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Thread: VysaTherm3000 Electric Underfloor Heating & EvoHome - Question?

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  1. #1
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    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!

    cheers

    Chris
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  2. #2
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    Quote Originally Posted by cjastennett View Post
    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!

    cheers

    Chris
    HI

    I have electric underfloor heating in two bathrooms and they operate as 2 Evohome Electric Zones

    Problem with the controller you mention is if you power it off ie put relay before controller when BDR Calls for heat the Controller will only then be powered up and it will boot up into an off state I think

    You are going to as i did have all automatic functions for the heating handled by Evohome so the VysaTherm 3000 is mainly redundant except for overheat function

    I used a very simple UF Controller for the overheat sensor and Evo BDR happily switches on/off the heating the simple controller is really only for overheat protection as I have a DTS92e in Each Bathroom to control the temp

    On the Simple Underfloor Controller I simply leave Temp set to max as EVO now controls the Temp This is the UF Controller I use

    https://www.amazon.co.uk/KETOTEK-Und...s%2C122&sr=8-8

    So I have BDR Switching Before the UF Controller and when BDR Calls for heat the UF Controller is already set to max and it is on and Floor heats up until DTS92e Setpoint is reached

    I used a R660D in Place of BDR it works perfectly and is the same as BDR only its rated for 10a restive so if you UF Heating Load is less than 10A which is almost 2.5Kw then you would not need a contactor or relay externally


    https://www.amazon.co.uk/Honeywell-H.../dp/B01H3K1HUQ

    If you have to use an external relay and decide to use SSR be aware these do not have a physical break contact they just stop firing a triac in the SSR never rely on one for physical isolation

    Mylesm
    Last edited by mylesm; 25th October 2019 at 09:35 AM.

  3. #3
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    Thanks mylesm - some great information here. Appreciated.

    What is your view of putting the relay after the controller, rather than before it?

    Doesn’t the R660D only have one-way RF comms, vs two-way comms with the BDR91. What are the implications of that with the Evohome system? Does it work fine with Evohome for you? Any gotyas?

    Thanks

    Chris
    Last edited by cjastennett; 27th October 2019 at 09:20 AM. Reason: Typo

  4. #4
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    Quote Originally Posted by cjastennett View Post
    Thanks mylesm - some great information here. Appreciated.

    What is your view of putting the relay after the controller, rather than before it?

    Doesn’t the R660D only have one-way RF comms, vs two-way comms with the BDR91. What are the implications of that with the Evohome system? Does it work fine with Evohome for you? Any gotyas?

    Thanks

    Chris
    Putting the relay after the controller will be better in your case as I think the controller will not power up in an on state as you need if you put it before controller then everytime the BDR or Relay or R660D switches off the controller is powered down and it will not come back on in a powered on state wheras if switching is after Controller then it can be powered up and calling for heat all the time and leave control to Evohome

    I have used the R660D to control Electric Heating I bound it in Evohome and it works Perfectly I was not aware of only one way Comms but it seems to work fine for me as an Electric Zone in Evohome

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