Zoned Storage Heater Circuits

24 Aug 2007
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United Kingdom
I've moved into a flat that has the off-peak E7 storage heaters. There is one in the hall (2.7Kw), one in the living room (3.4Kw) and there are also two panel heaters (one in the bedroom and one in the living room also).

There is an old Dimplex Zone conrtol timer box in the hall which I found is disconnected and the wires are connected in a junction box behind it.

The problem is, in my fuse box I have 2 32A MCB's controlling Zone 1 (living room with storage heater AND panel heater) and zone 2 (hall storage heater and bedroom panel heater). Occasionally through the winter I have had both the panel heaters and storage heaters on.

Usually in previous flats, there has been one MCB per storage heater. This one is different and I'm confused. To add to my confusion, the zone 1 MCB looks like it is overloaded and the cables to the consumer unit have gone black. I've pulled the MCB and an electrician is coming on Monday.

What I would like to know is, can storage heaters be wired like this? Is the zone 1 MCB overloaded?

The storage heaters have each have a 13amp FCU and timer next to them. I sense the electrician that installed them was wearing a 10 gallon hat as the off-peak is also live through the day, even though I do have 2 tariffs and a seperate meter!!

I would like some advice so I know what the electrician is talking about and also so I don't get ripped off (not that electricians are like that of course!). Any info / advice appreciated.
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From what I have seen it is normal practice to run a 15 - 16A radial to each point given the sizes you mention. How is the 3.4kw connected? What size cable is in use?
The size of cable in use is hard to determine as it is in black conduit, but it looks like 6mm2. Basically the cable goes from consumer unit to storage heater and then to the panel heater.

The 3.4kW heater is wired into a mechanical timer which is then wired into a 13amp FCU.

Like you, I was expecting a 15amp fuse / 16amp MCB supplying one storage heater alone, not a 32amp MCB supplying both a storage heater and panel heater.

If you need any more info, let me know.
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A 13A FCU is undersized for a 3.4kw load.
6mm should be adequate for a 32A circuit, apart from the fusing issue.
See what your electrician says when he see it.

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