A shower dilemma...

[CmdrBond]

I'm posting this here as I feel it is more electrical related than plumbing.

I'm half way through my bathroom refurbish - and having spoken with a knowledgeable work colleague, I'm now in a quandary about my shower.

We bought the house about 6 years ago. The current shower was installed at the previous owners instruction - I don't know when.

The current shower is a "Scalemaster Softline SL80", which from their website (scalemaster.co.UK) appears to be 8.5kW.

I'm no expert, but looking at the current connected cable I would say it is 6mm².



Also, our fuse box has NO RCD's. The shower fuse is the one on the far left. I haven't pulled it yet so I don't know if it's rewirable or cartridge. I'm guessing it's 30Amp.



Now, here is the dilemma - the new bath is L shaped. To centralise the shower head will mean moving it across about 4 inches from its current location. Which will require moving the control unit and it's associated feeds.

If I'm going to have to move the pipe and cable slightly, then maybe I should consider a new shower at the same time (before I tile it all up).

My colleague has recommended I change to a power shower, and now I'm totally confused as to which way to turn...

So I'm left with 4 options.

#1 - just put the existing shower back, just moved over a few inches.

Not really happy with this due to the discovery on the electrics - pushing the wire and the fuse to the max with no RCD.

#2 - replacing with a lower rated shower, 7.5kW?

We have quite high water pressure and I'm worried 7.5kW won't be man enough.

#3 - get the wire replaced with 10mm².

Not really an option as we're getting into the "complete rewire" area, I don't have the money!

#4 - power shower. Replace the 6mm² with a 1.5mm²? 13Amp cable spurred off of an existing 13Amp circuit.

My colleague thinks this is OK to DIY, but I'm certain this requires part P (whereas simply replacing like for like does not).

If I go this route I WILL get an electrician in to be safe.

The problem with this (and at least I have access to the wall and the floor right now) is that I will need to cap the mains water feed and run new gravity feeds from the hot and cold supply.

So based on the above, what do you guys recommend?

 

[flameport]

Option 4. Either a shower with the pump inside it, or a separate pump with a mixer valve on the wall.
The existing cable could be used for this, just put an RCD FCU on the end of it outside the bathroom or some other convenient place.

The other options are dead ends:
If the existing shower is above 7kW, it can't be used and should not have been fitted in the first place.
Fitting a new one would require an RCD, even if you could find a 7kW model.
New cable etc, will be notifiable and cost a non-trivial amount of money.
Even after all that, electric showers are hopeless and should only be fitted if that is really the only possible option.

 

[ericmark]

The 6mm is not the distance across the cable it is 6mm² which would need a go / no go gauge to measure the size.

The fuse box is the same type as fitted in my house which in my house is RCD protected. The RCD is not in the fuse box but located above the pair of fuse boxes one RCD to each fuse box. Be it before as in my case or after the fuse box RCD protection can still be added.

I use a simple thermostatic controlled shower mixer direct off my Main 7 instant gas water heater so my shower is limited to 27kW so using one with side sprayers is out. I only have a single shower head. If my hot water was pre-heated and stored in a cistern then I could consider a power shower. However the bath drain can't deal with the water as it is and it builds up in the bath so using a power shower with side sprayers would also mean some changes in waste management.

To be frank I would not consider an instant electric shower, I have got use to showering under loads of water and the pressure from the head near enough knocking off all dirt without needing soap. The whole idea of trying to wash under the dribble produced by most electric showers does not appeal to me. So I would say if you can use either a direct shower or a power shower then forget electric.

OK the power shower does need electric power but only for the pump so a simple RCD FCU is ample. With an instant shower you are looking at around 40 amp and first question is what is your supply? In my case just 60A so it would be a lot of work for me to down grade to an electric dribble system.

 

[Lectrician]

It certainly looks like 6mm, which would be fine, depending on install method. The fuse should be a 40amp.

For what it's worth, get a spark to swap your CU. Not only will the shower circuit benefit, but your whole installation.

 

[ericmark]

Looking a Batt cables sizes 5.7 x 10.9 mm = 2.5mm² and 6.9 x 13.4 mm = 6mm² other makes will vary but looking at that tape measure i would guess on 2.5mm². It does not look like 6mm² to me. I test with a blue and yellow crimp. Tight with blue then 2.5mm² will not fit blue but slack with yellow then 4mm² and tight with yellow then 6mm² will not fit yellow then try the 10mm² and 16mm² crimps but measuring overall dimensions of cable is really useless. Different makes will have more or less insulation so at best it is a rough guide.

