Noob needs more help (pics inside)

[DanS26]

OP you should have a "load analysis" performed before downsizing the main breaker. If 150 amps is not enough then a line side tap (if allowed) could be installed.

You stated the meter and first disconnect is 60 ft away from the main service panel in the same building. You also stated that the main service panel has a ground rod driven. Are there two ground rods driven on opposite corners of this building? If so the rod at the main service panel which is really a sub panel should be removed.

[ButchDeal]

How that would be done in practice? I wonder if the tap wires could run directly into AC disconnect combiner bus as it already has breakers for each inverter, just to reduce number of panels/subpanels/etc on the wall.

That is how we usually set them up.

[max2k]

2014 NEC uses 125% of inverter output rating for the 120% rule calculation, not the breaker size as previous cycles required. For 225 A bus, that means a 175 A main breaker could be ok, instead of dropping all the way to 150.

Good to know, thank you. At least something more realistic as using already increased breaker rating to rate bus bar was kind of ridiculous - that 25% 'head room' in breaker rating was not going to heat the bus bar anyway.

[sensij]

IF you have a 225A bus bar with a 200A main breaker you could have a larger main breaker.
225A * 1.2 = 270A
270A - 100A = 170A.
There isn't 170A main breaker, so you'd go with a 150A (*IF* you have a 225A bus bar)

2014 NEC uses 125% of inverter output rating for the 120% rule calculation, not the breaker size as previous cycles required. For 225 A bus, that means a 175 A main breaker could be ok, instead of dropping all the way to 150.

[sensij]

what about OP middle screenshot from msg #25? If that is his MSP and I'm reading it correctly it is 125A panel.

Looks like 225 A to me, based on the lug ratings. I don't think the middle picture is telling us anything about the bus bar.

[max2k]

...
Very doubtful.
I wouldn't say it's impossible, but it's really unlikely. I'd be pissed at the electrician if they did a 200A main breaker in a 125A bus-bar panel.
(and wonder how the heck it happened)
...

what about OP middle screenshot from msg #25? If that is his MSP and I'm reading it correctly it is 125A panel.

[max2k]

OP really needs a line side tap.

How that would be done in practice? I wonder if the tap wires could run directly into AC disconnect combiner bus as it already has breakers for each inverter, just to reduce number of panels/subpanels/etc on the wall.

[foo1bar]

I also prob wrongly assumed the bus was 200 due to the breaker size.

I would assume it is at least 200.
It may even be 225A bus

If the bus bar is 125 then it appears I have a hot mess on my hands.

Very doubtful.
I wouldn't say it's impossible, but it's really unlikely. I'd be pissed at the electrician if they did a 200A main breaker in a 125A bus-bar panel.
(and wonder how the heck it happened)

IF you can figure out what the panel model number/name is, you can find out what the bus capacity is.

IF you have a 225A bus bar with a 200A main breaker you could have a larger main breaker.
225A * 1.2 = 270A
270A - 100A = 170A.
There isn't 170A main breaker, so you'd go with a 150A (*IF* you have a 225A bus bar)


If you don't have 225A bus bar (or can't determine if you do)
then you can either upgrade the panel to one with a 225A bus bar.
OR you live with a 125A main breaker.
(I'm a cheapskate - I'd live with 125A main. I grew up with a 60A service. )

[ButchDeal]

OP really needs a line side tap.

[max2k]

No.


No. 3 hours a day would be continuous.


I believe that standard practice (and what would be expected by an inspector) is that it'd be 125% of the inverter outputs. So 75A * 125% = 93.75A, which means 100A breaker.

Well, that sucks- OP would need 100A backfeed breaker and downgrade main one to 140A to get under 240A limit on the bus bar.
Are there 225A bus bars available for 200A MSP? That would allow him to have (225 * 1.2) - 100 = 170A main breaker. I have a feeling neither 140A nor 170A are standard size breakers.

[foo1bar]

Can we say he doesn't have continuous load then?

No.

His system won't be producing at 75A more than couple hrs a day (if that) so it clearly falls under non continuous category .

No. 3 hours a day would be continuous.


I believe that standard practice (and what would be expected by an inspector) is that it'd be 125% of the inverter outputs. So 75A * 125% = 93.75A, which means 100A breaker.

[max2k]

"they can produce 75 A max together, this is the max current you can possibly feed back to MSP. Now the standard breaker for that is probably 80A and I believe you don't need 125% upgrade as 80A is its continuous rating"

This is incorrect and does not follow 690.9(B). 690.9(B) is very clear. 690.8(A)(3) tells use to use the inverter continuous output current which is 25 amps per the datasheet. You have three of them so the max output is 75 amps. "Overcurrent device rating shall be not less than 125 percent of the maximum currents calculated in 690.8(A)." There is an exception for continuous rated OCPD's but you will not find them in residential switchboard gear. Thus we end up with a 100 amp OCPD.for the MSP interconnection.

Can we say he doesn't have continuous load then? His system won't be producing at 75A more than couple hrs a day (if that) so it clearly falls under non continuous category and 125% requirement should not apply.

[tyab]

"Now the standard breaker for that is probably 80A and I believe you don't need 125% upgrade as 80A is its continuous rating"

This is incorrect and does not follow 690.9(B). 690.9(B) is very clear. 690.8(A)(3) tells use to use the inverter continuous output current which is 25 amps per the datasheet. You have three of them so the max output is 75 amps. "Overcurrent device rating shall be not less than 125 percent of the maximum currents calculated in 690.8(A)." There is an exception for continuous rated OCPD's but you will not find them in residential switchboard gear. Thus we end up with a 100 amp OCPD.for the MSP interconnection.

[max2k]

... My brother-in-law telling me I can't do it "because the electricity has no where to go". ...

Naysayer, eh? That's entire different level of confusion and while he is technically correct- it doesn't have anywhere to go it also doesn't matter .

Just keep in mind panels are always 'ON' when the Sun is shining on them and be safe. 45V voltage from a single panel is not dangerous but when you connect more in series it quickly gets there.

[diegodog]

Sweet I'm waiting on the proper galvanized hardware to get here and then I'm going to throw those panels up and get that job out of the way. There are certain things that are much better to do when its not -20. I came up with that question from My brother-in-law telling me I can't do it "because the electricity has no where to go". I have verified it a few places and the only fool that has ever heard of that is my brother-in-law. Although it did scare me enough to not do it until I confirmed it a bunch of times (LOL).

In the process of diagramming the wire plan up to the inverter. Also looking into the MSP bus bar and what exactly I'm dealing with there. Also shopping for a nice "box" to make the switch from PV to THWN-2 wire in.

I'll continue to post here and throw up pictures as I go along.

Thanks again for everything