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Thread: Evohome setup to incorporate a thermal store unit

  1. #1
    Automated Home Jr Member
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    Default Evohome setup to incorporate a thermal store unit

    Hi, I have an existing thermal store system, and I'm in the process of adding Evohome controls. My plumbing knowledge is next to nil!!
    I can't get my elderly head around what and how Evohome is going to have to control with this thermal store system. All the instructions deal with either combi or conventional systems! The thermal store takes mains pressure water in through a coil and directly out to the taps. The water around the coil is kept at around 70 - 80 o from what I've read. The central heating water comes from this surrounding water I take it?
    I'd appreciate any help or advice.
    cheers!!
    Dafydd

  2. #2
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    Quote Originally Posted by dafydd View Post
    Hi, I have an existing thermal store system, and I'm in the process of adding Evohome controls. My plumbing knowledge is next to nil!!
    I can't get my elderly head around what and how Evohome is going to have to control with this thermal store system. All the instructions deal with either combi or conventional systems! The thermal store takes mains pressure water in through a coil and directly out to the taps. The water around the coil is kept at around 70 - 80 o from what I've read. The central heating water comes from this surrounding water I take it?
    I'd appreciate any help or advice.
    cheers!!
    Dafydd
    Simple answer is Evohome won't work with Thermal Stores.

  3. #3
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    Quote Originally Posted by mtmcgavock View Post
    Simple answer is Evohome won't work with Thermal Stores.
    Not true according to other posts on this forum if you do a search.

  4. #4
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    You can make it work of a basic fashion but not how it should, and tbh wonít be very efficient.

    Arenít you thinking of Unvented cylinders? As which thereís a difference between a thermal store and Stored Hot Water.

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  6. #6
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    Quote Originally Posted by mtmcgavock View Post
    Simple answer is Evohome won't work with Thermal Stores.
    Whilst I've not got Evohome, I've got Drayton Wiser, I'm sure the principle is the same. I have a thermal store (fed by biomass which Drayton Wiser does not officially support) and my Wiser system simply switches my circulation pump on and off using the same 'wall mounted thermostat' wires that were there before I got a smart system. I have 2 heating zones with about 5 TRVs on each and a separate DHW circuit which runs independently of the Wiser system.

  7. #7
    Automated Home Legend paulockenden's Avatar
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    I have a thermal store but it's on the DHW feel to my combi, rather than on the heating side. It mops up solar export and means that I use no/less gas when having a shower or a bath.

    I don't let Evohome anywhere near it! ;-)

  8. #8
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    It’s some months back since this subject was raised but my interest in a thermal store has been aroused. I wonder if any of the professionals on this site can add anything about the use of Thermal Stores with an Evohome system. Presumably one does not use Evohome to regulate DHW temperature for obvious reasons but you let it control itself according to demand, but does the CH otherwise work as normal with zones calling for heat as I have now? Thus making the DHW aspect of the Control Panel redundant?

  9. #9
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    I'm no professional, but have installed my Wiser system myself - even against the advice of Drayton, so please take my advice with a pinch of salt. Assuming the evohome system signals like the Wiser system, then I'm sure it should work. My system prior to changing to Wiser, had (at one point) a simple open/closed set of contacts that would allow the circulatory pump to run. All I did was to take the zero volt contacts from Wiser and use them to switch the pump, rather than the 'old' simple wall thermostat, that also had a simple no-volt open/closed set of contacts. The Wiser hub (has the contacts) has either a 240 set of contacts or a zero volt set of contacts. Due to the number of TRVs I was going to need, I had to use 2 hubs, so got the basic ones (with zero volt contacts) and use 2 of them, via 2 logins to their app. My DHW is controlled by my boiler (as before) and I've not felt the need to integrate it into the boiler, but one other reason why not is because if my boiler gets too hot, it can dump excess heat into the DHW and I doubt the Wiser system could accommodate this (a safety feature).

    How is you system 'switched' currently? Does it use a 'dumb' thermostat on the wall that simply switches a set of contacts or something else?

  10. #10
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    My current system is an old gas boiler for heating and DMH. Working through a three-way valve. Evohome controls it all, sending messages when heat is needed or not. DHW is similarly set up with a strapped on thermostat talking to its base which in turn talks to its own relay. All works, no real problems. Pleased with it.

    Ahead though is a growing need to change the boiler. It’s getting old. A vented Thermal Store appeals because it gives DHW at mains pressure. No pumps for the showers as I have at present. Also they have some future proofing in that they can be used with alternative power sources. It also means I can get rid of the tanks in the loft and create more space for stuff - others will call it sh.t but then what they call “stuff” I would call sh.t.

    My current thinking is to install the DHW internal thermostat that works with Evohome (if that is possible) and possibly with time controls set up when it is to operate. With some Thermal Stores it seems you can. But perhaps better ignored and let the boiler just fire up when it senses the store needs a top up. I don’t know if that will work or prove expensive to run and am looking into that. Our DHW is only heated for 30 minutes in the morning and 30 in the evening.

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