Evohome with UFH and limit thermostat to protect vinyl floor...?

[Peter Baldwin]

Hi all

I'm looking at putting in an entirely new CH and HW system, using underfloor heating downstairs and radiators upstairs.

I'm keen to use Evohome, but am concerned that the thermostats don't appear to allow for the use of floor probes to measure floor temperature, and that this risks cooking my vinyl flooring under the proposed UFH.

I've seen suggestions that you could put some kind of separate limit thermostat with a floor probe in place to either turn off the UFH pump or close off a 2 way valve or some such. Has anyone seen this done? Am I barking up the wrong tree?

I'm aware that the UFH manifold will have a mixer valve to set the water temperature of the feed to the UFH circuits, and that a well designed system should be able to predict the resulting floor temperature, but I was looking for the added comfort of something which checked the floor temperature itself. My understand is that Amtico and others won't guarantee the floor covering without a floor probe being used.

Thanks in advance

Peter

 

[Dan Robinson]

There are several ways to achieve this depending on your level of understanding of electronics installation situation and/or knowledge of hysteresis.

 

[Peter Baldwin]

Thanks Dan, my knowledge of the electronics installation is moderate, and my knowledge of hysteresis is close to zero.

I'm just looking for a heads up on whether this is a viable path to pursue with my installer, when appointed, or whether I should abandon Evohome and go with something like Heatmiser which offers an integrated heat probe, but which isn't as good in other respects.

 

[reds42]

I've got an underfloor heating circuit in my kitchen which has a limit thermostat on the outgoing pipework from the pump to the heating circuits in the floor. The power to the circulating pump goes through it and if the water gets too hot it cuts the pump off to protect the floor.

Won't be as acurate as an in floor probe but does give some protection.

 

[Dan Robinson]

Where we have done this in the past we have done 3 methods.

1. Used an existing thermostat and floor probe to act as limit thermostats with Evohome controlling air temps with the original cutting in if the floor goes over.
2. Created our own thermostat and probe to go into the floor and interrupt the control signal to the floor emitters. On electric though, this will require a relay as the units we had weren't big enough for the load. Limit temperatures can be set as required as well as the hysteresis for the system switching back on.
3. Installed the Evohome as is and with the customer in full awareness that the floor is unprotected (this was largely down to budget and the fact that the floor was being ripped up in a few years anyway negating the need for electric UFH)

 

[Peter Baldwin]

Thanks Dan. That's very useful.

I think option 1 sounds most relevant to me. It's going to be wet UFH. When using the original non-Evohome thermostat as a limit stat, was this wired up to cut power to the pump or did it do something else?

Cheers

Peter

 

[Dan Robinson]

For option one, it wasn't an Evohome thermostat that was already there. It was some random POS electrical system, but we had the option within it to set the floor probe only and have it set to act as a high limit cut off and then put Eovhome in the control line to operate based on air temps.

Option two, which was wet central heating under a veeeeerrrrryyyyyy expensive and big wooden floor was designed to break the neutral wires on the manifold (as they were all common) which would kill the loops until the temperature dropped to a predetermined level.