Questions about Boiler and Electric Shower

[kai]

I've noticed that the shower is not on the RCD side - it could be a bodge install, looking at the way the cable has been run into it from the top....

 

[flameport]

Shower has a 50A MCB, which is not suitable for 6mm cable.

Boiler controls - the booster switch and whatever else the cable is connected to.
(as already pointed out, it's not a boiler anyway)

 

[electronicsuk]

Your 'boiler' is not a boiler! It is a water heater, a direct, unventedm, mains pressure water heater or 'cylinder'. There is very little to service on them at all - a service will not improve performance. As you only have one element, you cannot even say "perhaps one of my elements is faulty".

Not strictly true. I believe many manufacturers recommend yearly servicing, as the temperature and pressure relief valves need testing, expansion vessel charge may need topping up, pressure reducing valve inspected, and input filter/strainer cleaning.

I doubt that many are serviced this frequently in reality, but it would seem prudent to have it checked at least once every three years. After all, it is a pressure vessel, and we've all seen what a poorly installed and/or maintained unvented cylinder can do to a house when it goes off!

 

[xr4x4]

you seem to have two curcuits for your water heater.

which could poss suggest eco 7 heats during the night via the right CU and theres a second curcuit on the left CU for boost.

is that poss on those dual immersion controllers?

 

[flameport]

is that poss on those dual immersion controllers?

Yes, there is a single element, and the E7 circuit is connected on the normal setting.
The 'boost' function is a changeover switch which disconnects the E7 circuit and connects the 24h one for a short time.
They are designed so that you can't have both circuits connected to the element at the same time.

They are a poor choice, as you only get one element, so when it breaks, there is no hot water at all. Also means that the 'boost' function results in the whole cylinder being heated, which costs more and takes longer.

A better option is two separate elements, with the upper one used for boost only, so that the boost function will heat the upper half of the cylinder, which is cheaper and gets usable hot water much more quickly. Useful when the main element breaks, as you can still have some hot water while arranging for repairs.

Some systems had a dual element in a single mounting boss, with the main element full length and the boost one much shorter. However these are for top mounting only on the old type copper cylinders, which no one in the right mind would have installed today.

 

[hohingday]

The only other switch I can see is the on/off switch for the heater/boiler.

So going back to the other questions:
- What considerations would I need to take if I was to replace it with another 8.5kw unit? (As im pretty sure its not operating correctly)
- If I was to put in a 10.5kw unit, apart from the cable, what considerations would I need to take? mcb, rcb, etc

Cheers.

 

[riveralt]

So going back to the other questions:
- What considerations would I need to take if I was to replace it with another 8.5kw unit? (As im pretty sure its not operating correctly)

Assuming the cable is 6mm as suggested then you will need to lower the size of the MCB to 40Amps and put it on the RCD side of the CU.

- If I was to put in a 10.5kw unit, apart from the cable, what considerations would I need to take? mcb, rcb, etc

Cheers.

10mm cable 50Amp MCB and put it on the RCD side of the CU.
Contact your local Building Control.

But in both cases follow the Manufacturers instructions.

 

[hohingday]

Lectrician - images of shower with cover off attached.
Thanks

Untitled

• hohingday
• 6 Jan 2011
• 1

Untitled

• hohingday
• 6 Jan 2011
• 1

 

[xr4x4]

6mm is solid copper strand and 10mm is several strands.

is that right?

 

[riveralt]

6mm is solid copper strand and 10mm is several strands.

is that right?

Nope

 

[kai]

The 6mm cable has a Solid Earth conductor, whilst the 10mm cable has a Stranded Earth Conductor.

 

[riveralt]

The 6mm cable has a Solid Earth conductor, whilst the 10mm cable has a Stranded Earth Conductor.

Correct for modern cables - although was he talking about the cpc?

 

[Lectrician]

Unfortunately it looks like 6mm. Thats not good on a 50amp MCB! I wonder if it is 10mm from the consumer unit to the switch, and 6mm from the switch to the shower?

If the earth is solid, it is 6mm.

If it had been stranded it would more than likely be 10mm, but could be an older 6mm.

 

[xr4x4]

The 6mm cable has a Solid Earth conductor, whilst the 10mm cable has a Stranded Earth Conductor.

thanks for that, i knew it was something like that.

 

[hohingday]

So I've checked and the cable is 6mm throughout

Ok so i think i know what i need to ask for, time to choose a shower!
Anything to watch out for?

Also there was mention that the shower needs to be moved to the RCD side, on a side note, what sort of appliances generally go on that side?