Underfloor Heating over 13A??

[madger]

Hi there, I’m looking for some advice regarding underfloor heating. The conservatory is 20.9m2 and total power is 3.344kw. At 230v this gives me a current rating of 14.54A. The controller is rated at 16A, normally I supply controller via 13A switched fused spur but with this increased loading I believe I can supply via a relay? Could anyone please advise what type of relay I would require? and if possible where it can be purchased. It would need to fit locally into a dry lining box. Many thanks in advance.

 

[Richard]

Please forgive me if i'm being stupid guys, but if its 14.5 amps, and the controller is rated for 16amps, why cant he just have a 16amp radial circuit, through a local double pole 20amp isolator ?

My thoughts exactly.

 

[ultinator]

perhaps irrelevant now, but in regards to contactors, I have replaced one that was operating fine it was just mounted on the otherside of the clients living room wall but issue was the 'CLUNK', replaced it for a quiet type one and can barely hear the thing standing right next to it, much better IMO

 

[madger]

as i mentioned earlier "Should also have added that dedicated supply was no go due to construction of house/position of fuse board so local ring utilised".

​

 

[ultinator]

My apologies, I think I may have overlooked some of the information provided.

 

[Moses]

Can you clamp the circuit to see what it is actually pulling, it may well be taking a little bit less than you have calculated, especially if your voltage is higher than 230. You may find the current a little less than 13A. worth a look before you start trying to fit a contactor in.

Why does OP require a Relay/contactor?

He can use a 20A double pole isolator as mentioned earlier.

But its got to come from a dedicated CB from the CU and not from the Ring.

 

[Philpot]

Roger if the voltage is higher the current will be higher and vice versa... a misprint? Mind you the current is not always what is says on the box!! I have found showers especially variable.
madger
Moses and a few others have given the answer....a seperate cct, contactors clunk and hummmmm.

 

[RogertheBodger]

Roger if the voltage is higher the current will be higher and vice versa... a misprint? Mind you the current is not always what is says on the box!! I have found showers especially variable.
madger
Moses and a few others have given the answer....a seperate cct, contactors clunk and hummmmm.

Yes you are right Philpot, didn't have my thinking cap on straight for that one.
I divided the load (3344W) by a voltage higher than 230V and came out with less current, but of course it's a fixed resistance and the current will rise with the voltage, so thanks for pointing that out.

As far as the thread goes, the OP has stated several times that he can't supply the underfloor heating with a new circuit, so he is looking for a way to put it on the ring, The load is a little big for a ring in my opinion but I assumed the floor was laid and just needed connecting. He has since said that the floor has not been laid and he is considering supplying a heating mat of 130Wm2 and not the 160Wm2 that was his original choice, so that would be the best solution, it would go on a 13A Fcu and eliminate the need for a contactor/relay.

 

[needasparks]

Is the mat/wire heating done as one element or multible elements coming back to the controller ? just thinking it could be split up across two fused spurs, one feeding each possibly.

 

[madger]

Thanks everyone for their input on this, multiple mats are being used - if worse comes to worse i can emit 300mm wide mat (manufacturer states that 100mm min gap from walls) also can trim some off each length of each mat. Not had much luck with regards to using power relay (as oppossed to contactor) for larger loads (above 16A rating of controller) on dedicated circuit. This i must confess is beyond my experience - have looked at so many relays with no idea what type would be most suitable.