UFH brain teaser. think i know but......

[telectrix]

existing UFH (2 mats each 1.8kW) installed c 2015. on a single stat by a,n,other. customer had someone else replace stat. made a right mess of it and stat fried. I then get called in to fit new stat. removed the dual back box that previous guy had smacked out with a hammer so as to fit the new stat. (was FCU and stat on dual back box, but new stat would not fit). the 2 underfloor sensors were wired in parallel, so that's how I connected to new stat. customer complains that the floor does not warm up properly. on a visit, i found 2 smallish rugs on the tile floor. now, my thoughts are that maybe 1 of the sensors is under a rug and so switches off prematurely due to the rug retaining the heat. this then cuts both mats off. I'm thinking to wire the sensors in series so that both need to activate and go open circuit for the stat to switch off. anyone agree/disagree? current measurement when system is powered up from cold shows 15A, i.e 3.6kW. not ideal on a 13A FCU but that's what i have to work with.

 

[suffolkspark]

As Dave says basically lol.

Id leave the second probe coiled up in the back though incase one ever fails

 

[Toneyz]

As Dave says basically lol.

Id leave the second probe coiled up in the back though incase one ever fails

Can the stat take the current of both the mats?

 

[suffolkspark]

15.65A so its right on the limit they usually say 16A max...

But just read op again and its on a 13A fcu?? This needs more than a quick fix tel...

 

[suffolkspark]

Double post

 

[telectrix]

I think this would be the way to correct it how it was supposed to be wired. Is the UFH on its own radial or on the ring?

on the ring afaik.

 

[telectrix]

15.65A so its right on the limit they usually say 16A max...

But just read op again and its on a 13A fcu?? This needs more than a quick fix tel...

nowt i can do about that. all tiled in and no way of separating the circuits. however, it's never blown the 13A fuse in the FCU.

 

[telectrix]

i'll try dissing 1 underfloor sensor and see how it goes. these sensors are not a straightforward open/closed. so davesparks post has made me think.

 

[suffolkspark]

Correct.... If you check them on ohms youll see....

Theres a setting on the screen somewhere where you can select air temp youll want it on that anyway

 

[telectrix]

if i can, i'll select air temp.customer is loaded so sod the leccy bill. it's a warmup tempo stat.

 

[Pauls0212]

I went to one a while ago and the 13a fcu was pulling 20a, i was called out because it was getting warm and discoloured. why do people not think about things before they install. But back to the problem ... if the stat accepts temp as well as probe , use 1 sensor and air temp.