My CU must be earthed...but where ?! (with pics)

[Paul Barker]

I looked at a hotel the other day single phase supply 60 amp fuse, 4 electric showers before you even look at the rest of the installation. "What do you mean I need a 3 phase supply? it's never been a problem before"

Am working now on a 5 story house with two dwelling per floor, whole place is on one single phase supply and one gas meter. New landlady sick of paying for everyones gas (they had all bypassed their pay meters) has had a builder fit electric showers to every dwelling,

3 phase supply 100 amps per phase in both cases.

The landladies attempt to get money for services by having her previous electrician fit card meters has also proved fruitless. You don't honestly believe people with the cunning to bypass a gas meter aren't going to find a source of cards. I thought that would the the first thing they would do, but it seems there are two better ways, one is to break into the sub mains and run an extension leed to you flat. The other is to find a card that keeps on working time and again. I guess a quick google search or something like that will solve all these problems for tenants,

Her real mistake was to buy the place at all, but now her only hope is mass eviction and start again with people of a different profile. She'll never beat them.

I'm turning my phone off at night when they all take showers and blow the fuse in the head.

 

[mikej2005]

do you have enough water pressure to use both at once?

My water pressure is 3.6 bar, so yes - I think so !

 

[CallEdsFirst]

Her real mistake was to buy the place at all, but now her only hope is mass eviction and start again with people of a different profile. She'll never beat them.

Or just shut the juice off! That's what happens when you or I don't pay the electricity bill!

 

[Doctor Drivel]

Thanks for your comments guys.

I has a boiler installed recently and the installer identified that the incoming gas pipe near the meter needed bonding with 10mm2 earthing cable to the CU. He also spotted that the main earth cable needed upgrading to 16mm2 as mentioned above.

Thankfully, I don't have rubber cabling and the existing cable, whilst 35 years old, is in good condition.

I will consider a CU replacement soon. I'm starting to wonder whether the main 60A fuse and undersized tails would cope if the 10.8kW and 9.5kW electric showers were used at the same time, along with the electric fan oven !

Why didn't you have a combi installed and use the cold water mains pressure for showers? Cheaper to run and far better showers. Keep things gas where you can: showers, cooking, etc, especially when having a limited capacity electrical system. Look at a gas system boiler. A small white box on the wall giving 25 kW output. Imagine all the electrical parafinalia you would need to get 25kW.

A friend was doing a house up in the country with a limited electrical overhead supply. I suggested an LP boiler and LPG cooking range with all showers off the high pressure cold water mains. LPG when doing CH, DHW and cooking is cost effective to oil these days - and far cheaper to install.

I also suggested a plug and throw over switch to plug in a portable genny to keep essential circuits going in case of a power outage (common around there in winter): CH, limited lights, fridge and TV. I suggested a hot and cold fill washing machine and a hot fill dishwater to reduce electrical load - yes some can be hot fill too (just connect the pipe to the hot supply) and they still work out cheaper to run than using cold fill and electric heaters.

There are gas tumble dryers, however no LPG versions.

 

[Doctor Drivel]

Her real mistake was to buy the place at all, but now her only hope is mass eviction and start again with people of a different profile. She'll never beat them.

She should make then fully self-contained flats then the utilities bills are not her concern. It is also easier to sell them off doing that, She should consider a loan to convert to fully self contained and she may make a killing.

 

[mikej2005]

Why didn't you have a combi installed and use the cold water mains pressure for showers? Cheaper to run and far better showers. Keep things gas where you can: showers, cooking, etc, especially when having a limited capacity electrical system.

I did have a combi installed. We'll be living with the electric showers until I tackle the en-suite, at which time I'll probably install a thermostatic shower which the 37kW combi will be more than capable of running.

The CU will be upgraded once all this work has been done, but in the meantime the earthing/equipotential bonded issue has needed addressing.

Look at a gas system boiler. A small white box on the wall giving 25 kW output. Imagine all the electrical parafinalia you would need to get 25kW.

I have a gas-fired central heating system - why would I need to generate 25kW of heat electrically ?

 

[CallEdsFirst]

I have a gas-fired central heating system - why would I need to generate 25kW of heat electrically ?

If perhaps you wanted to generate enough steam for a small turbine power station?

 

[Doctor Drivel]

Look at a gas system boiler. A small white box on the wall giving 25 kW output. Imagine all the electrical parafinalia you would need to get 25kW.

I have a gas-fired central heating system - why would I need to generate 25kW of heat electrically ?

I think you missed the point.

 

[mikej2005]

I think you missed the point.

No offence, but it looks to me to be a poor point, badly made !

You seem to be implying that it would be a good idea to base my entire house's future electrical needs around a 35 year-old CU that doesn't meet current standards, rather than just replacing the consumer unit for a few hundred quid ?

How bizarre !

 

[CallEdsFirst]

Hmmmmm spend a lot of time in the plumbing forums eh? I think we got the measure of your advice!

 

[JohnD]

To return to the point about earthing as there appear to be three CUs and no main Bonding, I would suggest an earthing Block, mounted on one of the backboards.

Get an 8-way one

for a couple of pounds.
16mm G&Y to the PME point on the service head
16mm G&Y to each of the CUs (in the old Wylex it might be necessary to "fork" the strands and use two terminals in the earth bar. the holes at the end of the bar are the biggest)
10mm G&Y to Gas and water.

there will not be enough room in your CUs

This work is easy and not notifiable.

 

[mikej2005]

as there appear to be three CUs and no main Bonding, I would suggest an earthing Block, mounted on one of the backboards.
in your CUs

Thanks for the advice John - will get that sorted.

 

[RF Lighting]

I'm not sure if it's been said before on this thread, but beware the top of the main switch will remain LIVE even in the OFF position. On older wylex fuse boxes there should be shrouds to cover the live parts, but these are often missing so be very careful.