Immersion help...

[pluto]

Hi all. I said hello a few weeks ago and had a bunch of questions ready but seemed to get them answered via the search function, until now. I qualified at the end of 2008 and have finally got round to joining a scheme (assessment immenent) and have several jobs lined up. My neighbour called me in to look at his Immersion heater that has lost power to the switch and it looks like the original supply for it from the fuse has been redirected in the past to a SO :|

If I dig a bit deeper and this turns out right I'll probably put this into the main socket radial as a spur and free up the original fuse that`s marked I H ! I can then run a new supply to the I H switch. But... regarding RCD protection, the cable is only a short run (not in a wall) below floorboards and out in the airing cupboard, surface mounted in trunking. I know this route/method means that RCD protection is not required but what about the fact that the IH is in zone 2 (or is it?), reg. 701.411.3.3.

The shower in the en-suite is in the corner of the room and has a dummy stud wall on one side. The airing cupboard is at the other side of the stud wall. My confusion is because the I H is in the airing cupboard but is this officially part of the Special Location?

Any help much appreciated and apologies for the trilogy :coffee

Craig

 

[Apache]

Airing cupboard not part of SL - simples. You could fit a socket in there.

 

[sparkytim]

If the airing cupboard has a door on it then it is out of the Zone.

 

[Theorysparky]

hopefully not for the immersion !!!!

 

[Apache]

hopefully not for the immersion !!!!

I just meant you could not that you should!

 

[Theorysparky]

I just meant you could not that you should!

I know thats what you meant !!!!!

 

[Evans Electric]

As said, the cupboard is not a special location .

However ,on the subject of RCDs , In my opinion immersion heaters are notorious for developing faults and raising a potentional on the pipework etc without blowing fuses or tripping MCBs . This is usually due to the resistance of the water so I have always treated them the same as showers.

I have known a faulty immersion heater to cause a high potential diff. between a metal kitchen sink top and general mass of earth so its RCDs for me.

 

[pluto]

Blimey, they were sharp replies. Only nipped to put my lad to bed:O

Thanks for the responses. I appreciate that RCD protection is a preferred method and take on board your point of potential diff.

I was just wondering if a reg. stated RCD to be a must because protecting with an RCD will make the job more awkward. I`ll put this to my neighbour and give 2 prices accordingly. Regarding the RCD option, the board is an old Wylex so do you think the best option would be to fit a small enclosure with an RCBO?

Thanks again, Craig

 

[Evans Electric]

Yes.

 

[pluto]

Thanks for the replies, they were very helpful. I`ll certainly be pushing for the RCD route

Craig

 

[Apache]

If cable is surface run a RCD FCU might be cheaper and simpler.

 

[pluto]

AAAhhh, never considered that, i`ll get some prices.

 

[steptoe]

As said, the cupboard is not a special location .However ,on the subject of RCDs , In my opinion immersion heaters are notorious for developing faults and raising a potentional on the pipework etc without blowing fuses or tripping MCBs . This is usually due to the resistance of the water so I have always treated them the same as showers.

I have known a faulty immersion heater to cause a high potential diff. between a metal kitchen sink top and general mass of earth so its RCDs for me.

+1

and Apache's solution +1

 

[pluto]

On the topic of potential difference, what would be the best way of testing for this. Is it an example of earth leakage via the pipework?

 

[sparkytim]

FCU NOT SUITABLE FOR IMMERSIONS

Have found 13 A Fuse carrier burns out eventually if used extensively

i.e. not just for back up to boiler

20 A DP switch better option.

 

[a12jpm]

Agree with sparky tim, found a 13a today pretty much like melted cheese at the back of it. Fitted one of these instead:

 

[batty]

I have never had problem with 13 amp spurs controling immersion heaters although I tend to use quality ones rather than cheap tat. 13 amp sockets are a problem though.

 

[steptoe]

even with my earlier post approving paddys RCD FCU I still do think a DP switch is the only proper method,

OK, OK, I jumped up too fast and got it wrong,

but Im now saying a DP switch at 20A is the only method I would honestly use,

and if viable the deffo RCD protect it.

 

[pluto]

To conclude then, it seems the way forward would be to use the fuse in the wylex board, come out in 2.5 T&E (surface clipped/or in conduit) into a small enclosure with a 16A/30mA RCBO, 2.5 T&E up to a 20A D/P 'Heating Switch'. Out of that with heat resistant flex to the I H. Job done. I must admit this seems a much better, more professional option.

Just in case anyone is wondering and looking at my previous posts, I have intended to join a Competent person scheme (Elecsa) several times since qualifying 18 months ago but somehow something always got in the way. This does not mean to say i`ve been working continuously doing notifiable work. I have a full time job working shifts and would like to do domestic electrical work in my bulk time off.

This time is a definate and should be with Elecsa very shortly. The above job may be offered for assessment or done straight after joining. Just didn`t want anyone thinking it was a blag to extract information...

Many thanks, Craig

 

[Theorysparky]

Craig

Just wait for all the estimates you will do where the potential customers gleen the info out of you

and then do it themselves !!!!!! X(