Under floor heating system problem

[North]

Dear all,

I purchased an underfloor heating system from Livingheat http://www.livingheat.co.uk/

The system seems to be a bit unusual in the way that they sent us three independent matts to fit our kitchen layout rather than one single one to be cut to size.

Every matt has got two cables coming out of them and our fitters seem a bit puzzled by how to make the connections since the cables are only 2500mm long and they wont reach the junction box. Anyone has had similar undefloor heating system installed?

Thanks!

 

[Taylortwocities]

Why not try this (from their web site)


If you have any questions or require further assistance please do not hesitate to contact ourselves. Our time and advice is free.

Tel :0800 634 2737

Tel :01803 316060

Fax: 01803 312000

Email: [email protected] - See more at: http://www.livingheat.co.uk/

Edit:
The Installation guide (also on their site) shows all mats to be connected together in a JB. But it shows that each mat has only one cable. Do not understand how you have got two??

 

[ban-all-sheds]

I purchased an underfloor heating system from Livingheat http://www.livingheat.co.uk/

Serious question:

Why? What do you expect it to do?

 

[North]

I contacted them and they told me that i need to connect the cables together in parallel and then i would come up with just two cables to connect to the junction box. My issue is that crimping cables and let them under the floor will be a week link for the system to go wrong. My question would be do i need to use some special crimps for this job?
Thanks again

 

[ericmark]

When I fitted under floor heating it also had a sensor in a pocket to ensure the floor did not get too warm. So each mat should have a temperature sender in a pocket and an independent method of switching off each mat. So there should be a thermostat for each mat, not one central one for all, or at least three inputs for remote sensors one for each mat.

The main problem with underfloor heating is over heating, there are some which use a chemical which increases in resistance the hotter it gets so to some extent self regulating, but even they need some over heat sensor. 55°C is the maximum temperature for under floor heating this is not so much a problem with wet just keep water at 55°C but with electric some pocket is needed with a sensor in the pocket to stop over heating. At 55°C there is only around 25°C difference between temperature required and temperature of heater, with radiators there is around a 50°C difference and the transfer of heat is on a logarithmic scale so there is a problem getting enough heat into the house.

The other problem is the delay between switching on and getting heat and switching off and heat output stopping. So to work the house has to be very well insulated using heat recovery units for ventilation and be heated 24/7. Most people want to be able to switch off the heat when they go out.

One would not walk around a kitchen in bare feet, in my kitchen need toe protectors the way my wife over loads the counter space, but one can always drop items remember the cat getting my pancake he was not amused even if we were. So back ground heating in a wet room OK, but in a kitchen seems a little pointless.

But there will need to be three junction boxes as the cables on the sensors are not very long and if they were getting them in and out of the pocket would be impossible so since you need a JB for pocket entry clearly same JB can be used for feed cables.

 

[Taylortwocities]

Really Eric?
I have installed quite a number of UFH systems (usually WarmUp) and even their largest mats only have one sensor.
The only stipulation is "NOTE:When laying two or more heaters, ensure the coldtails reach the thermostat."

PS I still do not understand why

Every matt has got two cables coming out of them

North. do you really mean cables, or do you mean conductors?

 

[Echo the husky]

The instruction manual shows the mats with one cable at one end with line and earth, the other cable at the other end of the mat with neutral and earth. Hardly ideal from an installation point of view.

 

[Taylortwocities]

Blimey, Never seen that before. Mind you, never heard of Living Heat and not something i want to experience either!

I wonder how the OP is getting on…………..

 

[ban-all-sheds]

I wonder if he can send them back for a refund....

 

[ericmark]

The instruction manual shows the mats with one cable at one end with line and earth, the other cable at the other end of the mat with neutral and earth. Hardly ideal from an installation point of view.

Would that not cause EMC problems? It would be similar to using two instead of three conductors between two way light switches the RF hash is quite large with a 60W bulb with under floor heating it would be really bad.

I suppose one could expect if one bit of the floor is below the 55°C then so should the rest of the floor, that though relies on the heating mats never failing, if the mat with the sensor fails then rest of floor could over heat. In real terms the floor likely will not reach the full 55°C so I suppose is safe enough, the hot water system works but the electric is rather hit and miss. Like the hot air central heating it looks good on paper but in practice is a white elephant.

 

[North]

As far as I can see there are two cables coming out of each mat with no earth
I have been giving the attached plan from these guys. Does it makes sense?

 

[EFLImpudence]

There are two conductors (wires).

The mats have to be connected in parallel (with a maximum current stated for the single conductor used).
If these conductors will not reach wherever you want then you will have to use another cable (with two conductors)


It doesn't get much easier than that diagram.
What is it you and your fitters do not understand?

 

[ban-all-sheds]

The most basic things about wiring?

 

[EFLImpudence]

Are these mats stated as being Class II (double insulated)? with this symbol -

 

[ericmark]

Simple answer no, you should not use a crimp of that type to join two wires into one.

this crimp is the correct type to add wires used a lot with earth wires but it requires a hydraulic crimping tool. The standard crimp would maybe crimp two 1 mm cables one end and a 2.5 mm the other but if the crimp is designed for 2.5 mm you simply can't fit two x 2.5mm into the crimp and if designed for 4 mm using a single 2.5 mm it will not grip it well. One may get away with uninsulated crimps and fit in shrink sleeve but with pre-insulated that is not a method I would ever use.