Limited to 7.5kw shower?

Section62

GDB2222 said:

Section62 said:

grumbler said:

jamesd said:

Plumbworld has a list of requirements which includes showers above 7kW up to 9kW on 6mm cable with runs up to 18m

IMO, up to 18m (and 35m)  restriction on the distance from the fuseboard is absolutely nonsensical. The bigger the distance, the better as the current gets only smaller.

This undermines credibility of all their other requirements.

The longer the cable the greater the voltage drop.

The length of cable of a given CSA passing a given current has to be limited to ensure the total voltage drop isn't excessive.  If it is, then a larger CSA cable has to be used.

I guess Grumbler is saying that, if the voltage drop is too big, the expected output of the shower would not be achieved. That would not be dangerous, as long as the cable is not getting too hot?

But AIUI the voltage drop has to be limited in order to comply with regs.  In some cases excessively low voltage may also cause component failure.


I think somewhere here there is also a point that if you are running the cable so hard that the shower is not able to produce its rated output, then why not simply buy a lower rated shower and avoid the risk of melted cables, and energy wastage? (assuming installing a larger cable is not an option)

danrv

Section62 said:

I think somewhere here there is also a point that if you are running the cable so hard that the shower is not able to produce its rated output, then why not simply buy a lower rated shower and avoid the risk of melted cables, and energy wastage? (assuming installing a larger cable is not an option)

Maybe. I just know that while I was using the old 8.5kw Triton, it seemed to work well with low use. 
Not sure how good the 7.5kw showers are but I know that they’re the lowest rated available. Looking at getting a Triton T80 Easi-fit 8.5kw.

I need to get the shower soon as I can’t really continue with the bathroom so the replies help a lot.

Belenus

danrv said:

jamesd said:

In this case at least the attic looks most likely to be method C with a 47 amp (22.3kW) capability but not so sure about the stud wall and its insulation level and cable placement within it. danrv, you might want to read the method descriptions to see if you can sort out which one applies to the stud wall part of the route.

Thanks.
Around half of the cable is laying on loft insulation, some is covered but loft isn’t boarded.
It then drops down 2.4m into a hollow bedroom wall and probably not clipped in place.
Then under the floor for another 2m to the CU.

Is it possible to pull a 10mm cable through using the 6mm cable?

The 2m under a floor may be the trickiest bit.

Alternatively, is it possible to install a 10mm cable via another route and disconnect the 6mm cable?

danrv

Belenus said:

danrv said:

jamesd said:

In this case at least the attic looks most likely to be method C with a 47 amp (22.3kW) capability but not so sure about the stud wall and its insulation level and cable placement within it. danrv, you might want to read the method descriptions to see if you can sort out which one applies to the stud wall part of the route.

Thanks.
Around half of the cable is laying on loft insulation, some is covered but loft isn’t boarded.
It then drops down 2.4m into a hollow bedroom wall and probably not clipped in place.
Then under the floor for another 2m to the CU.

Is it possible to pull a 10mm cable through using the 6mm cable?

The 2m under a floor may be the trickiest bit.

Alternatively, is it possible to install a 10mm cable via another route and disconnect the 6mm cable?

I’d probably get the electrician if doing something like that. He disconnected the old shower before the plastering was done. He might say on inspection, that the wiring would be ok anyway.

Belenus

10mm cable would allow you to install a more powerful shower.

If you are happy with 8.5kw then ok but I find them a bit of a pain in the winter as I do like a hot and powerful shower.

Greta Thunberg hates me. 

FreeBear

danrv said: Looking at getting a Triton T80 Easi-fit 8.5kw.

Do consider the T80 Easi-Fit+ Thermostatic - I have one fitted here and find it copes with varying water pressure. Can also deliver a real hot shower even in the winter.

Edit - Just looked up the price at Screwfix.... Ouch. Pretty sure I didn't pay anywhere near that much....

coffeehound

GDB2222 said:

Section62 said:

grumbler said:

jamesd said:

Plumbworld has a list of requirements which includes showers above 7kW up to 9kW on 6mm cable with runs up to 18m

IMO, up to 18m (and 35m)  restriction on the distance from the fuseboard is absolutely nonsensical. The bigger the distance, the better as the current gets only smaller.

This undermines credibility of all their other requirements.

The longer the cable the greater the voltage drop.

The length of cable of a given CSA passing a given current has to be limited to ensure the total voltage drop isn't excessive.  If it is, then a larger CSA cable has to be used.

I guess Grumbler is saying that, if the voltage drop is too big, the expected output of the shower would not be achieved. That would not be dangerous, as long as the cable is not getting too hot?

Wonder whether the solenoid valve might start to play up if fed too low a voltage?  Also there are those instant showers that contain a small pump to boost pressure from a loft cistern, and they could overheat if under-volted, I suppose.

danrv

FreeBear said:

danrv said: Looking at getting a Triton T80 Easi-fit 8.5kw.

Do consider the T80 Easi-Fit+ Thermostatic - I have one fitted here and find it copes with varying water pressure. Can also deliver a real hot shower even in the winter.

Edit - Just looked up the price at Screwfix.... Ouch. Pretty sure I didn't pay anywhere near that much....

Thanks.
Yes. Don’t mind paying more for thermostatic if it makes a difference.
Non thermostatic looks good value though at £89.00 plus bathroom mains water pressure is good and consistent.

coffeehound

You still have a hot water tank @danrv?

danrv

coffeehound said:

You still have a hot water tank @danrv?

Yes, just across from the bathroom.
Useful for baths although I often heat up a tank full 
just for a bit of washing and dishes.

I did take out a tank fed cold pipe that was supplying a bidet so I suppose that could’ve been used for a power shower.
I’ve gone for electric as that was what was there before.