contactor cuestions [RE-wrenches]

[mlafferty at universalenergies.com]

All:

I gotta keep this short... (Whew!  For a lot of you, I'm sure!)

Marco posed the "contactor to take tare losses off system at night"
question....

Answer:  Yes.  DO NOT USE STANDARD "CONTACTOR".... Install Magnetic
Starter instead.  It's a higher equipment cost, but the contacts won't
arc up nearly as badly under inadvertent "On-Off" cycling.  Photocell
(Intermatic recommended) is acceptable... Timer (with "Astrological
Function") is also acceptable.

Longer diatribe on this issue available if you don't trust me....(Time
permitting, of course... Which it isn't right this second... Ce` la
vie....) 

2 Cents and a Coconut!

Matt Lafferty
Universal Energies Institute
mlafferty at universalenergies.com
(916) 422-9772
(916) 628-7694 Cell
(916) 914-2247 Fax
www.universalenergies.com


-----Original Message-----
From: Marco [mailto:marco at pvthawaii.com] 
Sent: Friday, December 05, 2003 12:05 PM
To: RE-wrenches at topica.com
Cc: douglas at pvthawaii.com
Subject: contactor cuestions [RE-wrenches]



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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