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Thread: Home Heating Automation Help Please

  1. #1
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    Question Home Heating Automation Help Please

    Hi Folks,

    I've been reading this sub forum for a few weeks now and have just registered as I think I need some advice!
    I should start by saying I'm UK based and have a BIOMASS system with a Thermal Store.

    I'm in the process of having UFH fitted which will run along side my existing radiator circuits (that are not being upgraded to UFH). The way my system currently works is as follows:

    It has 2 zones (or separate water flow/return pipes), one for all upstairs rads and one for all downstairs rads. There are 2 thermostats, one in each zone, which simply provide a set of open/closed no-volt contacts to my boiler/control. When the thermostat calls for heat, contacts close, boiler 'reads' this and turns on the circulating pump (which also has weather compensation so flow temp is dependant on outside temp, generally around 50 deg C). Rads have manual TRVs on them. My house is 1 room wide, 4 rooms long (so to speak), the flow/return/circ pumps are in one end of the house (lets call it room 1) and the rads are fitted in parallel (normal I think) to the flow/return pipes. Downstairs has rads in room 1 and 2 and will have UFH in rooms 3 and 4 (and the porch/wc). Upstairs is basically 4 beds, 1 bathroom, 1 landing and 1 en-suite/dressing room arranged as follows: radiators in bed 4/bathroom (above room 1 downstairs), bed 3, bed 2, the UFH will be fitted in bed 1 and ensuite (above room 4 downstairs).

    My UFH manifold and circ pump will fit on the end of my rad flow return pipes so when the UFH calls for heat, I need my rad circ pump to run, but when the rads call for heat, I don't want the UFH circ pump to run (assuming there is only 1 room at any time calling for heat). If all rooms call for heat (or more correctly if at least one rad AND at leat one UFH circuit calls for heat), both pumps will clearly need to run. They way I see this working is that I wire a 240v relay into my UFH pump which, when activated (by taking 240v from the UFH pump), will close the relay contacts which then provides the same signal as my existing rad thermostat, ie a set of closed contacts, to my boiler so the rad pump will also run, thus providing flow to the UFH pump/manifold etc. The relay contacts would be wired in parallel to my rad thermostat.

    Having done lots of reading, I think the Honeywell Evohome system is the one that best fits my needs, with a compromise here and there. I've actually got more than 12 zones, so would ultimately need 2 controllers, but for now I can configure it as 12 or less zones by combining beds 2,3 and 4 as required.

    So, onto the Honeywell Evohome system. Clearly I need HR91 or HR92s for each of my rads (I have 7 in total) which would then link to 2 BDR91s (1 for upstairs - 5 rads and 1 for downstairs - 2 rads). Here's my first problem. I think a BDR91 can only link to 4 HR91/92s? Is this correct? So would I simply need 2 BDR91s for upstairs? I need to control 5 UFH zones now and a 6th one in about 2-3 years time when we put an extension on - so can I get away with one HCC80R with an extension module but it wiring into 2 different manifolds (or sets of actuators) or would I need 2 as I need to run my 'relay' for upstairs/downstairs separately?

    Then comes the question of room thermostats (or room temp control). Do the HR91/92s act as thermostats or do I need T87RFs for each room? I realise I'll need them in the UFH rooms as how else does the system know it's up to temp? I also realise I can use the main controller as a thermostat in one room. So for UFH control, the T87RFs link to the controller, which in turn links to the HCC80R which operates the UFH pump and zone actuators. For rads, the HR91/92s link to the controller which links to the BRD91s which then runs my rad pump. Have I got this right or made a right mess of things?

    As with everything, a picture paints a thousand words, so hopefully attached is a room/pipe layout showing (most of) my system. For simplicity I've not shown all 5 rads upstairs or both rads downstairs, just an example and the existing bathroom is now bed 4 and the WC is the bathroom.

    If not the Honeywell system, what other automated system can do this control? I'd like internet/app access but not essential, I don't need location detection and I don't have any other home automation for it to sync or interact with (and doubt I will). I'd prefer wireless where possible as some of the rooms are already decorated so I don't want to run wires.

    Phew, that was a long first post! Hope you are still here! Thanks for any advice and help.
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  2. #2
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    You're overcomplicating things. You will only need a BDR91 to switch on anything, in this case you'll only need one to signal to your boiler and pumps there's a demand.

    A 'zone' in evohome terminology is any area that needs a separate schedule and/or temperature plan. A zone can have a whole array of devices within it, so a zone roughly equates to a room (but include your Hallway and corridor as a single zone in this sense too). The UFH manifolds can be directly controlled by an HCC80 and their wired valves, while the radiators can have an HR92.

