Sherwooddavid

I’m having a solar system installed in my home and the contractor says a Generac 7000 SMM is required to ensure the solar system is locked out when the power goes out and the generator starts up. This will prevent the solar from back feeding the generator and possibly causing it to motor and causing damage.I’m just curious if anyone has used a SMM for this purpose and how it is wired to your main panel and how it senses the generator is running. My generator is a 20kw Honeywell with a 200amp transfer switch...just curious 😊

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murphy
If you are grid tied the solar panels tie in at the power company meter.  That point then goes to the transfer switch.  When power fails the microinverters are required to immediately shut down when power fails.  The generator starts and throws the switch.  That isolates the panels from the generator.  I have 10 kW of PV solar panels on the roof of my house and a 20 kW generator configured this way.

If you have a single massive inverter instead of a microinverter under each panel it could be wired the same way as long as it shuts down in the absence of commercial power.  This is a safety requirement to protect the power company linemen from back fed power on a system they believe is dead.

I have a block diagram of my system but it is not on this computer.  If you want to see it post a reply and I'll add it when I'm on the main computer.
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Brian Baughman

I’m having a solar system installed in my home and the contractor says a Generac 7000 SMM is required to ensure the solar system is locked out when the power goes out and the generator starts up. This will prevent the solar from back feeding the generator and possibly causing it to motor and causing damage.I’m just curious if anyone has used a SMM for this purpose and how it is wired to your main panel and how it senses the generator is running. My generator is a 20kw Honeywell with a 200amp transfer switch...just curious 😊



Do NOT use a Generac 7000 SMM to lock out a PV system.  There is an auxiliary contact switch on the transfer switch that can be used to control a general purpose contactor to lock out your system.  The G007000 SMM's are normally closed contactors, so if the board in the SMM doesn't open the SMM contactor, your PV system will backfeed into your generator.

Only Generac PWRcell systems which combines PV and energy storage will be able to ac-couple to a Generac generator.
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Geoff Z
Some of the older transfer switches don’t have the auxiliary contact in place. However the threaded hubs are always there and the auxiliary contact can be added. The auxiliary contact can be arranged to be normally closed or normally open. Make sure the general purpose contractor you choose has a continuous duty coil. 
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BillM
How exactly is the SMM going to lockout the PV?  It will ONLY lockout IF the generator is OVERLOADED and good luck with that.  The LOCKOUT switch does not 'exactly' behave as one would naturally assume it does.  IT ONLY LOCKS OUT WHEN OVERLOADED.  NOT, I REPEAT NOT, just because the generator is delivering power to the house.
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grsthegreat
Too true. Even though it has a slide switch that is supposed to lock out on generator, it does not work. That switch does lock out occasionally with utility power i have found out.
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BillM
If you bought an SMM you can get a refund for it because the documentation that comes with them and available online is incorrect.  Generac wrote me a check for mine, and I still have it though it serves absolutely no purpose because of the 'lock out' switch not doing what the original documentation states.  All I wanted was for the SMM to lockout my EVSE while under generator power.  Not because of overload, just lock it out.
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BrianMartin
Is this a common issue with other dealers? To my knowledge we haven't had any issues locking out AC's using SMM's. I've personally not had an issue.
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grsthegreat
I have never had a smm work on total lockout. But mine never failed on power drop lockout. They failed during normal power use. I got tired of the calls about smm flashing led when no power loss occurred. 
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Sherwooddavid
Thanks everyone for your replies. It seems like some people had no problem with them and other's the lockout function didn't work. I'm wondering if the the discontinued SMM model 6783 had problems and the newer SMM 7000 are working better with the lockout feature working properly now ?? A local Generac dealer recommended the SMM 7000 and told me they put lots of them in and the work great with no problems, so at this point I'm not sure what to think. I'm leaning toward trying the 7000 and testing it thoroughly before I put the solar in service. If it's flakey the other option is using a shunt trip breaker for the solar feed that will trip if the generator starts up, but it would be more work and more expensive.
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BrianMartin
We've used a fair amount of them and have yet to get a call about them failing while utility is present. They sense frequency to determine wether or not the generator is powering the home.. Maybe the older models couldn't determine utility from generator power due to a sensor not being accurate enough when measuring frequency... Or maybe the utility frequency in some area's fluctuates enough that the SMM believes the generator is running? 
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Cobranut

It's VERY unlikely that the utility frequency would vary.  The grid ties multiple power plants together, and forces all their generators into sync.  The utility operators keep very tight control on the line frequency.
To vary that frequency would require overcoming the combined power and inertia of all of those generators as one.  Not likely to happen.

