Discuss Better way of doing this....? in the Electrical Forum area at ElectriciansForums.net

sythai

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Arms
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Working on a bathroom refurb at the mo....

Just decided they're having a new tank in the airing cupboard which needs supplies for 2 x immersions (3kW)

Nightmare job running new cables back to CU, basement flat concrete floors /ceilings etc. Opposite side of building.

But I can re-use the old 6mm shower feed. Was thinking could use this as a submain, supplying 2x16a mcbs in an enclosure in the airing cupboard, these then going out into a couple of 20a DP switches and on to each immersion.

Anything wrong with that/ better way, my only query really is the enclosure with the 2x mcbs in it, would this require its own local DP switch?


Cheers Sy
 
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sythai

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Arms
  • Thread Starter Thread Starter
  • #3
Why don't you use a little 2 way board, it'll have it's own main switch then..
It's just so tight on space thats all, will be lucky to get the enclosure in where it will be readily accessible. Every inch counts on this one!

If it is a requirement that I have main switch then I have no option but to find some way of fitting a small 2way CU in.

:smiley2:
 
C

ClarkeTheSpark

Thats what I did with a similar dilemma, small RCD garage unit with a spur coming off a 16A breaker for each spur. Marlanvil (i think) and Wylex do fairly small ones :)
 

darkwood

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Run the 6mm shower supply through a 45a switch then split to 2 mcb in a enclosure, this way the individual flexes have overload protection, the imm' heater can be isolated at one point locally and 40amp mcb covers cable if calcs suit the situe', mcb discrimination will only be partial but its rare you can acheive it in domestic anyway so ok.

This dosn't show auto or timer controls but gives you the jist' as a manual operation.
 

sythai

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Arms
  • Thread Starter Thread Starter
  • #6
Thanks Chaps
 
J

jpm646

If the 2 elements are in the same tank won't they b 24hr an e7 if so couldnt u take 6mm in to a time clock then the two flexes to the elements and down rate the 6mm at the board to 16amp??
 

sythai

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  • Thread Starter Thread Starter
  • #8
If the 2 elements are in the same tank won't they b 24hr an e7 if so couldnt u take 6mm in to a time clock then the two flexes to the elements and down rate the 6mm at the board to 16amp??


Good point come to think of it that may actually be the case, I'm back there next week so will check it out..... never seen a dual immersion set up with eco 7 before, but theres always a first.


If thats the case, problem solved and I will probably need something like this :

http://www.heatingcontrolsonline.co.uk/horstmann-economy-quartz-timer-p-54.html


 
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D

Dave 85

Why not just use 2 Fcu's as protection? Am I missing something here?
 
D

Dave 85

Nonsense. A 13 amp fuse doesn't pop on anything near 13amps....surely you guys realise this?
Just unnessecary work putting a CU in for a pair of immersions.
 
S

StuSpiers

Seen it done 1000's of times.

3000/240 = 12.5

one calculation is by the book, one is a reality.
 

Simlec

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Arms
Esteemed
The small board way is the only way for me! 2 x 6mm or 1 x 6mm + 1 x 4mm will not go in to a 13amp fused outlet as normally stated on!!
 

Rockingit

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Good grief! Nothing like over engineering a job! IF you DON'T have e7 to contend with, take the 6mm into a double pattress and out to 2 x 3kw FSU (suggest Click would be good for that) and feed it from a 32a MCB off the CU.
 

darkwood

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Nonsense. A 13 amp fuse doesn't pop on anything near 13amps....surely you guys realise this?
Just unnessecary work putting a CU in for a pair of immersions.
Although its rated 13amps what you will find over your career as a sparky is if it is fully loaded for long durations it will tend to fail on the internal contacts, most manufacturers of spurs and sockets alike will recommend that a full rated load only be done for short periods, i lost count of 3kw ovens on a plug top etc that has burnt out the socket. Immersion heaters by their nature may be on for hours at a time and more when demand high, so a fcu is a bad call in this case.
 
