Electric shower help.

[stevepeanut]

Hi everyone, I need a little help with my electric shower, please bear with me, as I don't know much about electrics or showers.

Since living in this house it had a 7.5 kw shower fitted. This worked fine for many years then something in the shower failed and it stopped heating the water. We bought a new 10 kw shower and an electrician who my girlfriend knows, fitted this for us.

This shower worked fine for a while and one day the power in the house went off while I was in the shower. We had to call the emergency helpline from our provider and an electrican came out, the main 3 inch long house fuse had blown. This person said he thought the shower cable we had would only be suitable for a 7.5 kw shower and not the new 10 kw one.

I shut the mains off myself, and removed the 10 kw unit. It took quite a bit of work searching the shops, as they are no longer popular but I found a new 7.5 kw unit that would be suitable for the existing cable. I had watched the other unit being fitted and it was only a case of tightening a water pipe and screwing in 2 wires so I put the 7.5 kw unit in myself. Also we had an old push in fuse downstairs, the kind with a length of wire. I threw that away and bought a 30 amp circuit breaker type fuse.

The shower worked ok at first but kept tripping the fuse every few minutes so I stopped using it. I asked the advice of another electrician and he said if the fuse is still tripping everytime the shower is on, then its most likely that the shower cable itself has a fault.

I have 2 questions.

1 Before I start spending money and getting a new cable, I need to ask, is the 30 amp fuse big enough to run the 7.5kw shower?

2 If the 30 amp is big enough, then I have a bigger problem. The cable will need replacing. The issue I have is the cable runs up from the pantry in the kitchen downstairs and is chased into the walls and upstairs to the bathroom, via the loft where it goes into a pull switch. But worst of all, the cable is behind the tiling, which was fitted with a new bathroom suite costing a lot of money. If the cable needs repalcing, what are my options? I don't want to rip out the new tiling so I need a way of getting a new cable to the shower from downstairs. The only thing I can think of is to run the cable out of the pantry, up the cavity wall, into the loft to the pull swtich. Then run the 2nd cable from the pull switch, through a hole in the ceiling and down into the shower, in some kind of sealed cable box. Is this possible and most importantly, safe? I can't think how of another way to get a cable in without pulling the tiling out.

For question 1, I would be happy to buy and change the fuse.

For question 2, I would be hiring a qualified electrican to do the new cable.

Thanks for reading and I would greatly appreciate any advice and help with this.

 

[bernardgreen]

and it was only a case of tightening a water pipe and screwing in 2 wires so I put the 7.5 kw unit in mysel.

There should be three wires.

Live ( brown or red)
Neutral ( blue or black )

and the most important one EARTH (bare copper sleeved green and yellow )

 

[stevepeanut]

and it was only a case of tightening a water pipe and screwing in 2 wires so I put the 7.5 kw unit in mysel.

There should be three wires.

Live ( brown or red)
Neutral ( blue or black )

and the most important one EARTH (bare copper sleeved green and yellow )

Sorry thats a mistake. Its over a year since I stopped using the shower, I just removed the cover, there are 3 three wires, red, black and the green yellow earth.

Now you have mentioned earth, just into the new year our combi failed and we got a new one. The local plumber put it in, and he got out an electrician to do some wiring work, the old boiler plugged into the mains, so a proper power swtich was fitted for the boiler.

I wasn't home, but the electrican mentioned something to my other half about our house having no earth at all and it should be sorted out at some point.

 

[Taylortwocities]

If your house really has no earth then nothing should be s
connected, or used until one is provided.

 

[stevepeanut]

If your house really has no earth then nothing should be s
connected, or used until one is provided.

I don't know what to say to that, in the pantry where the main fuse box is and the electric meter I can see earth wires going in and out. But the electrician says we have no earth. I have lived here 8 years, my other half, she's lived in this house 21 years, and everything electrically has been ok while she's lived here and when the lad working on the combi mentioned we had no earth thats the first she ever knew of it.

 

[PrenticeBoyofDerry]

I would suggest posting some pictures of your incoming supply, earthing arrangement and fuse board.

