We're in rented accomodation which has storage heaters - much to our surprise they were quite efficient during the winter - as the only source of warmth. I've picked up a spare and would like to install it in the lounge. Can I run it as a spur, breaking into the existing cable and fitting a junction box?
Will your landlord allow you to do that? My tenancy agreements specifically forbid tenants to make wiring alterations as you have no idea if the work is safe or not. We had one flat where the (Polish) builder tenants fixed an additional heater, which caused a fire and much damage. Fortunately we had let to a company who employed them, and were able to recover the £28,000 costs of refubishment!
AWEM
Harry coughed up some electrons that declared:
Hi Harry,
Depends - would doing so overload the circuit?
What does your landlord think of you doing this?
To work out the former, *assuming* that the breaker/fuse is correctly sized to protect the cable (as opposed to sized for the design current of the circuit which may be lower)[1]:
What rating is the MCB/fuse? What's the total current draw of all heaters that are currently fitted? What's the current draw of the one you are planning to fit? Thus determine the total current draw of all heaters, including your new one...
Is this less than or equal to the breaker/fuse rating?
You can't really use any diversity allowances here as all heaters come on at the same time and draw power for extended periods.
[1] Breakers must be sized to protect the cable. 32A breaker protecting 27A capable cable even if the design load is 25A isn't acceptable. However, it's good to do a sanity check as it's not beyond the bounds of possibility that some naughty person made such an assumption.Size of cable and installation methods would be needed to verify this, but I'd start with the first section, because this may rule out any additions. If it passes, then a double check of the cable size would be wise.
Cheers
Tim
I'd be very cautious with that, storage heaters are a heavy current load - are you sure that all the fixed wiring is rated for the continuous and high current draw when both heaters are charging?
Oi veh! OK, fair enough, I ought to ask first. One of the heaters has been moved from a bedroom to the hallway - not by me - by apparantly drilling through the connecting wall, extending the cable via a junction box and then feeding the extension through the drilled hole to the resited heater. This gave me the idea of using a junction box to add another heater in the lounge which could do with a boost, warmth wise. There are only three heaters in the entire two bedroom flat, nothing in the bathroom, kitchen or, originally, the hallway but they, together with an immersion heater, are all on the overnight meter. We don't use the immersion at all so thought one extra heater wouldn't be a problem. But thanks for the responses and yes, I'll tackle the landlord next.
Generally not - storage heaters are on radial citcuits which wouldn't normally have this spare capacity.
Just an idea.
Is the storage heater you have in mind less than 3kW?
If so, why not fit a 13 amp plug on the cable and plug into an existing socket through a timer, making sure of course you only used off-peak power?
Well there's the thing, this place has two, seperate meters, one off-peak and the other, umm, normal. The heaters all on the off-peak circuit while the immersion has two switches which are clearly labelled for either overnight or day-time use. Another reason I thought to plumb in to the existing wiring, there's no other way to add another heater bar getting the expert in to run a new cable. No worries.
you might be better off fitting insulation somewhere instead
NT
Generally, despite having two meters and two circuits, it doesn't mean that power consumed in the off peak period on the "peak" circuit is measure by the "peak" meter.
Normally the "off peak" meter measures power consumed in a 7 hour period from late night to early morning and power consumed throughout the rest of the day is measured by the "on peak" meter.
Believe that and there is little hope for you!
If there are two meters the standard system does not shift the ordinary rate loads to the off peak meter. This only happens when a double scale meter is used.
I bow to your knowledge. I recall a setup many years ago in the manner described on economy 7. We did away with the storage rads and at the time it was just marginal to remain with the economy 7 tariff with the mix of standard and off peak usage and charges.
Yes, but think about it - with this old-style set-up with a separate off-peak meter for the switched supply, the normal rate meter has no way of knowing what time it is.
The OP's original set-up, if really like this, might be on an old tariff
- possibly with an afternoon 'boost' period. Check what you're paying as it might be worth converting to Economy 7.
It is in this case because the characteristics of the load (fixed heating appliances) mean that overload won't occur. The MCB only needs to provide fault protection and 2.5 mm^2 cable is normally OK on a 32 A MCB - c.f. the unfused ring spur, where overload protection is provided downstream by the plug fuse(s). In general where Iz < In you should check thermal compliance with the usual adiabatic calculation.
Sticking to one 16 A circuit in 2.5 T&E per storage heater is best though and gives a good safety margin, without too much worry about grouping and insulation factors, etc., etc.
Yes I accept I was wrong. I wasn't aware that the likes of white meters were still in existance. Thinking back I'm not sure if I had a single dual rate meter, with a permanently live output and a switched output. I think there was a flag to say which dial was moving.
I also thought the economy 7 tariff has been quite a lot cheaper than the old style tariffs.
Andy Wade coughed up some electrons that declared:
I agree with you in a by-the-book way, although *personally* I would still stick to sizing the cable according to the overcurrent protection, because, at least for a circuit like this with multiple loads, one never knows whether someone will come along an replace a single load with a higher load (could be very easy to do with something like a storage heater replacement, where the user fancies a few more watts on one room), or indeed add to the circuit as in this case.
You can generally bet that future people don't always go and look at the design of the system - many would look at breaker rating and assume that's what they've got to play with. Unless comprehensive notes are kept, it could be hard to check what the actual capacity of the circuit is. The cable might be x-mm2 with a suitably high rating (matching or exceeding the overcurrent protection) as it leaves the CU, but may be noticibly derated by passing through a load of insulation in a wall, which was obvious to the guy who put it in, but later impossible to gain access to verify.
For the sake of a slightly beefier cable I'd go belt and braces and have a circuit installation that's easy to hack in the future.
I realise none of this helps the OP (except in as much as he should limit his assumptions), but it's just a pet peeve of mine :-o
Agree completely - much simpler for everyone :)
I'm sort of doing that for my heatbank. Single 45A RCBO distribution circuit in main CU provides all aspects of heating. That will run to a small panel with 3 x 16A breakers (and contactors) supplying 3 immersion heaters (backup heating when gas boiler on blink) and a 6A MCB for boiler and pump and control supply.
The advantages for me are one module in the main CU rather than 4, single point of isolation for everything hanging off the tank and as I need to house contactors, they might as well live next to the MCBs in the same enclosure.
Weakness - one RCD effectively for all heating, but as a faulty heater can be easily isolated, I don't care.
:)
Cheers
Tim
We moved in here last September. Two, separate meters, one billed as "Night energy @ 7.25p/unit" and the other, "Day energy @ 15.03p/unit".
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