Enphase and a Generator

Fatawan · March 2019

Hello all-- I am an old member who installed my first system back in 2011. I am building a new house and planning my solar install. I already have 36 330W LG panels with integrated Enphase microinverters(bought pre-tariff). These will be installed on a standing seam metal roof. I had the walkthrough with my electrician today, and, to his credit, he said he had no experience integrating solar into his installs.The house will have a whole-house Kohler generator (~20kW). How should the transfer switch and Enphase output be wired to completely lock out the panels during a power outage? I keep reading about connecting on the utility side of the transfer switch on my side of meter, but what exactly does that entail? I'd like to describe the setup exactly to the electrician(or at least feign knowledge when I describe it). He and I drew out the setup but he really didn't have a solution that he could implement. Just to add another variable, I was planning to run the wiring from the roof down conduit to a Midnite Solar combiner box/disconnect switch.

Thanks for your input

BB. · March 2019

The typical method would be to wire the Enphase output "upstream" amd the transfer switch (on the utility side) to the utility side main panel. The downstream side of the transfer switch is connected to a sub panel with all of your "protected loads" you want the genset to run...

Or, you need to create a main panel (directly connected to your meter/utility service)--This is your "unprotected" breaker panel and may have only a few connections (meter power in, Enphase AC in at the "bottom of the panel" (other side of bus away from main breaker), and a "branch circuit" out to your transfer switch.

And wire the output of the transfer switch to a sub-panel which will power all of your protected loads (or will look very much like a main panel if you are powering all of the branch circuits in your home).

Remember that the first "main panel" connected to the meter has to be large enough to manage your 11,880 Watt array's AC output... Roughly:

36 panels * 330 Watts per panel = 11,880 Watts
11,880 Watts / 240 VAC = 49.5 amps of AC current
49.5 Amps of continuous current * 1.25 NEC derating = 61.2 amps

(note: you need to figure out the exact rating of your 36 Enphase units and they will probably be divided among 3x 20 amp branch circuits for 60 amps total or possibly 4--You need to check).

If you have a 200 Amp main panel and 60 amps of solar, then the main panel will need a reduced main breaker (1.2x Main Panel rating to support solar branch circuits):

200 Amp main panel * 1.2 solar 'uprate' = 240 Amp max in panel
240 Amp rating - 60 amp solar = 180 Amp main breaker rating for panel (to utilty meter)

You might want to think about wiring up a generator transfer switch "bypass switch" of some sort. Allows you to bypass the generator auto transfer switch (for service) and bypass to supply utility power directly to your protected load panel.

This can be done with regular breakers and a generator interlock kit:

https://duckduckgo.com/?q=generator+interlock+kit&atb=v122-1__&iax=images&ia=images&iai=http%3A%2F%2Fi.ebayimg.com%2Fimages%2Fi%2F172244594942-0-1%2Fs-l1000.jpg

-Bill

mike95490 · March 2019

Wire the panels to the uitlity side of the generator transfer switch, not the generator side.

Your electrician should know what that means

Fatawan · March 2019

Bill--Thank you for the detailed explanation. I will forward that on to the electrician

Mike--I have told him that, but he was having trouble coming up with exactly how to implement it.

BB. · March 2019

More or less, you will probably end up with two main panels (and the associated expenses)... One connected to the meter (utility power). The second connected to the transfer switch AC output for the balance of your "protected" AC loads... Probably no way around that.

-Bill

garciajj74 · March 2020

Installing a generator myself soon But in my case I have the feed for the solar panels going through an 80 amp contactor so that they shut down at night. The Enphase micro inverters use power at night. In my case close to 4 Amps. So I installed a contactor controlled off a timer so the system shutsdown at night and restarts in the morning. I will run a sensing line from the emergency side of the Transfer switch and use a relay to open the contactor when the generator is running.

BB. · March 2020

Enphase should not use more than a 0.050 Watts (manual link) at night:

https://www.solar-electric.com/lib/wind-sun/IQ7-7plus-7X-Micro-Manual.pdf (manual page 32, 50 mWatt night/tare losses)

4 amps * 240 Volts = 960 Watts...

That is pretty close to what an electric room heater consumes (900-1500 Watts or so).

A typical relay based contractor may draw around 6 Watts, or ~100+ micro inverters should be drawing (0.050 Watts)

I would wonder if something else is going on... How did you measure the 4 amp draw?

