Fused Spur from Immersion Heater Point

KW

I am planning to install a pump which will power two showers. The most convenient place to site the pump is in the airing cupboard.
We already have a power supply in the airing cupboard to run the immersion heater.
The immersion heater power supply is a switched, fused (13 amp) unit with a flex outlet. It seems to be part of a ring (there are two cables entering it) - probably the socket ring main, but I have not checked that.
The instructions with the pump say the pump must be connected to a 230 volt 50Hz supply with a switched spur fused at 5 amps.
Can I just run a spur from the immersion heater supply point and stick a 5 amp switched spur on the end of it?
Are there any other (better) options?

Adam_151 · Posted: Thu Mar 03, 2005 8:03 pm Post Subject:

Yes you can connect your shower pump to the ring main via a fcu with appropiate fuse,

Whether the Immersion heater should be there or not is another matter, most would say not, but I can't see that it is immediatly dangerous

KW · Posted: Fri Mar 04, 2005 9:45 am Post Subject:

Thanks, but...

Would you like to elaborate on your comment about the immersion heater? What might be wrong with the immersion heater being there (and by "there" do you mean in the airing cupboard or in the ring main?).

It may not actually be in the ring main... all I know for sure is that it is not itself a spur because it has a cable coming in and a cable going out. It may be a totally different circuit - I did think when I looked at it that the wires looked a bit thicker than normal.

If it is on some other circuit does this affect whether I can run a 5amp fused spur from it?

mapj1 · Posted: Fri Mar 04, 2005 10:31 am Post Subject:

As a fixed load, if it is on the ring main, it is potentially hogging 12 or 13A of the 32 you have for all the other sockets on the ring, effectively reducing your capacity for running other things. If you don't get much nuisance tripping/blown fuses, you don't actually have a problem right now, but if you ever do have trouble when a number of appliances are on together, then the heater should really be hived off onto its own circuit and fuse or breaker at the board, and this has been the recommended practice for the last 20 years or so. 'In the airing cupboard' is fine - the means of isolation should be as near as possible to the load or clearly labelled, sounds like in this case it already is!
regards M.

KW · Posted: Fri Mar 04, 2005 10:53 am Post Subject:

And if it is on its own circuit is it still OK to hang a 5amp fused spur off it?

From your explanation I am guessing that it is... I would be putting a relatively small load onto a circuit which is already designed to take a large load.

In fact we hardly ever use the immersion heater - just when the gas fired boiler fails...

(and I think this discussion may have explained the fuse in my fuse box that I have never labelled because I couldn't work out what it was...)

Panjandrum · Posted: Fri Mar 04, 2005 11:12 am Post Subject:

KW: Do you have a switch somewhere else that controls the immersion heater? We have one in the airing cupboard, one in the kitchen. If you have, there would be two wires to the airing cupboard switch. even if on a dedicated circuit.

KW · Posted: Fri Mar 04, 2005 11:28 am Post Subject:

No additional switch elsewhere (or, if there is, it must have been in the ON position for the past 20 years!!)

As far as I am aware the switch in the airing cupboard is all that is needed to switch on the immersion heater

kai · Posted: Fri Mar 04, 2005 12:08 pm Post Subject: Immersion switch

There should be a 13amp fused connection unit to control the immersion within 2 metres of it, your setup seems correct in that respect.
An immersion circuit should not be shared with anything else really, but in theory you could safely run a 13amp immersion plus a 3amp fused supply for a small pump off the same B16amp MCB, as 13 + 3 amp exactly equals 16amps. use 2.5.sq.mm. cable, or 4mm cable where run is very long. (see the IEE on-site guide for exact rules).