Power Shower - Earth bonding required?

[kevsterdiy]

Hi
I'm looking to install a power shower in a bathroom refit. It is a Mira Vigour Thermostatic (low pressure water supply)

Question part 1:

Do I require earth bonding to be added to the shower?
The bathroom has not had an electric shower before. The bonding currently goes from one pipe of the radiator to the basin cold pipe (tee off for toilet), basin hot pipe, bath hot pipe and bath cold pipe. This is run in 10mm sq cable.
The bathroom has no electrics heaters or shaver sockets.
Does this need to be extended up to the hot and cold supply pipes to the shower?

The house is 20 years old, the consumer unit does not have an RCD and is the old fuse type.

I would appreciate some opinion after hearing that edition 17 of the regs has changed somewhat re bonding.

Question part 2:

Where is the best place to take the power for the shower?

The instructions do not advise, other than it pulls 150w max at 240v and that from source it will be wired in via an RCD at 30ma and a 2 pole FCU fused at 3A. Which I agree with. It does not have a low voltage transformer.
See page 9 here: http://www.taps4less.com/pdf/mira vigour guide.pdf

In comparison the shower I have in my own house (aqualisa aquastream) can be wired to a lighting circuit as well as a ring main via a RCD/FCU however it has a low voltage transformer.
See page 9 here: http://help.tradingdepot.co.uk/bathrooms/aqualisa/Install_Aquastrm.pdf

The Mira shower will mount on a wall with the airing cupboard behind. There is immersion power available but I would rather leave that as a dedicated radial circuit.

So I can drop power down from the lighting in the loft?

Or the last option is to use the last spare fuseway in the CU and run its own circuit but this is least preferred because the bath and bath floor would need to be taken up, but can be if it’s a must.
Unfortunately the shower was an afterthought, after originally asking for a mixer tap with a hose!

Thanks for your time!

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[EFLImpudence]

Do I require earth bonding to be added to the shower?

The shower will be earthed via its CPC.
If protected by an RCD (as you later state) it will not require bonding in itself.

The bathroom has not had an electric shower before. The bonding currently goes from one pipe of the radiator to the basin cold pipe (tee off for toilet), basin hot pipe, bath hot pipe and bath cold pipe.

Is the light fitting metal?

This is run in 10mm sq cable.

Are you sure?

The bathroom has no electrics heaters or shaver sockets.
Does this need to be extended up to the hot and cold supply pipes to the shower?

Are these the same pipes which will supply the shower?

Where is the best place to take the power for the shower? The instructions do not advise, other than it pulls 150w max at 240v and that from source it will be wired in via an RCD at 30ma and a 2 pole FCU fused at 3A. Which I agree with. It does not have a low voltage transformer.The Mira shower will mount on a wall with the airing cupboard behind. There is immersion power available but I would rather leave that as a dedicated radial circuit.

That would be the best place from which to supply the shower. You can obtain Switched Fused Connectors with integral RCD.
The shower is far less than 1 amp so it will be fine.

So I can drop power down from the lighting in the loft?

Not necessary.

 

[kevsterdiy]

Thanks for the reply.

To confirm in laymans terms the shower pipes do not need bonding as this is coved by the use of the RDC and its own CPC earth. (but see the supply pipe sources below)

The light fitting is plastic.

Yes it is 10mm cable, cores measure 4mm dia. surprise to me - it's normally 4mm

The hot pipe will be from the same hot pipe supply from the tank that feeds the bonded taps, tee'd off nearer the hot cylinder.
The cold is a separate pipe direct from the plastic tank in the loft gravity fed, it has no other contact with another pipe - bathroom is mains pressure cold.

Taking a spur from the immersion - as you say its pulls very little and the immersion is used once in a blue moon, this will be so much easier just wanted to check it's recognised as OK!

 

[EFLImpudence]

To confirm in laymans terms the shower pipes do not need bonding as this is coved by the use of the RDC and its own CPC earth.

Not exactly. If RCD protected bonding may be omitted.

The light fitting is plastic.

That's alright, then - no danger of touching a faulty wire or metal part.

Yes it is 10mm cable, cores measure 4mm dia. surprise to me - it's normally 4mm

Yes.

The hot pipe will be from the same hot pipe supply from the tank that feeds the bonded taps, tee'd off nearer the hot cylinder.

That's already bonded then. It can't be touched from shower cubicle anyway.

The cold is a separate pipe direct from the plastic tank in the loft gravity fed, it has no other contact with another pipe - bathroom is mains pressure cold.

This is just floating so does not need bonding.

Taking a spur from the immersion - as you say its pulls very little and the immersion is used once in a blue moon, this will be so much easier just wanted to check it's recognised as OK!

Yes, perfectly acceptable.

 

[kevsterdiy]

Many thanks.

 

[kevsterdiy]

To confirm in laymans terms the shower pipes do not need bonding as this is coved by the use of the RDC and its own CPC earth.