 

[CmdrBond]

Option 4. Either a shower with the pump inside it, or a separate pump with a mixer valve on the wall.
The existing cable could be used for this, just put an RCD FCU on the end of it outside the bathroom or some other convenient place.

There is a ceiling mounted pull cord isolator switch in one corner of the bathroom, right by the door. I am presuming this is directly connected to the fuse at the CU on one side and the shower on the other.

If I go down the route of the RCD FCU (I'll get a sparky in, but for understanding could you explain)

1. would this utilise the existing cable and fuse from the fuse box, or would it be spurred off a 13Amp circuit elsewhere?
2. Would the current isolator be bypassed completely or used inline with the RCD FCU?
3. If the existing cable fits, and all other wiring is done OUTSIDE the bathroom, is it notifiable?

The 6mm is not the distance across the cable it is 6mm² which would need a go / no go gauge to measure the size.

I am aware it is the cross sectional area. pi*d. So in theory, a cable just under 2mm in diameter per core would be 6mm² (pi2=6.28), whereas a cable just over 3mm in diameter per core would be 10mm² (pi3=9.42).

The fuse box is the same type as fitted in my house which in my house is RCD protected. The RCD is not in the fuse box but located above the pair of fuse boxes one RCD to each fuse box. Be it before as in my case or after the fuse box RCD protection can still be added.

I really don't seem to have ANY RCD.

This is my set up, looking at the writing and and damage to the wall, I guess the house has had at least 1 re-wire in its lifetime:

For what it's worth,
get a spark to swap your CU. Not only will the shower circuit benefit, but your whole installation.

Roughly how much is having a new CU

likely to cost?

Looking a Batt cables sizes 5.7 x 10.9 mm = 2.5mm² and 6.9 x 13.4 mm = 6mm² other makes will vary but looking at that tape measure i would guess on 2.5mm². It does not look like 6mm² to me. I test with a blue and yellow crimp. Tight with blue then 2.5mm² will not fit blue but slack with yellow then 4mm² and tight with yellow then 6mm² will not fit yellow then try the 10mm² and 16mm² crimps but measuring overall dimensions of cable is really useless. Different makes will have more or less insulation so at best it is a rough guide.

Understood. However that cable is closer to 15mm than 10mm, so I guessing 6mm²

 

[endecotp]

I am aware it is the cross sectional area. pi*d. So in theory, a cable just under 2mm in diameter per core would be 6mm² (pi2=6.28), whereas a cable just over 3mm in diameter per core would be 10mm² (pi3=9.42).

WRONG. Back to school for you!

 

[CmdrBond]

I am aware it is the cross sectional area. pi*d. So in theory, a cable just under 2mm in diameter per core would be 6mm² (pi2=6.28), whereas a cable just over 3mm in diameter per core would be 10mm² (pi3=9.42).

WRONG. Back to school for you!

DOH - it's pi*r*r isn't it?

I'm half asleep!, does it show?

So just approx 2.8mm diameter (1.4mm radius) is 6mm² (pi*1.4²=6.16mm²) and approx 3.6mm diameter (1.8mm radius) is 10mm² (pi*1.8²=10.18mm²)

 

[flameport]

If I go down the route of the RCD FCU (I'll get a sparky in, but for understanding could you explain)
1 would this utilise the existing cable and fuse from the fuse box, or would it be spurred off a 13Amp circuit elsewhere?
2 Would the current isolator be bypassed completely or used inline with the RCD FCU?
3 If the existing cable fits, and all other wiring is done OUTSIDE the bathroom, is it notifiable?

1 - Could be either, whichever is more convenient.
2 - Existing isolator removed, RCD FCU installed on end of cable. The RCD FCU is the new isolator.
3 - Wiring outside the bathroom is not notifiable, but if you get a power shower with pump inside that would be notifiable as the shower requires an electrical connection which would be in the bathroom. A separate pump outside the bathroom is not.

 

[EFLImpudence]

//www.diynot.com/wiki/Electrics:flatpvccables

 

[CmdrBond]

3 - Wiring outside the bathroom is not notifiable, but if you get a power shower with pump inside that would be notifiable as the shower requires an electrical connection which would be in the bathroom. A separate pump outside the bathroom is not.

