# Underfloor heating



## Dennis Alwon

Is it possible the floor heat is shorted? Unfortunately you would have to know what was in there to figure what the ohm reading should be.

You can by pass the rcbo and see what happens. I am assuming the rcbo is our equivalent to a gfci or an RCD


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## wcord

Sparkystevieboy said:


> Hey,
> 
> I have been called out to troubleshoot why an underfloor heating (electric) is constantly tripping out the RCBO. 2 underfloor circuits are on the one circuit, which is protected by a 20A RCBO. The heating cable is a coaxial format cable, with the earth braid on the outside and the eating element on the inside. Both cores, are closed circuit, which is normal condition. When taken of the RCBO and put onto an MCB, and left to heat, 2 hot spots arise, one were the cable was criss-crossed when layed, and another im not sure why. I have been advised that the hot spots are not rated 'hot enough' to be of concern. The electrician who installed power for the floor heats was extremely lazy, and tapped of a local supply, which also had a fridge/freezer/wash-mashine/microwave/tumble-dryer! the floor heats alone pull 14.4A. The floor heats were the only active electrical items when i was testing.
> Anybody got much experience with electric floor heating?


Assuming your floor heating systems are similiar to ours, criss-crossing is a sure way to have a fault.
Does your system trip immediately or after the cabling has warmed up?
If it occurs after the cable is warm, than the criss cross would be a sure place to look. Unfortunately, if this is the case, besides reinstalling the whole floor, you will have to try to get some sort of spacing between the cables.
Trouble shooting heated floors is a real pita.


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## Sparkystevieboy

Yea it trips after about 45 minutes of the cable heating up


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## wcord

Sparkystevieboy said:


> Yea it trips after about 45 minutes of the cable heating up


Gut feeling is that the cross over is your problem.

Question. How do you know that the installer crossed the cables? pictures? owner memory? Who told you that the hot spots were not of concern?
I would contact the manufacturer and see what suggestions they have for narrowing down the problem. 
IF the customer has any spare tiles, than I would suggest carefully removing the tile above the cross over, try to free the cable from the mortar and than separate the cables. If the system stays on, than what? I doubt there is enough height to get some insulation between the cables. 
The whole floor may have to come out and the system reinstalled.
Good case for floor heat installers to be properly trained.


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## Sparkystevieboy

I Have a thermal imaging camera that brought up the criss-cross, and it bought up the other hotspot. The supplier of the underfloor heating told me this, TBH, im not paying much attention to what he has to say. Hes not a sparky or anything close,he has no real knowledge if your with me.


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## ohiosparky99

I agree with wcord, we have installed probably 30 or so of these systems and you absolutely can't cross the cables, also like suggested earlier do you know the length of the cable??


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## ohiosparky99

Not really a texting guru, but what does THB mean??


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## wcord

Sparkystevieboy said:


> I Have a thermal imaging camera that brought up the criss-cross, and it bought up the other hotspot. The supplier of the underfloor heating told me this, TBH, im not paying much attention to what he has to say. Hes not a sparky or anything close,he has no real knowledge if your with me.


Well the cross over is a definite problem. Some of our systems won't let you lay the cable within 25mm of each other. Like I said, lift the tile at the cross over, separate the cables and hopefully that's the problem.
We have put in a few hundred of these cable types, about a half dozen different brands, and each one states point blank, NO cross overs.
Just thought of something else. Megger the cables while they are cold, and then after they have been on for awhile. IF the heat is the problem, compromising the insulation, the megger will show it.
Hope that your customer hasn't paid the floor installer yet. This is going to get messy and pricey.
Good luck


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