Underfloor heating .

[Megaohm7]

A friend of mine wants underfloor heating and is looking at the electrical type . He has asked me how reliable it is . I have no experience with this whatsoever , all I can see that it must be a pain to put right if a fault develops . His wife wants a stone floor so it will be under that , any advice on this would be greatly appreciated Pray

 

[Bez]

All you can do is test it before you lay it, continuity reading should match that of manufacturers. Insulation resistance to make sure all is well before you lay it. After that you're in the lap of the gods once it's covered. Main problems seem to be with floor sensor rather than the mat itself.

 

[ianmacd]

Have a look at rayotec as their ribbon mats claim that they do not need a floor sensor if under tiles as they never get hot enough to cause an issue. Something to do with the ribbon not needing to run at such a high temperature as the wire ones as it has a higher surface area.

 

[Evans Electric]

As I said in an earlier thread, there are two ways of approaching floor heating Option 1. The low wattage mats which are popular today , their function is to warm up a cold tiled floor.

Option 2. Floor heating system that is designed to heat a room in place of central heating.

Edit: Which option is the customer looking for.

Deke

 

[Megaohm7]

Thanks for the advice , I didn't realise there was different types that serve different purposes . I suppose if installed correctly to the manufacturers spec it should be reliable. If not then it's a kango job :_|

 

[jimleen]

I've thought about getting it myself. I met a sales rep, and sales reps don't lie, who told me that using underfloor heating as a primary heat source was more efficient than heaters etc. because it only heated up to 25 degrees. He then went on about temperature envelopes and stuff. It was at that point my eyes glazed over. Just after that point he told me the price and promptly lost a sale. :^O

As for laying it, same advice as the other chaps but with the proviso that you show the customer the test results. Even though you're doing it for a pal, if the tiler buggers up the element your pal will at least know it was undamaged when you left it.

 

[ian932]

Option 1 can be OK but fluffy slippers are more cost effective.

Option 2 would be a total waste of money and I guarantee they would turn it off after their 1st winter electric bill, if they want to heat the room use radiators or do a proper job with a wet system.

Any UFH on a concrete slab whether its a wet or dry system needs to be laid on an insulated floor with not less that 50mm of kingspan/celotex most firms will now say 70mm. If you don't then you are going to heat the subsoil.

They all work on the basis that the slab or screed becomes a thermal store and to work efficiently you need to run the system low and for long periods to get the benefit of heat, none of that oh its cold lets put the heating on and expect to be warm in 30 mins like rads.

Finally anyone who say's electric matting is cheap to run is a sure fire candidate for BBC rogue traders.

 

[batty]

Option 1 can be OK but fluffy slippers are more cost effective.Option 2 would be a total waste of money and I guarantee they would turn it off after their 1st winter electric bill, if they want to heat the room use radiators or do a proper job with a wet system.

Any UFH on a concrete slab whether its a wet or dry system needs to be laid on an insulated floor with not less that 50mm of kingspan/celotex most firms will now say 70mm. If you don't then you are going to heat the subsoil.

They all work on the basis that the slab or screed becomes a thermal store and to work efficiently you need to run the system low and for long periods to get the benefit of heat, none of that oh its cold lets put the heating on and expect to be warm in 30 mins like rads.

Finally anyone who say's electric matting is cheap to run is a sure fire candidate for BBC rogue traders.

My thoughts too had customer laid one in conservatory himself I wired it in. Rang me to say thought it had gone faulty. well I tested it and it was using 4 amps of electric for a 1000 watt element. I think it was just because temperature is down so it can't cope anyway he was going to ring Wickes as that was where he got it from. Good luck.

 

[Megaohm7]

I will pass on these comments to my friend , it's certainly food for thought . As it's for the kitchen dining area he could always tell the wife to look lively when she's cooking the family roast , that'll keep her warm ROTFWL Thanks everyone for the advice

 

[bengie]

my uncele installed the mat type in his bathroom and its not that great, apparantly it takes a long time to warm up(an hour or more) and then it only provides a warm floor rather than heating the room.

