Residential Meter/Main, with Generator & PV system

[maghazadeh]

PLease see sketch below and tell me if this install is in complaince with NEC.

Thanks

 

[suemarkp]

Only thing I see is the requirement that an ATS based system must have a generator capable of running the entire calculated load, or else you need automatic load shedding equipment. So you may need a larger generator depending on the NEC code cycle adopted or load shedding or move large non critical circuits to the meter main.

Also wondering how well the grid tie inverter will do with a generator as a source. I'd like to implement something like that myself, but I'm not sure if there are any compatibility issues.

 

[texie]

Is the goal to have generator and solar at same time? If so, this is not going to work as the generator can't be used as a source in lieu of the POCO with a grid tie inverter. You would need to have a battery system and charge contoller to do this as the generator can't act as a "battery" the way the POCO source can (voltage and freq. as well as other issues).
You could use this arrangment if you have contacts in the ATS drop out the inverter upon POCO failure.

 

[maghazadeh]

Residential Meter/Main, with Generator & PV system

View attachment 6343 [/QUOTE]

View attachment M-M, Gen, PV.doc

 

[maghazadeh]

View attachment 6343 [/QUOTE]

Hello everyone,
We are getting ready to install these equipments (Meter / Main service panel, 13 KW generator, 3 KW grid tie PV system) in a residential bldg. I would like to hear from you as to compliance to NEC of this install, and any problematic issues that you may see.
Major Appliances are gas, (Stove, Oven, W/H).
Here is a short description of what is being installed.

A) 200A, 120/240V, 1ph, 3w, N-3R, Meter / Main (Feed through), 12 full CB spaces dist. Sect. Located outside of bldg.
B) 3#4/O & 1#4 grd. XHHW-2 Alum feeder from M/M to ATS, ATS to Dist. Pnl. #2
C) 200A, 120/240V, 2 poles non-service rated ATS. Located in the basement/ eq. rm
D) 13 KW (GE) whole house (Natural Gas fired) Generator. MFG. claims unit can handle whole house load incl. (2) up to 4 tons A/C units.
E) 200A, 120/240V, 1ph, 3w, N-1, 42 space MLO dist. Panel # 2 (basement/eq. rm.)
F) 3 KW, 240V, Grid Tie PV system, tying to Panel #2.

NOTE: Neutral and Ground bonding will be at Meter / Main enclosure only. (Main
Bonding Jumper).

1) Q. What feeder size would you use? 1A) 3 # 4/O, 1 # 4 XHHW-2 Alum.
2A) 3 # 250, 1 # 4 XHHW-2 Alum
3A) 3 # 2/O, 1 # 6 THHN Copper
4A) 3 # 3/O, 1 # 6 THHN Copper

2) Q. Is Non-Service Rated ATS okay, or needs to be Serv. Rated?
3) Q. Is MLO Panel # 2 okay or needs to have a main breaker?
4) Q. Do we need to employ load shedding (time delay) for GEN. Or MFG. claim is
Good enough?
5) Q. PV system grid tie will be at Panel # 2 in the basement (Load side of ATS)
Would there be any problem if POCO power is lost and GEN and PV both
Supplies power at the same time?
6) Q. What wording needed for labeling to alert fireman that there is more than one
Power source exist?

Your reply is greatly appreciated, and to those who already replied Thank you.

 

[maghazadeh]

Only thing I see is the requirement that an ATS based system must have a generator capable of running the entire calculated load, or else you need automatic load shedding equipment. So you may need a larger generator depending on the NEC code cycle adopted or load shedding or move large non critical circuits to the meter main.

Also wondering how well the grid tie inverter will do with a generator as a source. I'd like to implement something like that myself, but I'm not sure if there are any compatibility issues.

Suemarkp, Thank you for your reply.
Manufacturer claims that thier 13 KW generator is capable of handling the
whole house load including two upto 4 tons A/C unit. I don't know if they mean that
by using auto load shedding equipment or not. Also I have posted more questions.
Could you please respond to questions. Thank you.

