[RE-wrenches] Head scratcher

Vince McClellan vince at solarenergydesign.com
Tue Oct 18 16:08:36 PDT 2022

Hi Kris
I've successfully used a double pole double throw relay to handle this
issue with a couple of solar power trailers that I've built over the years.
You will need to bridge the inverter side of the transfer switch so that
the 120V single-phase inverter powers both the L-1 and L-2 buses of your
tiny home's electrical panel. Also if you use a relay or contactor make
sure that it is rated for the amperage that you need at *continuous use*,
or make sure that it is rated for way more amperage than you need. There
are a whole series of electrical contactors and relays that will say they
are rated at a much larger amperage than they can continuously handle.

Your transfer switch idea may even work better if you have the physical
space for it.

Vince McClellan

Energy Design

NABCEP PV Installation Professional

p. (541) 485-8122  f. (541) 338-8202

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On Tue, Oct 18, 2022 at 10:30 AM Kristopher Schmid via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Hi All,
> I am hoping that someone on the list can help me think this one through.
> I have a client that builds tiny portable homes.  He is working on one
> where his client supplied the solar modules, charge controller, batteries,
> inverter, etc.  They bought them through some dot com.  The tiny home has a
> 240 volt mini split that they want to use when plugged into the grid.  The
> inverter that they bought is a 120 volt.  The inverter is not grid tied,
> but does have a 120 volt grid input for battery charging / pass thru.
> So, my issue is, how can I make this work?  I am thinking of using a 50
> amp automatic transfer switch like a Surge-Guard-40100 and connecting the
> solar inverter as primary and grid as backup but am not sure if that unit
> will disconnect the grid with only one leg energized.   Physical space for
> components is very limited
> If anyone has some ideas here, I would sure appreciate it.
> (other than "just walk away" or buy a 240 volt inverter)
> Thanks,
> Kris
> Shine On!
> Kris Schmid
> Legacy Solar, LLC
> 137 West 1st Avenue
> Luck, WI 54853
> www.legacysolar.com
> 715-653-4295
> NABCEP Certified PV Installation Professional
> Licensed Wisconsin Master Electrician
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