Powering House with Portable Generator and PV System

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mkgrady

Senior Member
Location
Massachusetts
When powering a home with a portable generator utilizing an inlet, generator breaker in the main panel and a mechanical interlock to prevent a back feed to the utility, is there anything that must be done when there is also a PV system in place?

I don't know much about PV systems but this one has roof panels, an inverter, a seperate meter and disconnect at the meter and some kind of controller near the main panel in the basement.

I'm thinking as long as the interlock prevents the generator from back feeding the utility it should not be an issue. And if that is the case, if the generator is feeding the home and the sun is shining will the solar synch up with the generator and just keep feeding the house? That seems unlikely but I really don't know. I'm guessing the solar system should just be shut down when the generator is running and wonder if it would be damaged if it were not shut down.
 
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GoldDigger

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Location
Placerville, CA, USA
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If the generator and grid tied PV are both installed, the PV must be connected only to the POCO side of the transfer switch.
Or a much more complex (expensive) PV system called a hybrid system and including batteries and generator support programming could be used.
 
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mkgrady

Senior Member
Location
Massachusetts
Thanks for the responses. I will not be using a generator interlock now. I assume I could use an interlock that would lock out both the mcb and the PV breaker in the main panel but I'm pretty sure there is no product that will do that easily.

I assume I could use one of those transfer panels where individual branch circuits (not the whole panel board) are fed thru and the panel is fed by a portable generator. Reliance makes one for a few circuits. I usually avoid these because of the limited amount of circuits they power.
 
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mkgrady

Senior Member
Location
Massachusetts
69gp said:
if you want to be able to use the PV system during a power failure you can check the link below. Sure you will only get power when the sun is out but you could run a refrigerator or some other small equipment.


http://www.sma-america.com/products...l-us-7000tl-us-7700tl-us.html#Overview-137449


steve
Click to expand...
The house already has a solar system tied into his panel. I'm trying to install something that will power his essential loads when the poco is down and the sun is not shining.
 
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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Consulting Electrical Engineer - Photovoltaic Systems
mkgrady said:
The house already has a solar system tied into his panel. I'm trying to install something that will power his essential loads when the poco is down and the sun is not shining.
Click to expand...
In general you do not want the PV inverter and the generator live to the protected loads panel at the same time. While it is possible under some conditions and with the right hardware to operate the PV system when the grid is down using a generator as the "grid", it is expensive and generally not worth it if the grid is usually there. Put a transfer switch between the PL panel and the main panel and interconnect the PV system to the main panel.
 
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GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
mkgrady said:
The house already has a solar system tied into his panel. I'm trying to install something that will power his essential loads when the poco is down and the sun is not shining.
Click to expand...
As long as he does not expect to have his existing (GTI) PV "help out" the generator during the day, there should be no problem using an essential loads panel with transfer switch.
Just do not land the PV backfeed in that panel!
If he wants to be able to use his PV when the sun is shining but no POCO he will have to redesign his PV system either using the SBs mentioned, a Sunny Boy / Sunny Island combo or a limited set of Xantrex or Outback models.
All but the first will also require a battery bank, but will allow the generator to be used to recharge the batteries (a DC coupled system).
 
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