[RE-wrenches] Generator choice for Sunny Island

Thu Jun 15 16:54:57 PDT 2017

August,

I don’t have a specific recommendation on a generator, but I do want to
make a few points considering your setup.

Since you only have one Sunny Island, you can only use a 120 VAC input. So
you will need a generator that either only has 120V output, or can be
re-configured for full output at 120V.

Some generators have a switch marked “120/240 VAC” on one side and “120 VAC
only” on the other, which will work if you switch it to the 120V only side.
Some generators just have a “full-output 120V” twist-lock plug on them, and
that will work too. Some hard-wired generators allow you to rewire them to
get full output at 120V.

However, if the generator is a 120/240 unit, and has no provision to full
output at 120V, you will need a second transformer to step the 240V down to
120V.

If you connect the SI up to just one leg of a 240V generator, you will only
get half of the generator’s rated power, and you will greatly unbalance the
genny, since you will only be pulling power from one leg. This is hard on
the generator’s bearings and will shorten its life (the bearing on the end
of the alternator’s rotor seems to get the biggest beating). You might also
get erratic AC voltages on the output. I don’t recommend it.

Another thing with “portable” generators is that if they have normal
receptacles on them, there may be an internal bond between ground and
neutral. This can be a problem. It’s been years since I have installed any
generators, but I tried a number of times in the past to separate the
bonding only to then have lost function of the remote start capability. If
this is the case, the only solution that I found was to not run the ground
wire from the genny to the inverter (it would only end up being a parallel
neutral if I did, since there is a bond at the power system where it should
be). Not exactly to Code, but safer.

I did recently read through a manual on a new Honda unit (7 kW I think),
and it specifically said that the neutral and ground were not internally
bonded. Great for connecting to an inverter system with its own bonding.
Check the manual, or do a continuity test, on whatever generator you end up
choosing.

Brian Teitelbaum

AEE Solar

*From:* RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On
Behalf Of *August Goers
*Sent:* Thursday, June 15, 2017 2:33 PM
*To:* RE-wrenches
*Subject:* Re: [RE-wrenches] Generator choice for Sunny Island

Good question – I was assuming a regular gasoline genny mostly because the
container will be moved from time to time. Whatever type of fuel, it
definitely has to be portable.

August

*From:* RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On
Behalf Of *Chris Mason
*Sent:* Thursday, June 15, 2017 12:03 PM
*To:* RE-wrenches <re-wrenches at lists.re-wrenches.org>
*Subject:* Re: [RE-wrenches] Generator choice for Sunny Island

Sho you want diesel,  propane or natgas?

Nathan is more reliable as it does not require a refuel.

On Jun 15, 2017 12:02, "August Goers" <august at luminalt.com> wrote:

Hi Wrenches, especially those of you who work on off-grid projects,

We have an upcoming off-grid project where we will be powering a storage
container with electronics in it. The loads are mostly 120 volt but there
is a 240 volt heat pump that might occasionally run. We’re AC coupling the
Sunny Island with a Sunny Boy PV inverter. So, we’ll be installing a
Outback PSX-240 autoformer to bump the Sunny Island’s output from 120 to
240 volt.

We need to select a generator for backup. We need a two-wire electric start
(in order to be controlled by the Sunny Island) and preferably a generator
that is okay just running 120 volt loads since the Sunny Islands input is
only 120 volt. Something in the 3 kVA -7 kVA range should be fine.

Does anyone have experience or ideas about what kind of two-wire start
generator we might select?

Thanks,

August

Luminalt

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