TT farm RCD protection

[mark@27]

hi

I've been pulling my hair out trying to finish a installation on a farm , but now i'm very stuck on what i can do

sec are upgrading the three phase supply to 200A and putting in a CT chamber, previously there was several supplies going to CUs from henley blocks and tails but now its being uprated and sec have asked me to put in 70mm tails i can no longer put them into henley blocks.

so what ives done is put a Iline board in and had all the existing CUs as sub boards feed via the Iline.
But now sec have come back and said because its a TT system and a farm that it needs a 300ma RCD, which is fair enough but Iline panels dont have RCD protection and neither can i find any RCD protection for anything above 125A RCCB main switch, nothing that will fit 70mm tails or 200A,

Please can someone help as Im really stuck

 

[SibertSolar]

Hi, I have a personal/business interest in the stipulations relating to Section705 and curious as to whether the DNO has specified a single all-pole RCD? Did they say "max 300mA" or simply "300mA"?

We supply the full range of Doepke products, does this help http://www.doepke.co.uk/rcd/DFL8-SK.html

 

[gazj82]

Hager make then to special order. 1500 quid last 300ma 250a one that I had tho

 

[mark@27]

Thanks for the reply but Unfortunately it's a Schnieder inline board, phoned the manufacturer and they thought I was crazy, I was thinking that if all the CUs that were connected to the iline had RCD protection would that be good enough, as I'm really struggling to find an alternative

 

[JD6400]

Thanks for the reply but Unfortunately it's a Schnieder inline board, phoned the manufacturer and they thought I was crazy, I was thinking that if all the CUs that were connected to the iline had RCD protection would that be good enough, as I'm really struggling to find an alternative

No is the answer to the last part of your question , as it will need to be at source . If you are using Schnieder , you will need to uprate ( from memory ) to the 630 amp panel board in order to fit a variable RCD main switch , as they do not make one for the smaller frame sizes , apparently ! Or use a stand alone 200 amp main switch that allows for the use of a RCD shunt trip arrangement . I know ABB do one as we fitted on last month , and I am pretty sure I was quoted for a Hagar one last week from Eddies as my other director had a nightmare of a job with that last ABB one we fitted and after a run in with the rather rude unhelpful and sarcastic ABB technical help line he told our Eddies rep to stick ABB where it don't shine !

 

[JD6400]

Hi, I have a personal/business interest in the stipulations relating to Section705 and curious as to whether the DNO has specified a single all-pole RCD? Did they say "max 300mA" or simply "300mA"?

We supply the full range of Doepke products, does this help RCDs-Type 'DFLS8 B-SK'

300mA is now the max , it was 500mA but that was the sixteenth .

 

[gazj82]

Hager's is a standalone unit, it doesn't fit in their panel board. You have to get a direct connection kit for the panel board. If you can get this for your Schnieder board you could still use Hager's RCD main switch. Myabe Schnieder even do a stand alone unit

 

[Engineer54]

300mA is now the max , it was 500mA but that was the sixteenth .

Whattttt???

 

[JD6400]

Whattttt???

705.411.1 (iii). Edit ; I can not find my old copy of the Sixteenth at the moment , but I think it is the same reg number and wording ( from memory ) ? Only with the 300 substituted for 500 .

 

[Engineer54]

705.411.1 (iii). Edit ; I can not find my old copy of the Sixteenth at the moment , but I think it is the same reg number and wording ( from memory ) ? Only with the 300 substituted for 500 .

Something else i'll choose to ignore in BS7671 then!! lol!! I stipulate components and design installations suitable for their use, and that can more than sometimes be with a 1A or more earth fault protection!! I think most of Europe use MCCB's with 500mA front end RCD protection on their standard TT system installations....

 

[JD6400]

I believe it is more for fire protection due to vermin and for want of a better example hay and straw , being in such close proximity . I tend to find that the regulation has been over looked on an average of about 70% of the new grain stores I get to see each year . So it would look like you are not the only one to take exception to it !

 

[Engineer54]

I believe it is more for fire protection due to vermin and for want of a better example hay and straw , being in such close proximity . I tend to find that the regulation has been over looked on an average of about 70% of the new grain stores I get to see each year . So it would look like you are not the only one to take exception to it !

Well we're talking front end here so, nothing is stopping you incorporating 300mA down stream for where any fire protection requirements may be needed. Same situation goes for 30mA breakers.

As i said, you design the electrical installation to cover the needs and requirements of the building and/or installation etc!! It may well be, that a front end 300mA is the correct value to provide on this and most other farm installations but it's not always going to be the case. Some of these modern farms with in house processing of it's products, can require it's own 1MVA TX!! mg_smile: lol!!

 

[Knobhead]

With a 1000KVA transformer I hope it’s not TT!

Could be interesting though.

 

[JD6400]

Well we're talking front end here so, nothing is stopping you incorporating 300mA down stream for where any fire protection requirements may be needed. Same situation goes for 30mA breakers.

As i said, you design the electrical installation to cover the needs and requirements of the building and/or installation etc!! It may well be, that a front end 300mA is the correct value to provide on this and most other farm installations but it's not always going to be the case. Some of these modern farms with in house processing of it's products, can require it's own 1MVA TX!! mg_smile: lol!!

Fair enough , and when you get to that scale of in house processing , I would have thought , that portion of the business will be so far removed from the original " Agricultural activity " then it would possibly not qualify for section 705 anyway ? But for a standard farm install , 300mA is what the powers that be ask for . And being as well they even went to the trouble of lowering the value from 500mA for the seventeenth edition , they must have a good reason .

 

[JD6400]

With a 1000KVA transformer I hope it’s not TT!

Could be interesting though.

Hi Tony , there is a bit of a quirk in the regs in so much as , only farms with livestock on them need to be TT ( even then it is not essential , dependent on the earthing arrangements ) . But all agricultural premises do need a max of 300mA on all circuits . 705.411.1 In circuits, whatever the type of earthing system , the following disconnection devices shall be provided: ---------