Polyscience chiller repair - Page 1
Forum section: electronics / repair

author: Alex
author_rank: Regular Contributor
timestamp: July 18, 2018, 03:14:06 pm
content: So I rescued a Polyscience chiller from the skip, it is current model and in very good condition. This onehere.The unit powers on and all electronics seem to be functional. The water pump also works. However, the unit would not chill the water so I opened it up, finding that a connector that powers the compressor and condenser coil fan had been disconnected. I connected that and the unit tripped the RCD. Obviously someone was in there before but gave up.Long story short, I have drilled down to the compressor motor and measured the resistances across the windings and earth. I am measuring 0.2 Ohms between one pin and earth as seenhere.Is this a definite sign that the compressor is dead and the source of this fault?Thanks,Alex

author: Cyberdragon
author_rank: Super Contributor
timestamp: July 19, 2018, 12:06:16 am
content: Shouldn't that just be a single phase 220V motor? In that case you should see low resistance between the other two connections, the low resistance to ground probably is another ground connection. The two 1.2K readings are weird though, the windings should be relatively open to ground.

author: amyk
author_rank: Super Contributor
timestamp: July 19, 2018, 02:04:52 am
content: Compressor is dead and has probably burnt out which means a repair will involve replacing the filter-dryer and recharging with fresh refrigerant.It should not be shorted to ground, one pin is common and the other two are the start and run windings. Here's an example:http://files.danfoss.com/TechnicalInfo/Dila/06/compressors_r134a_r404a_115v_60hz_02-2007_pb400d422.pdfHere is how to identify the terminals:http://www.furnaceman.com/techtips/c-s-r.htmEdit: after seeing the price a new one goes for, even with a new compressor might be worth fixing it. This isn't a consumer throwaway unit... what's the model of the compressor itself?

author: Cyberdragon
author_rank: Super Contributor
timestamp: July 19, 2018, 02:26:25 am
content: Ah, so it's a non-internal start motor.Then it got stuck in "start" and burned the insulation off the start winding. I would expect it to trip out if it failed to start though (unless it did and someone tried to force it, IE keep trying to start it).

author: Alex
author_rank: Regular Contributor
timestamp: July 19, 2018, 09:53:09 am
content: Thanks a lot guys, it sounds like I am in for a pricey repair. Worthwhile though given the cooling capacity of the unit.The internals can be seenhereThe system uses what seems to be a non-standard version of the Embraco Aspera UNE6187Z condenser system, nameplatehere.The compressor itself is Embraco Aspera model NE6187Z, nameplatehere.There are worrying signs that the technicians that discarded this system removed something from the refrigeration system. There are signs of a pipe cutter.If you look atthis picturethere are two unterminated copper pipes. I also found a small terminated piece loose inside the unit. My knowledge of refrigeration systems is very limited, however I believe the one higher is the 'process line' of the compressor and the one lower is the return from the condenser coil which should normally carry liquid refrigerant? I am almost certain this is now an empty system, normally it uses R134a.Replacing the compressor and filter/dryer (grey cylinder in-line) is one thing - my worry is they might have removed something critical?Alex

author: amyk
author_rank: Super Contributor
timestamp: July 19, 2018, 12:04:43 pm
content: Yes, that looks like they recovered the refrigerant before throwing it out.As for whether there's anything missing: follow the loop. Is there a compressor, condenser, capillary tube/expansion valve, and evaporator present? If so, probably not.It looks like you can still buy the compressor alone but any with the same specs should work just as well.R134a is not environmentally restricted yet (you can still buy duster cans with it...) so new refrigerant won't be much of a problem.It's not hard for someone with a gauge set and vacuum pump to fix this, but definitely not an electrics-only problem.

author: Alex
author_rank: Regular Contributor
timestamp: July 19, 2018, 12:49:47 pm
content: We have: compressor > condenser > filter > PWM controlled automatic expansion valve (i think) > evaporator > compressor.There are two open ports: 1) process line of compressor 2) between the discharge and condenser coil (tee). So the loop seems to be complete.My worry was that a Receiver was missing as I can see that in the commercial condenser unit (the vertical black cylinder). If there was one, it would be in-line between the condenser and filter (I think)?I can get a compressor for ~USD 150 and the same filter for ~USD 20. No idea if these are good prices. I have a highly overspec'ed vacuum pump (Agilent IDP-3) but no other relevant tools whatsoever. No oxy torch, manifold, valves, pipe cutter, flaring tool, refrigerant...The lower pipes have compressor lubrication oil in them (looks clear) and we know the compressor burnt out. In this case Embraco's videos suggest flushing all lines with solvent and nitrogen, which is ideally used when brazing the pipes too.It feels like this is a significant investment in tools and I wonder if it is better to hire a refrigeration technician instead? What sort of cost are we looking at in this case, 200$?Alex

author: Alex
author_rank: Regular Contributor
timestamp: July 19, 2018, 08:45:26 pm
content: Quote from: amyk on July 19, 2018, 12:04:43 pmIt looks like it is restricted and a listed 'F-gas'. From my reading a licence is needed to purchase any quantity of R134a.It seems that the cheaper canisters on the usual sites are a 'replacement' or 'equivalent' type. They are not R134a.All of the above is for the EU.Back to the usual websites and looking at the US, cans with the actual stuff will not ship to California nor to the EU.Oopsie.Alex

author: PaulAm
author_rank: Frequent Contributor
timestamp: July 20, 2018, 01:12:49 am
content: You may be stuck having to get a refrigeration tech to charge it. You may be able to do all the plumbing and take it to a shop for a charge to keep costs down. Note that is not soft solder on the joints. HVAC is typically either brazed or silver soldered (or at least a high % of silver, say > 15%).I had a builtin refrigerator go bad and the cost to replace everything and a day's labor ran to over $1K US. I think about a third of that was labor.In the US you could get a set of refrigeration gauges for $60 and .5Kg cans of R134a for $5. Due to the small size of the system it should be weighed when charging; there should be a tag specifying the charge amount.If it doesn't have one, it will need a service valve on the low side of the compressor. Brazed in ones are better, but you can get piecing valves that clamp over the tube and seal.