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  1. #1
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    Question new to evoHome - existing Honeywell wireless room thermostat

    Dear all,

    Apologies for a lengthy post and probably some very basic questions.

    Being a little tired of the wrong part of the house being too warm or too cold respectively I have just ordered the Honeywell evohome WiFi Controller and the Honeywell evohome Radiator Multi Zone Kit (aka HR92s)

    My current boiler is a Worcester Greenstar Ri, and I believe the heating system is wired up as an S-Plan with two motorized valves, a wireless Honeywell Room Thermostat (CM727 http://www.honeywelluk.com/products/...ats/TPI/CM727/), and a dual channel timer for HW and CH. I have attached a photo for clarification. The cable coming on from the top right part of the photo comes from the timer.

    DSCN0066_resized.jpg

    I have this idea that converting to Evohome might not be that challenging (that is if I want it to control CH only), but am going on a number of a assumptions and would be extremely grateful if someone could confirm or deny the below...

    From looking at my current setup I am assuming that

    a) my current setup is one, where once there is demand from the hot water cylinder thermostat or the room thermostat, the respective motorized valve opens, and the valve itself is then sending an on signal to the boiler + pump?

    b) My current room thermostat is already using a BDR91 as visible on the photo, which is the same box the new evoHome WiFi Controller can be linked to

    c) When I receive the WiFi Controller I can just take the batteries out of the old CM727 thermostat, follow the unbind procedure on the BDR91, and then bind the new evohome WiFi Controller to the existing BDR91

    d) That when I then further pair up all the HR92s with the new WiFi Controller I'm pretty much "done" as far as the CH goes - I can then switch the timer to "continuous", configure the HR92s as different zones, and if one of them drops below the set temperature it will operate the CH motorized valve through the existing BDR91, which will then turn on the pump and boiler through the existing wiring, in the same way it would have done so with the single wireless room thermostat - difference being it now does this "from every zone"

    e) That I do NOT configure the BDR91 as a boiler relay in evoHome, as it controls a motorized valve

    e) That I could, if I wanted, add another BDR91 to control my second (HW) motorized valve. That this new BDR91 would be linked up with a new CS92 transceiver that would in turn be connected to a CS92 strap-on sensor. I would have to follow the wiring from the current strap-on sensor (which is a Honeywell L641), which probably runs to the current junction box and controls the HW motorized valve. This would be disconnected, an instead the new BDR91 would be connected to that motorized valve.

    As I said I'm completely new to this. I hope this makes sense and would be extremely grateful for any answers.

    Please let me know if anything is unclear

    Many thanks - Martin
    Last edited by mart1711; 24th October 2016 at 11:32 PM.

  2. #2
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    Quote Originally Posted by mart1711 View Post
    a) my current setup is one, where once there is demand from the hot water cylinder thermostat or the room thermostat, the respective motorized valve opens, and the valve itself is then sending an on signal to the boiler + pump?
    Yes, boiler+pump
    Quote Originally Posted by mart1711 View Post
    b) My current room thermostat is already using a BDR91 as visible on the photo, which is the same box the new evoHome WiFi Controller can be linked to
    Yes
    Quote Originally Posted by mart1711 View Post
    c) When I receive the WiFi Controller I can just take the batteries out of the old CM727 thermostat, follow the unbind procedure on the BDR91, and then bind the new evohome WiFi Controller to the existing BDR91
    Yes
    Quote Originally Posted by mart1711 View Post
    d) That when I then further pair up all the HR92s with the new WiFi Controller I'm pretty much "done" as far as the CH goes - I can then switch the timer to "continuous", configure the HR92s as different zones, and if one of them drops below the set temperature it will operate the CH motorized valve through the existing BDR91, which will then turn on the pump and boiler through the existing wiring, in the same way it would have done so with the single wireless room thermostat - difference being it now does this "from every zone"
    Yes, the Evohome will provide the programmer function from that point forward. YEs, every zone will then demand heat as required.
    Quote Originally Posted by mart1711 View Post
    e) That I do NOT configure the BDR91 as a boiler relay in evoHome, as it controls a motorized valve
    Yes, absolutely correct, that's the mistake I made at first, so well deduced. I followed the guided configuration.
    Quote Originally Posted by mart1711 View Post
    e) That I could, if I wanted, add another BDR91 to control my second (HW) motorized valve. That this new BDR91 would be linked up with a new CS92 transceiver that would in turn be connected to a CS92 strap-on sensor. I would have to follow the wiring from the current strap-on sensor (which is a Honeywell L641), which probably runs to the current junction box and controls the HW motorized valve. This would be disconnected, an instead the new BDR91 would be connected to that motorized valve.
    Yes, completely correct. You could use the wire from the existing tank-thermostat as it will go the junction box. The wiring diagrams in the installation guide are set-out identically to the junction box, so the probability of making a mistake is minimal.

    If you do fit another BDR91, make sure it is at least 30cm (radius) from the existing BDR to help prevent communication issues.

    I foresee a straight-forward installation of your new system.
    Last edited by g6ejd; 24th October 2016 at 11:37 PM.

  3. #3
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    This is brilliant, thank you very much!

