Electric UFH & evohome

[Rameses]

Dear All

Sharing a pet project which might help. I recently renovated our kitchen, wall knock down etc. We had to lose a radiator (out of 2 for the room) and had no where to put one. Only option available to us was to use electric UFH (from http://www.prowarm.com/underwood-heating) . Trouble is I wanted to keep it as part of evohome.

The BDR from Honeywell has a limitation of being only to switch 1000 kw (1500 tops). Most UFH solutions bigger than 10m2 need more than this.

After discussing with some electrical engineers , they suggested using a contactor from https://www.mkelectric.com/en-gb/Pro...s/default.aspx

A contactor is like a relay (don't shoot me here as this is my understanding) - the BDR provides a voltage input which can 'switch' the larger amp rated 'switch' function inside.


The trick is to put the BDR after the UFH Thermostat. This then means the UFH thermostat is set to permanently on but has the safety measure of the UFH sensor to set a floor limit. The BDR then switches the 'post thermostat' current to the floor mat.

I then bound this into the evohome as a zone (as zone valve). Then bound in an external sensor (SZT or you can use DTS92). Hey presto E-UFH controlled by evohome.

Will do some tests but right now seems to work well.

R

[SensibleHeatUK]

That approach works just fine and providing the contactor is not somewhere where the noise of it switching would cause annoyance then there are no problems. There are solid state relays available (at significant cost) which have silent switching, but are better suited if the contactor needs to be used next to bedrooms etc.

If there are several zones of EUFH then you could use a Manifold Controller instead of several BDRs, which avoids the problem with module spacing and keeps the installation looking neater.

[nevetsecirp]

Any chance you could share how you wired in the EUFH probe that sits within the electric mat. I want to change the current Wall thermostat I have that has a simple timer operation with a internet enabled device. I have 2 options, option 1 is use evohome, as I have just had all the valves on my radiators changed to TRVS in preparation of fitting the evohome system around sept/october. Option 2 I use Lightwaverf for lighting and power and they have brought out a 3000kw electric switch. However I am unable to work out how to wire the probe to either the BDR or the electric switch.

Any help much appreciated

[SensibleHeatUK]

You must keep the existing floor thermostat (to which the floor probe is currently connected) as it is a safety feature to prevent excessive high temperature from the mat damaging itself or the floor.

[Rameses]

Any chance you could share how you wired in the EUFH probe that sits within the electric mat. I want to change the current Wall thermostat I have that has a simple timer operation with a internet enabled device. I have 2 options, option 1 is use evohome, as I have just had all the valves on my radiators changed to TRVS in preparation of fitting the evohome system around sept/october. Option 2 I use Lightwaverf for lighting and power and they have brought out a 3000kw electric switch. However I am unable to work out how to wire the probe to either the BDR or the electric switch.

Any help much appreciated

Sure - let me try and knock something up. As sensible says there are other options. To just say the contactor I have literally there is a small click (like an rcd tripping) no other noise. But as sensible says - the thermostat supplied with the heating mat needs to stay in play to protect the maximum limit for the floor as it has a floor sensor. Laminate for instance cannot go above 27c