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Juggernaut_337
27-05-2015, 12:21 AM
Hey guys,

Long time member, first time poster. I'm no expert and always looking to learn more, so take it easy, cool beans? :D

I was the second engineer to look at a display unit very similar to the Danny 120 model by Nisbets, was even called Danny.

Anyways, first engineer to site changed the compressor out, reporting it cutting in and out consistently, I knew it was going to be the Klixon, especially when the new one had the same symptoms.

Condenser was clear
Compressor drawing 15.7 Amps (nominal running should have been around 6 Amps)... Klixon

Unit was probably about 7+years old and had just been moved to it's new location (about 100 meters up the road)
Apparently, not tipped.

Only place to put the gauges on was the service port on the compressor.

Refrigerant R404a

As the budget to fix it wasn't a lot, I had to diagnose and try something to chance a fix.
My one and only experience with this kind of problem was a filter/drier change where the desiccant had become blocked.
I changed the filter/drier, but the problem remained.

I explained to the client it was more than likely a blockage causing the Klixon to go out on over current, and as the budget was small, he had no interest in trying to resurrect it, especially when the cost may have been more than the other 2nd hand fridge (that was working) was waiting to be used.

Never run for more than a few seconds or long enough to give good indication of where the blockage might be (if it was), saying that, the liquid line felt a lot cooler to the hand than it should have... (Oil, tipped from move?)

I kind of wished I had brought it back home and opened it up to find out where the fault was.
Time was not on my side, so, no pics, no actual temperature readings, it was about a week ago, a lot happens in a week.

In your experience, what would you have done next to diagnose or diagnosed it as?

Cheers

mikeref
27-05-2015, 08:24 AM
No mention of pressures so i would forget about possible blockages for now.
Start with power supply to compressor, look for a significant Voltage drop on start up... and test the capacitors, Start and Run.
Edit: Did the compressor turn over or sit there and hum? Start Relay?

Tayters
27-05-2015, 08:24 AM
First move I'd make would be to check starting electrics.
Get yourself a capacitor tester and read up on current and potential relays. Looks complicated but once you understand the theory it's easy and you'll be surprised how many compressors get condemned for a faulty start capacitor.
Keep a stash of second hand ones to get things going.

Cheers,
Andy.

mikeref
27-05-2015, 08:34 AM
First move I'd make would be to check starting electrics.
Get yourself a capacitor tester and read up on current and potential relays. Looks complicated but once you understand the theory it's easy and you'll be surprised how many compressors get condemned for a faulty start capacitor.
Keep a stash of second hand ones to get things going.

Cheers,
Andy.

Well said o'l chap.:D

Juggernaut_337
27-05-2015, 09:35 PM
Hey Mike,
Did the compressor turn over or sit there and hum? Start Relay?
Compressor started no problems, and lasted 20 - 30 seconds when unit was off for an hour or more, but after the first cut out on the klixon, the compressor lasted a second or 2, then cut out for 4 or so seconds, then back in for 2 seconds again etc....
I had 240V to the compressor on the run and 300V on the start.

Hey Andy
Get yourself a capacitor tester and read up on current and potential relays.
Am very much with you on the capacitor failure increasing the current draw from the compressor, I've changed quite a few in the past, but usually easily indicated by intermittent tripping of a dedicated circuit breaker. I also admit, I have probably changed a few compressors in the past without knowing it may have been the capacitor that needed changing.

Sorry guys, should have mentioned, new compressor fitted came with new capacitor and start relay.

mikeref
28-05-2015, 08:18 AM
[QUOTE] Anyways, first engineer to site changed the compressor out, reporting it cutting in and out consistently, I knew it was going to be the Klixon, especially when the new one had the same symptoms.

Same symptoms? Can you expand on this and provide running pressures from the engineer who changed the compressor?

Juggernaut_337
28-05-2015, 09:58 PM
Hey Mike,

Same symptoms was continuous cutting in and out on the klixon due to over current, same deal on the first compressor.
And, I can't expand with the pressures (which really is the key here), I would have had to braze a couple of schrader valves on the system, high and low sides, or a couple of line taps (did not have to hand), but, like I said, the budget on this was low and only the service port on the compressor was available, and the compressor would cut around 4.5 bar. I say around because the pressure was still going down when the over current protection cut the supply.

Sorry again for the vague readings etc, it's a pain, didn't know if anyone had come across similar problems on these small units (0.7kg R404a) and had rectified in some way, or if anyone had come across a system that would cut out on over current due to a blockage in the capillary line etc?

Thanks again

mikeref
29-05-2015, 09:17 AM
OK. So your customer forked out for a dome change and has cut funding to find a relatively simple problem.:(

Might as well call it as it is. Previous tech most likely failed to follow procedure. No pressure readings so that alone limits the ability to determine original fault. (there can be more than one fault that leads to a system shutdown.)
I'd question the refrigerant type and volume after the swap......we might never know.

Regards, Mike.