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Thread: Can you tell which BDR is which? (Radiators getting hot when heating hot water)

  1. #1
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    Default Can you tell which BDR is which? (Radiators getting hot when heating hot water)

    Context is below. Thanks in advance for any suggestions.

    The problem I'm trying to solve is the radiators heating up when only the hot water has been requested. The circulation pump kicks in either during or at the end of the boiler running to heat the hot water.

    The attached photos show that there are two BDR91's and a hot water thermostat transceiver (CS92) installed all pretty close together. I have read they are meant to be spaced further apart to avoid comms problems.

    The first move I propose is to completely reset the system and rebind all the elements and see if that solves the problem. If it doesn't, then I'd use my very basic DIY skills to move one of the BDR's along by 30cms in case it's comms interference causing the issue.

    Questions
    1) Does this sound like the best two steps to take first?
    2) Is there an obvious / easy way to tell which BDR is which when I am re-binding them?
    3) Do I need to space all the boxes out equally or can I leave the CS92 near one of the BDR's if I go to step 2?

    Cheers loads!



    Context:
    - User (me) is computer tech savvy, DIY basic and heating / boiler numtpy
    - Boiler is ~ 20 year old oil fired boiler which has an integral hot water tank and heats the radiators for a fairly big old house in rural France
    - Honeywell Evohome was installed ~ 3 years ago by a well meaning heating engineer who was fairly new to connected stuff
    - System is very basic - just the old style controller non-wifi (also working as the single room thermostat), hot water controller and tank probe thermostat plus the internet connection from RFG100
    - Comms check reports strong signals between all 4 bits of kit (but the DHW comms check reports finding 2 Actuators - see second photo!)
    - The engineer left the sticker on one of the BDR's with the wiring option crossed out (no idea if that helps!)


    IMG_2095 (1).jpg
    IMG_2093.jpg

  2. #2
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    Is it an S-Plan system with two zone valves ? How are the zone valves wired ?

    First thing I would check is pressing the manual override on each BDR91 and see what it is controlling.

    If its a standard S-Plan system with two zone valves one should open each zone valve and either zone valve should fire the boiler. Doesn't sound like this is happening though.

    Another possible scheme is that you only have a hot water zone valve and the second relay is configured as a boiler control relay directly firing the boiler instead of a heating relay.

    In the settings do you have a boiler control relay configured or not ?

  3. #3
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    Thanks loads for taking the time to reply.

    Quote Originally Posted by DBMandrake View Post
    Is it an S-Plan system with two zone valves ?
    I have no idea, sorry. Any easy/idiot proof way to tell?

    Quote Originally Posted by DBMandrake View Post
    How are the zone valves wired ?
    No idea again - I could take the plates off the front of the BDR's and photo them if that helps?

    Quote Originally Posted by DBMandrake View Post
    First thing I would check is pressing the manual override on each BDR91 and see what it is controlling.

    If its a standard S-Plan system with two zone valves one should open each zone valve and either zone valve should fire the boiler. Doesn't sound like this is happening though.
    Here are the results of that test:

    Test Right Hand Side BDR
    Controller says HW is 43 degs. (Target point is 55 degrees)
    Press overide on RHS BDR - boiler fires.
    c. 5 mins later, boiler stops, circulation pump starts and green light goes out on RHS BDR
    Circulation pump runs for c. 5 mins

    Test Left Hand Side BDR
    Controller says HW is 43 degrees
    Press override button on LHS BDR - boiler fires and then stops immediately
    Circulation pump does nothing
    Press override button again on LHS BDR this time boiler fires and stays running
    Circulation pump starts running after about 4 mins
    About 10 mins later boiler stops
    Green light on LHS BDR goes out
    Circulation pump runs for another c. 10mins

    Quote Originally Posted by DBMandrake View Post
    Another possible scheme is that you only have a hot water zone valve and the second relay is configured as a boiler control relay directly firing the boiler instead of a heating relay.

    In the settings do you have a boiler control relay configured or not ?
    Yes - I think so - under "System Configuration" it says "Boiler Demand - BOILER RELAY"

    If I could be sure which BDR is which, I would do the full reset / re-bind.....

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    Had something similar with my initial install. I had S-Plan at the time. The installers had a) left the CH BDR91 double bound, and b) set the system up as having a boiler relay, even though it hadn't got one.

    As a result, every time the boiler fired (even for hot water) the CH valve opened.

    They were from the top-tier of accredited installers, too. I had to fix lots of things like this after they left.

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    Quote Originally Posted by Cracker View Post
    Here are the results of that test:

    Test Right Hand Side BDR
    Controller says HW is 43 degs. (Target point is 55 degrees)
    Press overide on RHS BDR - boiler fires.
    c. 5 mins later, boiler stops, circulation pump starts and green light goes out on RHS BDR
    Circulation pump runs for c. 5 mins

    Test Left Hand Side BDR
    Controller says HW is 43 degrees
    Press override button on LHS BDR - boiler fires and then stops immediately
    Circulation pump does nothing
    Press override button again on LHS BDR this time boiler fires and stays running
    Circulation pump starts running after about 4 mins
    About 10 mins later boiler stops
    Green light on LHS BDR goes out
    Circulation pump runs for another c. 10mins
    The circulation pump should always be running when the boiler is firing I'd have thought ? Something pretty wrong if it's not.

