Max Electric Shower Kw on 10sq cable?

astrofool

I have a 15m run on 10sq cable, unbroken, direct to fuse box, can I run a 10.8kw shower on it, or better off going with a 9.8?

Davy

Depends what the cable is inside. I would probably go with 9 in anycase

eoghan.geraghty

Do you mean unbroken as in no isolating switch?
The first thing you need is an isolating switch.
What rating RCBO are you using, this will help determine what size shower you can use.

astrofool

RCB is still to be fitted.

I mean unbroken as far as the isolating switch.

What does "Depends what the cable is inside." mean? It's standard 10.0mm cable, as in: http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=9290439&fh_view_size=10&fh_location=%2f%2fcatalog01%2fen_GB&fh_eds=%c3%9f&fh_refview=search&ts=1282405076806&isSearch=true

seaniefr

astrofool wrote: »

RCB is still to be fitted.

I mean unbroken as far as the isolating switch.

What does "Depends what the cable is inside." mean? It's standard 10.0mm cable, as in: http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=9290439&fh_view_size=10&fh_location=%2f%2fcatalog01%2fen_GB&fh_eds=%c3%9f&fh_refview=search&ts=1282405076806&isSearch=true

what it means is that with the cable being supplied at the moment the 10mm squared is measured to include the inner pvc insulated core whereas the old one just included the copper in the measurement so they are a slight bit undersized to the eye.

seaniefr

seaniefr wrote: »

what it means is that with the cable being supplied at the moment the 10mm squared is measured to include the inner pvc insulated core whereas the old one just included the copper in the measurement so they are a slight bit undersized to the eye.

Other factors need to be considered also i.e. the age, condition of the board, room for RCBO?, existing circuits already on fuseboard which your existing mains might not be able for when you add a 10kw or a 9kw load to an already overloaded fuseboard so worst case scenario would be a fire..............................
also any experienced sparkie would pick up on other things he/she might spot when covers are being removed.........loose connections, burning smell, maybe something getting hot that should'nt be?

Davy

astrofool wrote: »

RCB is still to be fitted.

I mean unbroken as far as the isolating switch.

What does "Depends what the cable is inside." mean?

If its clipped to a wall, in studding, insulation etc. These de-rate the cable differently.

2011

I have a 15m run on 10sq cable, unbroken, direct to fuse box, can I run a 10.8kw shower on it, or better off going with a 9.8?

A 10mm sq T + E is large enough for a load of that size if the run is 15m.

If its clipped to a wall, in studding, insulation etc. These de-rate the cable differently.

Correct methods of installation will require a larger cable to be used however in this case the OP is covered. All of the methods of installation that you have described are normal for a domestic installation.

Other factors need to be considered also i.e. the age, condition of the board, room for RCBO?, existing circuits already on fuseboard which your existing mains might not be able for when you add a 10kw or a 9kw load to an already overloaded fuseboard so worst case scenario would be a fire..............................

Valid points, but the question is about the cable size for the circuit.

also any experienced sparkie would pick up on other things he/she might spot when covers are being removed.........loose connections, burning smell, maybe something getting hot that should'nt be?

+1.
No offense intended to the OP, but this work should really be carried out only by a qualified electrician.

M cebee

i think the simplest way to size cable is to size the breaker according to the load
and then divide by the correction factors to size the cable

for a 10.8kw that would be a 50amp rcbo

make sure you're getting the 10.8kw at 230v (and not 240v)-9.8 should be fine anyhow
you'd need to check for supply suitabilty as well

2011

10.8kw that would be a 50amp rcbo

Is there such thing in Ireland as a 50A RCBO?
I have used 40A B type on instantaneous showers of this size with no issues.

M cebee

it'll prob run for an hour before tripping

the breaker wouldn't be considered when sizing the cable if you were doing that-just the current draw and correction factors

50amp switch for shower

2011

it'll prob run for an hour before tripping

I would hope that the MCB would trip after running for an hour.
I don't think that instantaneous showers are designed to run for over an hour.

astrofool

2011 wrote: »

A 10mm sq T + E is large enough for a load of that size if the run is 15m.


Correct methods of installation will require a larger cable to be used however in this case the OP is covered. All of the methods of installation that you have described are normal for a domestic installation.


Valid points, but the question is about the cable size for the circuit.


+1.
No offense intended to the OP, but this work should really be carried out only by a qualified electrician.

The cable itself is going behind plasterboard for about 3m, open air (clipped to attic beam) for 5m, then about 3m under floor and 2m to the shower.

I've simply ran the cable, and am looking to have the bits and pieces in place correctly, before a good electrician hooks it up. I wouldn't dare touch the fusebox myself

There's plenty of room on the fusebox, and it's a 20 year old (1991) build.

I'll likely go for the 9.8kw Mira Orbis.

2011

All sounds good (without seeing it I can't say 100%). Make sure that you have plenty of slack at the shower, isolation switch and distribution boards. Nothing worse than a cable that is too short to connect properly.

I'll likely go for the 9.8kw Mira Orbis.

The Mira are popular. I always liked the Trition showers myself. IMHO the larger rating is the better shower because for a given temperature you get increased flow.

Good idea getting a sparks to connect everything.

Good luck

RoundyMooney

seaniefr wrote: »

what it means is that with the cable being supplied at the moment the 10mm squared is measured to include the inner pvc insulated core whereas the old one just included the copper in the measurement so they are a slight bit undersized to the eye.

That can't be right, surely :eek:

M cebee

dunno what that's all about

2011

RoundyMooney wrote: »

That can't be right, surely :eek:

+1
I'm with RoundyMooney on this one.

seaniefr

2011 wrote: »

+1
I'm with RoundyMooney on this one.

get out your calipers and check it out!

seaniefr

seaniefr wrote: »

get out your calipers and check it out!

or else i have been getting dodgy cable...hmmmmm

astrofool

seaniefr wrote: »

or else i have been getting dodgy cable...hmmmmm

From doing a quick search, you should be able to measure the width of (using vernier callipers) one strand, and multiply it out by the number of strands. e.g. one strand = 1.3mm * 7 strands = 9.1mm total. (I of course stand to be corrected on this )

cast_iron

astrofool wrote: »

From doing a quick search, you should be able to measure the width of (using vernier callipers) one strand, and multiply it out by the number of strands. e.g. one strand = 1.3mm * 7 strands = 9.1mm total. (I of course stand to be corrected on this )

I think seanie may be confusing the meaning of "10 sq". It refers to the the cross sectional area of a core. It does not mean 10mm in core diameter.

2011

Without a doubt you are correct cast iron.