help needed - electric shower

[jab]

Hi All

Please excuse my complete lack of knowledge, I do not know anything about electrics at all and the terminology.

We've moved into a very old house that's very outdated and requires a lot of work, we are hoping to start renovations in spring next year and until then things will just have to make do. Unfortunately our electric shower broke and I need to order a new one, before showering we always had to turn on a toggle which I assume gave the shower power (?). Unfortunately this seems to have blown and the shower no longer works. I've read online that you need to order the right kw as specific cabelling/wiring is needed - 8.5kw, 9.5kw, 10.5kw seem to be the most common ones. How do I know which one I need to order?

As you can see from the switch there is some black smoke coming out so I'm a bit worried and want to make sure this is done properly now. Is this a difficult job which requires a lot of work and will cost a lot as clearly something has blown and a new electric shower has to be installed? Do I need to get anything else other than a new shower unit?

Any advice, recommendation is much appreciated! We will of course get a professional in but I wanted to get a feel of cost and order the shower in advance so we only have to get the electrician in once to do the job.

 

[Geoff1946]

There is a good chance that there is nothing wrong with the shower unit, just a failed switch. However I would strongly advise you to have an electrician attend to it. That really doesn't look like a proper and safe installation. Electric showers are (IMO) the most potentially dangerous appliance in a house.

 

[Murdoch]

That's not pretty.

Any chance you could post a photo of the fuseboard / consumer unit?

 

[jab]

@Murdoch @Geoff1946 thank you both for your responses. I've actually just opened the shower unit and it seems something has blown there as well. And the current unit is 10.5kw, would this be the right one for the cabelling/wiring installed?

I'd rather get a new unit just to be safe but don't want to completely re-do everything as the bathroom will be fully renovated in spring next year so we just need something that works but is also safe at the same time.

Here are some photos of the fuseboard and blown shower unit.

 

[Murdoch]

That incoming live connection at the shower doesn’t look good and I’m not sure the connecting cable from the isolation switch to the shower is big enough

 

[Geoff1946]

I still think you probably don't need to buy a new shower unit; that bit of burned terminal block can be easily replaced,

HOWEVER you do need to invest in some re-wiring. As Murdoch suggests there is no way that flex is capable for 10kW. Just compare the size of the internal wire it connects to.

Getting an electrician on the job before you spend anything will likely save you money, as well as preventing burning the house down!

 

[binky]

That incoming live connection at the shower doesn’t look good and I’m not sure the connecting cable from the isolation switch to the shower is big enough

Doesn't even look bigger than 2.5mm

 

[johnb2713]

Doesn't even look bigger than 2.5mm

It will be fine, it's water cooled?

Jeez, that all looks horrendous to my eyes.

 

[Murdoch]

Did you get an EICR done before you bought the property?

 

[binky]

It will be fine, it's water cooled?

Jeez, that all looks horrendous to my eyes.

It is . Reminds of a flat I rewired many years ago, the cooker cct had 2 sockets spurred off it along the cable run, the gas boiler, and having reached the cooker, a cable went through the wall for the shower...

 

[SPECIAL LOCATION]

@Murdoch @Geoff1946 thank you both for your responses. I've actually just opened the shower unit and it seems something has blown there as well. And the current unit is 10.5kw, would this be the right one for the cabelling/wiring installed?

I'd rather get a new unit just to be safe but don't want to completely re-do everything as the bathroom will be fully renovated in spring next year so we just need something that works but is also safe at the same time.

That to me looks like the classic DIY / Builder installation....
Where the basic assumptions went something along the lines of:-

Get the biggest powered shower you can buy for the cheapest price from B&Q.
Connect it up with any bits of wire/flex switches you have available...
(such as a ceiling cord pull switch fixed to the wall.. a bit of 13Amp flex to connect a device that actually requires circuit wiring capable of 45Amp+)
Then switch it on, if it works.. it must be ok!!!

Buying a new shower "too be safe" will NOT be safe if the circuit supplying it is not electrically safe or has capacity to carry the supply current required for the shower power rating.

The shower MCB in your consumer unit appears to 40A rating....
which suggests to me it was previously installed to supply a max 9.5kWatt rated shower, NOT a 10.5kW.

The cord-pull switch is probably only rated at 40A.. when a 50A rated switch would be more suitable for a 10.5kW shower

IMHO BEFORE you do anything..
you need the whole circuit from the CU to the shower electrically tested to confirm it is safe for continued use,
and will not present any dangers such as starting a fire or electrocuting anyone..

A competent electrician with suitable calibrated test meters, should be able to fully test this circuit:
"Continuity / Polarity / Insulation Resistance / RCD operating times / Earth loop impedance" etc..
All within the charges for an initial 1hour call out...
(Actual costs would vary depending upon whereabout in the country you are.. and how local the electrician is to you).
Following these tests, they would be able to advise accurately what item(s) need replacement / upgrading..

If you were within 15 to 25mins travel from my home,, I would probably charge £55, for a full test of the existing shower circuit, and to provide a written report of my recommendations.

