Need some help with a generator and PV

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Blue Star Services LLC

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Vineland, NJ, USA
I have installed a lot of large diesel generators and only about 8 residential generators. I am currently installing a 22KW Generac for a residential house for a friend. They already have a PV system. I have already went through the Generac ATS manual and there are no provisions for this. I have also did my research on line and some phone calls. The PV system is currently tapped into the load side of the meter socket. All I can get from any one is that I have to move the PV leads to the line side of the ATS? The big question that I have! No matter were the PV system is attached to the circuit: It will still tell the generator that it has power and the genset will not turn on? Do I need to put in a contactor to shut the PV off so that the generator will start. I feel really stupid about this, but any advise would help.
Thank you everyone.
 
Blue Star Services LLC said:
I have installed a lot of large diesel generators and only about 8 residential generators. I am currently installing a 22KW Generac for a residential house for a friend. They already have a PV system. I have already went through the Generac ATS manual and there are no provisions for this. I have also did my research on line and some phone calls. The PV system is currently tapped into the load side of the meter socket. All I can get from any one is that I have to move the PV leads to the line side of the ATS? The big question that I have! No matter were the PV system is attached to the circuit: It will still tell the generator that it has power and the genset will not turn on? Do I need to put in a contactor to shut the PV off so that the generator will start. I feel really stupid about this, but any advise would help.
Thank you everyone.
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When the power fails, the inverter won't see the line side 60Hz signal and will shut down. After that, the ATS takes over and switches on the generator. Never do the PV system and generator "talk" to each other.
 
Thank you for your response. I thought that everything from the inverter to the the ATS corresponded to incoming voltage. Learn something new everyday. Thanks again. I am safe to tap the PV system on the line side of the ATS?
 
If the PV system is tapped on the utility input side of the ATS, then things should be fine. If the utility power goes out, then PV system will shut down and the utility input of the ATS will be appropriately 'dead'.

I know you didn't ask this, but your customer might. Be prepared for the question 'why won't my PV system work at the same time as the generator'. In a nutshell it _usually_ isn't worth having such capability, because inverters that have such functionality are quite a bit more expensive than regular grid tie inverters. (Search for other discussions on this topic.) If the customer wants to pay for it, it it can be done.

-Jon
 
winnie said:
If the PV system is tapped on the utility input side of the ATS, then things should be fine. If the utility power goes out, then PV system will shut down and the utility input of the ATS will be appropriately 'dead'.

I know you didn't ask this, but your customer might. Be prepared for the question 'why won't my PV system work at the same time as the generator'. In a nutshell it _usually_ isn't worth having such capability, because inverters that have such functionality are quite a bit more expensive than regular grid tie inverters. (Search for other discussions on this topic.) If the customer wants to pay for it, it it can be done.

-Jon
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I guess maybe it could be done, but why? To save a little generator fuel? You'd be spending a dollar to save a dime or less.
 
We've discussed this many times in other threads. It is something that people keep asking for, is possible, and as you note does not pay for itself in most circumstances.

IMHO the question is common enough that anyone doing a generator install with PV involved should have a ready answer, along the lines of 'it is possible but costs $$$ and with these caveats'.

-Jon
 
Thank you everyone for your responses. One more question: Why would it make a difference if the PV system is tied into the load side of the meter socket or to the line side of the ATS. It would be the same thing if I am correct: It is all the same circuit. The load side of the meter socket feeds the line side of the ATS. From what I am getting from some phone calls that I made to a couple of solar company's: They are saying that it has to be tapped at the ATS system. Is there a reason for this? Just trying to learn some things. I can not find anything in the NEC to address this situation. Thanks again for any responses.
 
Blue Star Services LLC said:
Thank you everyone for your responses. One more question: Why would it make a difference if the PV system is tied into the load side of the meter socket or to the line side of the ATS. It would be the same thing if I am correct: It is all the same circuit. The load side of the meter socket feeds the line side of the ATS. From what I am getting from some phone calls that I made to a couple of solar company's: They are saying that it has to be tapped at the ATS system. Is there a reason for this? Just trying to learn some things. I can not find anything in the NEC to address this situation. Thanks again for any responses.
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It doesn't make a difference. 'Line side of the ATS' in this context can mean the ATS utility side terminals or anywhere else upstream towards the utility (assuming compliant lugs or connectors and otherwise compliant interconnection under 705.).
 
Blue Star Services LLC said:
Thank you everyone for your responses. One more question: Why would it make a difference if the PV system is tied into the load side of the meter socket or to the line side of the ATS. It would be the same thing if I am correct: It is all the same circuit. The load side of the meter socket feeds the line side of the ATS. From what I am getting from some phone calls that I made to a couple of solar company's: They are saying that it has to be tapped at the ATS system. Is there a reason for this? Just trying to learn some things. I can not find anything in the NEC to address this situation. Thanks again for any responses.
Click to expand...

The utility may not allow foreign connectors for a tap inside a socket for their service meter.
 
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For a full time off-grid situation, combining PV and generator with the right kind of control system can allow you to avoid running a diesel generator at partial load. Long term partial (1/2 or less typically) load compared to the prime mover's capacity can cause problems with the diesel engine, such as wet stacking. It also allows the generator to be shut down during "quiet hours" but restart automatically if the batteries go critically low.

Oh, didn't you know that this hybrid configuation really requires a substantial battery bank?
 
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