Not a ring, not really a radial...

Conor · 15 Jul 2010

Hello all

I've just been looking at my heating circuits (I have all electric heating with storage and panel heaters), and I've noticed that I have 3 panel heaters running from the same mcb. They're not in a radial or ring circuit - each heater has it's own 2.5t+e coming from the same mcb. This isn't something I've come across before so just thought I'd ask if this was ok or if there is a reason to get it changed.

Each heater is 1.5kw, it's 2.5t+e, and a 20A mcb.

If I haven't explained it well enough please say.

Thanks

Conor

ban-all-sheds · 15 Jul 2010

It's fine - I take it that each heater has its own fused switch?

LoveRocket · 15 Jul 2010

That is still classed as a radial circuit and as such is absolutely fine.

Conor · 15 Jul 2010

Ok, cheers guys.

Just hadn't seen it before so thought I'd ask.

Yep, each heater has a fused switch.

Thanks

Conor

OwainDIYer · 15 Jul 2010

Not quite absolutely fine IMHO.

3 x 1.5kW = 4.5kW, so slightly over 18A at 240V.

If it's a 20A MCB then that will usually provide adequate protection for 2.5mm.

However there is no spare capacity if a larger heater is installed.

It would be better to have them on separate MCBs, or at least double up rather than triple up. It's a little bit of a bodge - is there a shortage of ways in the CU?

ban-all-sheds · 15 Jul 2010

If the circuit had consisted of a 2.5mm² cable leaving the CU, and running to 3 heaters in turn, each on a switched FCU, would you have the same criticisms?

skenk · 15 Jul 2010

If a larger heater is installed it will become only a problem then (a minor one, assuming spare ways are available), the only deficiency with it currently is that if it trips it takes out 3 heaters which may be a large part or all of your central heating (no different from most central heating systems though, being on a single MCB . . .)

So . . . absolutely fine and not a problem

1john · 15 Jul 2010

I would say it is quite well thought out, if anyone wants to install a larger heater, they can take that circuit off the current MCB and onto another one suitable for the cable and new load.

OwainDIYer · 15 Jul 2010

ban-all-sheds said:
If the circuit had consisted of a 2.5mm² cable leaving the CU, and running to 3 heaters in turn, each on a switched FCU, would you have the same criticisms?

Yes.

At least with 3 cables to the MCB it will be easy to separate into individual circuits if required.

On the other hand, running in turn it would be easier to turn it into a ring!

Either way is parsimony.

LoveRocket · 15 Jul 2010

OwainDIYer said:
Not quite absolutely fine IMHO.

Bucking follcoks.

I suppose my B32 6mm cooker circuit is not absolutely fine, because I might want to install an 18kW induction furnace.

Stop trying to make yourself look impressive by spouting nonsense.

Thanks.

ebee · 16 Jul 2010

A radial may have any topology.
So it's OK.
It is a radial circuit

Taylortwocities · 17 Jul 2010

And the circuit design completely follows the requirements for cable selection.

Ib <= In <= Iz

If you change Ib then the design has to change.

But the OP has not suggested that he needs a larger heater. That has been added - to confuse things - by Mr DIYer.

Conor · 19 Jul 2010

Cheers for all the thoughts

The heaters are staying, so no problems in regard to increasing heater size.

I couldn't see a problem with it, but thought I'd ask in case there was so I've no plan to get it changed to a ring or split them to different mcbs.

Thanks

Conor

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Not a ring, not really a radial...

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