What would you recommend on a 36kW grid tie.. 3units of Sunny Boy 7.0 In Parallel or 5units why?

dks1 · May 2021

Will 3units Solar inverter in parallel maxed at 12,000w pv input yield better production & electricity savings compared to 5units of Sunny Boy 7.0 core inverter in parallel? What would you recommend?

mike95490 · May 2021

First, what will your power company allow to be installed. over 10kw is often a change from homeowner to a commercial install.

BB. · May 2021

I am not quite sure I understand your questions... Very roughly, they will produce the same amount of energy per day/year/etc... SMA has a pretty good reputation. Don't know the other brand (unless you did not give a brand). All of them are around 97% efficient or so.

You can look at the features (networking). And the SMA offers "secure power"--Basically a 2,000 Watt AC output that can be used for emergency power while the sun is up and the sky is clear.

Other things to look at... The solar input (Vmp-array. Any parallel strings, 1/2/x MPPT separate inputs, etc.). Generally have to match the solar panels (series/parallel) with the acceptable range of input for your GT Solar systems.

More or less, you should do several paper designs and see what works out best for you. The solar panels have to be matched to the GT inverters' input--And different panels (Vmp and Imp/series & parallel) vs what is available to you, costs of panels, etc....

And with the new NEC requirements--You may need to look into roof top shutoffs (unless you are ground mounting racks). See what safety devices are needed...

Also check with your local energy supplier (PG&E)--Systems that are >~10,000 Watts can have different rules to follow/need upgraded utility distribution lines, etc. And the rate plans (money you get paid back) for commercial can be quite different vs residential power plans.

-Bill

dks1 · May 2021

mike95490 said:

First, what will your power company allow to be installed. over 10kw is often a change from homeowner to a commercial install.

This is for Asia & 36kW Solar Rooftop is acceptable. The power configuration is Three Phase 230V Delta. & I will be using SMA Sunny Boy Core 7.0 that is a 1Ø. I am contemplating if i should use 5 units Of Sunny Boy 7.0 or just 3units designed phase to phase. Since a Sunny Tripowe Core 33kW is WYE High Voltage & would be out of phase with the present utility configuration of this install..

dks1 · May 2021

BB. said:

I am not quite sure I understand your questions... Very roughly, they will produce the same amount of energy per day/year/etc... SMA has a pretty good reputation. Don't know the other brand (unless you did not give a brand). All of them are around 97% efficient or so.

You can look at the features (networking). And the SMA offers "secure power"--Basically a 2,000 Watt AC output that can be used for emergency power while the sun is up and the sky is clear.

Other things to look at... The solar input (Vmp-array. Any parallel strings, 1/2/x MPPT separate inputs, etc.). Generally have to match the solar panels (series/parallel) with the acceptable range of input for your GT Solar systems.

More or less, you should do several paper designs and see what works out best for you. The solar panels have to be matched to the GT inverters' input--And different panels (Vmp and Imp/series & parallel) vs what is available to you, costs of panels, etc....

And with the new NEC requirements--You may need to look into roof top shutoffs (unless you are ground mounting racks). See what safety devices are needed...

Also check with your local energy supplier (PG&E)--Systems that are >~10,000 Watts can have different rules to follow/need upgraded utility distribution lines, etc. And the rate plans (money you get paid back) for commercial can be quite different vs residential power plans.

-Bill

This is For an install for Philippines.. thank you for your inputs very well noted😇🙏🏼 I will be cimplementing SMA Sunny Boy 7.0 single phase inverter for this install. It has a max pv input of about 12,000watts, would it be better to have just 3 solar inverter for a 36kW system or should i make it 5 units of SMA Sunny Boy 7.0? Will there be a difference with the AC nominal power for 3 inverter or would 5 inverter give higher AC nominal power on a 36kW system..?

BB. · May 2021

You have to check with your utility... Yes, 1/3/5 single phase units can work on a 3 phase system. However, at least in the USA, there can be some 3 phase specific requirements... Such as a maximum of 10 kWatt of "imbalance" between phases, and that if there is a single or two phase drop--Then all 3 phases must be shutdown (no 1/2 phase power feed).

-Bill

dks1 · May 2021

BB. said:

You have to check with your utility... Yes, 1/3/5 single phase units can work on a 3 phase system. However, at least in the USA, there can be some 3 phase specific requirements... Such as a maximum of 10 kWatt of "imbalance" between phases, and that if there is a single or two phase drop--Then all 3 phases must be shutdown (no 1/2 phase power feed).

