Achieving descrimination with RCD protection

[Richard3009]

Split load main CU in the house, all the ways have RCD protection, we now supply the garage/shed from one of those ways and install a neat little 2 way submain in the garage, is there any real benefit in having an RCD in the submain, because the only way to descrim is by fitting an S type in the main CU, one option would be to henley block main tails in the house and power the garage via an MCB with no RCD using SWA, and then protect in the garage with its own RCD, also creating the chance of getting the freezer off RCD protection with a bit of steel conduit. Any thoughts.

 

[Darkwood]

SWA - are fine rcd in garage... as for the fridge or freezer then rcbo' it regardless of the install nature a socket outlet requires rcd protection.

If this is your house you could use a get out clause of a responsible persons reg' but really not what its designed for so go with a separate rcbo on the freezer.

If it trips that then you have a faulty freezer or circuit end of ad need to ensure your family stay fully protected

 

[telectrix]

split tails as you say. in garage fit a 3 way sub. MCBs for freezer and lights. RCBO for general sockets. ( assuming surface wiring in garage)

 

[Flanders]

SWA - are fine rcd in garage... as for the fridge or freezer then rcbo' it regardless of the install nature a socket outlet requires rcd protection.

If this is your house you could use a get out clause of a responsible persons reg' but really not what its designed for so go with a separate rcbo on the freezer.



If it trips that then you have a faulty freezer or circuit end of ad need to ensure your family stay fully protected

Can't you use the exception in
Reg 411.3.3 (b) A specific labelled or otherwise suitably identified socket outlet provided for connection of a particular item of equipment.

But you do have a good point if there is a fault on the freezer it will trip the RCBO out, better loosing a load of food then a life

 

[Richard3009]

If I caused the contents of our freezer to defrost i would lose my life anyway

 

[Darkwood]

split tails as you say. in garage fit a 3 way sub. MCBs for freezer and lights. RCBO for general sockets. ( assuming surface wiring in garage)

With regards to 411.3.3 (b) - giving exception of RCD cover for labelled ad outlets for use of a specific item .... I might consider it for a Kidney Dialysis machine in domestic where a unwanted trip could be costly but for the extra safety a rcbo will give the family I don't think the OP needs to omit rcd protection its highly unlikely to trip unless fridge/freezer is actually faulty.

Ps My freezer has been on a rcbo several yrs and never tripped although the rcd covering sockets has --- I do like to experiment with control gear

 

[Richard3009]

With regards to 411.3.3 (b) - giving exception of RCD cover for labelled ad outlets for use of a specific item .... I might consider it for a Kidney Dialysis machine where a unwanted trip could be costly but for the extra safety a rcbo will give the family I don't think the OP needs to omit rcd protection its highly unlikely to trip unless fridge/freezer is actually faulty.

A fair point, back to my point on RCDs in series, best avoided difficult to descriminate.

 

[Darkwood]

A fair point, back to my point on RCDs in series, best avoided difficult to descriminate.

Yes your garage prone to damp, water ingress normally more so than house electrics .. don't do rcd in series you asking for nuisance tripping of half the house possibly ...Swa as i suggested earlier or other mechanically protected option.

 

[Flanders]

With regards to 411.3.3 (b) - giving exception of RCD cover for labelled ad outlets for use of a specific item .... I might consider it for a Kidney Dialysis machine where a unwanted trip could be costly but for the extra safety a rcbo will give the family I don't think the OP needs to omit rcd protection its highly unlikely to trip unless fridge/freezer is actually faulty.

Good point , but the reg doesn't state specialist equipment just a particular item, this reg could easily be abused and could put lives a risk, although I not yet herd about any one being electrocuted by a fridge yet

 

[Flanders]

A fair point, back to my point on RCDs in series, best avoided difficult to descriminate.

Not sure on size and configuration of the The CU, if there room you could put a separate RCBO in the board fed from the main switch ,But as Darkwood says the best way is MCB and feed Garage with SWA

 

[Darkwood]

Consumer death rates are nationally very low given the size of our population and yes we functioned ok for several decades without them, now their here they often are preached as the magic bullet of safety but i reality they just reduce the risk but at the end of the day what £20 extra - a good return for the safety that it provides in my mind - and most freezers will hold temp for 4hrs plus if power loss anyway.

 

[Octopus]

SWA from house, surface cabling in the shed, cut plug off freezer and connect to S FCU. No RCD required.

 

[Darkwood]

With the new amendments due and I believe a tightening up on circuits exempt from RCD protection my thought is we shouldn't really be looking for ways now to omit the need for an RCD in domestic environment. They do provide extra level of safety so should be implemented especially on circuits with items that usually supplied with a plug top - trying to step around this to reduce costs or try eliminate what is ill perceived as nuisance tripping (Ive fitted loads of dedicated circuits to rcbo's and never had issues with nuisance tripping)..... its rare on dedicated circuits so shouldn't be an argument for a case of no earth leakage protection nowadays.