Under floor heating system problem

[RF Lighting]

What's the combined load of all 3 mats?

It sounds as though your elements do not contain an internal earth. Have you got an earthed metallic mesh to install over the elements as required by BS7671?

Quoting my self as the op seems to have missed this.

 

[SimonH2]

Goodbye.

Wayhey - this must be a first. Look everyone, BAS gives up on a discussion he can't cope with.
Believes in time going backwards, doesn't understand physics of heating systems, gives up.

 

[North]

My fitters I do not trust them too much

Hmmm.

You know what the best solution is to all the problems arising from that....

Poison them?

 

[SimonH2]

My fitters I do not trust them too much ...

That is a reasonably healthy attitude. Unfortunately all trades have an element who don't really understand what they are doing, and will just bodge what they thing should be done. Floor fitters and electrics seems a likely candidate for this, adding in products of "questionable" design and the options for "mistakes" increase.

The problem is, the poor end user usually isn't in a situation to recognise whether the job is being done right or not.
While not exactly an expert, you probably have enough knowledge now to be able to ask the fitters what they are going to be doing and have some clue if it sounds right or not - you can always come back and ask for clarification here if you need to. But be sure they do know what they are doing before they start cutting anything - it's a lot harder to put it back than to cut it off in the first place.

 

[ban-all-sheds]

Wayhey - this must be a first. Look everyone, BAS gives up on a discussion he can't cope with.

That's funny - I could have sworn it was you giving up.

Oh look - it was:

Then there is no point discussing the issue with you.

Believes in time going backwards,

No, I don't.

But I do believe that you must either be genuinely incapable of understanding how that graphical representation I used works, or are pretending to be in a pathetic and doomed attempt to try and salvage your argument that stone floors do not exhibit any lag when applying and removing heat to them.

doesn't understand physics of heating systems, gives up.

I do understand them.

I do understand that if the air in a room with UFH is not at 20° then the physics says that it is not at 20°.

I do understand that the k-value of a material does not change when you put it in contact with pipes containing hot water instead of pipes containing hot wire.

I do understand that the amount of heat which a given area of floor will radiate into a room depends on its surface temperature and emissivity.

I do understand that if the combination of the amount of free area, the temperature which can be sustained, and the emissivity means that not enough heat will be radiated into the room then the physics says that not enough heat will be radiated into the room.

 

[SimonH2]

But I do believe that you must either be genuinely incapable of understanding how that graphical representation I used works

I am quite familiar with the graphical representation of a hysteresis loop, not that it's appropriate to the discussion. The term you are looking for is overshoot (caused by lag), there will be no hysteresis in the system other than that induced into it by the controls (eg setpoint hysteresis in the thermostat). I did offer you the chance to think about it again ...

, or are pretending to be in a pathetic and doomed attempt to try and salvage your argument that stone floors do not exhibit any lag when applying and removing heat to them.

I don't believe I ever said that they don't exhibit lag, hysteresis no, lag yes. The lag will depend on many factors, will be different between electric and wet systems, different for different types of controls, and different between heating and off modes.
And I will point out that the heating element is not the whole system, you have shown the typical blinkered attitude that because a radiator is small in thermal mass, that it doesn't suffer lag and overshoot - once combined with the rest of the components needed to make it work, that is no longer the case. Hint - I have dealt with such issues in the past, and I have studied the spec sheets for the controls I've used, and I know that some of them do have considerable lag. In fact, some of them have exhibited sufficient lag as to create instabilities - needing changes to the (commercial) systems I was using.
And for another hint, consider the effect on the system of a combi boiler.

doesn't understand physics of heating systems, gives up.

I do understand them.

But then demonstrates otherwise ...

I do understand that if the air in a room with UFH is not at 20° then the physics says that it is not at 20°.

So you still maintain that the function of a heating system is not to heat a space to be comfortable for the occupants, but to heat it to a precise temperature ? The actual temperature really is not that important (outside of some bounds, such as recommended lower limits for infirm/immobile people), the perception of temperature by the occupants certainly is (and depends on many factors other than just temperatures). The big issue is that measuring the latter is in practical terms impossible, so we have to measure actual temperature as a (sometime unreliable) proxy.

I do understand that the k-value of a material does not change when you put it in contact with pipes containing hot water instead of pipes containing hot wire.

See, just what I said, you've failed to understand the physics. Open up your mind, and consider the other factors - k-value is but one of them. I'll give you a hint - an electric element is (within the sort of temperature ranges for this application) a constant power input while turned on - work the rest out for yourself.

I do understand that the amount of heat which a given area of floor will radiate into a room depends on its surface temperature and emissivity.

I do understand that if the combination of the amount of free area, the temperature which can be sustained, and the emissivity means that not enough heat will be radiated into the room then the physics says that not enough heat will be radiated into the room.

Well yes, that is true - IF the result of those calculations is that not enough heat is provided. You seem to be of the opinion that it cannot ever be, practical observations says you are wrong because there are many installations where it is.
I have not ever argued that UFH will be suitable for all situations, clearly there are many where it won't be. But where the combination of factors allows, then it can be an effective method of making a room comfortable to occupy.
For some situations, it may be that it can make a valuable contribution in conjunction with out methods.

