[RE-wrenches] offgrid system question

Peter Parrish peter.parrish at calsolareng.com
Fri Aug 22 15:11:07 PDT 2008


Darryl, see my post yesterday (I think). If you have the tonnage and the
SEER/EER you know the operating current, period. 

As for start up transient, I think we need to get help from someone who has
actually measured the transient (I think I saw a post about that a couple of
days ago?). And, when comparing the surge current with an inverter capacity,
make sure you get the compliance voltage. An inverter that is rated at 25 A
steady state, but claims to provide 40A for 4 sec, will do you no good if
the voltage drops to 150 VAC while providing the 40A!  

- Peter

Peter T. Parrish
peter.parrish at calsolareng.com 


-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Darryl
Thayer
Sent: Friday, August 22, 2008 2:30 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] offgrid system question

I use for a short cut 1 AC ton is 1 HP mechanical or 1kW electrical.

So If I have a 3 ton heat pump I figure the compressor is about a 1 horse
power motor and about 1 kW running load.  If that is 240 volts that is about
4 0r 5 amps. Because I have had some starting problems, I say that the
running amps times 10 are the start amps, so this unit should have inverter
capable of starting 40 amps Surge.    If the SEER is higher than 12 it will
start comiing down, but I do not know for inverter sizing  

If you are doing and energy anaylsis you would want better numbers from your
AC manufacturer. 

The 9000 watts for 2.5 tons is to high.  
Darryl

--- On Fri, 8/22/08, jay peltz <jay at asis.com> wrote:

> From: jay peltz <jay at asis.com>
> Subject: Re: [RE-wrenches] offgrid system question
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Friday, August 22, 2008, 9:23 AM
> Can someone tell me how to convert AC "tons" to
> rough electrical load?
> or is there a way?
> 
> I've got a customer who is wanting to install a AC unit
> and they tell  
> me its a 2.5 ton and uses 9000 watts.
> ( they haven't given me make or model yet)
> 
> thanks,
> jay
> 
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