[RE-wrenches] offgrid system question

[Peter Parrish]

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. A 3.5 ton A/C may be excessive, but is a 3/4
ton A/C, too? What about a swamp cooler, a whole house fan or a 1 hp water
pump? Each client (in my book) deserves well reasoned guidance based on
facts (regardless of how clients we need to provide it to).

 

BTW, I agree 100% that we need to preach energy efficiency and heating with
gas vs. electricity.

 

- Peter Parrish

 

Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com 

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From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Tom Elliot
Sent: Wednesday, August 20, 2008 2:57 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] offgrid system question

 

Thank you Jeff, for asking the obvious.  I've been agog that no one seemed
to think this was a nutty situation for an off-grid home.

 

T.

 

 

----- Original Message ----- 

From: Jeff Yago <mailto:jryago at netscape.com>  

To: RE-wrenches <mailto:re-wrenches at lists.re-wrenches.org>  

Sent: Wednesday, August 20, 2008 10:57 AM

Subject: Re: [RE-wrenches] offgrid system question

 

I may be out of line here, but most of these comments have been related to
making the right program settings and startup surge current issues.  I did
not read any comments that this client is nuts to try and run a 3.5 ton air
conditioner from a solar off-grid system, let alone a system with such a
very small capacity.  

 

I would be surprised if this small existing solar array and batteries can
keep up with the regular loads like lights, kitchen appliances,
refrigerators, and entertainment equipment, let alone also running a central
air conditioner.  .   

 

I would not  just debate the problems of surge current, I would like to know
how this little solar system is going to keep up with the constant load of
approx. 4,000 watts for the AC unit plus another 500 watts for the air
handling unit which he did not mention.  With a constant drain of 4,500
watts, just how long do you think this battery bank will last?   For most
locations, during peak summer days a typical AC unit needs to run constantly
12 to 16 hours per day.   

 

I would be interested in hearing from others on this, but here in the humid
and hot east it is not possible to provide air conditioning for an off-grid
home unless we are just cooling one or two rooms with a low energy Sanyo
type split system in the 1/2 to 3/4 ton range.  Of course if you have enough
solar modules and batteries you could run anything, but can you afford it?

 

We do lots of off-grid systems and the first thing we tell clients is to not
even think about having air conditioning, electric hot water heaters, or
electric clothes dryers unless they have a really big bag of money.

 

Jeff Yago


 


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