Central Heating Electrical System

R

ryanj

Just finished the plumbing side of a new central heating system, we're now doing the electrics, I thought I'd run it by you first, to check for any potential errors.

I've drawn a diagram of what I propose to do:

http://www.jcra.net/diagramch.png

I plan to have the system supplied by an MK 3amp circuit breaker, which will then be connected to a MK Fused Connection Unit with a 3amp fuse.

1. What size of cabling between the consumer unit and connection unit do you recommend, is there any benefets to using anything over 1.5mm2?

2. What size of cabling between the components of the system (thermostats), do you recommend, I was also thinking 1.5mm2 woukd be a good choice for this?

3. I was planning on using heat resistant flex between the boiler, pump and valves. Should I? And what sizes should this be? Is Butyl a good choice?

4. Is running the cables in the wall cavity, okay?

5. Lastly, I've read in my on-site guide that I should provide a 10mm2 earthing connection to any central heating systems, where should this be connected? 600mm from the boiler?

Thanks for any input, I consider by self a slight perfectonist, and I like to get things spot on. Thanks.
 
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1.0mm through out is fine (including the heat proof flex parts). CU can be a 6amp MCB feeding a 3amp FCU.

Your diag shows no time control?!?

All flex runs should be visable, and generally no more than a meter or so. (use 1.0 T+E cable in walls, lofts and under floors, with a flex outlet plate on the end to convert to flex.) If the boiler needs more than 2 cores, run a 3 core+e cable, or a couple of 2 core+e together.
 
R

ryanj

Sorry, there is a time control, it requires a 4 cables. Which is a bummer as i don't think there is a 4c+e. What could I do about that?

Also, i said 3 core flex, I should have said 2core+earth.

Thanks!
 
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3 core flex is the correct term for flexible cables, twin and earth, or 3 core and earth is the correct term for installation cables.

Use 2 runs of twin+e cable
 
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Don't jump on me - this is a deliberate question...

What would be wrong with a 3A breaker at the board and a DP switch at the boiler?
 
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A 3amp breaker is hard to get (and prob more expensive!)

Dont do a plumber job and run flex everywhere - its cable where conceiled, and between room stat, programmer etc.
 
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Earthing is an odd one.

Obviously the standard 10mm to the gas and water, and the supp bond for the bathrooms.

Cent heat pipes are mentioned in the regs, but i dont see a need to main bond them, as they cant introduce an outside potential unless they run between buildings or outside. I am sure many people simply run a 10mm to the valve/pump/cylinder area, and bond to a convenient place there.

The lack of replys to your earthing needs speaks volumes 'so to speak' !!!
 
R

ryanj

Recently finished this project. As being part of my rewire, here's some photos of what I did.

cables.jpg

Holes been cut out, and all cables run down cavity wall.

boxes.jpg

Boxes installed

fcu.jpg

Installaton of FCU, 16amp supply with a 3amp fuse.

finish.jpg

Finished.

Hope you found some interest in that.

A simple question though, is my means of indication of live on the blue cable in terminal 10, okay? And my indication of neutral on the grey cable going into the 4 vertical terminal up, okay?

Thanks!
 
R

ryanj

And do the other phase colours black and grey, need to be identified brown? Or are they okay as they are?
 
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Personally, I would mark all lives red or brown (depending upon which colour system you are using) and all neutrals black or blue.
 

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