-Bill

What do you mean by a “single or two phase drop” in Philippine we can separate a three phase by A B C . A & B is 230v & B & C as another 230V . ABC 230V 3phase connection for machine load

BB. · May 2021

A phase drop is anytime that you do not get full 3 phase power... You can have a pole transformer fail, and that will give you a single phase drop. Or you can have an A/B/C wire or local fuse/breaker pop, and that would be a 2 phase failure.

Generally, the GT inverter needs to monitor the power source--And if anything goes "wrong" (loss of voltage, loss of frequency, poor wave form, etc.), the GT inverter is supposed to shutdown.

3 phase power is really neat from an engineering perspective--But it also has other issues with utility network design, motors that will continue to run if one or two phases fail (the motor can easily overheat/reduced output torque), and if shutdown and restarted, will not start (just continue to draw current and overheat/fail/trip motor protection).

What also could happen... When you run a 3 phase motor on single phase AC (after you get it started)--It actually does a fair job of "reconstructing" the other two missing phases and becomes a "motor generator set"... I have done this multiple times when setting up a 3 phase lathe or mill in a single phase home garage. Setup a large 3 phase motor, get it turning (have even used a "pull cord" like starting a lawn mower) and turn on the single phase power... Then run the 3 phase equipment from the single phase utility power.

What happens when you connect a single phase GT inverter to the "regenerated" phase(s)--I don't know. And that is why (at least in the USA), shutting down all power on loss of phase is important for safety.

-Bill

dks1 · May 2021

BB. said:

A phase drop is anytime that you do not get full 3 phase power... You can have a pole transformer fail, and that will give you a single phase drop. Or you can have an A/B/C wire or local fuse/breaker pop, and that would be a 2 phase failure.

Generally, the GT inverter needs to monitor the power source--And if anything goes "wrong" (loss of voltage, loss of frequency, poor wave form, etc.), the GT inverter is supposed to shutdown.

3 phase power is really neat from an engineering perspective--But it also has other issues with utility network design, motors that will continue to run if one or two phases fail (the motor can easily overheat/reduced output torque), and if shutdown and restarted, will not start (just continue to draw current and overheat/fail/trip motor protection).

What also could happen... When you run a 3 phase motor on single phase AC (after you get it started)--It actually does a fair job of "reconstructing" the other two missing phases and becomes a "motor generator set"... I have done this multiple times when setting up a 3 phase lathe or mill in a single phase home garage. Setup a large 3 phase motor, get it turning (have even used a "pull cord" like starting a lawn mower) and turn on the single phase power... Then run the 3 phase equipment from the single phase utility power.

What happens when you connect a single phase GT inverter to the "regenerated" phase(s)--I don't know. And that is why (at least in the USA), shutting down all power on loss of phase is important for safety.

-Bill

Hi Bill,

Very informative inputs really appreciate it. But for my case this is a single phase grid tie inverter that will be connected on “A B” and other inverters in “B C” it will work in Parallel since SMA Sunny boy 7.0 Core is Single Phase & has a voltage range of 211-264VAC.. so maybe 2 inverters for AB & another 2inverter on BC side perhaps?

dks

BB. · May 2021

You may need to hire a local power engineer that has installed such GT systems before on 3 phase power.

What you are asking for (only feeding 2x phases with >10 kW per phase, no single phasing protection, etc.)--Would not be allowed here in the USA (at least with my limited knowledge).

Just for FYI: Taylor is a respected brand for 3 phase protection gear:

http://www.taylorphaseguard.com/phaseguard/

There can be other 3 phase issues--Such as somebody reversing the wiring and running the 3 phase motors backwards... Not an issue for a group of single phase inverters--But could be an issue for a true 3 phase GT inverters (if they detect rotation reversal as an "error").

-Bill

BB. · May 2021

i should even add to the wonderful thing that is 3 phase power... The utilities can install just two delta transformers (open delta) for full three phase power:

https://www.brighthubengineering.com/power-generation-distribution/112567-three-phase-with-two-transformers-the-open-delta-connection/

So--the actual acceptable configuration for the GT inverters can depend on "exactly" what the utility may be supplying to the customer's meter.

-Bill

dks1 · May 2021

Thank you guys!! 🙇🏻

What would you recommend on a 36kW grid tie.. 3units of Sunny Boy 7.0 In Parallel or 5units why?

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