Help with - Contactor UFHeating

llamatron71 · Sep 26, 2009

Hi all,
Finally got around to installing UFH (loose cable type)

40sq metres being laid in a kitchen using 4 kits (10sqm each)
main heating source, 2000w per cable, Underfloor thermal board used on timber floor,

I was just wondering what amp size contactor to use to connect x4 cable to > stat.
(note.. I've actually ordered a 35amp contactor already but could change for another if unsuitable)
Also could someone help with the wiring diagram for such a module.
TIA

Also (yet another) i'm planing on fitting the stat about 300mm away from the combi boiler, Whould this effect the stat "thermostat" if i disable "air" stat and only use the floor probe? (thinking of the heat generated effecting the stat and reporting a false reading)

(Kitchen fitter as main trade, Part P Qualified)

Regards Dave

sparks1234 · Sep 26, 2009

I would run off the floor stat in that situation.

2000 watts only equates to about 8 amps, a 20 amp 4 pole contactor will be fine if you have 4 feeds, also, if you start getting larger contactors you will get a bigger "clunk" when it turns on (annoying)

llamatron71 · Sep 27, 2009

Thanks Sparks, sorry i should of been more clear, It's 2000w x 4
2000w per cable = 8000w
It's a warmsoles system,
[FONT=&quot] 4 X WARMSOLES® Underfloor Heating Cable [/FONT] [FONT=&quot]10.0 - 16.6 m²[/FONT] [FONT=&quot]2000w[/FONT]
Or am i not reading the info correct?

Yes someone already recommened a 20amp and someone else no go with a 40amp..
Would i do any damage to the cable if i used a 20amp

Regards Dave

[FONT=&quot]2000[/FONT]

[FONT=&quot]6000[/FONT]

Notsosmart · Sep 28, 2009

llamatron71 said:
Thanks Sparks, sorry i should of been more clear, It's 2000w x 4
2000w per cable = 8000w
It's a warmsoles system,
[FONT=&quot]4 X WARMSOLES® Underfloor Heating Cable [/FONT][FONT=&quot]10.0 - 16.6 m²[/FONT] [FONT=&quot]2000w[/FONT]
Or am i not reading the info correct?

Yes someone already recommened a 20amp and someone else no go with a 40amp..
Would i do any damage to the cable if i used a 20amp

Regards Dave

[FONT=&quot]2000[/FONT]

[FONT=&quot]6000[/FONT]

Hi Dave
The contactor rating is per pole (& contactors are usually 3 pole) so you may have to purchase an auxillary block. So 2000W/230V = 8.7A Therefore you could get away with a 10Amp contactor & Auxillary block.

How do you intend to feed the live side of contacts; 4 off seperate feeds from 4 off breakers or 1 meaty cable & breaker?
Personally I would opt for the former that way if one of your underfloor cables go down, you will still be able to operate the others.

llamatron71 · Sep 28, 2009

Notsosmart said:
Hi Dave
The contactor rating is per pole (& contactors are usually 3 pole) so you may have to purchase an auxillary block. So 2000W/230V = 8.7A Therefore you could get away with a 10Amp contactor & Auxillary block.

How do you intend to feed the live side of contacts; 4 off seperate feeds from 4 off breakers or 1 meaty cable & breaker?
Personally I would opt for the former that way if one of your underfloor cables go down, you will still be able to operate the others.

Thanks a million for that info, i will have to see what my local electrical wholeseller has in stock, Also I'm going to pass this info onto my partner who is more up on these matters, but i will be taking the best correct route..

Thanks again

Regards Dave

sparks1234 · Sep 28, 2009

Notsosmart said:
Hi Dave
The contactor rating is per pole (& contactors are usually 3 pole) so you may have to purchase an auxillary block. So 2000W/230V = 8.7A Therefore you could get away with a 10Amp contactor & Auxillary block.

How do you intend to feed the live side of contacts; 4 off seperate feeds from 4 off breakers or 1 meaty cable & breaker?
Personally I would opt for the former that way if one of your underfloor cables go down, you will still be able to operate the others.

I think most contactors are now 4 pole so that should be better for you

llamatron71 · Oct 6, 2009

Notsosmart said:
Hi Dave
The contactor rating is per pole (& contactors are usually 3 pole) so you may have to purchase an auxillary block. So 2000W/230V = 8.7A Therefore you could get away with a 10Amp contactor & Auxillary block.

How do you intend to feed the live side of contacts; 4 off seperate feeds from 4 off breakers or 1 meaty cable & breaker?
Personally I would opt for the former that way if one of your underfloor cables go down, you will still be able to operate the others.

Hi Again...
Would someone advise on this layout..
40 amp breaker supplying a 40 amp contactor (two pole) with two feeds sharing each pole, is this possible or a no no? and should i really have a breaker supply per pole
Also by meaty cable do you mean tails or 6mm

Info... each wire is 8.7 amps x 4 cables,
Contactor is 40 amp
Breaker 40amp..
Also do contactors have a life span?

Regards and TIA
Dave

Notsosmart · Oct 7, 2009

Hi Dave,

I wouldn't supply with just one 40A breaker as the element cables are probably rated at 13 or 20 amps maximum so you will be limited by these (if you have any paperwork the info will be possibly within the technical pages). If you were to put all the elements upon the one 40A breaker then if you had a major fault then you run the risk of a fire (worst case scenario btw; I don't mean to scare you) or at least blowing an element which probably then means that you won't be able to reset the breaker. This is why I suggested seperate feeds & breakers.

If you don't have the spare capacity within the consumer unit for four breakers then you could double up on the contactor (still requiring 2 off 20Amp breakers (as long as the element cables are rated as such) & fed with at least 2.5mm cable), personally I would also double pole through the contactor. (ie contact 1 = element 1&2 supply, contact 2 = element 1&2 Neutral, contact 3 = Element 3&4 supply, contact 4 = Element 3&4 Neutral.)

Life expectancy depends upon usage, loading etc but it is the coil that will usually burn out first, years of use can be expected though; lets face it, they are designed for heavy industry.

Regards,
Gaz.