Good grief! Nothing like over engineering a job! IF you DON'T have e7 to contend with, take the 6mm into a double pattress and out to 2 x 3kw FSU (suggest Click would be good for that) and feed it from a 32a MCB off the CU.
Im with this, hate making work for my self when its not need
 
J

jpm646

Good point come to think of it that may actually be the case, I'm back there next week so will check it out..... never seen a dual immersion set up with eco 7 before, but theres always a first.


If thats the case, problem solved and I will probably need something like this :

http://www.heatingcontrolsonline.co.uk/horstmann-economy-quartz-timer-p-54.html


I've seen quite a few normally the top element is the boost one as it only heats water at the top and the bottom element is a the economy7, these ate usually used when the tank is just for hot water when they don't have gas.


P.s that is the timer you want and if u live near the midlands I've got a few spare from when I was subbing can sort u one out cheep if needed
 
J

jase

If the 2 elements are in the same tank won't they b 24hr an e7 if so couldnt u take 6mm in to a time clock then the two flexes to the elements and down rate the 6mm at the board to 16amp??
If it was for E7 then there would have to be 2 supplys, one from the peak board and one from the off peak board
 
S

Shaun1987

If its E7 you can do it from 1 supply but you will need an E7 controller to boost the top element. But if theyre on superdeal you will need 2 circuits, unless you put a BX2000 at the mains and just control the bottom heater.
 

i=p/u

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Arms
i had econemy 7 once and it only had one supply and i think it kicked onto cheaper rate at midnight... am i right???:61:
 
O

One_of_them

I've lost count the amount of 3kW water heaters I have seen locally supplied by a 13A FCU. Only time the fuse has popped has been if the element has popped. And some never has as the MCB had gone first
 

Taylortwocities

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Arms
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If its E7 you can do it from 1 supply but you will need an E7 controller to boost the top element. But if theyre on superdeal you will need 2 circuits, unless you put a BX2000 at the mains and just control the bottom heater.
It depends on the E7 supply.

Some E7 supplies have a separate feed out of the meter and a separate consumer unit for the off peak devices (eg bottom immersion) for this you need two feeds. One off peak, one boos for the top immersion.

Also an E7 can be delivered on a timed basis so that anything used in the off peak time is cheaper. That is the time when using the existing sohower circuit could be used with one of them horstman timers.

SYTHAI:::::::::::::> Think we need more detail on the supply that is there or we'll just talk ourselves to death without all the info.
 

Rockingit

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Erm.....no you don't need two CABLES for e7 and normal; nothing to stop you joining two feeds together out of two CU's (remember to mark it for multiple isolation), fit a timer (and probably a contactor) in between the 24/7 CU and the junction to disable it when the e7 kicks in. It's a little messy I know, but just trying to demonstrate that you don't always need two cables - just some initiative!
 

Taylortwocities

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Arms
Esteemed
Erm.....no you don't need two CABLES for e7 and normal; nothing to stop you joining two feeds together out of two CU's (remember to mark it for multiple isolation), fit a timer (and probably a contactor) in between the 24/7 CU and the junction to disable it when the e7 kicks in. It's a little messy I know, but just trying to demonstrate that you don't always need two cables - just some initiative!
I'm not sure if your multiple RCD installation would appreciate that, unless you are planning to switch over the line and neutral with your timer?
 

Rockingit

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I'm not sure if your multiple RCD installation would appreciate that, unless you are planning to switch over the line and neutral with your timer?
Hence my comment about probably wanting to put a contactor (2 n/o 2 n/c) in the mix.
 

sythai

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Arms
  • Thread Starter Thread Starter
  • #28
SYTHAI:::::::::::::> Think we need more detail on the supply that is there or we'll just talk ourselves to death without all the info.
2 x Cu's peak and off peak
 
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