 

[North]

Well thank for all replies so far. I as many of you i presume, normally try to avoid tradesman as if they were the Devil himself chasing me with a blowtorch and a jarry can full of fuel but sometimes i need to get someone to do things I am not capable of doing myself.
Despite all the arguments among you i really appreciate the input. I just wish I could understand what all these arguments are about. One day maybe...

 

[stillp]

While I'm sure Simon is correct that good installations of UFH exist, my experience is limited to a few hotel rooms, and a holiday apartment. The problem was the time taken to get up to temperature, and to cool down when that temperature was reached. Actually the best of them was a hotel with a small en-suite bathroom, in which the UFH was run from a dimmer, no thermostat at all!

 

[ban-all-sheds]

I am quite familiar with the graphical representation of a hysteresis loop, not that it's appropriate to the discussion. The term you are looking for is overshoot (caused by lag), there will be no hysteresis in the system other than that induced into it by the controls (eg setpoint hysteresis in the thermostat). I did offer you the chance to think about it again

So if you were to plot temperature over time using these axes, what sort of shape would you get?

I don't believe I ever said that they don't exhibit lag, hysteresis no, lag yes.

So hysteresis loops cannot arise because of a lag?

And I will point out that the heating element is not the whole system, you have shown the typical blinkered attitude that because a radiator is small in thermal mass, that it doesn't suffer lag and overshoot - once combined with the rest of the components needed to make it work, that is no longer the case.

And now much does it exhibit compared to a stone or concrete floor? How quickly does the latter respond to an acute need for heating, or an acute disappearance of the need for heating?

So you still maintain that the function of a heating system is not to heat a space to be comfortable for the occupants, but to heat it to a precise temperature ? The actual temperature really is not that important (outside of some bounds, such as recommended lower limits for infirm/immobile people), the perception of temperature by the occupants certainly is (and depends on many factors other than just temperatures). The big issue is that measuring the latter is in practical terms impossible, so we have to measure actual temperature as a (sometime unreliable) proxy.

That's not physics.

Do not accuse me of not understanding physics, and then when I say that if the air in a room with UFH is not at 20° then the physics says that it is not at 20° claim that that shows I don't understand it because of perception. What the people perceive in a room will not, and cannot change what a thermometer measures. The former is not physics, the latter is.

I do understand that the k-value of a material does not change when you put it in contact with pipes containing hot water instead of pipes containing hot wire.

See, just what I said, you've failed to understand the physics. Open up your mind, and consider the other factors - k-value is but one of them.

I'm rapidly losing all tolerance for your false allegations.

Please explain how the k-value of a material changes when you put it in contact with pipes containing hot water instead of pipes containing hot wire.

Well yes, that is true - IF the result of those calculations is that not enough heat is provided. You seem to be of the opinion that it cannot ever be, practical observations says you are wrong because there are many installations where it is.

And how many of those installations are of DIY-install electric heating mats in properties not designed with UFH in mind?

I have not ever argued that UFH will be suitable for all situations, clearly there are many where it won't be.

Why? What do you expect it to do?

But where the combination of factors allows, then it can be an effective method of making a room comfortable to occupy.

Why? What do you expect it to do?

For some situations, it may be that it can make a valuable contribution in conjunction with out methods.

Why? What do you expect it to do?

Having now had a look at the supplier's site - I see they don't provide this pocket and conduit.

Still think they are selling a quality product?

 

[RF Lighting]

What's the combined load of all 3 mats?

It sounds as though your elements do not contain an internal earth. Have you got an earthed metallic mesh to install over the elements as required by BS7671?

Quoting my self as the op seems to have missed this.

Are my quotes not showing up?

 

[Iggifer]

What's the combined load of all 3 mats?

It sounds as though your elements do not contain an internal earth. Have you got an earthed metallic mesh to install over the elements as required by BS7671?

Quoting my self as the op seems to have missed this.

Are my quotes not showing up?

They are to me! I realise you're not being 100% serious. But for some reason, seems you're being ignored. More fool the OP tbh

 

[SimonH2]

So if you were to plot temperature over time using these axes, what sort of shape would you get?

Something with no resemblance whatsoever to your original image - I think even you realise that now

So hysteresis loops cannot arise because of a lag?

I doubt it - they are different phenomena.

OK, take this situation. You set the stat at 20˚C and leave it for a while.

Lag means that regardless of what state the system started, there will be delays, and it will take a long time to reach a stable temperature - it may (depending on a load of factors) not actually reach a stable temperature, but cycle around the set point; or it may settle to a stable temperature (the latter is actually quite achievable with electric heating and a burst mode controller). But regardless of whether it was previously cold, or you'd previously had it set to (say) 25˚C it will settle at the same point.

Hysteresis means that the final state the system settles at depends on whether it was previously cold or hot - so it might settle at (say) 18˚ if previously cold, or 22˚ if previously hot.

Two very different effects - and barring dead bands in the stat, hysteresis isn't an issue for domestic heating systems.

