High PFC issues

Tama: 
 

Hi all,

First post coming in…

I have a installation that we have been asked to Test, I conducted the usual tests for the Ze & Pfc.  I got 0.4 ohms & 11.7kA respectively.  Its a commercial block and the transformer is behind a locked door about 20m away, so probably reasonable to assume it’s accurate.  So here is my question given the absence of 15kA RCBO’s and the rarity 15kA MCB’s, what are my options?

Thanks in advance.

What type of consumer unit is it?

If it's a type-tested unit to BS EN 60439 or BS EN 61439, tested in accordance with the UK “national Annex” of one of those standards, and has all the manufacturer's recommended devices in it for the product range, then those standards permit protective devices with lower fault current ratings (usually 6 kA mcb's and RCBO's) to be used for prospective fault currents up to 16 kA - provided the service fuse is 100 A or less to either BS 1361 or BS 88-3. Where a specific protective device leads to a prospective fault current rating, this is termed in BS 7671 a “conditional prospective fault current rating”.

See:

• Regulation 536.4.201 (pages 179-180 of BS 7671:2018)
• Page 42 of Guidance Note 1 (8th Edition)
• Page 72 of Guidance Note 3 (8th Edition)

Tama: 
 

Hi all,

First post coming in…

I have a installation that we have been asked to Test, I conducted the usual tests for the Ze & Pfc.  I got 0.4 ohms & 11.7kA respectively.  Its a commercial block and the transformer is behind a locked door about 20m away, so probably reasonable to assume it’s accurate.  So here is my question given the absence of 15kA RCBO’s and the rarity 15kA MCB’s, what are my options?

Thanks in advance.

What type of consumer unit is it?

If it's a type-tested unit to BS EN 60439 or BS EN 61439, tested in accordance with the UK “national Annex” of one of those standards, and has all the manufacturer's recommended devices in it for the product range, then those standards permit protective devices with lower fault current ratings (usually 6 kA mcb's and RCBO's) to be used for prospective fault currents up to 16 kA - provided the service fuse is 100 A or less to either BS 1361 or BS 88-3. Where a specific protective device leads to a prospective fault current rating, this is termed in BS 7671 a “conditional prospective fault current rating”.

See:

• Regulation 536.4.201 (pages 179-180 of BS 7671:2018)
• Page 42 of Guidance Note 1 (8th Edition)
• Page 72 of Guidance Note 3 (8th Edition)