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    If you want the Evohome to control and schedule your hot water, you'll want the Hot water kit as well, which includes the CS92 and another BDR91.

    The CS92 provides a strap on or immersion sensor depending on whether you have a vented or unvented hot water cylinder. The second BDR91 is then wired to control the hot water zone valve, while the original one you already have should be wired to control the heating zone valve. (Which it probably already is)

    You then bind the two BDR91's as heating and hot water zone valves and do not bind any boiler relay, if you are using the zone valve contacts to fire the boiler.

    I don't think you can buy either the Wi-Fi controller or the Hot water kit without the included BDR91's so you may end up with a 3rd left over BDR91. It is possible to use a three BDR91 configuration where two control the zone valves and the 3rd controls the boiler directly instead of using the switches in the zone valves - this is the configuration I have, although I'm not sure that there are any huge benefits in it over a two BDR91 configuration in hindsight, as hot water overrun is the only feature it really adds.

    By the way, I see you have a bypass gate valve (the red knob) rather than an automatic bypass valve. While it's not critical, I'd recommend that next time you drain down your system for yearly maintenance you replace that with a modern Automatic Bypass Valve, particularly if you plan to use HR92's on all radiators and not have any bypass radiator.

    They're not expensive and fairly easy to fit if you've done a bit of plumbing before. A gate valve in this location is the "old fashioned" way of providing some bypass when radiators close down, but the problem is it always flows even when radiators are open causing inefficiencies, and conversely it doesn't flow enough (too much pressure differential) when all radiators close - adjusting it is fiddly and always a compromise.

    An automatic bypass valve is an adjustable spring loaded pressure relief valve - you set it to a pressure between 0.1 and 0.6 bars typically and it will not open at all when sufficient radiators are open but will automatically open to regulate the pressure when few/no radiators are open and the pressure tries to rise. This is definitely recommended on a system where all radiators have HR92's fitted, and it can also help reduce radiator noises when only one or two radiators are on.
    Last edited by DBMandrake; 25th October 2016 at 11:28 AM.

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    Sorry, I take that back.

    On further inspection it looks like that red gate valve may be a balancing valve for your hot water cylinder indirect loop.

    It's hard to be certain due to the pipes disappearing in the walls and under the floor so not all of the piping is visible.

    In that case you probably don't have any automatic bypass valve - so you must leave one radiator open and uncontrolled. If you want to put HR92's on all radiators you will need to fit an automatic bypass valve, but they are recommended in building regulations now anyway so it's a good idea to have one.

    I notice your pump is also installed with the control board at the bottom - this is definitely not recommended by grundfos, (I have the exact same pump as you which I fitted about a year ago and its in the installation documentation) the control board should be orientated to the sides or above the housing.
    Last edited by DBMandrake; 25th October 2016 at 11:38 AM.

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    Quote Originally Posted by DBMandrake View Post
    I'd recommend that next time you drain down your system for yearly maintenance....
    WHAT?????

    Does anyone (apart from Simon, obviously!) do that?

    P.

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    Quote Originally Posted by paulockenden View Post
    WHAT?????

    Does anyone (apart from Simon, obviously!) do that?

    P.
    Not sure if that reply was slightly ironic or completely serious but no, I imagine that "most" people just keep running their system without any maintenance until it breaks and then call the experts to fix it! I assume that people on this forum are just a little more proactive though.

    I remember when we were renting a flat for four years the yearly "maintenance" performed under maintenance contract by the gas provider, paid for by the owner of the flat was to basically check for gas leaks, turn the heating on and see if all radiators got hot and then leave! 10 minutes tops. They didn't even so much as attempt to bleed air from the radiators, let alone check inhibitor concentration or do any sort of flush/refill, over the entire 4 years we were there.

    That was a fairly old sealed system, which required the pressure topping up every 2-3 months, which I informed them of every time they visited but they didn't even try to find the leak or check inhibitor concentration. When I had to disconnect a radiator once the rusty coloured water suggested that there probably wasn't any inhibitor left due to all the top ups...

    I also had to bleed the bathroom radiator monthly probably due to Hydrogen build up and told them about this but again nothing was done about it. So yeah, I'm sure that's how much maintenance many systems get.

    I'm sure on a nice new clean system a drain and refill with fresh inhibitor every 2-3 years is probably enough but on an older system like mine with radiators in varying states of repair and unknown provenance it seems prudent to do so more frequently. When I drained this time to do the S-Plan conversion the water looked pretty clear, when I filled it back up for a test run I threw in a bottle of X800 and let it run for a few hours and drained again - completely black with magnetite that had been dislodged by the cleaner, so well worth flushing in my opinion.

    I guess it all depends on how proactive you are and whether you are starting from a new clean, known system or whether you are trying to salvage and rejuvenate the system you have been landed with when you moved house. I'm sure there are a lot of systems out there in pretty awful state of repair.

  8. #8
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    Interesting discussion - and nothing wrong with hi-jacking this thread. Thanks for all the responses!