 

[maghazadeh]

Is the goal to have generator and solar at same time? If so, this is not going to work as the generator can't be used as a source in lieu of the POCO with a grid tie inverter. You would need to have a battery system and charge contoller to do this as the generator can't act as a "battery" the way the POCO source can (voltage and freq. as well as other issues).
You could use this arrangment if you have contacts in the ATS drop out the inverter upon POCO failure.

Texie, Could refer me to some article and etc. that I could read more in detail regarding the
issues you mentioned in your reply.
Thank you

 

[texie]

Texie, Could refer me to some article and etc. that I could read more in detail regarding the
issues you mentioned in your reply.
Thank you

This would be a ggod place to start: http://www2.schneider-electric.com/...:Backup+and+Off-Grid+Systems~!NNM3:Xantrex+XW.

You could also look at sma-america.com.
You need to be looking at off grid systems with generator and utility inputs. These will require battery banks as well. This will get expensive.
There are a lot of things to consider here for what you are proposing. Your present design has fatal flaws (meant gently)

 

[suemarkp]

There won't be any load shedding unless you provide it, or unless you're using some generator panel thatincorporates it. A manufacturer's claim that a 13KW generator will "run the whole house" depends a lot on the house. There is no way their claim will work without load shedding or a load calculation. It wouldn't run my house with a 4 ton heat pump, 20KW strip heat, and electric everything else (range, water heater, clothes dryer, swimming pool, multiple refirgerators...).

You need to do a load calculation and see what it comes to. Depending on where this is installed, the NEC as written may or may not apply.

Wire sizes would be chosen based on length. If the feeder is less than 100' long, I woudn't oversize. Aluminum costs less than copper to install, and many people use it. I tihnk copper is better, and that is what I install for myself. But it costs a lot more.

ATS does not need to be service rated, because it is not the Service Disconnect (the 12 space panel is your disconnect).
MLO panel is Ok as long as meter main is installed on the building.
Others have provided better answers for how to deal with the generator nad PV intertie.
NEC 702 tells you what labeling is required at the meter main regarding the standby generator system.

 

[maghazadeh]

This would be a ggod place to start: http://www2.schneider-electric.com/...:Backup+and+Off-Grid+Systems~!NNM3:Xantrex+XW.

You could also look at sma-america.com.
You need to be looking at off grid systems with generator and utility inputs. These will require battery banks as well. This will get expensive.
There are a lot of things to consider here for what you are proposing. Your present design has fatal flaws (meant gently)

suemarkp
There won't be any load shedding unless you provide it, or unless you're using some generator panel thatincorporates it. A manufacturer's claim that a 13KW generator will "run the whole house" depends a lot on the house. There is no way their claim will work without load shedding or a load calculation. It wouldn't run my house with a 4 ton heat pump, 20KW strip heat, and electric everything else (range, water heater, clothes dryer, swimming pool, multiple refirgerators...).

You need to do a load calculation and see what it comes to. Depending on where this is installed, the NEC as written may or may not apply.

Texie and Suemarkp, Ok how about moving the PV grid tie to Meter / Main dist. panel out side a head of ATS?
Would a battery bank still be required?
I will do a load calc. and will incorporate auto load shedding. is this it ? by moving PV grid tie to M/M sect. and load sheddingrest of proposed install will fly

 

[texie]

Texie and Suemarkp, Ok how about moving the PV grid tie to Meter / Main dist. panel out side a head of ATS?
Would a battery bank still be required?
I will do a load calc. and will incorporate auto load shedding. is this it ? by moving PV grid tie to M/M sect. and load sheddingrest of proposed install will fly

Yes, putting the grid tie ahead of the ATS would be OK and make things much simpler. Also, Suemarkp's comments are on the money. Keep in mind that a 13 KW gen of the type you are dealing with is not much more than a glorified portable unit and inherently not very stable, so I would take load shedding and calcs seriously.

