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  1. #1
    Automated Home Lurker
    Join Date
    May 2019

    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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