Underfloor heating

[Guybrows]

Hi all, I am 2nd fixing a job that someone else 1st fixed. I hav two wire coming out from under the tiles. One is a two core. One brown and one blue. The other is a bit bigger diameter cable and one core is blue and one is grey. As i did not install it i dont know which is the sensor and which is the load. I dont want to risk it as im afraid i will blow up the sensor if i get it wrong. Does anyone no a dead cert way of finding which is which. I thought about a resitance test but i dont have the instructions to check what they should be.

Many thanks for your help

 

[Guest123]

Do you know the make???

 

[Guybrows]

Unfortunately not, the previous electrician didnt leave any paperwork!

 

[jimsky007]

Hi

The only way you are going to check this for sure is with a resistance meter I reckon your elements are brown and blue?? so if you have

a. 250 watt element you should measure = 212 ohms approx

b. 500 watt element = 105 ohms

c. 750 watt = 70 ohms

d. 1000 watt = 52 ohms and so on

The sensors are normally a thermistor type which have a negative temp/ heat coeficient as heat increases resistance decreases but if you dont know the type it will be difficult so best to measure the element resistance

 

[Guybrows]

Thats brilliant thanks alot for your help Jimsky!

 

[Eggster71]

The power cable should have an earth braid incorporated! If not there should be an earthed screen above the element.