shower and fusebox advice

[geoffrunci]

Hi guys
I'm fitting a new shower and could do with some advice.
The shower is a 10.5Kw unit
The cabling will be 10mm, the run consisting of about 3mtrs to ceiling mounted switch, then 4mtrs across the loft plus a further 4mtrs down to the fuse box, and this is where the problem starts. The fusebox is an old one with only 6 fuses (see pic ).

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• geoffrunci
• 14 Jun 2009
• 2

from left to right I know the first 2 (white 5amp) are for lighting circuit upstairs and down, the next 2 (red 30amp) are the ring mains upstairs and down, but don't know about the last two. 1st is blue 15 amp and the last again red 30amp. Could one of these be for central heating?
Firstly is this unit too small? Secondly can I fit a larger fuse carriage of i.e. 45amp. I will be connecting via an RCBO as recommended but I'm wondering wether to upgrade the consumer unit instead.

 

[RF Lighting]

The two mystery fuses would by convention supply your immersion heater and your cooker, but it is common these days for a combi boiler to be fitted and the immersion heater removed.

You also might find the cooker has been replaced with gas at some point.

As for the new shower, you can not supply a load of that size from your existing fuse box.

You would either need the existing unit replaced, or install a henley block and fid an additional consumer unit for the shower only.

All of this work is notifiable to your LABC.

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I can not see a main earth wire from your cutout to your fuse box, which is a big worry if one is not present.

Also, someone has nicked your garage key

 

[geoffrunci]

Thanks RF guess you've confirmed what I thought, new consumer unit it is then.
As for the earth lead, this is the unit as wired when house was built in 1984 so I assumed it was wired correctly, if not I'd better get it checked out.
Again many thanks

 

[geoffrunci]

P.S.
Not just the key the whole bloody garage, it's a dining room now

 

[RF Lighting]

Can you take us a photo of your cutout and supply cable?

(the bits below your meter)

We should be able to tell the supply type and see if there is actually an earth present.

On a 1984 installation, I would expect to find a main earth present (albeit undersized by todays standards)

You will probably also need your main protective bonding upgrading before you can have this work to install the shower done.

 

[geoffrunci]

Thanks RF here's the pic, I guess you mean that earth cable at the bottom, so at least it is there.
Also, given that I will be adding a further two showers, (ensuites), what size unit would you recommend?
The house is 4 bedrooms but I think not very well built in the firstplace

 

[geoffrunci]

Helps if you add the pic though eh!!!!

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• geoffrunci
• 14 Jun 2009
• 2

 

[JohnD]

You will not be able to get an RCBO for that CU, and is is rather elderly.

Have a think about getting a new CU fitted. If you can afford all new RCBOs as well, so much the better.

It will be considerably more expensive though but at least you will only need one large one with space for future expansion (a large CU costs very little more than a small one, as you are mostly paying for fresh air)

p.s you really ought to identify the circuits served by those fuses, and label each of the ways on the CU. You must not remove or replace a fuse without turning off the main switch first, as there may be arcing. A good way to make labels is with a permanent marker and white vinyl tape. You can write neater on the kitchen table, then peel it off and stick it to the (freshly wiped) CU case

p.p.s. RCBOs are great

 

[Taylortwocities]

Also, given that I will be adding a further two showers, (ensuites), what size unit would you recommend?

You should seriously think about your strategy for showers. Your main fuse will probably be 60 or 80 amps. A single 10.5kw shower will pull 45amps.

So two showers running at the same time let alone a toaster/kettle will get you over budget.

Suggest you look at just shower pumps if your problem is low pressure or consider a combi boiler or a Megaflo (pressurised) system to get mains pressure from your hot and cold water.

Instant showers are VERY expensive and not green.
A five minute power shower uses more water than filling a bath.

 

[Steve]

IMO an instant electric shower is the greenest option available.

It gives instant hot water, direct to the user. Theres no storing it, insulating it, venting it, waiting for it etc, and you'll never have too much (as with a cylinder)

 

[ColJack]

ah but a cylinder that is fed from solar hot water panels with a circulating pump fed by a PV panel and a gas boiler rigged to run on hydrogen that is obtained from rainwater and another set of PV panels and you've got free hot water, after the initial cost and maintainence costs...

can't get much greener.... short of showering under a tropical waterfall in the middle of the rainforest..

60A seems a bit on the small side for 3 showers..

 

[securespark]

can't get much greener.... short of showering under a tropical waterfall in the middle of the rainforest....

Done that. It's fantastic, but not as warm as you'd think. Gotta watch the leeches, though...

 

[ColJack]

it's the candiru fish you wanna watch out for.. they swim up your junk if you pee in the water and start eating from the inside out...

 

[Space cat]

a gas boiler rigged to run on hydrogen that is obtained from rainwater and another set of PV panels

So you use the electricity from the photovoltaic panel to split hydrogen out of water and then burn it. I don't get it - unless yours is a deuterium fired boiler?

Also, given that I will be adding a further two showers, (ensuites), what size unit would you recommend?

I would recommend a gas fired boiler (methane, not deuterium - though I won't tell the NII if you don't ) because Taylortwocities is correct. If all three showers are ever used at the same time, you'll be seriously overloading your CU and you'll risk blowing the main service fuse. That's not something you want to happen when you're dripping wet and covered in shampoo!

 

[stuartsjg]

ah but a cylinder that is fed from solar hot water panels with a circulating pump fed by a PV panel and a gas boiler rigged to run on hydrogen that is obtained from rainwater and another set of PV panels and you've got free hot water, .

No point in making H2 from the PV electricity to then burn. Just heat from the electricity directly. Unless you are storing the H2 to allow for seasonal variations.

If not storing at all, then dont even use PV, have it all thermal and increase the efficiency of solar gathering!

On the showers:
I'm all electric and if the storage heaters are on and the shower is on then im over my 60A fuse. Add kettle and minor appliances then ill be about 80A.

I did once try and blow the fuse by adding cooker and oven to the mix but no luck despite being over 100A!

Im sure i once seen the fuse curve for these fuses and they can take double overload for several minutes, i may be wrong though.

Needless to say, i think 2-3 showers are going to give problems unless you have no more than 1-2 minute overlap between the two being on. 3 at the same time will probably blow a 60A incomer within a minute - and thats ignoring other loads.

I know B&B's using electric showers tend to have a 3 phase supply. One i seen had two bedrooms on one phase, another 2 on the other phase then the 5th bedroom and rest of the building incl owners shower on the 3rd phase.

As things were nicely balanced across the 3 phases of a 100A/phase supply so they could happily have 6 of 10.5kW showers on with no problems.

Stuart