Compressor faulty?

[monkey spanners]

Had a call to a counter with a 1/3hp danfoss r12 comp, walked in to hear that familiar 'hummm click'
Checked the start cap at 79uf which was ok, checked the windings which all added up ok.

I carry potential relays for bigger stuff, anything from 1hp up to 5hp but nothing for these little current relay compressors.

I would normally try a new set of electrics before condeming a compressor but in this case i settled for putting the amp meter on the live feed which showed 16.2A and also the start cap wire which showed 5.3A when it was trying to start, to me this showed the relay was doing its job as if there was no contact no current would flow. Decided comp was seized and advised a new fridge due to the age and condition. I don't supply new ones so its not like i'm trying to make money for myself :)

What do you think of this method of checking for a relay or compressor failure?

I know some friends in the trade who condemn a comp on hearing the hum, without taking any tools out, so am interested to learn whats acepted practice for this size of equipment :D

Cheers Jon

[james10]

I normally would listen for the "hum click" then check how hot the compressor body then the amp clamp and meter would come out if still wasn't sure

[chemi-cool]

When they "Humm" they are gone.
Even if you can make it run for a while, it will be a short run.

Don't waste your time trying to put life into it.
Its dead.

[monkey spanners]

Thanks for the replies James and Chemi, so if you found one humming it would be dirt nap time for the comp :D

[thebigcheese]

if it has a blockage and wont start because of head pressure then it will also hummmm click

[oldesky]

I wouldnt condemn a compressor on a hum. Most manufacturers will tell you of the number of compressors returned as faulty for the sake of a relay/capacitor and many times nothing wrong at all. It was either overcharged flooded on start up etc. Many years ago a co in USA called Annie made a hermetic analyser. It wasnt cheap but was worth the money it saved. Maybe the guys in USA will know if it is still available there as they stopped exporting to Aus many years ago. I still have one of their very early metal case models.
Alternatively get a box and install a press button switch and a range of start and run capacitors on a rotary switch to suit various small hermatics. Or even simpler just a push button switch with common start and run alligator clips. you can add capacitors depending on compressor model. This will save you a lot of time and in combination with meters take out the guess work

[paul_h]

I've got an Annie just for this reason.
Removes the guesswork involved on deciding whether the relay is buggered. But my annie is really old and I got it s/h.

Otherwise what testing was done is about all you can do, ie check windings, capacitor and current, if there's a circuit and the relay + capacitor is good but it's drawing too many amps, then yes, I'd say it was seized.

Annies are good though because you can run the motor in reverse, trying to rock it forwards and backwards.

[Quality]

I've got an Annie just for this reason.
Removes the guesswork involved on deciding whether the relay is buggered. But my annie is really old and I got it s/h.

Otherwise what testing was done is about all you can do, ie check windings, capacitor and current, if there's a circuit and the relay + capacitor is good but it's drawing too many amps, then yes, I'd say it was seized.

Annies are good though because you can run the motor in reverse, trying to rock it forwards and backwards.

I also have an old annie but still works a treat . Ideal folr this kind of fault

[Andy AC]

I use an annie too, but just because you can run the comp through it, doesn't mean the compressor will start with its own starting gear afterwards. Allways worth a go though.

Andy

[monkey spanners]

My dad used to have a box with a couple of toggle switches on, one was power on and the other you flicked to power the start winding, and a socket on the side to plug in a loop for the amp probe, might have a go at making one, will come in usefull for the one or two of these i get a year :D

Cheers Jon :)

[paul_h]

I use an annie too, but just because you can run the comp through it, doesn't mean the compressor will start with its own starting gear afterwards. Allways worth a go though.

Andy
Too right, sometimes you get them running through the annie and they are drawing 30A! But at least running! edit: joking of course, no way is that a working compressor, but fun to see them do something.

Obviously completely stuffed compressor and like I said, just removes all doubt because you are bridging out everything besides the compressor without using new parts (relay, overload, capacitor etc).

Though I have bridged a t/stat or two, left the annie hooked up overnight and went home to sleep when satisfied nothing was wrong with a compressor, just the relay or something like that :D

[Peter_1]

Thanks for the replies James and Chemi, so if you found one humming it would be dirt nap time for the comp :D

Sure, especially when it's an R12:confused:
I do exactly the same as Chemi, they're not expensive enough to try something.

[Peter_1]

My dad used to have a box with a couple of toggle switches on, one was power on and the other you flicked to power the start winding, and a socket on the side to plug in a loop for the amp probe, might have a go at making one, will come in usefull for the one or two of these i get a year :D

Cheers Jon :)
Do a search here on RE for Annie starting device for hermetic compressors, Mark Fiddy posted once the complete schematics for it.

[lowcool]

if you know the locked rotor amps this is a good place to start also.

[graydog]

Can anyone help me? Iv got a copeland scroll and I push the contactor in and the scroll runs so I think it's the controls? Iv changed the klixon but that's not worked, any ideas plz?