OK.

Which would you recommend?

Separate pump located in loft or airing cupboard...

Or combined shower and pump? (Which I will get a sparky to wire up)

I think I've got a 13 Amp feed in the airing cupboard, so that's a possibility?

 

[Lectrician]

Looking a Batt cables sizes 5.7 x 10.9 mm = 2.5mm² and 6.9 x 13.4 mm = 6mm² other makes will vary but looking at that tape measure i would guess on 2.5mm². It does not look like 6mm² to me. I test with a blue and yellow crimp. Tight with blue then 2.5mm² will not fit blue but slack with yellow then 4mm² and tight with yellow then 6mm² will not fit yellow then try the 10mm² and 16mm² crimps but measuring overall dimensions of cable is really useless. Different makes will have more or less insulation so at best it is a rough guide.

Don't be silly, it's 6mm. You can tell by the tape measure, rad pipe etc. It's certainly not 2.5mm.

 

[ericmark]

Widest part 10.9 mm = 2.5mm², 11.8 = 4mm², 13.4 = 6mm², 17.2 = 10mm² and 19.4 = 16mm² with BATT Cables 624Y Twin & Earth PVC Cable BS6004 A05VVH4-U with others it may vary. Since the cable is white it could be 624B Twin & Earth LSZH Cable 300/500V BS7211 in which case the size changes 9.9 mm = 2.5mm², 11.5 = 4mm², 13.5 = 6mm², 15.9 = 10mm² and 18 = 16mm² again BATT Cables. Now the cable is not being measured with a calliper so we have to accept that the distance between the camera lens and tape can result in getting an incorrect reading. To me it looks like 15 mm and white so likely 10mm² I don't have the 90°C chart for twin and earth only the 70°C chart so likely Reference Method 100 (above a plasterboard ceiling covered by thermal insulation not exceeding 100 mm in thickness) it will be around 55A clearly more that the 45A for 70°C cables.

But here I am assuming and to assume is dangerous. It may be made by another manufacturer it may be 70°C not 90°C in spite of being white. Using a Yellow crimp is a far better method to judge cable size than measuring the outside.

 

[CmdrBond]

Widest part 10.9 mm = 2.5mm², 11.8 = 4mm², 13.4 = 6mm², 17.2 = 10mm² and 19.4 = 16mm² with BATT Cables 624Y Twin & Earth PVC Cable BS6004 A05VVH4-U with others it may vary. Since the cable is white it could be 624B Twin & Earth LSZH Cable 300/500V BS7211 in which case the size changes 9.9 mm = 2.5mm², 11.5 = 4mm², 13.5 = 6mm², 15.9 = 10mm² and 18 = 16mm² again BATT Cables. Now the cable is not being measured with a calliper so we have to accept that the distance between the camera lens and tape can result in getting an incorrect reading. To me it looks like 15 mm and white so likely 10mm² I don't have the 90°C chart for twin and earth only the 70°C chart so likely Reference Method 100 (above a plasterboard ceiling covered by thermal insulation not exceeding 100 mm in thickness) it will be around 55A clearly more that the 45A for 70°C cables.

But here I am assuming and to assume is dangerous. It may be made by another manufacturer it may be 70°C not 90°C in spite of being white. Using a Yellow crimp is a far better method to judge cable size than measuring the outside.

Based on that I will say it's likely 6mm²

It's less than 15mm. From memory (it's been 3 weeks since I isolated, disconnected, and made "safe" with a 30A choc block and electrical tape) the earth is sheathed and it's multi strand as opposed to solid cores.

 

[Simon35]

3 - Wiring outside the bathroom is not notifiable, but if you get a power shower with pump inside that would be notifiable as the shower requires an electrical connection which would be in the bathroom. A separate pump outside the bathroom is not.

OK.

Which would you recommend?

Separate pump located in loft or airing cupboard...

Or combined shower and pump? (Which I will get a sparky to wire up)

I think I've got a 13 Amp feed in the airing cupboard, so that's a possibility?

Bear in mind the noise from a pump in the loft. Whatever it's mounted on will vibrate a bit, plus the pump makes some noise. If someone gets up early and has a shower before others are wanting to be awake, might not be appreciated.....