PV & Podco at the same time

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Dennis Alwon

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Is it legal to have 2 sources of power feed circuits in a house. For example, when the Power goes off the photovoltaic will energize a small 110 volt panel with a select few circuits. The HO then wants the 7000 watt manual generator to be able to be cranked up and feed other circuits in the house. I don't think this is legal.

I proposed that the 7kw gen could feed the PV panel and the gen panel. With the use of 2 transfer switches I think this can be done.

What the ho wants to do is use the PV when there is an outage however if the power is out for more than 36 hours she wants to be able to use the gen. to energize the wine cooler, etc that are not part of the PV.

Am I correct in stated that the first scenario is not compliant?

I guess I am thinking 225.30-- are the gen & PV considered feeders at this point?
 
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iwire

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Dennis Alwon said:
are the gen & PV considered feeders at this point?
Yes they are feeders, services only come from utilities.

I don't see and issue, any multiple sources will only become more common with solar and wind power.
 
L

Lxnxjxhx

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multiple sources will only become more common

multiple sources will only become more common

Maybe someone already makes a battery-backed-up programmable microprocessor control that drives large relays to do this kind of thing.
Inputs to this box would be the HO's program and sensors so it knows where the current is going.
 

dbuckley

Senior Member
Assuming a normal style of PV installation, the PV feeds (via the inverter) power back to the "grid" via breakers in a panel. When PoCo power is lost the inverter will shut down to prevent grid backfeeding and islanding. So you will somehow have to isolate the panel that the PV is fed to, and then inform the inverter that it can start producing power again. And when poco power comes back up, reverse the process. Sounds like a PLC needed.

Also, when the genset is running, should it feed the PV supplied panel, and the PV continues to supply power helping the genset out? From the perspective of the PV panel and inverter, this is equivalent to the PoCo coming up again.

Other than that gotcha, the other panel and the genset is just standard fare.

Not impossible, but requires a local power source; most PV systems have batteries which would do the job.
 

Dennis Alwon

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I am not installing the PV system as I know very little about them. We have a company that will install their end. I need to provide a sub panel with the required circuits. The way I see it I think we are going to supply an ATS that will feed the PV circuit panel and another sub panel with the extra circuits.

From there drawings , which are just sketched on paper it looks as if they have two Iota ATS (whatever that is).

My biggest question was whether you can energize different circuits in a house from 2 different power sources--- the generator and the PV at the same time as long as they don't control the same circuits. I don't think we will be doing this but was curious if it was compliant.
 

davedottcom

Senior Member
Dennis Alwon said:
My biggest question was whether you can energize different circuits in a house from 2 different power sources--- the generator and the PV at the same time as long as they don't control the same circuits. I don't think we will be doing this but was curious if it was compliant.
Sure can. As long as neither system is back feeding the grid. It really depends on the PV system though... a stand alone pv system with batteries would work. A grid-tie PV system does back feed the grid but it will have a lockable disconnect by the meter if the poco wants to lock them out in the event the home owners try to power it up during a power outtage & the generator just needs a transfer switch.
 

quogueelectric

Senior Member
Dennis Alwon said:
I am not installing the PV system as I know very little about them. We have a company that will install their end. I need to provide a sub panel with the required circuits. The way I see it I think we are going to supply an ATS that will feed the PV circuit panel and another sub panel with the extra circuits.

From there drawings , which are just sketched on paper it looks as if they have two Iota ATS (whatever that is).

My biggest question was whether you can energize different circuits in a house from 2 different power sources--- the generator and the PV at the same time as long as they don't control the same circuits. I don't think we will be doing this but was curious if it was compliant.
An ats is an automatic transfer switch so it seems to me they are going to feed the two xfer points pv and poco so it seems ok to me as long as discos are provided and labeled this is no different than having a standby generator.
 

iwire

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If it is a 'grid tied' PV system it will have a controller that prevents back feeding the utility during a utility power outage.

If it is a stand alone system a back feed is imposable.
 

