1 Home Electrical Question...

kilasser

I need a new shower wired in to the mains. Got the electrician round this morning. There are two vacant 30-amp fuse in the fuse box. I thought it would be a simple matter of wiring it in to one of these. But he said no and that I needed a complete new fuse box Because the shower cant be added to the existing one. Even though the existing one is fine. Does this sound correct??

wyndham

what kind of fuses do you have. old type or flip-switch type. Electric showers do take a heavier cable.

johnnyrotten

Electric Showers need to be wired into an RCD.

Hagar

kilasser wrote:

I needed a complete new fuse box Because the shower cant be added to the existing one. Even though the existing one is fine. Does this sound correct??

Is this a second electric shower? If it is I had a similar situation. The power drain for two showers at the same time is apparently too high for a domestic fuseboard. The electrician had to put in some sort of isolator/relay thingamajig to stop both showers being used at once. It hummed in use and was a bit of a pain.

kilasser

It’s the old type fuses, not flip-switch type. It’s the only shower in the house.

chuckles30

My mother was getting an electric shower installed last year and it was the first time we'd had an electric shower in the house. We also had the old fuse board and the electrician also advised her to update to the 'trip-switch' model, so she did that. But it didn't surprise me as I reckon the original one was in since rural electrification!!!

crosstownk

When I moved into this house it had an electric shower and the old style screw-in fuses (45 years old). The shower was on two seperate trip switches (each 40A) and dedicated wiring ran to the shower. I've since had the house rewired but when the shower is turned on every light in the house dims slightly. You may also need to renew your earth rod before installing an electric shower.

Steve

Are you in UK??? you can find out from local BCO. The regs in IRL are a lot different.

davelerave

kilasser wrote:

It?s the old type fuses, not flip-switch type. It?s the only shower in the house.

well then you're better to change the box

incisor71

johnnyrotten wrote:

Electric Showers need to be wired into an RCD.

I have yet to see an example of an electrical feed for a shower going through an RCD. The same is not true of 13A sockets, however.

Hagar wrote:

Is this a second electric shower? If it is I had a similar situation. The power drain for two showers at the same time is apparently too high for a domestic fuseboard.

You can have more than one shower running in tandem on a domestic "fuse"board, but only if you have more than one phase supplied. In my parents' current house we have four electric showers and storage heating, so we have no choice but to opt for a three-phase supply.

davelerave

incisor71 wrote:

I have yet to see an example of an electrical feed for a shower going through an RCD. The same is not true of 13A sockets, however.

You can have more than one shower running in tandem on a domestic "fuse"board, but only if you have more than one phase supplied. In my parents' current house we have four electric showers and storage heating, so we have no choice but to opt for a three-phase supply.

electric showers have their own rcd/rcbo

Lex Luthor

a consumer unit should cost about €100 to buy and then add a few extra hundred for installation

Hagar

incisor71 wrote:

You can have more than one shower running in tandem on a domestic "fuse"board, but only if you have more than one phase supplied. In my parents' current house we have four electric showers and storage heating, so we have no choice but to opt for a three-phase supply.

I have no experience of normal domestic fuseboards running off a 3 phase supply. I stand corrected.

Steve

ETCI rules ET212-2004 States:

INTRODUCTION

New electrical installations must comply with the current National Rules for Electrical Installations. The Rules also cover
"the extension or alteration of an installation and parts of the existing installation affected by the extension or alteration"

(Rule 11.2).

BASIC PRINCIPLES

New work must comply with the current National Rules.
An extension, addition or alteration must not impair the safety of the existing installation, and the existing installation must not impair the safety of the new work.

DEFINITIONS

Addition: An addition to an existing circuit.

Alteration: Replacement of part of an installation.

Extension: Installation work involving one or more circuits.

As this is classed as an extension (addition of a circuit), the following applies:

EXTENSIONS TO EXISTING INSTALLATIONS
An extension to an existing installation must comply with the current National Rules.

In order to ensure that the protective device or devices operate correctly, the installer must check the existing earthing and main bonding arrangements, which should comply with the following:

The earth electrode should be driven to a depth of 1200mm and should have a minimum diameter of 12mm. If replacement is required, or if none exists, an earth electrode having a minimum diameter of 16mm should be installed.

The earthing conductor and main bonding conductors should have a minimum cross-sectional area of 6mm2 copper. Where replacement is required, or where these conductors are absent, conductors having a minimum cross-sectional area of 10mm2 copper should be installed.

Main bonding clamps should be of a type with screws that provide tightening. Perforated metal strip is not permitted for the purpose.

Part V of national rules says:

Water heating appliances
Circuits supplying water heating appliances shall be protected by a residual current device having a rated operating current not exceeding 30mA.
A shower unit will require a separate RCD.
An immersion water-heater circuit shall be protected by a residual current device having a rated operating current not exceeding 30mA.
Note: All water heaters in bathrooms must be protected by a residual current device. (Section 701)

Therefore you must install an RCD - there is no choice for the electrician. The old type fuse board is not suitable for this and the internal loading may not be rated for a shower. The only "safe" thing he can say is to replace the CU with a modern one.

davelerave

if the supply and earthing are adequate a sparkie might be better putting his own rcbo in a box beside the cu unless he's asked different.it's only a small job changing a cu but there is a responsibility to test afterwards and a risk of rcds tripping and from experience better avoided depending on the customer