[RE-wrenches] offgrid system question

[Peter Parrish]

My point continues to be, the facts. If you have a good understanding, how
about sharing it with us all so that collectively we can sit clients down
and show them the consequences of what they are asking for, wean them away
from the nutty, and perhaps lock onto a reasonable compromise. Time of use
is important but if they can't kick off the motor in question, then it's a
moot issue, right? I guess that my first instinct is to educate, and I
usually find that there is a subtle but important difference between
"telling a client they're wrong" and "helping them discover the right
answer". 

 

Peter T. Parrish, CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com 

  _____  

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Jeff Yago
Sent: Wednesday, August 20, 2008 7:50 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] offgrid system question

 

 

As the two of you stride away from this issue with self-congratulatory back
slaps and dismissive comments about nutty clients, you might also find time
to arm yourself with a modicum of facts about current surges in motors and
surge response of inverters. - 

Peter Parrish 

 - - - - - - - - - - - - - - - - - - - 

Peter, 

As I tried to explain, I am well aware of surge loads from motor driven
equipment, but this is not relavent to this problem.  My point was we had 20
emails trying to resolve ways to make something work by minor tweaking
things when someone should have told this client - this ain't gonna work
with your under-sized system no matter what you do.  I  assure you that
powering a swamp cooler fan is nothing like the power drain from a 3-1/2 ton
air conditioning compressor and 1/2 HP supply fan running 12 hours each day.
I have engineered the air conditioning systems, chillers, pumps, and air
handling units for entire hospitals, research laboratories, university
buildings, and hundreds of homes and I believe I have a good understanding
of the power requirements for a simple split AC unit as well as the effects
of surge loads on the inverter and battery. 

I would rather loose a job that I know is wrong, than have it hang around my
neck from now on.   There are plenty of good solar projects and clients out
there who are willing to pay for a system that is properly sized and
designed.  Sometimes you just have to tell clients they don't have the
budget for what they are trying to do and no amount of tweeking will make an
under-sized  2 kW solar array power a 5 kW compressor load for very long
even if you install 10 inverters to handle the surge load.  

Please excuse me now,  I have to go slap myself on my back. 

Jeff Yago 

Licensed Professional Engineer 

NABCEP Certified 

Licensed Electrician 

Certified Energy Manager 


 

  _____  

Netscape.  Just the Net You Need.

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