 4 months, the amperage is starting to go up, and cycle much too frequently. This particular unit is giving me
many headaches. Any tips would be welcome, THX!

There is a possibility there is a problem with the compressor It has happened to me in the past.

Before you return the compressor though, you need to ensure that the lines are clear, and clean. No blockages and the gilter is fine, condenser clear, fans working and plenty of air.

Providing all this good, check the compressor on bench, see if it cuts out. Usually under no load conditions compressors work fine, it could just be an overload, I had one erratic overload on a tecumseh.

Replaced it and compressor has been fine last three years

[Andy]

Replaced a small 1/4 hp compressor, on beverage cooler. Leak checked, evacuated, charged just enough refrigerant in the lines, to get pressure about 5 psi. Started compressor, and the overload cut out?? What the heck goes on here ?? Did this 2 or 3 times, then finally kicked in. This is what I have done on any change out, and this is the first time it has ever cut out, on OL, especially at such a low pressure. ( also checked voltage on start up, and no problems with voltage drop ). Its a Tecumseh compressor. Is there any chance of getting a dud ??Now, after 3 or 4 months, the amperage is starting to go up, and cycle much too frequently. This particular unit is giving me
many headaches. Any tips would be welcome, THX!

Hi Northern Tech

If it was me I would check the head pressure. Either decant and fit a shreider valve or a line tap (line tap would need replaced not left on the discharge as it would leak after a while).

Could be a partially blocked capillary.

Kind Regards Andy

[northern-tech]

Condenser fan is fine, and condenser is clean. However, clearance around the compressor may be an issue. Its under the counter, and blocked in on 3 sides. Its been this way since day one, which has been quite some time. In order the check if the cap is partially blocked, is there a an approximate time, that when the compressor shuts off, how long should it take for the high and low side to equalize ?? Now, if it was partially blocked, would this not just make the evaporator colder, due to the increased pressure drop.....or am I off track here ?? thanks!

[Andy]

Now, if it was partially blocked, would this not just make the evaporator colder, due to the increased pressure drop.....or am I off track here ?? thanks!

Yes but without a head gauge the unit would have been charged to a given back pressure, so the head would be quite a lot higher to compensate and so would the charge. (unless the charge was weighed in)
On the equalisation, impossible to judge.

Me I would fit a head gauge

Kind Regards Andy

[The MG Pony]

I'm with Andy, with out knowing the head and low side you are going in half blind and with yer arm tide up.

Knowing that you can get to a conclusion faster and much more accurately.

[northern-tech]

Handy man for restaurant, was supposed to install a small fan underneath, to help disipate the heat. There are also service valves on this unit, so will check head pressure, and see what goes on. Did check it before, but can't remember what it was at the time.