Not exactly. If RCD protected bonding may be omitted.

The light fitting is plastic.

That's alright, then - no danger of touching a faulty wire or metal part.

Yes it is 10mm cable, cores measure 4mm dia. surprise to me - it's normally 4mm

Yes.

The hot pipe will be from the same hot pipe supply from the tank that feeds the bonded taps, tee'd off nearer the hot cylinder.

That's already bonded then. It can't be touched from shower cubicle anyway.

The cold is a separate pipe direct from the plastic tank in the loft gravity fed, it has no other contact with another pipe - bathroom is mains pressure cold.

This is just floating so does not need bonding.

Taking a spur from the immersion - as you say its pulls very little and the immersion is used once in a blue moon, this will be so much easier just wanted to check it's recognised as OK!

Yes, perfectly acceptable.

Spoke to a spark who is a relation. I'm not saying you are wrong but advises bonding the shower supply pipes from the bathroom bonding, hot and even stand alone cold, and onward to the FCU. The lighting without an RCD should be bonded in too, so any metal light fitting in the future would be safe. His interpretation of the 17th edition.

Although omitting the light is safe for now because it isn't metal.

He speaks interms of an inspection it maybe rated as a level/grade 4 without most of the above.
Not that I'm planning an inspection!

 

[EFLImpudence]

Spoke to a spark who is a relation. I'm not saying you are wrong but advises bonding the shower supply pipes from the bathroom bonding,

hot

It is already bonded and not in the bathroom.

and even stand alone cold,

NO. It is not an extraneous conductive part.

and onward to the FCU

It is an RCD FCU and the only electrical circuit in the bathroom apart from the plastic light fitting.
If it were required it should be to the shower.

The lighting without an RCD should be bonded in too,

I suppose I assumed it already was

so any metal light fitting in the future would be safe.

Fair enough but future possibilities are for the future.
You may fit new CU in the future with RCDs protecting all circuits when, with a few exceptions, NO bonding will be required.

Although omitting the light is safe for now because it isn't metal.

Precisely.

He speaks interms of an inspection it maybe rated as a level/grade 4 without most of the above.

Bonding is to equalise potential between simultaneously touchable exposed metal parts.
Apart from the sink pipes and taps, there aren't any.

 

[kevsterdiy]

The bonding would go back to the FCU, which the showers CPC goes back to.

I'm now confused why two sparks vary....I can understand both opinions, are these two interpretations of the regs or is someone 'wrong'?
By having the extra bonding to the bathroom and shower pipes back to the FCU is it a problem or just belt and braces.


Is this trusted: http://www.diydoctor.org.uk/projects/bondingbathroom.htm
Points towards your view.

 

[EFLImpudence]

The bonding would go back to the FCU, which the showers CPC goes back to.

Same difference but usually done at the appliance.
How about also wiring the bathroom light from the RCD FCU?
Two birds with one stone - shower and light would be bonded. However because ALL circuits in the bathroom would be protected by an RCD you wouldn't need ANY bonding.

I'm now confused why two sparks vary....I can understand both opinions, are these two interpretations of the regs or is someone 'wrong'?

Look at some of the other threads to see varying opinions from far more than two.
I don't think that your relation and I have disagreed really.
That is, apart from bonding the cold supply pipe (see below)

Many, if not most, of the regulations ARE open to interpretation to some extent. They do not usually state that 'something' should be done as a matter of fact but measurements taken and conditions met to decide if 'something' is needed or not.
For example, if your house is not large then measurements may determine that the bonding you already have is not actually required.

By having the extra bonding to the bathroom and shower pipes back to the FCU is it a problem or just belt and braces.

Bonding the hot pipe would just be belt and braces.
Bonding the cold pipe should not be done. It could be a problem when you were in the loft (I'm assuming cold tank is there). It is not an extraneous or exposed conductive part, nor can it be touched from the bathroom. (It would be akin to bonding a metal object you keep in the airing cupboard.)

However, having said that, if it were installed with the cable stuffed into the same hole (through the wall) as the cold pipe then you may decide that it would be wise to earth the cold pipe - same wire but different purpose but that would just be to counteract poor design and the lesser of two evils by creating a possible hazard in the loft.

Is this trusted: http://www.diydoctor.org.uk/projects/bondingbathroom.htm[/QUOTE]It seems alright.
However, I note in the diagram there is no light shown.
Certainly a lot of belts and braces in it, too.

Points towards your view.

There have been no dissenting contributions from others.

Tempting fate?

 

[kevsterdiy]

A bit of a minefield all in all. Weighting up what is required and the OTT. If either is safe i'm happy.

Was comparing what you'd said to my relative and other posts/webpages.

I did suggest the CU was replaced which would cure most things! It maybe done in the not so distant future anyway.

The location of the pipes/earth bonding in question means it's easily added or removed either way in the future.