Under floor heating

[KB009]

Hi there, can I ask a qualified person....
What is the difference in the wire that is used to go under floor?

I assume the main cost is the controller to provide the watts to heat the floor. I can buy a controller relatively cheap. Why are these kits so expensive?

appreciate any help

 

[bernardgreen]

What is the difference in the wire that is used to go under floor?

Assuming you mean the difference between the type of wire that heats the floor and the type of wire that carries electricity around the house.

The type of wire that carries electricity around the house to lights and sockets has to carry current without creating heat. This is achieved by using copper for the conductors as copper has a very low resistance.

The type of wire that heats the floor has to create heat when current flows through it. This is achieved by using a metal alloy that has a high resistance for the conductors. A common alloy used for this is NiChrome ( Nickel and Chromium )

 

[KB009]

thank you for that, so I assume NiChrome wire is readily available? in the UK. Being as you are very knowledgeable would you buy a 5 amp or 16 amp under floor controller? I assume the 16amp will heat up faster.

I cant see why these underfloor heating kits are so expensive.

cheers

 

[bernardgreen]

You cannot just bury NiChrome in the floor. The heater wire has to be sleeved with insulation and a protective metallic sheath that has to be Earthed,

The length of the heater wire determines the resistance and this together with the voltage applied to the wire are critical when designing the installation.

A kit is the only sensible way to go for a DIY installation and even then it is not a "no risk" process.

 

[ericmark]

There are two types of underfloor heating elements, one is a simple resistance wire and it needs a pocket with a sensor in to ensure the floor does not over heat, the other uses a chemical most common is Reychem and the element is self compensating so does not need the sensor and special thermostat.

With the heating elements it is often in sections so it can be cut at special points, some can't be cut, the Reychem can be cut to any length I think.

 

[KB009]

If anyone knows a good reliable source for the wire and or matting....I would appreciate it. I need enough wire to cover 9m long and 1m wide....9 sq meters
I can buy the controller for around £50

 

[ericmark]

It was around 5 years ago when I wanted to install under floor heating, I could find the heating wire with earth brade easy enough but the Reychem for the wet room required an earth mat.

In hind sight the version I fitted with earth brade was an error, the pocket had too sharp of a bend and the sensor when I came to change it got stuck.

The heat from the UFH did get the tiles to the max permitted 27°C but the wet room was cold without the towel rail running.

The problem with UFH is time, it took at least an hour to get tiles warm, so really needed to be on 24/7 as takes so long to heat up, and the same cooling down, so if any windows in the room, the sun can heat the room up before the floor can cool causing a massive over heat.

I had the problem with mothers house even a radiator was too slow to cool, really needed a fan assisted radiator to react fast enough.

It all depends on the room, and if sun can shine through windows. UFH in an old peoples home works well, nothing too hot for them to touch, and a good back ground heat, often also radiators for fine control. But it is very limited as to where it will work.