High amps on new TL series inverters

[Zee]

NEC says to use inverter output amps if provided, in calcs for sizing the PV breaker.

Why does the new SMA TL series show such high amps on the spec sheet?
I mean what is the technical reason behind it, not legal or code compliance?
How can - for example the 4000 W inverter - generate 20 Amps, at 240 Volts AC??
The spec sheet itself shows its AC output limited to exactly 4000 Watts.
3000: 15 A
4000: 20 A
5000: 22 A

I would have assumed
12.5 A
16.66... A
20.83 A

It looks like they figured out the minimum breaker size you would otherwise get, if you just divided output W by VAC and then bumped up the amps to the max within that breaker's limits.

 

[ggunn]

NEC says to use inverter output amps if provided, in calcs for sizing the PV breaker.

Why does the new SMA TL series show such high amps on the spec sheet?
I mean what is the technical reason behind it, not legal or code compliance?
How can - for example the 4000 W inverter - generate 20 Amps, at 240 Volts AC??
The spec sheet itself shows its AC output limited to exactly 4000 Watts.
3000: 15 A
4000: 20 A
5000: 22 A

I would have assumed
12.5 A
16.66... A
20.83 A

It looks like they figured out the minimum breaker size you would otherwise get, if you just divided output W by VAC and then bumped up the amps to the max within that breaker's limits.

If I am interpreting their spec sheet correctly, they quote the maximum current at the bottom of the voltage range rounded up to the next amp. For example, for the 6000TL they quote 29A at 240V while 6000/240 = 25A. However, the AC voltage range at 240V is 211V to 264V; 6000/211 = 28.4A and they rounded it up to 29A.

29A X 1.25 = 36.25A, so it takes a 40A breaker, not a 35A breaker if the max current were 25A.

 

[Zee]

If I am interpreting their spec sheet correctly, they quote the maximum current at the bottom of the voltage range rounded up to the next amp. For example, for the 6000TL they quote 29A at 240V while 6000/240 = 25A. However, the AC voltage range at 240V is 211V to 264V; 6000/211 = 28.4A and they rounded it up to 29A.

29A X 1.25 = 36.25A, so it takes a 40A breaker, not a 35A breaker if the max current were 25A.

Yes, exactly their "rounding up" of inverter output amps can be a real problem when combining several inverters .......and trying to meet the 120% rule.

Even so, i still don't get the math: 4,000 Watt inverter at 211 VAC (the lowest V on the 240 VAC range) = 19 A. (18.96 A). Yet they say 20 A.
In a way, i see it doesn't matter in the 3 , 4 and 5 KW TL inverter sizes as the brkr size is still the same, 20 A, 25 A , 30 A.


Perhaps my real issue is that in all three sizes they still - annoyingly enough - just barely exceed the amps allowable for a smaller breaker....
This 120% rule strictly applied is a real headache and I hoped SMA of all, would figure it out for U.S. installers.
It is frustrating to constantly just exceed what is allowable on the standard breaker sizes.

3000 Watt inverters: 12.50 at 125% = 15.6 A so we need 20 A brkr
4000 Watt inverters: 16.66 at 125% = 20.83 A so we need 30 A (maybe 25 A)
5000 Watt inverters: 20.83 at 125% = 26 A so we need 30 A.

 

[GoldDigger]

It looks to me as if the only alternatives that SMA would have (to figure it out for US installers) would be to sell a unit with an odd output rating (say 2850 Watt) or restrict the low end voltage operation of the unit (so that it only delivers 2850 W when the POCO voltage is 211).

 

[Zee]

hence, the 3800 inverter which several mfctrs make. They may just call it 4000.
They also current limit the 8000 to exactly 32 A, as they would hardly sell any as it would have just exceeded the amps allowable on a 200A service.

 

[jaggedben]

It seems that the spec applies to both 208V and 240V inverters. The amps make sense for 208V, not 240V. I don't know if in this case they are the same physical inverter.

Kind of a big mistake on SMA's part, if you ask me. Previous data sheets always had separate values for different voltages.