Electric UFH problem

[Nightlight]

Hello,

We have a large kitchen with EUFH which used to work but not now.

It is confugured in two zones each with two mat sets in parallell and each zone is controlled with an aube TH132-F themostat on a PB130-230 base.

Both zones are not heating, each thermostat is showing the UF temperature ok.

When power is applied to the thermostats I can hear the internal relays activate and see a full bargraph (81 to 100%) on their lcds.

I have measured each of the four mats at approx 88 ohms with no resistance to their earths.

There is 240V across the mats and the current to each pair is approx 5.9A. this equates to approx 1.4kW being drawn by each pair.

As I do not know how the heating wire / element works I'm flumoxed as to why both zones are not heating, so I'm hoping someone here can suppy an answer
I'm sort of resigned to the fact that I can say goodbye to the UFH as there is no way we're going to destroy the floor to replace the mats but I'd love to know why there is no heating

considering the anount of power being drawn.

 

Many thanks for your time,

Nightlight.

[ProDave]

Is that 88 ohms per mat, all 4 of them, or 88 ohms for all 4 connected in parallel?

 

if 1.4kW of power is going into the floor then something must be getting warm somewhere, energy can;t just disappear.

 

What is the power rating of the UFH supposed to be?

[Nightlight]

Thx for the reply ProDave,

 

It's 88 Ohms per mat and I have no idea of the spec of them .

Each zone has 2 x 88 Ohm mats in parallell = approx 44 Ohm per zone.

 

I agree with you..energy just cannot disappear, that's what is confusing the hell outa me!!

It baffles me why the two seperate zones are behaving in exactly the same way, that's why I thought it might be the wire/element that might be faulty and not giving out the heat it should.

I'm going to up the temp to 29C on the thermostats to see if I can feel if the floor is getting hot in any place.

will keep you posted.

 

Night....

 

Edited February 21, 2021 by Nightlight

[ProDave]

So 22 ohms in total you should be looking at just over 10A total with a power input of 2.3kW for the whole lot.

 

Check the current actually going into each mat.

[Nightlight]

Hi ProDave,

Just to clarify things

There are two seperate zones each controlled by their own aube TH132F control module.

Each zone has two 88 Ohm (+- 5%) mats connected in parallel therefore each zone is loaded with approx 44 Ohms

The total current measured in each zone is approx 5.5A ( 240V/44R) and that is approx 1.3kW (240V x 5.5A) per zone.

Each individual mat is taking approx 2.7A.

I'm wondering if the actual heating cable is faulty in so much as it's not giving out the heat it should..

I.E. is heating wire supposed to give out more heat per Amp than a straight piece of copper wire?????

 

Night...

 

 

Edited February 21, 2021 by Nightlight

[ProDave]

It's simple physics.  With electric resistance heating, if you put say 1kW of electrical power into it, you get 1kW of heat out.  That 1kW has to go somewhere.

 

So first of all measure accurately how much electrical power is going in.  If it does not seem to be delivering the heat you expect you have to ask where is it all going?  e.g is it a suspended floor and all the under floor insulation has fallen out and it's now heating the under floor space?

[Nickfromwales]

Bypass the controllers. 
Leave the mains inputs powered up to the controllers so you have the displays up. 
Power the EUFH mats up directly off the fused spur that supplies the mats and sit for an hour or two to observe what happens. If the displays register a rise in temp and the floors start to warm then it’s the controllers, if not, it’s the mats. 
I’d say it’s the controllers as 4 mats dying together is lightning strike odds. 

[Nightlight]

Thank you both for your input

 

The kitchen is on the ground floor and has a large concrete base on top of which the matting was laid then the Indian slates were laid on top, that's all I know.

I had thought the controllers might be at fault but when I measured mains at the output of both and saw current being drawn by the mats I assumed they were working ok but I may try what you suggest Nick and see what happens.

I'll be in touch...

Thank you both for taking the time to reply, watch this space..

 

all the best to you both,

 

Night....

 

[Evs]

Do your thermostats use temperature probes that are also under the floor? 

[Nightlight]

Hi again

 

Ok, I did as NickfromWales suggested and lo and behold the floors started heating up..sigh of relief there!

 

So I ordered up and replaced both TH132 controllers with the upgraded version TH232, fitted them and all seems good yoo-hoo!!

 

What confused me was the old controllers apparently supplying 240V @ 6A per zone whilst the floors were'nt heating..I can only assume that

the waveforms were being chopped and the meters I used did'nt pick that up...weird!!

 

Anyway it's all sorted now and again I thank you all for replying to this topic.

 

all the best to you all,

Nightlight.

Edited February 24, 2021 by Nightlight

[Nickfromwales]

Excellent news, result! ?