-Bill

garciajj74 · March 2020

I measured the amperage on the feed from the solar panels and on the utility side of my breaker panel.

garciajj74 · March 2020

When I opened the solar panel breaker the Amperage I was reading on that phase would drop off of the utility phase as well. It didn't make sense to me either that the panels were drawing so much at night.

BB. · March 2020

In general, these should be connected to a double pole (ganged) 240 volt breaker.

Was the one you cycled a single pole/120 VAC breaker? That would be the "wrong one" (usually).

It is also possible there is something else connected (other load like HVAC or similar)?

-Bill

garciajj74 · March 2020

It was a double Pole breaker. And I am a 100% sure that there is no additional loading on that circuit. I'm not sure if this makes a difference but 27 of my micro inverters are of the older Enphase M215 and 10 micro inverters are of the newer IQ7.

garciajj74 · March 2020

I live in New York and the way it is wired is directly from the solar panels it goes into a subpanel which in turn goes into a production meter then out to a fused disconnect then back in to the main panel. In my case when it comes back in from the fused disconnect I have it going to my contactor then back into the main panel.

jrboss · October 2021

Hi everyone, new here ... but many questions about my install, specifically, no seems to have any specific information on combining a generator with solar. I have a 200 amp meter/panel, 20 kw generac whole home generator and 15kw solar array with enphase inverters. The solar array was the last thing installed ... and the installer apparently wasn't sure how to hookup with a generator. He wired the panels in on the load side of the generator transfer switch. My understanding is in that configuration, if the power goes out, the generator fires up, which also allows my panels to generate ... all is good, until the panels are generating more than my home is using, at which point the generator "absorbs" the additional power ... which is bad (I'm not sure how bad, but bad enough and expensive enough I don't want to find out). I asked the installer to move the connection point to the line side of the transfer switch ... he seemed to understand what I meant, but he never did it ... so I did it myself. Everything has been running fine for about 2 years now.

BUT - it kills me that if power goes out for an extended period ... I'm burning propane, even though I have 15kw of generating capacity sitting idle on my roof ... so I'm considering adding battery storage for my solar as well, but that brings up several questions I have not been able to find an answer to ...
1) Does solar with battery storage act like an UPS or a backup generator (ie. if utility power goes out, is the home power interrupted?)
2) How do I configure things so (in the absence of utility power) I run on solar and battery ... and only fire the generator up to charge the batteries if they are low when solar isn't available (would prefer to run backup generator only when necessary and at 50-75% capacity to charge batteries)
3) Does the Enphase Enpower smart switch have the capability to handle a generator? Everything I've seen says "future" ... does that mean it can't handle it? ... or that is has the capability to handle it if I choose to connect a generator now or in the future?

My thoughts on configuration:
1) bi-directional meter with 200 amp "main panel"
2) Enphase Enpower Smart Switch (this would replace my current generator auto-transfer switch)
3) in-home main panel connected to the load of the Smart Switch
4) 15kw panels connected to the "solar" connection on the smart switch (with wifi connection to enphase envoy in the combiner)
5) 4 - 10kw enphase batteries connected to the battery (looking for 15kw output capability for whole home backup)
6) Generac generator connected to the generator connection on the smart switch

I'm assuming the smart switch would talk to envoy to control the panels as needed and it would have an output to replace the "sensing" line for the generator, so it could tell the generator when to start and stop.

Any thoughts on this would be much appreciated. (for background - I'm an electrical engineer, not currently working in the profession ... with 2+ decades of experience in DIY home electrical work ... everything from adding an outlet to replacing main panels ... haven't killed myself yet, so I think I'm doing ok. It KILLED me to hire an installer for my solar install, but all of the legal requirements for my power company and local government were beyond my knowledge/patience ... so I hired them ... and then had to move the connection point for the panels to avoid destroying my back up generator)

mike95490 · October 2021

I'm not familiar with the enphase battery system, or how it would work with a generator.

If the inverters did manage to sync with your generator, and the sun came out bright, it's a guess as to which is more rugged, inverters or generator & it's voltage regulator.... 15 KW can do a lot to a generator !!

First you need to put only your critical loads on your transfer switch, or have a plan to shutdown all the extra stuff, so you don't drain your batteries on a cloudy day because you forgot to un-plug the spa ! If the power grid goes out, it's not going to be because of good weather, so you need to conserve power till conditions improve.

Enphase and a Generator

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