    In any room with more than 1 rad, or more than one heat source, it's strongly recommended to get a separate thermostat like a DTS92 (and they're required in a UFH room), and also in any zones that temperature readings need to be taken from a more ideal place than next to a radiator.

    The HR92's and BDR91's are controlled centrally by the evohome controller - they can be configured to talk to eachother directly because they can be used in isolation, but in an evohome system, everything talks to the controller.

    From your plan, I can only count 9-10 zones, which would mean evohome is fine for this job. If you do need more than 12 zones, then I'd recommend against using evohome, and using Genius Hub which will handle more than 12 zones. And since your biomass boiler is unlikely to do OpenTherm, there's no net advantage of evohome vs Genius Hub.

    (Edit)

    Thinking about it a little more, I think Genius Hub will actually be better fit for you, because of your slightly unorthodox zoning. Evohome isn't very good at being used in in an unorthodox manner (that is one heating ring, one hot water ring and up to 12 zones). Genius Hub is much more 'hackable'.

    In particular, the key pointer is this feature, Grouped Zones, which mean the zone valve and pumps for each zone will be independently controlled, and they will trigger when/if there is a demand in that particular zone.

    Just like evohome, Genius Hub is happy as Larry with UFH, and while Footprint is a gimmick, do get the Room Sensors, because unlike evohome's HR92's, Genius Hub's radiator valves don't all have temperature monitoring in. And they're pretty cheap by comparison to a DTS92.

    Like I said before, OpenTherm isn't supported by GeniusHub (yet), but it will have full TPI regulation for your boiler and with your existing weather compensation you will have a Class VII zoned system as opposed to a fully modulated Class VIII system as is evohome when using OT.
    Last edited by jvallis; 4th May 2019 at 07:03 PM.

  3. #3
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    Quote Originally Posted by jvallis View Post
    You're over complicating things. You will only need a BDR91 to switch on anything, in this case you'll only need one to signal to your boiler and pumps there's a demand, though I would go with 3, one to demand the boiler, and the other two to switch the pump and zone valve in their respective flow/returns.
    Thanks for your reply, much appreciated. Currently I have 2 pumps, one for down stairs, one for upstairs, so I need at least 2 BDR91s, one per circuit. The BDR91 won't directly interface with the pump, it will simply signal my boiler (control) and that will control the switch-on of the pump (which has a blending valve to control the heat flow of water) I currently don't have any zone valves - my hot water runs off another separate circuit.

    Quote Originally Posted by jvallis View Post
    A 'zone' in evohome terminology is any area that needs a separate schedule and/or temperature plan. A zone can have a whole array of devices within it, so a zone roughly equates to a room (but include your Hallway and corridor as a single zone in this sense too). The UFH manifolds can be directly controlled by an HCC80 and their wired valves, while the radiators can have an HR92.
    Great, that follows what I've read and how I understand things to be and I think, how I've described it in my first post.

    Quote Originally Posted by jvallis View Post
    In any room with more than 1 rad, or more than one heat source, it's strongly recommended to get a separate thermostat like a DTS92 (and they're required in a UFH room), and also in any zones that temperature readings need to be taken from a more ideal place than next to a radiator.
    Each room will either be a single radiator or an UFH zone, no room will have more than 1 heating 'device' in it. So I need a DTS92 for my UFH rooms? Why can't I use a T87RF linked to the main Evohome controller?

    Quote Originally Posted by jvallis View Post
    The HR92's and BDR91's are controlled centrally by the evohome controller - they can be configured to talk to each other directly because they can be used in isolation, but in an evohome system, everything talks to the controller.

    From your plan, I can only count 9-10 zones, which would mean evohome is fine for this job. If you do need more than 12 zones, then I'd recommend against using evohome, and using Genius Hub which will handle more than 12 zones. And since your biomass boiler is unlikely to do OpenTherm, there's no net advantage of evohome vs Genius Hub.
    My existing plan, ideally, has 6 zones downstairs (kitchen, dining room, hall, porch/wc, lounge and future extension room) and 8 zones upstairs (beds 1-4, bath room, ensuite, dressing room, landing). So 14 in total. From an earlier conversation with an Evohome reseller, I understand that if I have 2 controllers, I can control up to 24 zones but I'd probably combine rooms into a single zone to keep it all within one controller, eg bedrooms (currently unused).

    I've already had a quick look at Genius hub but couldn't make sense of which bits I'd need. I did try to configure a system but it came out more expensive than the Evohome system. As to Opentherm, no I don't believe my boiler can do this but as I'm running off a thermal store and not directly off the boiler, I'm guessing it's irrelevant. My biomass is a log/batch boiler so it does a big burn, heats up my 2000l store and I then draw heat from this.

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