[paul_h]

Got a wiring diagram, have you followed the circuit path?
eg thermostat controller sends signal for compressor to run, that has to pass safetys (LP, HP, LOR etc) and of course the contactor coil has to be good.
Could even be the control c/b tripped or fuse has blown due the CC heater
So use a multimeter to find where you are loosing voltage, or give a make and model of the unit and the thermostat type so people have an idea of the control circuit

[graydog]

Same old story I'm in tesco so no diagrams, iv checked the crankcase heater and that's working good and cuts out once I get the scroll running via pushing in the contactor, I will try the hp/Lp switches, this compressor has been alarming out for 59 weeks!!

[graydog]

The make and model of the unit is a linde ag model No 26581/586130 with danfoss controls, and honestly I can't even find the thermostat!!

[monkey spanners]

The make and model of the unit is a linde ag model No 26581/586130 with danfoss controls, and honestly I can't even find the thermostat!!

If you look at the wires to the contactor coil you will have a switched live and a neutral (there is a slight possibility of it being another live if its a 415v coil but its not likely, check the coil voltage rating to see)
Once you have found the switched live (which will eventually come from the thermostat or pressure switch or controller) trace this wire back to see where it goes, when you get to a control with live coming in and nothing coming out, this will be what is stopping the compressor running.
Next you need to find why it is being stopped from running.

[graydog]

Thanks pal, iv done that i started at the A1 on the contactor but its sent me to a different compressor! Iv traced it back but the numbers on the wires and came to comp1 where I'm lookin at fixing comp3?

[monkey spanners]

Is this on a pack? If so check its not off on low oil level, there will be some sort of level sensor/float/solenoid thingy where the oil level sight glass usually is.

I don't work on supermarket stuff so don't know any 'typical' faults for theses systems. It would be a good idea to start a new thread for your problem in the supermarket section.

It might be worth phoning Linde and asking them to fax or email you the wiring diagram, i have no idea how helpful they will be.

[cold.man]

when you checked A1 on comp 3 was that comp running sounds like you have the wrong contactor.
once found contactor for comp you are looking at if this comp is not running you should not have 240 on A1 if you have and comp is not running possibly a neutral down to contactor coil.
saftey switches must make before 240 onto A1 asuming it is a 240v coil on contactor.
sounds like somthing simple just have to work out wiring circuit.

[paul_h]

I got a compressor going with my annie on saturday :)

CF motor seized up, and compressor tripping on OL drawing 15A.
Got the annie out, and rocked it forward and back, and then it was running at proper current.

So the annie don't always work, but I guess it is the reason why a compressor seized determines whether you can successfully resusitate.

Old compressor or a static condenser, annie will just confirm.
Fairly newish compressor that has overheated due to something like CF motor failure, the annie may work.

I've got my old 1980s annie because I service a lot of LUH 2420z condensing units out on bagged ice freezers at delis and work sites.

Now if someone could tell me how to stop the seizing up of the CF motors that come with LUH 2420 or 2440 condensing units, tell me please ;)


edit:
Most of these units are 2-3 years old, and as they are a homebrew design (static 1/2" piping looping around a box made of 100mm coolroom panelling), they probably have a high duty cycling running at -10C.
But so many condenser fan failures I've seen in the 18mths I've been repairing them, never seen such a high failure rate. This time I was lucky, but sometimes I have to replace the compressor.
I can't do much about the design, I don't build them or even service any of them, just get called when they are broken.
So anyone know of a better cf motor that fits the standard LUH unit, maybe a betts ball bearing style instead of the sleeve bearing square little original/EBM-papst/random italian or original style motors?
Nearly all the breakdowns are the sleeve bearing motors failing.

[monkey spanners]

I read somewhere that those plain bearing motors need to be over 200rpm before the lubrication works in the bearing, i guess with units that cycle frequently they go through 0-200rpm and 200-0rpm a lot. I have seen them used on farm milk coolers where they will only turn on and off a couple of times a day and they last for years.

I think you are right, a ball bearing motor would be the way to go, i think a lot of the ec motors have ball bearings.

Jon :)

[robin r33 gtr]

Do a search here on RE for Annie starting device for hermetic compressors, Mark Fiddy posted once the complete schematics for it.



can anyone help find the thread ? I tried to find but had no luck thanks.

[monkey spanners]

can anyone help find the thread ? I tried to find but had no luck thanks.

Have a look here,

http://www.refrigeration-engineer.com/forums/showthread.php?t=2138&highlight=annie

Jon :)

[robin r33 gtr]

Have a look here,

http://www.refrigeration-engineer.com/forums/showthread.php?t=2138&highlight=annie

Jon :)

Thanks for the link. After looking I think I will buy one. Now to find a uk supplier.

[mikeref]

Paul h, what are the chances of having a previously seized compressor to not seize up again? A little too much risk for me.