    Quote Originally Posted by DBMandrake View Post
    I don't think you can buy either the Wi-Fi controller or the Hot water kit without the included BDR91's so you may end up with a 3rd left over BDR91.
    I had to hunt around a little, but PlumbNation do sell the controller as standalone https://www.plumbnation.co.uk/site/h...fi-controller/. With hindsight, however, I should have bought the pack WITH the BDR91 though (https://www.plumbnation.co.uk/site/h...ermostat-pack/) as that would have given me a spare BDR91 for 13.50, which does appear cheap compared to other sites....sigh.

    Quote Originally Posted by DBMandrake View Post
    By the way, I see you have a bypass gate valve (the red knob) rather than an automatic bypass valve. While it's not critical, I'd recommend that next time you drain down your system for yearly maintenance you replace that with a modern Automatic Bypass Valve, particularly if you plan to use HR92's on all radiators and not have any bypass radiator.
    As you said in your other post, this is indeed a balancing valve rather than a bypass. My bathroom rad is an always-on bypass rad.

    I'm hoping to receive the CH kit on Thursday, and if that goes well I'll look into the HW kit too. Surely it must be more economical in the long run to let EvoHome manage both, rather than having HW on its own thermostat / timer clock. I did try and time it so that CH is likely on anyway when there is HW demand from the thermostat. To my mind, that means that the pump and boiler are already running anyway so in theory probably consume marginally less energy than if HW periods were timed for when CH is likely off. Not at all sure about that one, though.

    WRT to draining the system - we bought this house back in 2014. It had an old Potterton Flamingo boiler that had not been serviced in 5+ years. I was luckily enough to find a good, local plumber who did NOT rip me off (I got three quotes for the same job (boiler replacement, new pump, new valves, new thermostat) with a 1500+ difference between the cheapest and the most expensive quote). He drained the system for the boiler change - the water was disgusting, so was the stench. He also advised on getting a Spirotech magnetic trap fitted, which gets cleaned out during planned yearly maintenance.

    Had a rad replaced last year and again a complete system drain / refill + inhibitor. So hopefully we should be good for a couple of years! Now just left with an annoying combination of one brand new rad and a mix of old / very old ones - which means that I have one room that goes from cold to toasty in 5 minutes, where the rest of the house is still decidedly cold. The HR92s should help with that, though.

    Either way - I'll report back when it's all done - sounds like it will be extremely easy with the BDR91 already in place and wired in.

    Again, thanks for all the help.

    Martin

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    Quote Originally Posted by mart1711 View Post
    I'm hoping to receive the CH kit on Thursday, and if that goes well I'll look into the HW kit too. Surely it must be more economical in the long run to let EvoHome manage both, rather than having HW on its own thermostat / timer clock. I did try and time it so that CH is likely on anyway when there is HW demand from the thermostat. To my mind, that means that the pump and boiler are already running anyway so in theory probably consume marginally less energy than if HW periods were timed for when CH is likely off. Not at all sure about that one, though.
    I'm not sure that there is actually any efficiency benefit to running HW and CH at the same time just because the boiler is "already on". Whether the boiler just cycles on and off to maintain a range around the target flow temperature (like my antique boiler) or is a modulating boiler that varies the flame size and therefore heat output of the burner to try to maintain the set flow temperature, at the end of the day heating+hot water requires more energy than heating alone or hot water alone. Either way the boiler will try to maintain the same set point but will have to work harder when both are drawing heat at the same time.

    If you already have a 7 day programmable timer for your hot water then the only extra functionality you would really gain by using the Evohome hot water kit apart from combining heating and hot water control in one interface would be to see the current hot water temperature on the control panel/phone app, and have the ability to override the hot water schedule remotely. (Such as turning on the hot water remotely using your phone before you came home unexpectedly early)

    You can program a different hot water schedule per day with up to 6 switch times per day but you can probably do that on your existing timer, and the schedule is only ON or OFF, you can't set different temperatures in the schedule. (Although I'm not sure why you would want to)

    You can do a timed or permanent override as well. For example set hot water to be on for the next 2 hours during a period when it would normally be off. You can also adjust the hot water temperature, but that is a setting buried in the installer configuration menu, not exposed in the normal user screens.

    So if you already have a good timer/programmer it may not be worth the expense - for me it made sense because I've just converted my system from gravity circulation to S-Plan and had no existing hot water timer, so I thought I might as well use the Evohome hot water kit rather than buying an independent, conventional timer and cylinder thermostat.

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    Quote Originally Posted by bruce_miranda View Post
    Like I said before, use boiler demand relay to control your ch zone valve. Yes Honeywell did remove the Sundial configuration in the wifi controllers.
    I've been through this journey and today finally taken a new turn. I unbound the ch bdr91, put the valve in the manual open lock position and rebound my system as a single HW valve configuration with a boiler demand relay (opentherm in my instance).
    FYI

    If you want your CH zone valve to remain open whenever the system is running ("bypassed") you should wire it to the pump power feed - the manual fill position on many zone valves including the ubiquitous Honeywell V4043 that I use opens the valve less than half way which causes quite a flow restriction when the system is operating.

    The manual latch position is only intended for filling and draining not for normal operation.
    Last edited by DBMandrake; 3rd November 2016 at 07:15 PM.

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