half a megawatt solar interconnection

[Ken Forest]

i am at this commercial site getting ready for solar interconnection (supply side tapping) 1200A main bringing half a megawatt solar production into the facility through 600A fused disconnect.
the existing wires supplying the building is 5 sets of 400kcmil polaris tapped with 4 sets of 400kcmil going to the main breaker with 10 port blocks (9 of them are taken so only one port is left). we are bringing two sets of 400kcmil into the panel and need to tap into each leg. The space is limited and my plan is to upside the polaris to 12 port blocks and another poparis of inline block with 400 kcmil cable limiter (x2 each leg) into them. Does anybody has any recommendation better way to deal with this interconnection? again i am worried about the limited space available inside.
Thanks for your input!

 

[ggunn]

What inverters are you using and what is your service voltage?

 

[Ken Forest]

they are SMA sunny tri power. 33k. (x12) the system voltage is 600V.

 

[electrofelon]

Just curious why were there five sets dropped down to four sets? Presumably they had five for voltage drop but the terminations only allowed for four on the lugs?

One strategy may be to get large enough blocks so the 4 conductors can pass through the block to the gear connections. Although I'm guessing those incoming five sets are not long enough for that?

Sometimes the manufacturer of those blocks require the connections to be staggered, make sure you are aware of that.

 

[Ken Forest]

i asked about that (5 sets/4 sets) to the guy who had previously talked to their facility manager who said to him that the breaker had only 4 terminals to land into. i m thinking that one of the five is not necessary but i don't really want to mess with the existing system. yes. wires are not long enough for passing through. Thanks for your advice.

 

[jaggedben]

Would it help to get 6 port blocks large enough to pass through and put them on the load side of the existing splices?

 

[Ken Forest]

I am not sure if I understood your suggestion correctly. 5 of the incoming wires landing into the 10 port polaris from utility are met in the same polaris using 4 other ports going to the main breaker (supply side). our drawing that is approved by the state of KY is to do a supply side tapping. i guess an alternative is to upsize the 4 wires to two using larger size polaris with 8 port blocks to bringing our two 400kcmil solar input to it, but i am guessing it would take as much space or more if i do that.... Thank you for your input!

 

[jaggedben]

I am not sure if I understood your suggestion correctly....

You'd leave the existing splice as is. (Actually you will remove the existing 4 conductors on the load side while doing the work, then put them back, but it will end up as it started.) Your new 6-port double-entry Polaris block will be a few sizes bigger than 400mcm, big enough to pass the 400mcm through without removing the insulation. (Maybe 600mcm size, you'll have to check yourself what's actually big enough.) You'd remove the insulation only where the Polaris lugs land on the conductors, then reterminate the conductors on the existing 10 port splice block, all without cutting them. Then land your solar on the remaining ports of the new 6-port blocks.

 

[winnie]

Could something like this work?

https://www.ilsco.com/Ilsco/ccrz__ProductDetails?sku=PTA4-750-500-W%2FC-ILSM-ILS&cclcl=en_US

I don't work with stuff that large, so don't know if using lay in taps makes sense.

Polaris also claims the capability of custom connectors, including 'double stack' connectors.

Jon

 

[Ken Forest]

Jon, i never new that product exists. i like it though i am not sure if i can use it on this job.
Jaggedben, i understood what you are saying, but i don't think i have that much space to add 3 more of 6 port blocks in there.

Thanks both for your comments.

k

 

[ggunn]

they are SMA sunny tri power. 33k. (x12) the system voltage is 600V.

600VAC? Why so many small inverters?

 

[winnie]

Jon, i never new that product exists. i like it though i am not sure if i can use it on this job.

I didn't know about that particular product. I knew about the 'lay in' splicing blocks and saw it during my search.

Back in your original post you mention using cable limiters. What is their intent?

Jon

 

[jaggedben]

....

Back in your original post you mention using cable limiters. What is their intent?

Jon

See 705.31 Exception in the 2017 NEC, or 705.11(c)(2) in the 2020 NEC. This is gone from the 2023 NEC.

 

[winnie]

Ok, so cable limiters are allowed to extend the distance to the OCPD for these taps. Thanks

Jon

 

[ggunn]

See 705.31 Exception in the 2017 NEC, or 705.11(c)(2) in the 2020 NEC. This is gone from the 2023 NEC.

705.11(C) in the 2020 code only applies to indoor line side connections; there is no limit to conductor length outdoors and cable limiters are not needed.

 

[Ken Forest]

our engineer wanted to put cable limiters so that when something happens on our conductors like causing tripping the customers main.

 

[ggunn]

our engineer wanted to put cable limiters so that when something happens on our conductors like causing tripping the customers main.

I don't think that they do anything besides providing short circuit protection and isolation of faulted conductors, as shown by https://www.eaton.com/content/dam/e...-tech-lib-cable-limiters-and-applications.pdf

 

[Ken Forest]

I am questioning about the whole deal with the limiter to my engineer now as this is costly and taking a lot of space. i am going to read the document you provided so i can understand better. i am not an engineer, but i would like to challenge one if he is wrong about this.
thanks for your input

 

[ggunn]

they are SMA sunny tri power. 33k. (x12) the system voltage is 600V.

That is the AC service voltage? That sounds odd to me; I have not seen that before. The SMA STP33-US-41 inverter is a 480/277V native inverter. If it is 600V DC that you mean, why is that? The SMA STP inverters can run at 1000V DC.

Also, I ask again why you are using so many small inverters; the SMA STP series inverters are also available in 50kW and 62kW versions. Your AC connections would be a lot simpler with fewer and larger inverters.

 

[electrofelon]

600VAC? Why so many small inverters?

I worked on a 2.7 MW 5 years ago that used the 33 KW tripowers. OMG it was so annoying, there must have been like 6,573 inverters there. I heard they "got a real good deal" on the inverters, but not sure the designers took into account that additional labor.