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I'd like to know the reasons for & against for installing a running capacitor on a Copeland scroll compressor.
Compressor : ZR34K3E-PFJ
Running capacitor : 50/370 MFD
Supply : 220V, 50Hz, single phase
The compressor is used in a heat-pump application, under terrible power supply conditions, with frequent power outages, brown-outs & so forth.
The system design has been set up to cope with this poor power & protect the heat-pump system, as far possible.
Thank you for your applied wisdom. :)
single phase power in country areas can vary as you say i bump up the standard run cap by about 5mfd on smaller units in refrigeration applications it helps cope with lower voltages than design.what would be the standard cap fitted to your copeland ?
^ Thanks so much for your reply 'lowcool'
I'd assume it means 50Hz, 370 microfarad.Quote:
Running capacitor : 50/370 MFD
manufacturers could try a bit harder me thinky to much english confuses china man.back to the subject i would say the description is 50 mfd at 370 volts,370 mfd is one hell of big run capacitor.if you took whats actually written 50/370 mfd one would have to think thats its a split capacitor ie two capacitors in one,havent seen one of those since moses played full back for jerusalem.
^ These seem to be recommended supply in SE Asia & come as an 'optional extra'.
Some scroll compressors call for the run capacitor as an essential item, whereas the Copeland seems to show it in their Technical documents, but say almost nothing about it.
I've seen some machines without them, but it has been recommended for this region, by the compressor supplier. My one heat-pump has it installed.
Measured the voltage today at an almost steady 202V, on a supposed 220V system. Awful stuff we have to cope with.
Capacitors don't know nothing about scrolls......;)
Single fase compressor has a start winding and without the capacitor it will not run .
50/370 means that its 50mf and 370 is volt.
capacitor should be connected between the R and s
Thanks very much for your input 'chemi-cool'.
First visit here... Were you talking about wanting to add a start capacitor to a scroll which is generally not favored or actually beefing up the original specs?
^ Many thanks Guvner.
More of wanting to know the following:
1. Reason for having a run capacitor in the first place;
2. Effect, or usefulness, of beefing up the recommended capacitor;
3. Why does the scroll compressor not come with a run cap supplied, but treat it as an optional extra, if it's a critical component?
I'm coming at this as an OEM designer, not from a maintenance perspective.
Perhaps you could also elaborate on your statement:
Quote:
to add a start capacitor to a scroll which is generally not favored
Hello DesA.
Chemi-cool put it quite right - it is impossible to use a 1phase asynchronous motor without the run cap. It provides another - "split" phase for rotor turning. Some applications demand additional capacitance for starting the engine - in such case a currant relay is being used. I do not know whether your compressor's motor demands one.
Compressors are often sold without cap-s, but this does not mean they are dispensible. They are not - in no case.
Sorry, voltage-drop relay, not currant one are being used in applications where additional phase split is needed at start.
Thanks Yuri.
Can you perhaps explain more about the idea of 'additional phase split' - what is it & how does it influence the operation of the scroll compressor?
How would larger, or lesser capacitance value affect the 'phase split'?
Here I found some "smart starter".
http://www.emersonclimate.eu/Literat...ESC__35055.pdf
You may chose it if you do not want voltage droppings at starts and also, prolonged lifetime of the motor may be achieved. In it is incorporated a starting cap 200...240 mF, as you see from the technical data On the wiring diagram is seen a run capacitor. Only what is its capacity - I cannot find. I guess the numbers 50/370 you have are from a plate on a Copeland at your hands already. Then the question is install or not to a START cap. But without the RUN one you simply cannot do away.
Start cap gives greater phase(s) split at start, more flux in the poles, more torque. One or two seconds after the start it should be off, otherwise nothing good neither to the motor nor the cap itself.
Most probably, it would be wiser to use just that "starter" to eliminate risks.
Both cap-s are connected between R and S - at start there are (if start one is used) 2 cap-s in parallel.
Thanks Yuri.Quote:
Originally Posted by Yuri B.
The 50/370 is the run cap listed by the Copeland compressor supplier, as the suggested cap to be used with the ZR34K3E-PFJ scroll compressor.
This is a new application development & I'm challenging each & every design decision at this stage, until I have definitive answers, rather the than the typical 'its always been done this way' approach.
Copeland Technical Information Ref: C7.10.1/1202-0308/E Date : 03-08 - "Single phase scroll start assist components" - has also been rather useful.
Another useful reference is : http://www.tpub.com/content/neets/14...s/14177_97.htm
DesA, the referenced doc has only confirmed: you cannot do without the RUn cap (and for your comp model it should be 50mF 475V). But whether use or not use the START cap depends on the application (on the torque), its use is not obligatory in all applications, while RUN's use IS in ALL.
Best regards.
You seems to be confusing start capacitor with run capacitor.
^^ Thanks Yuri... you are 100% correct, you know - well spotted. It is indeed recommended to use 50 muFD / 475V. I will have to investigate this further with Copeland.
The supplier catalog has ZR34K3-PFJ listed with run(mfd) cap as 50/370 under R-22.
Some thoughts:
1. I wonder if there is a difference for R-134a refrigerant?
2. I'm using a 220V ZR34K3E-PFJ version, not 110V, or 200V. I wonder if there are differences between the different supply voltages, in terms of run cap.
Very interesting - I'm glad this came through now, rather than later. Excellent!!! I owe you a refreshment, or 12. :)
Thus, the best solution on my view, considering the conditions you described, would be the Alco smart starter. So, the run cap 50mF 475V + Alco (the start cap is incorporated in it).
^ My fabricator & I have been debating the issue of whether a smart-starter is required. We initially had some language confusion over the terms 'run cap' & 'start cap', but this has been ironed out - much thanks to this thread. That's why I wanted to make sure I wasn't missing something fundamental.
We have built in voltage protection (under/over) & a timer. Based on this, my fabricator kicked back against the smart starter. So the main technical issue remaining would then be whether the 'start cap' effect would have been beneficial, or not.
I'm going to have to get him to check with the Copeland factory & confirm the single 'run cap' size requirements.
Thank you DesA, but it is nothing especial on my part.
I too have only seen 50Hz 220 phase, 380 line voltages. (apart from 50Hz 12V...10kV). Yes, one should be so careful and precise and catious in making el components orders from catalogues.
Thanks so much everyone, for your input. This thread has been very, very helpful.
desA,
I think you are looking for reasons to use a start capacitor. You could use the following tips for start-up:
1) Use start cap & relay always with TXV. The system pressures will not equalise before compressor starts
2) The compressor will operate down to 90% of rated voltage. If your supply voltage is around that range or a shade below that, go for start cap.
3) In cap tbe system, if for some reason, the compressor is required to start before system pressure equalisation, you will need a start cap.
Lot of information on products specs (incl. different voltage ranges) and application manuals are available on OPI section of www.emersonclimate.com. You can register yourself and do a bit of searching to locate the information you are looking for. Good luck!