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Thread: Evohome for 5 radiators and 2 underfloor zones

  1. #1
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    Default Evohome for 5 radiators and 2 underfloor zones

    I'm new to home automation but am planning to spend a small fortune and install Evohome in my bungalow to control my heating and would appreciate feedback on my proposed setup and queries.
    I have an Ideal Vogue gas combi boiler, 5 radiators and 2 wet underfloor zones that have there own pump and manifold with 5 actuators.
    An ATC928G3000 will control the new set up with a R8810A1018 Open Therm Bridge connected to the boiler.

    My plan is to put HR92s on each of the 5 radiators. There is a Honeywell 2 port valve that currently controls the flow to the radiators. Will I need a BDR91 to control this or can it be permanently set open or removed? I'm assuming that it will no longer be needed because the HR92s will shut off the flow when the radiators don't need heat.

    There is currently a 6th small radiator in an airing cupboard that has lock valves that permanently allow a small flow. This is on the boiler side of the 2 port valve. Is this OK, or do I need to install an automatic bypass valve?

    The existing underfloor heating controller will be replaced by an HCE80. Horribly expensive! If the ATC928G3000 is just the other side of a wall, will I need the HRA80 External Aerial?

    Currently there is no valve that prevents hot water that is called for by the radiators going into the underfloor circuit. I'm assuming that I dont need a valve because when the underfloor is not calling for heat, the underfloor pump is off and the manifold actuators are all shut and no problem is caused. Am I right about that? I think its a standard manifold, pump and mixer valve set up.

    Each of the 2 underfloor zones will have a DTS92 thermostat. One of the zones is a bathroom and an ensuite shower room where condensation is normal. I'm told the thermostat should therefore be positioned outside these rooms to protect it, but this obviously stops it taking the correct temperature. Is it possible to have this zone without a thermostat? I want to schedule for a nice warm floor in the morning but the rest of the time it's OK unheated (subject to change by the wife).

    We dont live in a particularly large bungalow (4 bedrooms) so I expect not to have a problem with signal strength but having said that I do have an internet extender to get the WiFi signal between the opposite far corners. I expect to place the ATC928G3000 pretty well in the middle. I know the Evohome Shop can provide a strength tester but want to keep the cost down where I can. Any thoughts?

    This missive has ended up longer than I anticipated when I started. I shall be very pleased if I get answers to all of this. Thanks in advance.

  2. #2
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    the biggest misconception that people have is think that the only way to control UFH is via a UF Controller. BTW if you do go down that route, I would recommend the one that doesn't need the external antenna.
    A manifold needs an UF controller only if it is serving multiple zones that each need separate temperature and the zones can indeed be separated out. Many outputs on a manifold do not automatically mean multiple zones. I have a 10 port manifold but they are all serving a single zone. In that case, you just need a DTS92E or a T87RF with a single BDR91. The thermostat controls the BDR91 which opens a zone valve/starts the UFH pump.
    As for the CH radiator loop, you dont need a zone valve on it. But if you have one, rather than just locking it open (which doesn't actually open it fully), you wire it to open with the boiler pump. So when the boiler pump runs, that CH Valve opens. This then takes care of boiler frost protection too and keeps the CH Valve from seizing.

  3. #3
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    Thanks v much for the reply.
    That's good information about not needing a UF Controller if you only have one underfloor zone. Unfortunately, I definitely need 2 zones. I'm having a wobble over whether I want to spend more than the cost of a Evohome controller just for the underfloor controller. Some mulling to be done on whether Evohome is really for me.
    Again, good information on the need for a valve in the radiator loop. If I go ahead I think I will take the existing valve out (as part of other work needed).
    Thanks again.

  4. #4
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    Are there two UFH zones being driven off the same manifold or different manifolds? I know this might sound bonkers but by the time you buy the Evohome UFH controller and all the actuators, you could zone the two UFH zones via separate manifolds and not require any of those components. Also you could do 2 zones on a single manifold too without a Evohome UFH controller. Just get the BDR91 to power the powered actuators. You wont get TPI based valve positions but timed. TBH, I am not even sure if the Evohome UFH is capable of opening and closing the manifold ports like the TRV controllers or if it just runs them as timed TPI anyway.

  5. #5
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    Quote Originally Posted by bruce_miranda View Post
    Are there two UFH zones being driven off the same manifold or different manifolds? I know this might sound bonkers but by the time you buy the Evohome UFH controller and all the actuators, you could zone the two UFH zones via separate manifolds and not require any of those components. Also you could do 2 zones on a single manifold too without a Evohome UFH controller. Just get the BDR91 to power the powered actuators. You wont get TPI based valve positions but timed. TBH, I am not even sure if the Evohome UFH is capable of opening and closing the manifold ports like the TRV controllers or if it just runs them as timed TPI anyway.
    Done many systems UFH systems with BDR91s and T87RFs paired up to the EvoHome panel and they work fine as a TPI zone. You either need a 4 wire actuator or a wiring centre of the underfloor. 4 Wire Actuators are easier, but a wiring centre is also an easy option.

  6. #6
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    I have a similar setup in my home. Sort of a long term project as I've never come around to actually add the control valves for the UFH.

    Essentially the bathroom is more like a giant heater panel. There's no pump, only a flow limiter on the exit. The UFH in the living room is controlled by a computerized pump that uses input and output temperatures to control the flow. As I don't want to disrupt the computer's functions, which includes expanding the pump's life span, disconnecting the power is not an option. For both systems I thus need to install a valve and I actually have two spare HR92s that are already configured to control those (currently missing) valves. This does allow me to set the temperatures for both spaces and activate the central valve (boiler), but of course at present they will also heat up when another zone calls for it.

  7. #7
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    Does anyone know if the Evohome UFH controller can control the actual pin position inside the Actuators depending on the Heat Demand, similar to how a HR92 works or is that too just Fully Open or Fully Close. Because if it's just Fully O/C then it is no better than a Traditional wiring centre and 230V powered Actuators.
    However @gordonb3 makes a good point. These solutions assume you dont have a fancy pump on the UFH system. My own system suffers slightly because of the TPI switching because my Pump is one of those self regulating ones which starts off low and slowly ramps up based on flow rates. TPI does mean that it does through its start up process several times an hour. And I don't believe you can adjust the TPI functions of a BDR91which is not the Boiler Relay.

  8. #8
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    According to the specifications the actuators are binary, i.e. there is no mentioning of them opening only half way if you feed them with half the voltage. They do appear to be extremely slow though,requiring at least 3 minutes to complete the opening cycle (assuming `normally closed` version) for the short pin version and up to 6 minutes for the long pin version. I assume that the mechanical unwinding will require a similar amount of time to return to the `zero` position. It should thus be possible to keep them somewhere half way by modulating the feed to the actuators.

  9. #9
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    I thought the Honeywell UFH actuators supported PWM and hence could be made to open and close slower/faster partially etc. If it doesn't then I am struggling to see the benefit the Evohome UFH controller provides. Especially now when we know the HCE80 doesn't even publish the Heat Demand per zone. I could have seen the benefit if the Evohome UFH controller expands the total number of Evohome zone but it doesn't do that either.

  10. #10
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    Quote Originally Posted by bruce_miranda View Post
    I thought the Honeywell UFH actuators supported PWM and hence could be made to open and close slower/faster partially etc.
    I think I implied PWM to be a possible method for supporting partially opened valves in the last sentence of my previous post?

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