Dennis Alwon

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The PV system will feed back to the power company under normal situations. It will have large Batteries for storage and will feed the house in times of podco outage. The generator will come on if the power is out for more than 24 or 36 hours to feed the pv panel and the extra circuits. This is a manual generator. 7000 sq. foot house with heated Towel bars that cost $1200 each and they didn't want an automatic generator. We could have provided a 30 kw gen. and an energy management system to do the entire house for $22,000. They didn't want it. Wheel out that gen. every time they need it....:D:D

Thanks for the responses. It seems we can do what I thought we couldn't but I think we are going the route I posted most recently.
 

frenchelectrican

Senior Member
Dennis.,

The only object i have is the storage batterys i just hope the owner will realized that the batteries need ventation for it.

But otherwise as what other been talking about they are right on the target with it due more and more solar and wind turbine is getting more common nowdays.

Merci,Marc
 

dbuckley

Senior Member
Dennis Alwon said:
The PV system will feed back to the power company under normal situations. It will have large Batteries for storage and will feed the house in times of podco outage.
Just to note that this may not be as simple as stated, you need either an inverter specifically designed to do this job, or some fancy wiring.

Would be interested in what the inverter is.
 

Dennis Alwon

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dbuckley said:
Just to note that this may not be as simple as stated, you need either an inverter specifically designed to do this job, or some fancy wiring.

Would be interested in what the inverter is.
I don't know what they are using although I know it is an inverter. Other than that I am not sure what they are supplying. I will try & get more info.
 

iwire

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dbuckley said:
Just to note that this may not be as simple as stated, you need either an inverter specifically designed to do this job, or some fancy wiring.

Would be interested in what the inverter is.
The NEC requires an inverter or AC module listed for that purpose and requires that it automatically prevents a back feed into a dead utility.

690.60 and 690.61

In the next few weeks I should be installing a 75 KW PV system that will be tied into the utility. Any 'extra' power will be sold back to the utility.
 

davedottcom

Senior Member
iwire said:
In the next few weeks I should be installing a 75 KW PV system that will be tied into the utility. Any 'extra' power will be sold back to the utility.
Bob, do you mean a 7.5KW?
A 75KW is one serious power plant!

I've done a bunch of 5KW and one 15KW. I can't imagine a 75KW! How big is the roof!?!?!?:D
 

dbuckley

Senior Member
Yeah Bob, know that, backfeeding power to the utility has rules, but many inverters support it. The inverter has to have anti-islanding provisions, so that when utility power is out, the inverter stops, so as not to present a shock hazard to PoCo folks.

But... the OP wants the inverter to operate without utility power to feed critical appliances. In many installations the PV system is just connected to a breaker in the panelboard, as thats all that is needed. But in this case that wont do. Either the inverter has to have separate supply in and load out terminals, and the inverter has internal relaying so that it can isolate the utility terminals whilst feeding downstream equipment, or an external relaying mechanism is needed, and the inverter has to be dual mode (inter-tie / standalone) with external control to switch between modes.

Many inverters cannot handle this arrangement, which is why I am interested in what the inverter is.
 

iwire

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davedottcom said:
Bob, do you mean a 7.5KW?
A 75KW is one serious power plant!

I've done a bunch of 5KW and one 15KW. I can't imagine a 75KW! How big is the roof!?!?!?:D
75 KW, about 280 panels.

They are also bidding a 750 KW system at a school.
 

iwire

Moderator
Staff member
dbuckley said:
But... the OP wants the inverter to operate without utility power to feed critical appliances. In many installations the PV system is just connected to a breaker in the panelboard, as thats all that is needed. But in this case that wont do. Either the inverter has to have separate supply in and load out terminals, and the inverter has internal relaying so that it can isolate the utility terminals whilst feeding downstream equipment, or an external relaying mechanism is needed, and the inverter has to be dual mode (inter-tie / standalone) with external control to switch between modes.
You make it sound like rocket science, some switching is all you need and it is also covered by 690.61.
 

dbuckley

Senior Member
iwire said:
You make it sound like rocket science, some switching is all you need and it is also covered by 690.61.
Actually, anti-islanding mechanisms to comply with UL 1741 (which is basically what 690.61 requires) is rocket science, and most folks have no idea how it works.

And yes, "some switching is all you need", but you still have to get a grid intertie inverter to start up whilst it is islanded, which is exactly what it doesn't want to do, in compliance with 690.61...
 
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