And I will point out that the heating element is not the whole system, you have shown the typical blinkered attitude that because a radiator is small in thermal mass, that it doesn't suffer lag and overshoot - once combined with the rest of the components needed to make it work, that is no longer the case.

And now much does it exhibit compared to a stone or concrete floor? How quickly does the latter respond to an acute need for heating, or an acute disappearance of the need for heating?

Well a wet system will heat the slab quite quickly - having 10s of kW of boiler behind it gives a distinct advantage over an electric system with a few hundred W or couple of kW. But speaking of some of the actuators, (from memory) some can take TWO minutes between application of a signal and starting to open, and if they've been open for a while, can take FIVE minutes before starting to close and SEVEN minutes to fully close. When you've got these on heat/cool air handlers it can cause some issues - and one we had was that the temperature could overshoot enough, and for long enough, that it would switch modes (eg start cooling while the heating valve was still open). Originally they were installed with mechanical stats, and being heat-off-cool dual switching, they didn't have compensating resistors - so these stats did have considerable hysteresis (as much as 3˚ depending on mechanical tolerances). When we started retrofitting electronic controls, I had the manufacturer add a lockout so the unit couldn't switch (say) to cooling mode too soon after it had been in heating mode.

Just for good measure, many radiator systems oscillate - with the TRV opening wide, the rad getting hot, the room overheating, the TRV (eventually) fully closing, the room cooling off, rinse and repeat. In part, it's because so many system never get balanced - with people wrongly believing that it's not required with TRVs.

I'm rapidly losing all tolerance for your false allegations.

Don't blame me for your lack of comprehension.

Please explain how the k-value of a material changes when you put it in contact with pipes containing hot water instead of pipes containing hot wire.

I did not say it does. What I did say is that it's but one factor or many - and the physics with a wet system is significantly different to an electric system. An electric system is a constant power input, a wet system is nominally a constant temperature input and heat input will reduce with reduces delta-T between water circuit and slab. Electric systems are generally installed to not heat a large slab - for the OP it will (I assume) be laid on insulation and the laminate laid on top, thus having a fairly low thermal mass. Wet systems are frequently laid in a slab, but with a significant surface are of pipe, and a fairly powerful heat source, heat up times aren't actually that long. But some wet systems are instaleld without a slab, so rapid heatup again, but not a significant thermal mass - more water than a slimline rad, probably something akin to the old fashioned cast iron segment rads that seem trendy these days.
Ignoring all the differences in typical installation arrangements, just the difference between heat inputs makes a significant difference to the heating curves.

And how many of those installations are of DIY-install electric heating mats in properties not designed with UFH in mind?

And that's relevant how ? Perhaps you could explain what is different for a property designed to be heating with UFH - other than aiming to be energy efficient just the same as a property designed to be heated by rads ?

I have not ever argued that UFH will be suitable for all situations, clearly there are many where it won't be.

Why? What do you expect it to do?

Why? What do you expect it to do?

Why? What do you expect it to do?

And your actual question is ? You just seem to be asking the same question for dramatic effect.

I've merely pointed out that you cannot be correct when you assert that "UFH doesn't work". I've witnessed it working in several properties, so either all those were figments of imagination, or you are wrong - I don't have that vivid an imagination. I've also pointed out that, like everything else, if it's not properly designed, installed, and configured then it may not work very well - which still doesn't support your view that "UFH doesn't work". Well is that a surprise ?

Still think they are selling a quality product?

Please state where I've passed comment either way on the quality of this particular product, and perhaps more appropriately, assuming that it actually does what the vendor says, why that is an issue as to whether it actually works or not ? Apart from issues like safety and reliability, please explain how a "poor quality" heating element will perform differently to a "good quality" element of the same general arrangement and power rating ?
If the element works, and if the power rating is adequate for the requirements of the room, and if the thermostat works, then I'd expect it to be able to heat the room - the "if"s because I've not seen any figures, so no I don't know if it has the required capacity, and no I have not offered any opinion on this installation in that respect. Laminate is fairly low mass, electric is very fast acting (turn on and turn off at the speed of the relay), so I'd expect it to not suffer from huge lags and overshoots.

 

[ban-all-sheds]

Something with no resemblance whatsoever to your original image - I think even you realise that now

No I don't.

So hysteresis loops cannot arise because of a lag?

I doubt it - they are different phenomena.

You are needed over at Wikipedia.

Please explain how the k-value of a material changes when you put it in contact with pipes containing hot water instead of pipes containing hot wire.

I did not say it does.

And with that untruth from you:

I'm going to stop discussing it. I won't be surprised if you crow about how that means I know I'm wrong and you're right, or how it means I've "lost" and you've "won", but frankly I no longer have any regard for what you "think".

 

[North]

I am afraid I have some more issues about this.
My electrician came and is not willing to sign the warranty card because the wires need to be extended. I told him to extend the cables himself the way he wanted and he refuses to sign off the card. Acording to him the cables should be one piece and should not be extended.
Any views on this?

 

[RF Lighting]

I'd have done the same.