Immersion Heater Wiring issue...

[MasterAbacus]

Hi guys,

Just doing some work on the house, and discovered a wire, all taped up behind some tiles in the bathroom.... Good old prev owners....

Ive traced it back and isolated it at the CU.

Its connected to a 20m MCB and runs the Immersion Heater.
It looks like its 2.5mm FTE cable.

What i want to know is, as this is on its own mcb, im going to replace the run of the cable, rather than leaving this bodge of a job. I assume 2.5 is ok for Immersion Heaters?, and the 20m MCB is ok too?.

The Current switch is located in a cupboard in the bathroom, and out of that is a flex cable to the Immersion Heater. Do you see any problems if i run the new cable to another part of the house (ie Kitchen) and fit a new switch there?, then run back from the switch and connect the 2.5mm directly to the Immersion Heater?

Thanks again guys, Good job i love DIY.....

 

[plugwash]

you'll have trouble terminating T&E directly on to the heater and its probablly best to have a switch local to the immersion header for extra protection during maintinance anyway.

a 20A breaker is fine for protecting the cable but i'd use a 13A FCU somewhere to provide better protection for the immersion heater itself.

 

[JohnD]

I assume 2.5 is ok for Immersion Heaters?, and the 20m MCB is ok too?.

2.5mm is quite usual, though sometimes when you do the calculation it comes out at 4mm. the MCB for an immersion heater is usually 16A as they are usually just under 3kW

The Current switch is located in a cupboard in the bathroom, and out of that is a flex cable to the Immersion Heater. Do you see any problems if i run the new cable to another part of the house (ie Kitchen) and fit a new switch there?, then run back from the switch and connect the 2.5mm directly to the Immersion Heater?

You can fit a 20A DP switch (pref with neon), durably labelled "Immersion heater" anywhere along the length of the cable. However, the immersion heater will need to be serviced and replaced from time to time, and the person doing it will want to be able to see the isolating switch while he works to be sure no-one has turned it on. Otherwise he should put a padlock on your consumer unit. Isolating switches are for this reason fitted with 2m of the thing they control, and in plain view of anyone working on them.

The final connection to an immersion heater should be in heat-resistant 15A flex. PVC T&E is not suitable. You can buy this by the metre. It is normally fitted between the local switch and the top of the immersion heater, with a modest loop of slack.

edit - outpaced by plugwash!

 

[MasterAbacus]

you'll have trouble terminating T&E directly on to the heater and its probablly best to have a switch local to the immersion header for extra protection during maintinance anyway.

a 20A breaker is fine for protecting the cable but i'd use a 13A FCU somewhere to provide better protection for the immersion heater itself.

Thanks for that, Silly question no doubt, but whats an FCU?

Also the Current switch location is next to the boiler / Immersion Heater, which is in a cupboard in the bathroom, i wasnt sure if that was ok for it to be where it is as once her in doors has spent far too long in the bathroom, she manages to steam things up pretty well...Hence my thaughts into moving it elswhere while i had to replace the cable

 

[JohnD]

The cupboard will be too warm to suffer from condensation. The switches I use (MK or Crabtree) are all brass and plastic (no rusting parts) apart from a single tiny stainless steel spring - I imagine other major brands are the same.

You need an extractor fan in there, automatically switched on by the light switch. It will make a tremendous difference.

 

[MasterAbacus]

You need an extractor fan in there, automatically switched on by the light switch. It will make a tremendous difference.

Thanks for that, Ill leave it in the cupboard..... As for the extractor fan theres one installed, it comes on when the shower is turned on, but it hasnt got much umph.....Knowing the state of this house so far, it wouldnt suprise me if its sucking in air rather than blowing (If thats possible)...


Many thnks.

 

[JohnD]

If you get it wired to the light switch instead, it will carry on sucking after she's got out of the shower and is surforming her elbows, picking her ears, plucking her nostrils, etc.

Bathroom fans are very cheap to buy.