To answer some of your questions:
You could indeed route cable to pullcord isolator and back down enclosing in trunking.
I would suggest installing 10mm cable, this should give you plenty of scope for upgrades to showers with greater output than your existing one.
Any upgrade would require increasing size of MCB, you should also be installing RCD protection for this circuit/shower.
The reason for the MCB tripping could be many, faulty shower, overload, damaged or loose conductors, faulty protective device and insulation failure.
I would strongly suggest that if you have any doubt of the existence of an earth connection at supply, you promptly employ an electrician to confirm either way.

 

[stevepeanut]

I would suggest posting some pictures of your incoming supply, earthing arrangement and fuse board.

To answer some of your questions:
You could indeed route cable to pullcord isolator and back down enclosing in trunking.
I would suggest installing 10mm cable, this should give you plenty of scope for upgrades to showers with greater output than your existing one.
Any upgrade would require increasing size of MCB, you should also be installing RCD protection for this circuit/shower.
The reason for the MCB tripping could be many, faulty shower, overload, damaged or loose conductors, faulty protective device and insulation failure.
I would strongly suggest that if you have any doubt of the existence of an earth connection at supply, you promptly employ an electrician to confirm either way.

Cheers for the info, what about running a cable up the cavity? would that be ok, the cavity is empty, there is no wall insulation. I will get this earth situation looked at asap. I will put some pictures up tomorrow.

 

[PrenticeBoyofDerry]

No do not run cable up cavity.
The cable must also only be routed in permitted safe zones, so cannot just route anywhere.
//www.diynot.com/wiki/electrics:installation_techniques:walls

 

[riveralt]

If your house really has no earth then nothing should be s
connected, or used until one is provided.

I would strongly suggest that if you have any doubt of the existence of an earth connection at supply, you promptly employ an electrician to confirm either way.

That is what you need to do first before worrying about cable routes and sizes!!!!

 

[stevepeanut]

No do not run cable up cavity.
The cable must also only be routed in permitted safe zones, so cannot just route anywhere.
//www.diynot.com/wiki/electrics:installation_techniques:walls[/QUOTE]

Having a re think, its possible a cable could run up the inside of the pantry wall, which would lead up into the side wall of the bathroom, this could be done from the outside on the landing without having to touch the tiling on the inside of the bathroom.

But... maybe a good electrician might be able to find the fault thats causing the fuse to trip and the cable might not need changing.

 

[riveralt]

But... maybe a good electrician might be able to find the fault thats causing the fuse to trip and the cable might not need changing.

Pound to a penny you have burned out your pull switch.
Don't forget you will likely need to have RCD protection on the new shower as per manufacturers instructions.
BTW you should be chasing the original 'electrician' for the cost of this work it was his negligence that has caused you this problem in the first place.

 

[Taylortwocities]

while she's lived here and when the lad working on the combi mentioned we had no earth thats the first she ever knew of it.

Maybe he was referring to Equipotential Bonding. Often (incorrectly) called 'earthing'.
These are conductors that connect the main earth of the installation (at or near the consumer unit) to incoming service pipes like water, gas, oil.

Whatever, you should have a competent electrician check this out. A first step could be to call the guy who made the comment and ask him to explain.

 

[stevepeanut]

But... maybe a good electrician might be able to find the fault thats causing the fuse to trip and the cable might not need changing.

Pound to a penny you have burned out your pull switch.
Don't forget you will likely need to have RCD protection on the new shower as per manufacturers instructions.
BTW you should be chasing the original 'electrician' for the cost of this work it was his negligence that has caused you this problem in the first place.

The original lad that fit the 10kw shower didn't charge anything. A fuse the same as this is what the shower cable runs through near the mains box, is this a MCB?

Whats a RCD? Is that similar to the box that between the plug and socket when I mow the lawn?

Sorry if these are simple things to ask but this is all new to me.

 

[Taylortwocities]

That is an MCB.

You are correct, an RCD is what saves your life if you run over the lesd of your lawn mower.
You should /must have one on the shower. It is a requirement from most manufacturers and the Wiring Regulations.

Please tell us that you have one protecting you when you and yours are in the shower

 

[stevepeanut]

There might be one, I will look and photo it all tomorrow and put pics up. We did have an old style fuse that blew, I got sick of changing the fuse wire, so bought a MCB one so when it was tripping I could just flick it back into position rather than getting out the fuse wire.

I am not sure wether there is a RCD.

Whats the difference between a MCB tripping out and stopping the power, and a RCD tripping out and stopping the power?