 

[SPECIAL LOCATION]

Wired a small conservatory system up last year, customers own purchase, & the customers floor tiler was doing the laying etc..

All I had to do was connect up the timer switch & thermostat sensor jobbie..

(it had the under floor probe & room temp sensor as well).

This mat was rated at 2400watts and as per manufactures instructions it was connected via a 13amp FCU.

As far as I know it works ok for the customer (never had any call backs)..

But 2.4kW taking 10amps+ whenever its running!

I think a small convector heater 700w or 800w would probably have achieved the same warmth?

so in terms of the 'Juice-use'**, league tables I guess its in the top 4, could be playing in Europe next season....

lets recap the top of the table:-

1. Electric Showers

2. Electric ovens / cookers

3. Immersion heaters

4. Electric Underfloor heating

5. Electric fires & room heaters

6. Tumble driers

7. etc...

8. etc...

taking into consideration Juice needed & Duration of Juice-Use..

although some pundits suggest suggest positions 3 & 4 could easily change due to goal difference. O)

Admin!!! me medications slipping again :_|

** "Juice-Use" - Todays unofficial forum honorary technical term for the day"!

Guinness

no I wont have a beer yet

Admin2's got the kettle going again!

put the kettle on

{Batty is going to be very angry we nicked the kettle from his van!

looks like is Cake but NO tea on Monday :_| }

 

[Lurch]

But if specified and fitted properly and you use the right stuff for the job then it is more efficient than a wall mounted convector heater. A wall mounted heater is fighting against the cold floor and no matter what the heater is on the floor is always cold, which makes the room feel cold.

Personally If I was using underfloor heating in my own home I'd go for a wet system, electric is fine for retrofitting and using in the odd room as an addition.

 

[kme]

I`ve got electric UFH (wire type) through kitchen, dining room & hallway downstairs, under tile (no rads there), rads in the lounge; and ribbon type in the bathroom, under laminate.

No problems whatsoever.

The kitchen & hallway are 1 zone, with a 3.2KW load. The dining room is another 1.6KW, and the bathroom ribbon is 400W.

I wouldn`t change it - wet would have been impossible, without raising all the downstairs floors, then I`d keep hitting my head on doorframes!

 

[bengie]

i've just replaced the rad in my bedroom with underfloor heating(wet system) and it was actually quite easy and cheap(did it all myself) costing about

 

[ianmacd]

Retrofitted? Can you explain how you got the space? Was it one that is in the floor cavity?

 

[steptoe]

i've just replaced the rad in my bedroom with underfloor heating(wet system) and it was actually quite easy and cheap(did it all myself) costing about

 

[Lurch]

Retrofitted? Can you explain how you got the space? Was it one that is in the floor cavity?

Who did what?

 

[bengie]

lift boards and fit at least 50mm celotex tightly between joists as high as possible in the void whilst still leaving room for the pipe, notch joists where pipes must pass at 90 degrees and fit decent thickness hit plates over the pipes/notch to protect the pipe as wel as try and replace some of the lost strength in the joist due to notch, tee off of the flow/return pipes like a normal rad and also fitting a trv is a good idea so you can still control it like a normal rad. luckily as i went from a rad to underfloor i already had the trv in place as well as the flow/return points.

by the way this is how i was told to do it by a gas fitter and i got the ok on the joist notches by a builder before i went ahead(location/size of joists and the metal plates).

works well so far

apparantly this method is ok if your only looking at doing one room as a retro fit, if your doing an installation from scratch then your looking at zone valves, manifolds etc etc

 

[bengie]

obviously the thicker the insulation the better, i have a picture here of mine part way through

here is a guide i found on notching joists

that room is 5m long with 6x2 joists so i was lucky that i could do it. I also used a guide on the layout of the pipes, i'll try and find that too.

http://www.eastdevon.gov.uk/bc-guidancenote7-notchingofjoists.pdf

 

[bengie]

i've been looking and i can't find it, sorry.

the general gist of what i wanted to show was that the flow and return should spiral around each other and be kept about the same length to keep the average water temp in the pipes as equal as possible rather than a long spiral on the flow and short return. this is what the guide said anyway so i went with it