underfloor heating controller showing signs of melting

[egginyourface]

Hi all

I was called out to investigate a heating matt which had stopped working. On closer investigation I found the unit and connections had melted and same for fusespur.

Could this be a fault with the matt, mayb thermostat fitted in the wrong place and not operating how it should.


Is there a way to check if matt is ok?

 

[Specialist]

Isolate the Mat from controls & do continuity test ? Any bad or loose connections ?

 

[micknew]

99 times out of 100 this type of damage is caused by loose connections and not wrong connections.
Could not be caused by incorrect connections of matt or stat.

 

[egginyourface]

Its all been connected correctly with no loose connections.

What reading should i excpect to read if i did ohms test?

What would happen to the matt if the thermostat probe was installed incorrectly?

 

[GLENNSPARK]

It`l be a high resistance someware here egg....as the othere have already suggested......check the integrity of any crimps/joints etc....including any manufacturers joints/terminations etc........

 

[Specialist]

[QUOTE = What reading should i excpect to read if i did ohms test?

What would happen to the matt if the thermostat probe was installed incorrectly?[/QUOTE]

The end to end resistance reading across the mat depends on the Size / Wattage of the mat but will be resonably high, more important is what you don't need: A very low resistance. if the stat was'nt installed properly then normally the only problem it would cause is incorrect sensing of temperatures, it won't cause overheating of the controller.

 

[egginyourface]

thanks all

 

[PC Electrics]

You could check the resistance of the heating element by estimating the floor area covered and assuming 150W/m^2. Use this to calculate back to arrive at an expected resistance and compare with readings (making allowance for estimating errors). It'd have to be a massive floor mat to overload an FCU - I'm in the 'loose connections' camp.

 

[telectrix]

as above. a 400watt unit will read around 130 ohms ( cold ). that's about a 3 sq.m. element. also an IR test would be a good idea.

 

[needasparks]

From what you say in OP you found both the controller and FCU suffering heat damage, this can only be either a loose conection (money on this one) but that would mean two loose conections unless they are close enough for heat to travel up the cable (unlikely) or there may be more heating fitted than the controller could take, a quick ohms law calc on the element will answer this.
you don't mention where on the FCU has heat damage as if it is at or slightly higher loading of the equipment it will be damaged at the fuse carrier if loose conection at the termination.

 

[egginyourface]

The fuse was stuck in the fuse holder

 

[needasparks]

The fuse was stuck in the fuse holder

would appear to be overloading then if this happened to controller also.

What was the reading of the element ?

 

[topquark]

When the element was installed it should have had a resistance reading taken (both before install, after install, and after tiling). Ask the homeowner if those readings are available (should have been given to them). If they are check if the reading still matches or if some damage subsequent to the install appears to have been done.

 

[egginyourface]

By the looks of the overall installation dont think any recordings of readings were made.

looks like one of those wire and f off jobs...