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BillM

Thanks everyone for your replies. It seems like some people had no problem with them and other's the lockout function didn't work. I'm wondering if the the discontinued SMM model 6783 had problems and the newer SMM 7000 are working better with the lockout feature working properly now ?? A local Generac dealer recommended the SMM 7000 and told me they put lots of them in and the work great with no problems, so at this point I'm not sure what to think. I'm leaning toward trying the 7000 and testing it thoroughly before I put the solar in service. If it's flakey the other option is using a shunt trip breaker for the solar feed that will trip if the generator starts up, but it would be more work and more expensive.


I have had one 6783 and I'm on my second 7000.  To be clear, my 3rd SMM.  None of them ever failed.  They just did not work according to the instructions that came with them and I assumed they were defective.  After the second one arrived and to me, dead on arrival I drove 3 miles down the road to Generac Corporate HQ and told them what I thought of it.  All of them failed to work as advertised, including the final one that arrived with Generac employee's, who installed it for me.  My problem, which is most likely unrelated to your situation is that my desired effect was for the SMM to SHED THE LOAD whenever I was on generator power.  Period.  I believed, based on Table 2-2 and reading the manual and I am quoting the manual; "Module sheds load and does not reconnect until utility returns."  This is the function and result when you are on generator power and the lockout switch is in the 'on' position.  IT DOES NOT DO THIS AS STATED.  Generac came out with addendum that is supposed to be in the box that 'corrects' the original manual.  The same manual you can download today on their website.  The addendum is titled; "Lockout Switch Updates - UPDATED INFORMATION"  It provides a corrected Table 2-2 and it also corrects some verbage in the manual.  So now, the function of the SMM when the lockout switch is in the ON position AND you are on generator power is now this; "If overloaded, module sheds load until utility returns".

So, for me, the SMM does not do what I wanted it to do and what sales and others who believed the instructions 'sold' me on it.

I have never ever seen the SMM actually shed the load, even when, in my opinion based on perception (very dangerous assumption), the generator was overloaded.  Now, take this sentence with a boulder of salt, it's an unscientific observation.  Generac wrote me a check for $500 for my 'trouble' and I in turn handed that check over to Ziller who sold me a Hyper Engineering Sure Start which I wanted.

I have 18 PV panels, 360 watts each and two Tesla Powerwalls as I embark on a net zero electron journey.  And sitting quietly in the corner is my 22kW Guardian for pretty much enjoying a semi-retirement.  I'm running in Solar Self Consumption mode (and hybrid Load Shifting) and deployed physically as a whole home backup.  I have my PV's setup for export mode but the Powerwall does all it can to make sure there is no export.  It will increase charge power if there is an excess of PV.  If the Powerwall is full, it will then allow export of PV energy to the grid.  If the Powerwall, or when the Powerwall hits declared minimums and needs to charge from utility, it will only do so during TOU favorable rates unless it falls way below the glideslope at which point the Powerwall will declare TOGA and take power on demand until it hits minimums.  I'm new to all of this, and only brought it up since Solar was in the original post.  I'm on month one of all of this.  I may add another 9 panels, I only have room for 36 total.  I don't see adding a third Powerwall at this point with the initial numbers coming in slowly.  

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BillM
My only point is that they won't lockout your solar, if I understood your initial post correctly.  They will not.  I can provide you more info if you need it.  There are lots of really cool and better ways to do that, to prevent any backfeeding in any unwanted direction.  For me, I don't want to backfeed the generator or the PV and I've got plenty of power generation/storage sources in my mix.  The one part that sucks with my setup, is I cannot charge my Powerwalls from generator.  In my perfect world, I would like to be able to do that.
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