Spur and underfloor heating of ring.

notevenadiyer · 17 Aug 2008

Hi

Just built a conservatory and thinking about installing electric underfloor heating. Also want to put a double socket in there.

Can i spur of the existing ring main and run both from this spur? If so what is the best way of going about this, spur to double socket then fused spur to underfloor heating.

Help appreciated as very difficult to get to any another sockets apart from one near conservatory.

ericmark · 17 Aug 2008

Your question is like asking how long is a piece of string. If there is very little else running off the ring main then it may be able to take extra load on the other hand if the ring main also supplied a kitchen with all the heavy loads there is could be overloaded. The socket is OK but heating can be very high loads and you have not said how big of a load you are considering.
There is no magic wand to work out what we can do. We look at load and building, and even though we may not put it all down on paper we consider things as a whole and I would suggest you need advice from someone on site as to what can be done not a remote forum.
All best Eric

Chri5 · 17 Aug 2008

Anything beyond a fused spur is restricted to 13A.

From a simple web check:-

Tile Warming Mat system
The Bush Nelson Tile Warming Mat system
has been specifically developed to provide heat
under tiles to eliminate the uncomfortable feel of
ceramic and terracotta tiles.

Approximate Area Covered: 8.8 (m²)
Mat Size: 17.6 x 0.5(m)
Output: 1.40 kW

So a rough per m sq think in the region of 160w (you MUST confirm load for the system you use!!).

Say your floor is 12m sq, of which 9 m sq will be heated (no point in heating storage footprint areas.

So 9 x 160 = 1.44 kw or 1440w / 230v = 6.25A

13A - 6.25A = 6.75A (or 6.75 x 230v = watts) available for socket use, fine for TV and stereo, but useless for ironing, electric heater or any high load plug in item.

Synapse · 17 Aug 2008

You also cannot spur from a spur.

notevenadiyer · 17 Aug 2008

Thanks all. Room is only 2mx2m (4 sq meters) as only a small conservatory. Was thinking 160 watt mat as laying under lino. Wattage is only about 3 amps so well under the 13 for the spur. My main problem which someone has already mentioned is that you shouldnt spur of a spur.

Because i need power to sockets in conservatory my question is can i have the sockets and uf heating all run of the same spur and if so whats the best way to go about this. As to load on sockets should only be small value stuff.

Synapse · 17 Aug 2008

It is acceptable to spur from a spur if there is a 13amp FCU before the two spurs, this ensures that the 2.5mm cable doesn't exceed it's rated current capacity.

Chri5 · 17 Aug 2008

Chri5 said:
Anything beyond a fused spur is restricted to 13A.

Synapse Posted:

You also cannot spur from a spur.

You can have as many spurs off a fused spur as you wish- the total number is restricted by the 13a fuse at the 1st spur.

Carp from a design point of view and best avoided, but it can be done.

Synapse · 17 Aug 2008

Apologies, seems I didn't read through your post properly.

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Spur and underfloor heating of ring.

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