IF the main cable from the CU does need replacing, in light of your future upgrade plans, to get you working it could be worth considering run in a new cable, but leave a few metres spare looped in a ceiling void ready to accommodate later changes, without the need to extending cables or add unnecessary cable joints..

Basically....
DO NOT BUY ANYTHING... until you have had the shower circuit wiring fully tested!

p.s.
IF this circuit is of a similar standard to the wiring in the rest of the property...
It would be VERY wise to get the whole installation fully tested & inspected ASAP!.

While the current consumer unit not an excessively out-dated design... (although there are some more up to date solutions.).
it is not uncommon for a consumer unit replacement to hide other poor wiring practices.

Guess work and assumptions are NOT good practices when evaluating the safety and functionality of any electrical installation.

 

[jab]

That to me looks like the classic DIY / Builder installation....
Where the basic assumptions went something along the lines of:-

Get the biggest powered shower you can buy for the cheapest price from B&Q.
Connect it up with any bits of wire/flex switches you have available...
(such as a ceiling cord pull switch fixed to the wall.. a bit of 13Amp flex to connect a device that actually requires circuit wiring capable of 45Amp+)
Then switch it on, if it works.. it must be ok!!!

Buying a new shower "too be safe" will NOT be safe if the circuit supplying it is not electrically safe or has capacity to carry the supply current required for the shower power rating.

The shower MCB in your consumer unit appears to 40A rating....
which suggests to me it was previously installed to supply a max 9.5kWatt rated shower, NOT a 10.5kW.

The cord-pull switch is probably only rated at 40A.. when a 50A rated switch would be more suitable for a 10.5kW shower

IMHO BEFORE you do anything..
you need the whole circuit from the CU to the shower electrically tested to confirm it is safe for continued use,
and will not present any dangers such as starting a fire or electrocuting anyone..

A competent electrician with suitable calibrated test meters, should be able to fully test this circuit:
"Continuity / Polarity / Insulation Resistance / RCD operating times / Earth loop impedance" etc..
All within the charges for an initial 1hour call out...
(Actual costs would vary depending upon whereabout in the country you are.. and how local the electrician is to you).
Following these tests, they would be able to advise accurately what item(s) need replacement / upgrading..

If you were within 15 to 25mins travel from my home,, I would probably charge £55, for a full test of the existing shower circuit, and to provide a written report of my recommendations.

IF the main cable from the CU does need replacing, in light of your future upgrade plans, to get you working it could be worth considering run in a new cable, but leave a few metres spare looped in a ceiling void ready to accommodate later changes, without the need to extending cables or add unnecessary cable joints..

Basically....
DO NOT BUY ANYTHING... until you have had the shower circuit wiring fully tested!

p.s.
IF this circuit is of a similar standard to the wiring in the rest of the property...
It would be VERY wise to get the whole installation fully tested & inspected ASAP!.

While the current consumer unit not an excessively out-dated design... (although there are some more up to date solutions.).
it is not uncommon for a consumer unit replacement to hide other poor wiring practices.

Guess work and assumptions are NOT good practices when evaluating the safety and functionality of any electrical installation.

@SPECIAL LOCATION thank you so much for this, it's incredibly helpful and we'll get an electrician in to do some testing. The estimated charge is really helpful, we previously have received a range of quotes for the same job and it's astonishing to see how they differ at times!

 

[Murdoch]

@SPECIAL LOCATION thank you so much for this, it's incredibly helpful and we'll get an electrician in to do some testing. The estimated charge is really helpful, we previously have received a range of quotes for the same job and it's astonishing to see how they differ at times!

Given the OP is in London I suspect the local prices will be higher

 

[BorisJ]

The purpose of that switch is to isolate the shower when working on it or possibly when you go on holiday. It is not necessary to turn it off after every shower. It is not even a requirement in the regs to have such a switch.

Do you intend to continue with an electric shower after your bathroom refurbishment, or will you get a proper shower off a central heating boiler?

All things to consider.

 

[Murdoch]

The purpose of that switch is to isolate the shower when working on it or possibly when you go on holiday. It is not necessary to turn it off after every shower. It is not even a requirement in the regs to have such a switch..

It may not be explicit in the regs but most , if not all MI's state RCD protection and local DP isolation

 

[BorisJ]

MI are guidance only and can be taken account of but don’t have to be followed, especially when they are wrong, which is quite common as they are written by marketing people not engineers.

 

[Murdoch]

MI are guidance only and can be taken account of but don’t have to be followed, especially when they are wrong, which is quite common as they are written by marketing people not engineers.

Hum. Only fools ignore Electrical guidance when it comes to showers

And on dual rcd boards it’s essential to have DP isolation too

 

[johnb2713]

And on dual rcd boards it’s essential to have DP isolation too

It's probably obvious but I cant see it, may I ask why?

 

[Murdoch]

It's probably obvious but I cant see it, may I ask why?

very simply, when the rcd starts tripping, without DP isolation you can’t isolate the shower ….. so you can‘t check if the shower is the problem easily

 

[johnb2713]

very simply, when the rcd starts tripping, without DP isolation you can’t isolate the shower ….. so you can‘t check if the shower is the problem easily

But why only on a dual RCD board?