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Thread: VysaTherm3000 Electric Underfloor Heating & EvoHome - Question?

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  1. #1
    Automated Home Lurker
    Join Date
    Oct 2019

    Default VysaTherm3000 Electric Underfloor Heating & EvoHome - Question?

    Hi All,

    I wonder if you could assist me.

    I am specifying a Honeywell evoHome installation, and one room has electric underfloor heating that needs to be controlled by the evoHome system

    After reviewing a number of posts on these forums and information from other locations, I can see that this certainly is very feasible - and given that the load of the underfloor heating is rated above that a BDR91 can handle, I need to use a contactor or solid state relay to switch the load.

    The underfloor heating controller is a VysaTherm 3000, and given that this has many overheating and sensor functions built in, I will need to keep this controller very much in the loop. I have also decided to use a solid state relay over a contactor due to the available space and layout restrictions, and have identified that a 240v AC controlled Crydom CWA2450 (Solid State Relay, SPST-NO, 50 A, 280 Vrms, Panel, Screw, Zero Crossing) will more than suit the needs here.

    The question I have is - Should the solid state relay be switching the power before or after the underfloor heating controller? I attach two different sketches of the design for your perusal and opinion.

    I would be very interested in any views on this? My gut feeling is that it would be better to switch the load on and off after the controller, to avoid high frequency toggling of the controller on and off which it may object to. Also, there does not seem to be any error condition on the VysaTherm 3000 that would warn of an open underfloor heating circuit, which means that it should cope OK with this arrangement.

    Also, would be interested to understand if I need to include an resistor, or any other kind of componentry, in the solid state relay switch circuit, or whether the illustrated arrangement would work OK in your opinion?

    Thanks for any help you can give - appreciated!


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