2 x SMA 5000 TL's

[waverider]

I read in the manual that if you use 2 x SMA 5000 TL's for one system, then they each need their own MCB before combining into the Generation Meter. I've never done this before but I guess that means I would have to install a 2 way unit with two 20A MCB's and RCD at the Inverter side and a 40A MCB at the CU side.

Any ideas?

 

[BruceB]

Maximum AC output current of one 5000TL is 22A so probably needs to be 32A mcbs. 20A ones likely to get too hot.
Only need RCD if cable concealed.
Can either have 45A mcb at CU end or put both 32A ones there and have double the cabling

Regards
Bruce

 

[waverider]

Thanks BruceB, Unfortunately there is a 16mm SWA 50 meter run some of it underground so I cant double the cable and they both have to go into 1 generation meter.

I was thinking of using MCB's and an RCD on the inverter side and a MCB into the mains which does not have a RCD on the CU side.

 

[waverider]

Thanks for your help BruceB, I didnt really understand when you said I dont need an RCD, but now that I see the manual they say no RCD or 100mA RCD recommended for each inverter. I cant get a 200mA RCD so will need to get a 300mA RCD. The project manager wants me to use a 300 RCD but I'm inclined not to use a RCD at all.

what do you think?

 

[BruceB]

I cannot really tell from what you have said, but you need to ask yourself or your project manager why you are thinking of putting an rcd in. There is already one in the inverter I believe, so what are protecting against?

Is is cables buried in wall, then 30mA
Is it TT supply, then normally 100mA
Is it agricultural setting, then 300mA

Regards
Bruce

 

[waverider]

The SMA manual recommends a 100mA RCD per inverter. But it also says you dont need a RCD.

It is an agricultural setting (barn). It is a TNS system and the cable run from the inverter to the CU is 30 meters 16mm SWA - 15 meters underground, 15 meters cleated to side of the barn. The plan is to use two 32A MCB's, and a 300mA RCD in a garage unit in the barn near the inverters. Then combine them from the garage unit to the Total Generation Meter in the 16mm SWA. From there to the split CU using a 45A MCB on the main side (no RCD).

Would this work or would it be better to leave out the 300mA RCD?

 

[BruceB]

It is not that SMA recommend an rcd, what they are saying is that if you are required to have an rcd then it should be 100mA or greater.

I think what you are suggesting is fine. You are required to have a rcd with a rated residual operating current not exceeding 300mA as I read it to comply with 705.411.1(iii). Arguably, the rcd shoild be at the consumer unit end of the swa, but that adds complication you may not want and safety improvement is small.

Regards
Bruce

 

[waverider]

Thank you, your help is greatly appreciated. I think I will try to persuade the project manager that we do not need a RCD at all. Why complicate things for no reason. Thanks again.