contactor cuestions [RE-wrenches]

[Marco]

Commercial grid-connected systems using the Xantrex PV series 3-phase
inverters with their dedicated isolation transformers mean that there's
going to be a not insignificant parasitic power loss during the nighttime
hours.  According to my own measurements and conversations with others, this
loss can somewhere between 3-5 percent, or even more, of the previous day's
kWh production.  One way around these inverter and transformer core losses
would be to install a three-pole contactor/relay that would disconnect the
PV equipment in the evening and reconnect it early the following morning.
The issues as I see them are: 1) extra cost for the labor, contactor and
additional control electronics, and 2) additional means of system failure in
case the contactor stays open.  One could use a photosensor to control the
contactor or even a standard mechanical or digital timer.  

Has anyone out there gone this route of using a contactor?  Any feedback on
the pros and cons?

thanks,
marco 

Marco Mangelsdorf
President
ProVision Technologies, Inc.
69 Railroad Avenue, Suite A-7
Hilo, Hawaii 96720 USA
(808) 969-3281, fax 934-7462
www.provisiontechnologies.com



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