Graham Harrison
02-08-2011, 09:14 PM
:confused:Has anybody any knowledge of refrigerant polarization? I haven't and I've been repairing and servicing large chillers for over 40 years so any help would be great.
I am informed by a normally reliable expert business associate on soft start and power factor correction that he has had experience of several centrifugal chillers consistently blowing pcb's
He initially considered over enthusiastic electricians carrying out insulation testing with a 1000V megger and also spin down generation after the starters have dropped out.
He eventually installed monitoring equipment and recorded very high static voltages at the compressor terminals (3-5,000Volts) up to an hour after the compressor has stopped!
On discussion with the manufacturer they mentioned 'refrigerant polarization' and had seen the phenomenon previously and apparently an academic study has been carried out and is available on the web.
He would not be drawn on which manufacturers equipment it was!
Unfortunately all I get from Google is some 'refrigerant polarization oil additive' which is claimed to improve performance.
I am intrigued as to how a static charge builds after stopping or during operation and then accumulates at the winding as I thought refrigerant was an insulator and the compressor casing and all pipes and heat exchangers are grounded; there also must be tens of thousands of installations where this cannot be a problem or there would be wide knowledge of it and lots of very surprised service technicians!
The problem was apparently solved by installing resistors across the winding terminals as with Power Factor Correction capacitors but how does it happen in the first place?
Can refrigerant become statically charged?
Any explanations much appreciated - You can never stop learning!
I am informed by a normally reliable expert business associate on soft start and power factor correction that he has had experience of several centrifugal chillers consistently blowing pcb's
He initially considered over enthusiastic electricians carrying out insulation testing with a 1000V megger and also spin down generation after the starters have dropped out.
He eventually installed monitoring equipment and recorded very high static voltages at the compressor terminals (3-5,000Volts) up to an hour after the compressor has stopped!
On discussion with the manufacturer they mentioned 'refrigerant polarization' and had seen the phenomenon previously and apparently an academic study has been carried out and is available on the web.
He would not be drawn on which manufacturers equipment it was!
Unfortunately all I get from Google is some 'refrigerant polarization oil additive' which is claimed to improve performance.
I am intrigued as to how a static charge builds after stopping or during operation and then accumulates at the winding as I thought refrigerant was an insulator and the compressor casing and all pipes and heat exchangers are grounded; there also must be tens of thousands of installations where this cannot be a problem or there would be wide knowledge of it and lots of very surprised service technicians!
The problem was apparently solved by installing resistors across the winding terminals as with Power Factor Correction capacitors but how does it happen in the first place?
Can refrigerant become statically charged?
Any explanations much appreciated - You can never stop learning!