1.7kW Storage heater plugged into ring main?

[xena]

I have just moved a small (1.7kW) storage heater to a temporary location (next to my desk!) where I plan on using it until March-ish. We are on E7, and downstairs (where the heater now is) has separate fuseboards to upstairs. I could wire it into the off peak fuseboard (which feeds just the lounge storage heater), but it would be easier for me to plug it into the mains (on a timer) on account of its temporary status.

Other items that run off the downstairs mains overnight are the immersion, the washing machine and the tumble dryer. I tend to have these come on about 5am so they're all nice and fresh for me in the morning. I imagine the storage heater would have done most of its warming up by then and would be cycling on and off according to its thermostat.

On balance, would it be ok to plug it into the mains, or do I really want to be hard wiring a new spur into the off-peak board?

Many thanks, xena

[Roger Mills]

Are you posing this as a technical question - or one of economics?

From a technical point of view, the heater will work perfectly well if connected into the ring main.

However, it will cost considerably more to run - since it is using electricity at peak price rather than off-peak price.

If you assume that it will use an average of (say) 5kWh** per night for 60 nights = 300 kWh in total - you can multiply this by the difference in unit price of the two tariffs in order to work out how much extra it will cost you. Then compare that with the cost/hassle of providing an off-peak supply for it - and decide which solution suits you better.

** Substitute your own assumption. Worst case - if the heater was running flat out for the whole off-peak period - would be 7 x 1.7 = 11.9 kWh per night - but it will of course be going on and off on its thermostat

[xena]

Unless I am *extremely* mistaken, all my leccy switches over to cheap rate at 12.30am and back onto peak rate at 7.30am. I have one meter outside that shows "normal" and "low" readings, and this is controlled by a teleswitch.

[xena]

Sorry to follow up my own post, but my immersion also runs off the mains (on a timer) so I certainly hope that goes on my cheap rate! I'm sure it does, as our leccy consumption split over the last 2 years has been 62% off peak /

38% peak.

[Owain]

It would be better to hard wire into the off-peak board, but *provided* your immersion is not on the ring, you'll probably get away with it.

If your house burns down, however, it's not my fault.

Owain

[Harry Bloomfield]

Er, well no.

The entire system switches over to off-peak, or rather just the meter does. Two dials in the meter which record off-peak and peak consumption the times of which are defined by a time clock, therefore any consumption during off-peak periods will be charged at off-peak rates.

[Roger Mills]

If that is truly the case, it doesn't matter *how* it's connected - but the OP mentioned having a separate off-peak fuse board so I assumed (seemingly wrongly) that there was a separate meter and a timer which only made the off-peak part live for the designated seven hours.

My f-i-l's bungalow certainly used to be like that. Maybe the OP has got what used to be called a "White Meter"?

[John Rumm]

This is my understanding also. The extra consumer unit is just there to provide the convieneance of auto switching a bunch of circuits feeding a class of appliances together rather than needing to have individual timers for the each of them.

(it also prevents their use during peek times (assuming there is no extra wiring to provide for this (i.e. a boost capability) and they are hard wired)

[xena]

Immersion is on the ring. Think it's 3kW. Doh! Cheers for the advice tho. And at least if it burned down we'd be warm for a bit...

[meow2222]

The 1.7kW load is only 7A or so, so this isnt a significant issue in itself. However you say 3x 13A loads are all on timers using the same time slot. Those need to be timed to be on at different times else you may be overloading the ring quite a bit. Around 50A on a 30A ring, very roughly. If youre overloading the ring now, adding another 7A would be a Bad Idea. So it all depends on your timers.

NT

[Roger Mills]

Why that proviso? It's only 1.7kW - less than lots of other things which may be plugged into the ring. The ring should be able to support a total load of

7 or 8 kW without too much difficulty.

[John Rumm]

The ring is good for 7.2kW usually (assuming reasonably standard current wiring proactices have been used).

[John Rumm]

My guess is the OP probably has something like this setup (although perhaps without the prehistoric CU to the right!):

[Derek Geldard]

Perhaps a bit odd, or is it an old "White Neter" installation ?

That will work fine from the tarrif POV.

There was a previous system some indeterminate time ago in the dark ages when storage radiators had a hard wired circuit of their own run through a "White meter".

Users could not take advantage of the night rate to run their other appliances unless they broke into the hard wired circuit. OTOH the stotage heaters got a short "boost" during the afternoon.

Are these hard wired in?

I would expect the immersion is on it's own circuit. The W/M & T/D together with the addition of 1.7Kw of storage won't overload a ring main given the diversity factor.

It's OK.

DG

[Owain]

Immersiion + washing machine + tumble dryer + storage heater = overload even if the other things are only 2kW. I know the washing machine heater will be short-term but even so...

Owain

[Owain]

Yes, but it's a continuous load for several hours as it charges up, and uses about a quarter of the ring capacity by itself. Add the immersion, washing machine, and tumble, and the diversity assumptions for a 32A ring fly out the window.

Owain

[zaax]

mechanical timer with clock work spring which switch over the meter and switch on the E7 cables

[John Rumm]

Which is pretty much what is shown in the picture.... The E7 cables are powered from a separate CU to the left of the meter board in this case.

The meter has two sets of readings and an arrow which indicates which is currently in use. The mechanical time switch is to the right of the meter. When it switches it signals the meter and energises the tails that feed the E7 CU.

[Harry Bloomfield]

The separate fuse board is simply to make the installation easier. A time clock sets the on/off times and that (usually) operates a contactor, the contactor then feeds a separate fuse board. So nothing at all to stop you using separate clocks, one per heater, other than the inconvenience of checking/setting several clocks.

[xena]

I've just checked the fuseboard again and the immersion is on it's own circuit, not on the ring main as I posted earlier. I'm happy now that I can just plug the storage heater into the mains.

Thank you very much to everyone who posted on this thread. xena