Underfloor heating

[char123]

Hi, we had our under floor heating thermostat fitted Ocotber ish. It’s turned out company I bought off sent wrong one so send me new one - should have been like for like swap but keeps tripping. It ran before on 13AMP fuse plug - paper work said 16AMP do bought some 16AMP but blows straight away - also tried 13AMP. I have done everything like for like. These pictures are how it is wired now. Am I missing something really simple? Just before I call an electrician

thank you
Apparently red and white wires are sensor and does not matter which way round it goes.

 

[char123]

These pics are how it was wired before...

 

[Andy™]

sensor will not cause it to trip. almost guaranteed that the heating element is faulty

appears as though you have 4 connected to it? youll need to test each one to find out which one is faulty

 

[Geoff1946]

Temporarily disconnect the controller output and see if you can power the controller alone up without the fuse blowing.
I agree it looks most likely faulty heating element, but if it's been blowing successive fuses I wouldn't be surprised if the controller has been damaged too.

 

[SPECIAL LOCATION]

If you say it was off a 13A fuse..
I am guessing its via a switched, (or maybe unswitched), Fused Spur...

If a fuse blows the solution is never just stick in a bigger fuse as that will only make matters worse..
You need to find the cause of the original fuse blowing..?

If you are via a bog-standard 13 FCU, you could have too many, (too higher power), elements coming from the same supply...
I've Seen that before where some idjut floor heating fitters had connected 2x8A elements to one 13A FCU..
(basic maths tells us 8A+8A=16A... which is NO good via a 13A supply!)

Customer found the FCU was overheating.. which then melted the fuse carrier & switch contacts..

It didn't actually blow the fuse.. just melted the switch preventing power getting to the thermostat..
In this instance the supplies to the mats needed changing...

While the thermostat switch contacts are typically OK for 16 load..
I would have probably put this from a 20A radial..
Guessing yours is a 13A spur off a ring?

Really we need to know the actually spec of the heating element(s) your thermostat is feeding to give an accurate answer..
(you are correct about the sensor polarity.. also the sensor will NOT be causing any fuse blowing problems..)