 

[jaggedben]

5) Q. PV system grid tie will be at Panel # 2 in the basement (Load side of ATS)
Would there be any problem if POCO power is lost and GEN and PV both
Supplies power at the same time?

Yes, there would be a problem. Best case both will shut down when they 'see' each other. Worst case, the PV system will damage the generator. It is definitely bad to have an ATS that would switch power without turning off the PV breaker, while possibly nobody was home to shut down the PV system.

It would be advantageous to interconnect the the PV system on the utility side of the ATS, to avoid this scenario. Otherwise, I would turn the ATS into a manual switch, and make sure that the customer knows to shut off the PV breaker before engaging the transfer switch. A third possibility is to engineer a relay system that would disconnect the PV if the utility power went out, but that seems like a bigger pain than the first two options. Some inverters have a built in contactor, but still seems like a pain to me.

6) Q. What wording needed for labeling to alert fireman that there is more than one
Power source exist?

See 702.7.

 

[jaggedben]

Texie and Suemarkp, Ok how about moving the PV grid tie to Meter / Main dist. panel out side a head of ATS?
Would a battery bank still be required?
I will do a load calc. and will incorporate auto load shedding. is this it ? by moving PV grid tie to M/M sect. and load sheddingrest of proposed install will fly

Didn't see this before last post. You have the right idea. Batteries are not necessary if the customer is willing to live only on the generator (no solar) when the grid is down.

 

[electricguy61]

Only thing I see is the requirement that an ATS based system must have a generator capable of running the entire calculated load, or else you need automatic load shedding equipment. So you may need a larger generator depending on the NEC code cycle adopted or load shedding or move large non critical circuits to the meter main.

Would you please back this statement up with a code reference? Is this required for residential ATS/generator systems?

I just bid a 400amp service change with an ATS & 17kw generator, due to the actual load, not including AC. Bid clearly stated that if AC would be used during generator usage, a 30KW was needed.

 

[texie]

Would you please back this statement up with a code reference? Is this required for residential ATS/generator systems?

I just bid a 400amp service change with an ATS & 17kw generator, due to the actual load, not including AC. Bid clearly stated that if AC would be used during generator usage, a 30KW was needed.

702.4(B)(2)

 

[maghazadeh]

Texie and Suemarkp, Ok how about moving the PV grid tie to Meter / Main dist. panel out side a head of ATS?
Would a battery bank still be required?
I will do a load calc. and will incorporate auto load shedding. is this it ? by moving PV grid tie to M/M sect. and load sheddingrest of proposed install will fly

BTW, I am wondering that ATS wouldn't transfer to generator power, because of seeing voltage generated by PV on its line terminal.

 

[texie]

BTW, I am wondering that ATS wouldn't transfer to generator power, because of seeing voltage generated by PV on its line terminal.

Yes it will because if the POCO fails the PV invertor will shut down because it looses it's utility reference. This is inherent for grid tie invertors.

 

[maghazadeh]

Yes it will because if the POCO fails the PV invertor will shut down because it looses it's utility reference. This is inherent for grid tie invertors.

Sorry texie, I am not following well, but I think what you are saying is that transferring to generator power will not be an issue since invertor will shut down its out put voltage when poco power is lost. Correct?

 

[texie]

Sorry texie, I am not following well, but I think what you are saying is that transferring to generator power will not be an issue since invertor will shut down its out put voltage when poco power is lost. Correct?

Correct.

 

[K8MHZ]

Correct.

Since the PV system is connected to the breaker panel, it will see power from the generator when the generator comes on. How does the PV system know the difference between POCO and genny power from it's connection at the bottom of the panel?

I think an anti-islanding device is the best, safest and easiest way to go.

SMA used to make a cool anti-islanding device called the Sunny Island where you could connect multiple power sources to it along with the grid and it would provide safe and proper connections. I just went to their site and now Sunny Island is the name for their inverters, which seem to incorporate the features of the previous Sunny Island devices.