Under Floor Heating

[wreck-it-steve]

Hi,

When installing under floor heating is it OK to extend any cables to a position where the controller can be located? Also is it OK to install on the ring main via a FCU or better on its on independent RCBO way?

Thanks

 

[RF Lighting]

Need more info.

Wet or dry heating?

What's the total overall load?

What cables are you wanting to extend?

How are you planning on jointing them?

Will the joints remain accesible?

What room(s) will this be in?

 

[wreck-it-steve]

Need more info.

Wet or dry heating?

What's the total overall load?

What cables are you wanting to extend?

How are you planning on jointing them?

Will the joints remain accesible?

What room(s) will this be in?

Not sure on most of this yet as its all still in the planning stage. The heating will be under a tiled floor in a bathroom. The controller will need to be about 10m or so away from the bathroom as this is the only place to put it. They would be joined under the floor (i can walk the entire span of the house under my floors) in a junction box using some sort of wago type connectors.

 

[pjcomp]

Heating mats are constructed on the basis that the heat they deliver is commensurate with the length of wire involved (the heat coming from the resistance). So if you extend the mat in any way, even if it's the cold tails, you'll alter the performance in some way. Best put to the manufacturer's helpdesk before you buy - I've always found them very helpful

pj

 

[ricicle]

So if you extend the mat in any way, even if it's the cold tails, you'll alter the performance in some way.pj

I wouldn't have thought the alteration of cold tails would affect it as their resistance is negligible compared to the resistance of the heating wire.
That being said you will probably find most manufacturers will prohibit the extension of said tails for warranty purposes.
There is also the floor temp. probe to consider.

 

[ban-all-sheds]

The heating will be under a tiled floor in a bathroom.

Why?

What do you think it is going to do, i.e. what's your reason for installing it?

 

[ericmark]

There are two completely different types of electric underfloor heating you do need to be careful as instructions vary vastly between the two.

One type uses a pure resistance cable this is the type normally used in bathrooms as normally nothing on the floor and you can get the special coaxial version where the earth is around the whole cable removing the need to install an earth mat above the heating cable.

The other uses a special chemical impregnated cable which resistance changes with heat so compensating to some extent for items placed on the floor similar to the Raychem trace heating system. As far as I am aware this type has to have a earth mat fitted over it when used in a bathroom.

I seem to remember that the chemical type can be cut to lenght using special seal where the resistive type can never be cut. However I have fitted trace heating where there are nodes and it can be cut so likely there are versions which do allow cutting.

However what I am saying is there are two main types which are then sub-divided into many more so with so many variations there is only one place to direct your question to.

So ask the manufacturer for their advice. Even if you had said what type you were using it is too easy for some one on here to get it mixed up with another make or type so has to be a question for the manufacturer not the forum.

 

[wreck-it-steve]

Looking at the booklet for the underfloor heating (trace heating type) it says that the probe can be extended up to 50m! does that mean the mains supply can be too? the problem is that we have no place to put the stat out side the bathroom and it cant be installed in the bathroom.

 

[ban-all-sheds]

Stevo - this was a genuine question:

The heating will be under a tiled floor in a bathroom.

Why?

What do you think it is going to do, i.e. what's your reason for installing it?

You might be very wrong about what you think the UFH will do, or how well it will do it.

 

[AdamCH]

Looking at the booklet for the underfloor heating (trace heating type) it says that the probe can be extended up to 50m! does that mean the mains supply can be too? the problem is that we have no place to put the stat out side the bathroom and it cant be installed in the bathroom.

I'm being told by Ambient that none of their controllers can go in the bathroom (even outside zone). I suspect that it's a protecting from humidity / warranty thing. I think there are other suppliers that do say it's okay for installation in OZ though.

I've read a post on another forum where the installer had been told by http://www.warmup.co.uk/uk/warmup-underfloor-heating-thermostats.phtml that their 3iE™ Energy Monitor Thermostat could be placed in OZ.

 

[SimonH2]

Yes, there's no problem extending the cold tails - it's no different to using lengths of cables between the element and the substation transformer
Extending the sensor probe needs a little more care - the controller senses changes in the resistance to determine temperature. But as long as you use a reasonable low resistance cable then it should be fine - ie don't use something like thin "bell wire" or phone cable.

As mentioned above, joints need to be done according to regs etc.

 

[wreck-it-steve]

Stevo - this was a genuine question:

The heating will be under a tiled floor in a bathroom.

Why?

What do you think it is going to do, i.e. what's your reason for installing it?

You might be very wrong about what you think the UFH will do, or how well it will do it.

We have a rad in the bathroom already and this is just to warm the tiled floor for walking on. Not my choice.

 

[wreck-it-steve]

Yes, there's no problem extending the cold tails - it's no different to using lengths of cables between the element and the substation transformer
Extending the sensor probe needs a little more care - the controller senses changes in the resistance to determine temperature. But as long as you use a reasonable low resistance cable then it should be fine - ie don't use something like thin "bell wire" or phone cable.

As mentioned above, joints need to be done according to regs etc.

The cable will go through a hole to a void under the floor (accessible) then jointed in an enclosure using the correct connectors.