Replacing old electric shower

[greengiant12]

Hi all,

I'm new on this forum, and would value some advice on replacing an old electric shower. Our shower (installed some time ago by previous owner) has just broken down and we don't know what its kilowattage is. Have opened it up, there's no info on its kW inside, but it has a 6mm cable and a 30A fuse on the consumer unit - what kW shower should we go for to replace it?

Many thanks!

GG

 

[Taylortwocities]

There should be a rating plate, probably on the bottom.

240v * 30amp = 7.2KW

So you would probably be OK with a 7.5KW shower. (not great)

You would need an electrician to assess if the circuit could be upgraded to allow a bigger shower, but it sounds like you have a very old fuseboard, and that may limit the maximum current that can be drawn.

Also, does the fuseboard, or the shower circuit, have a safety RCD? That is a must have.

 

[PrenticeBoyofDerry]

Hi all,
I'm new on this forum,

Welcome to the forum greengaint12 or should I say" HO! HO! HO!"

and would value some advice on replacing an old electric shower. Our shower (installed some time ago by previous owner) has just broken down and we don't know what its kilowattage is. Have opened it up, there's no info on its kW inside, but it has a 6mm cable and a 30A fuse on the consumer unit - what kW shower should we go for to replace it?

The existing shower will be rated no greater than 7.2kW.
Your 6.00mm cable can carry more current than the 30A being provided.
It would be possible to install a higher rated fuse up to 45A on 6.00mm cable providing the cable is not contained in conduit/trunking or routed through thermal installation, this could allow for a higher output shower to be installed. Are the fuses rewireable or cartridge type? As this may also require a derating factor.
Also is 30mA RCD protection given to this circuit?

 

[ban-all-sheds]

Welcome to the forum greengaint12 or should I say" HO! HO! HO!"

That's a bit corny.

I'm amaized you had the nerve...

 

[PrenticeBoyofDerry]

I'm amaized you had the nerve...

Oh I have the nerve! Those giants don't scare me!

 

[greengiant12]

Many thanks for the comments! Yes, this is what we suspected (i.e. up to 7.2kW best, 7.5kW might be okay but best not), so it's helpful to have the confirm. Trouble is, we're struggling a bit to find showers up to 7.2 kW - have found a few, but not the bigger brands (Triton, Mira) - if we consider up to 7.5 kW, we're finding a bigger range to choose from. Any suggestions for brands & where would be good places to look for 7.2 kW showers?

Couldn't obviously finding a rating plate. As regards the CU, yes, we have 30mA RCD protection. Not sure whether fuses are rewireable or cartridge type - how to check? Also not sure what route cable takes from CU to shower, or how straightforward to upgrade. How much might a CU upgrade cost? The other thing we thought about is whether changing from a 30A fuse to a 32A fuse might make much difference (and would be safe and straightforward)??

Many thanks!

 

[EFLImpudence]

Any suggestions for brands & where would be good places to look for 7.2 kW showers?

Google is good.

As regards the CU, yes, we have 30mA RCD protection.

Separate unit ?

Not sure whether fuses are rewireable or cartridge type - how to check?

Just take out one and you will see.

Also not sure what route cable takes from CU to shower, or how straightforward to upgrade. How much might a CU upgrade cost?

It depends. It's not really necessary.

The other thing we thought about is whether changing from a 30A fuse to a 32A fuse might make much difference (and would be safe and straightforward)??

If you have a Wylex rewirables you can change to a plug-in 32A mcb.

A picture of the consumer unit and RCD would help.

 

[PrenticeBoyofDerry]

If you are struggling finding a lower rated shower, you may have an option
of retro fitting one of these in exchange to the existing 30A fuse,

Untitled

• PrenticeBoyofDerry
• 21 Jan 2013
• 1

Then it could be possible have a higher rated shower, something like 9.5kW on a 40A device.
But as previously stated, the method and route of 6.00mm cable will need confirming.

A 32A amp device is not going to increase you options of shower.
A new CU change will be relevant to the condition of existing installation, number of circuits, size of property,circuit accessories access, cable entry access, location of new board, any space confinements and the location you live as regional prices vary.
Expect it to be somewhere around the £500 mark.

 

[ban-all-sheds]

But as previously stated, the method and route of 6.00mm cable will need confirming.

As will putting a 40A device into the CU. It almost certainly will not be possible to do that - they aren't rated for it.

 

[EFLImpudence]

A 32A amp device is not going to increase you options of shower.

7.5 is an increase on 7.2.

May not be much improvement but ...

 

[Taylortwocities]

As BAS has pointed out, many of the old "fuseboxes" are only good for max 30amp per way.

Your best route would be to have a qualified electricien check and test the existing wiring and determine if the route and EFLI will allow the CPD to be increased to 40amp.

He/she could then install a new, separate 40amp shower CU with RCD.
Then you would be OK for an 8.5KW shower.

 

[securespark]

But as previously stated, the method and route of 6.00mm cable will need confirming.

As will putting a 40A device into the CU. It almost certainly will not be possible to do that - they aren't rated for it.

Wylex boards with a sub-100A main switch cannot support any CPD >32A.

However, there are a goodly number that have 100A main switches.

 

[PrenticeBoyofDerry]

But as previously stated, the method and route of 6.00mm cable will need confirming.

As will putting a 40A device into the CU. It almost certainly will not be possible to do that - they aren't rated for it.

As stated in my post I said it could be possible, but it's a fair point, would really need to know the design of the unit.
But if we take the old wylex boxes for instance, they have an insulation voltage rating of 500V and the 6 and 8 way unit has an isolator rated at 100A.
Albeit the 3 and 4 way is rated at 60A
and the 2 way at 45A.

 

[greengiant12]

Many thanks all! We've decided to get an electrician round to see what our options are.