Advice would be appreciated

[sparky05084]

Hey all.

Not been on here in ages so first off a big hello and would like to let you know that I passed my 2391. Feels really good and because of it I have been given a pay rise.

Right then, basically I feel a bit embarrassed asking as I would say that I am a bit rusty and need to get back into the knowledge of BS7671 so go easy on me guys please.

I work for a housing association and I am currently in an upstairs flat that forms part of a block that we own. Currently it is a void property and all work has to be completed etc before hand over and prior to it being relet.

Whilst doing the periodic I was performing the usual continuity tests to prove a connection to both gas and water where I found that I was getting open circuit on water.

Hmmmmm, strange this as I have already identified + proved the gas so this has to be water and I am clamped onto pipe.

So, put down a code 3 and jump into the communal loft to investigate. To my surprise I find that the 10mm to water has been cut clean. Whilst I am up there I think I better have a good look around (even though a peridoic does state that no inspections have been carried out in lofts, cables buried in walls or under flooors blar blar - using ECA forms) to see if anything else has been cut.

I don't find any more cut cables or damaged ones (thank fully) however, what I do find is a spur of the ring (via a 30A JB) going down to a 20A DP in the kitchen that is engraved "washer". This in turns feeds a twin socket outlet in the washer space (realised I need to change this to a single outlet but this was before jumping into loft).

Now, in the lounge there is a twin socket that is again a spur directly off the ring via another 30A JB so that is 2 JB's in total and 2 spurs off the ring. So, taking into account load factoring etc and of course further study of App 15 here is my question:

Is the spur of the ring supplying the washer DP acceptable?

Now, as it is a double pole isolator and not an FCU as prescribed in BS7671 then I would assume that in theory what I have here is a typical example of a "spur off a spur" scenario.
One would then suggest to simply change the DP to an FCU so that it satisfies BS7671. But, this to me leaves a problem because then aren't you making the sole purpose of a DP switch obsolete?

I mean it doesn't say in App 15 that you can supply a single or double outlet from a DP switch as only FCU is mentioned and a DP isn't fused.

Also, am I being a little to in depth here considering that this is informative only and talks from a design criteria point of view?

 

[Kevin]

Sparky,

I'm by no means an expert, but I would suggest that if the spur is feeding a DP isolator, and then a single socket, then only one point of utilisation is served by the JB, as the DP isolator is not a load, the only load on the spur would be what was plugged into the socket, so the radial would not be overloaded, and not considered a spur off a spur.

 

[sjm]

I agree with Kevin.
Also a spur from ring supplied by 2.5 T+E, assuming installation methods are OK, can be single or double socket so IMO there would be no need to change the washer socket to a single.

Edit due to numptyism!
Of coarse you need to change socket to single as 20A DP switch won't handle potential 26 amps, sorry.

 

[Deleted member 26818]

There is no limit to the number of unfused spurs you can have on a RFC.
The DP isolator is just a switch, and as Kevin says is not a load, so can be ignored.
BS1363 requires double socket-outlets to be rated at 20A, so there's no need to change the socket-outlet.

 

[Engineer54]

You could also change the 20A DP swtch for a switched FCU which is DP also, and leave the double outlet in place.... Your choice!!! lol!!!

 

[sparky05084]

Cheers for the replies guys. Then I will leave it as it is. Apart from the twin socket of course

However is that not a bit of a grey area though?

I mean currently it is as I said a 20A DP but in the regs it mentions that an FCU "not directly connected to the ring" (as is the case here) can supply a number of socket outlets, obviously dependant on load and diversity factors.

So, the only difference between the 20A DP is its rating and the fact that it isolates both line and neutral conductors but no mention of it in App 15.

Am I missing something?

 

[sjm]

The difference is that an FCU has overcurrent protection in the form of a fuse. Therefore no matter how many socket outlets it supplies the current that will flow along the spur is limited.
The 20A DP switch is purely for isolation and therefore does not limit current so only 1 spur should be fed from the ring.
Both devices isolate line and neutral conductors.

Hope that helps.

 

[Engineer54]

If what Spin is saying is correct, and BS1363 require double outlets to be rated at 20A, then he's right nothing needs to be changed.

 

[sjm]

If what Spin is saying is correct, and BS1363 require double outlets to be rated at 20A, then he's right nothing needs to be changed.

I don't know the requirements of BS1363 but would be a little concerned that a double socket outlet could, in theory, have 2 x 13A loads connected simultaneously. Rating them at 20A would seem a little underated to me but then I'm only a simple sparks.
If you can call a double socket outlet a 20A load, by regs or british standard, then no need to change it.
Don't we all love a grey area lol.

 

[Engineer54]

I don't know the requirements of BS1363 but would be a little concerned that a double socket outlet could, in theory, have 2 x 13A loads connected simultaneously. Rating them at 20A would seem a little underated to me but then I'm only a simple sparks.
If you can call a double socket outlet a 20A load, by regs or british standard, then no need to change it.
Don't we all love a grey area lol.

To be totally honest, i don't know the full requirements of BS 1363, but generally find Spin to be well versed in quoting the various regulations that govern our industry,. Even if he sometimes does go into grey areas...

 

[Sparks-R-Us]

1. Every twin-socket outlet counts as two single-socket outlets.
2. The number of non-fused spurs must not exceed the total number of points on the ring.
3. The fuse rating of a fused connection unit must not exceed 13 A and the current rating of all points
supplied by the fused spur must not exceed 13 A.
4. Non-fused spurs must supply no more than one single or one double socket or one stationary
appliance.
5. For domestic premises of area less than 100m2 , a ring circuit may serve an unlimited number of points.
6. Cable sizes for ring circuits using copper conductors are: 2.5 mm 2 PVC insulated or 1.5 mm 2 m.i.
7. Both ring and radial socket outlet up to 20 A for general use by ordinary persons must be 30mA RCD
protected.

Hope this helps...

 

[Chr!s]

BS1363-2:1995 requires for double socket outlets that both socket outlets have loads applied via test plugs, 1 test plug having a load of 14 amps whilst the other has a load of 6 amps, making a total load of 20 amps on the cable supplying the double socket outlet. The double socket outlet is then subjected to this loading for a minimum continuous period of 4 hours or longer until stability is reached with a maximum duration of 8 hours (stability being taken as less than 1 degC rise within 1 h). The test is passed if neither the terminals / terminations, nor the accessible external surface, increase in temperature by more than 52 degC.