Klima ufh mat - am I being stupid here?

[ban-all-sheds]

I'd say that it's a total waste of resources to install, and electricity to use.

Other options such as a warmer surface (e.g. wood) or using mats or wearing slippers are nicer.

 

[flameport]

It will probably do nothing when I turn it on but an hour or two later the floor won't be icy cold in the winter.

Your assumptions are correct.

However there have been many people previously who expected electric UFH to actually heat the room, or warm up the floor in a few minutes.
After installation, they were not pleased when they discovered the truth about it's operation.

300 watts

Your resistance reading implies 400W.

 

[SimonH2]

... or wearing slippers are nicer.

I don't see the attraction in wearing slippers in the bath/shower

 

[ban-all-sheds]

.

 

[ban-all-sheds]

Your resistance reading implies 400W.

The resistance probably increases when it is hot.

 

[SimonH2]

The resistance probably increases when it is hot.

Probably not by much.
The wire temperature isn't going to be "very high", and a quick look at something like Nichrome (it's just the first that came to mind, no I don't know what they use in these systems) suggests that even for a 300˚C rise in temperature, the resistance will only change by something in the order of 3-5%. Other materials will have different co-efficients, but I doubt that any of them have one so high as to change the resistance (for only a few tens of ˚C temperature change) enough to change the element between 300W and 400W.

 

[JohnW2]

... a quick look at something like Nichrome (it's just the first that came to mind, no I don't know what they use in these systems) suggests that even for a 300˚C rise in temperature, the resistance will only change by something in the order of 3-5%. Other materials will have different co-efficients, but I doubt that any of them have one so high as to change the resistance (for only a few tens of ˚C temperature change) enough to change the element between 300W and 400W.

Probably true. However, the "first material which came to your mind" gives a rather distorted picture unless (as is far from impossible) the UFH elements use Nichrome, since that material is rather 'out on a limb' as far as temp coefficients are concerned. If it is anything else, most metals (copper, aluminium, iron, lead, tungsten, nickel, gold, platinum, zinc, tin - to name but a few) have a temperature coefficient of resistance which is around 10 times, or more, higher than that of Nichrome.

Kind Regards, John

 

[Spherehopper]

there have been many people previously who expected electric UFH to actually heat the room, or warm up the floor in a few minutes. After installation, they were not pleased when they discovered the truth about it's operation.

I have experience of that, the previous owners of the house I am in now installed it everywhere including in a large kitchen. When I moved in during the winter, I left all settings how they had them to see how it went. After two weeks, I checked again, the house was consuming £200 a week in gas and electricity.

Looking into the stats, located in a cupboard outside the room, they had been left on default (air sensing) with a temperature of 24 degrees for large periods of the day. As soon as I tweaked them to 18 degrees, floor temp, twice a day, the bills plummeted.

Your resistance reading implies 400W.

My mistake, the manufacturers state 150w per sq m. I remembered the mat being 2 sqm but it's 2.5sq m so 375 watts it is (plus or minus whatever manufacturing tolerance there is in the heater wire).

 

[ban-all-sheds]

I don't see the attraction in wearing slippers in the bath/shower

I don't see where that has been suggested.

It really would be better if you were to reply on the basis of posts you read, rather than just making stuff up.

 

[aptsys]

Here's the response I got from technical.

 

[SimonH2]

I don't see where that has been suggested.

It really would be better if you were to reply on the basis of posts you read, rather than just making stuff up.

Ah, so you are now going to deny having suggested that

... or wearing slippers are nicer.

A logical interpretation of what you actually wrote (not what I made up) is that a reasonable alternative to stepping out of the shower/bath with wet feet onto a cold floor is to wear slippers. Note that the OP has stated that this is a tiled en-suite above an unheated space.
For a tiled bathroom floor, UFH is a logical choice - to warm the floor so it's comfortable to stand on with bare (and wet) feet. And your statement that

I'd say that it's a total waste of resources to install, and electricity to use.

is false for some scenarios. I wouldn't want to heat the room with it, but then for the cost of ripping up a floor etc to retrofit wet UFH (vs using electric which doesn't need the substrate ripping up), you can afford a fair bit of lecky. And of course, if you already have electric heating (as many have) then UFH isn't going to be any more expensive than other forms of heating.

I would suggest that your problem is deciding that it's not a sensible option for situations you recognise, and failing to allow for others having situations you haven't considered. The "it doesn't work for me, therefore it won't work for others" thinking seen so often in many fields.

And just an FYI ...
I helped a friend fit UFH in his bathroom before tiling it - he is very happy with it. It's not there to heat the room, only to make the floor comfortable.

 

[ban-all-sheds]

You prize *&$^.

Ah, so you are now going to deny having suggested that

... or wearing slippers are nicer.

I'm going to deny that that was the only alternative option I presented.

Other options such as a warmer surface (e.g. wood) or using mats or wearing slippers are nicer.

A logical interpretation of what you actually wrote (not what I made up) is that a reasonable alternative to stepping out of the shower/bath with wet feet onto a cold floor is to wear slippers.

So what is the logical interpretation of the fact that out of 3 alternatives, 2 of which would be very reasonable alternatives to stepping out of the shower/bath with wet feet onto a cold floor, you decided to pretend that the only alternative I had offered was the other one.

Why, Simon? Why did you behave so pathetically?

It's not there to heat the room, only to make the floor comfortable.

Exactly.

It's a waste of electricity. There are alternatives.

 

[SimonH2]

You prize *&$^.

Oh how very adult of you

 

[bernardgreen]

It's a waste of electricity.

Expletives are a waste of internet bandwidth

and soggy wet slippers are just dismal

 

[Spherehopper]

I'd say that it's a total waste of resources to install, and electricity to use.

Other options such as a warmer surface (e.g. wood) or using mats or wearing slippers are nicer.

Of course, that is an opinion however, my house has electric ufh in all other bathrooms to supplement the old cast iron/steel pipe heating system which is being replaced at the moment. The finished project is very high spec as it will be sold in a market where buyers expect this sort of thing.

The ensuite is immediately adjacent to the bed and the rest of the house is carpeted so I don't tend to wear slippers around the house. The room was being constructed from scratch so installation cost is low (cost of mat) and running costs I estimate about 30p a day when in use. Not only will it take the chill off the floor but will help keep the room dry. The extractor fan (required by building regs) cost me around £500 to install since the roof needed work to install the duct. By comparison, the floor was cheap.

Here's the response I got from technical.

They didn't even answer my email. I work in the aviation industry where we are taught to question any ambiguity lest it causes an accident. They seem surprised that this is the first time someone has noticed this.