    You're going to need to figure out what sort of configuration you have by tracing the pipes from the boiler. A two port zone valve used in an S-Plan system looks like this typically, and you would most likely have two, but may have more:

    https://www.amazon.co.uk/Honeywell-V.../dp/B001ANU6UA

    If it's a Y plan system you'll have a valve that looks something like this with 3 ports, in which case you would only have one zone valve:

    https://www.amazon.co.uk/Honeywell-V...l+3+port+valve

    If you can find either of these and take a picture of them and the nearby pipes that might be helpful.

    It's possible you might also need to trace the wiring from the BDR91's to see where it goes. The cover pops off a BDR91 fairly easily with a small flat blade screwdriver at the bottom (it hinges at the top) but turn the boiler power off at the switchboard first of course and verify it's dead before doing so.

    Yes - I think so - under "System Configuration" it says "Boiler Demand - BOILER RELAY"

    If I could be sure which BDR is which, I would do the full reset / re-bind.....
    Having a boiler relay bound is probably wrong if you have only 2 relays, but it does depend on the plumbing and wiring configuration, so nailing that down first would be advisable.
    Last edited by DBMandrake; 21st August 2018 at 03:22 PM.

  6. #6
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    Honeywell state that, for reliable communications, the BDR91s and CS92 are supposed to be at least 300mm from each other and from anything metallic. The installers have got that wrong so get them back to correct it and, at the same time, to sort out the other problem.

    As others have said, you need to know what motorised valves you have. Do you have one valve with 3 pipes going into it (Y-plan), or 2 valves, each with 2 pipes (S-plan). The valves (whichever system) will have a spring loaded lever sticking out to allow you to operate the valve manually, but they also allow you to tell what position the valve is in. Assuming it's S-plan: the spring pulls the valve into the closed position and, when energised, the motor drives it into the open position. Give the lever a push to see which position it's in - you can't do any damage! This is much easier and certain than listening to the boiler firing or measuring temperatures.

    A quick numpty summary: the tank and room thermostats control the motorised valve(s), when a valve reaches the open position it switches on the pump, when the temperature inside the boiler drops the boiler thermostat fires the burner. With an S-plan system heating and HW are independent. With a Y-plan system the single valve either routes water to the heating coil, the rads, or both.

    Because I was having my entire heating and HW system replaced (20+rads, pipework, boiler, HW tank and oil tank in a fairly large house) I had my system "professionally" installed, but the installers got a lot of things wrong. In their defence they came back a few times to try to fix things (with input from me) but a couple of Evohome problems eluded them so they got Honeywell tech support to suggest someone else to help them - the recommended "experts" managed to mess things up. I fixed the problems, with help from this group, in less than 20 minutes.
    Last edited by DorrisMancer; 22nd August 2018 at 11:10 AM.

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    Thanks Dorris Mancer - I'll put my reply in the thread above - TLDR: I cannot find the kind of valves that you seek, unless it's the one inside the cabinet! If I can work out which BDR is which I'll do a full re-programme. Full reply will be above shortly.... thanks again!

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    Quote Originally Posted by Cracker View Post
    Thanks Dorris Mancer - I'll put my reply in the thread above - TLDR: I cannot find the kind of valves that you seek, unless it's the one inside the cabinet! If I can work out which BDR is which I'll do a full re-programme. Full reply will be above shortly.... thanks again!
    Follow the cables from the BDR91's to see where they go...

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    Quote Originally Posted by DBMandrake View Post
    The circulation pump should always be running when the boiler is firing I'd have thought ? Something pretty wrong if it's not.
    My bad - I meant the red radiator circulation pump (Grundfos) that is at the back of the pipework. That should only run when central heating is required, right?
    Review view showing pipework.jpg

    Quote Originally Posted by DBMandrake View Post
    You're going to need to figure out what sort of configuration you have by tracing the pipes from the boiler. A two port zone valve used in an S-Plan system looks like this typically, and you would most likely have two, but may have more:

    https://www.amazon.co.uk/Honeywell-V.../dp/B001ANU6UA

    If it's a Y plan system you'll have a valve that looks something like this with 3 ports, in which case you would only have one zone valve:

    https://www.amazon.co.uk/Honeywell-V...l+3+port+valve

    If you can find either of these and take a picture of them and the nearby pipes that might be helpful.
    Unfortunately I cannot find anything that looks like that. See pictures. All of the wires from the BDR's go into the "Spaghetti" at the back of the control panel. Those wires then go to the valve / pump thing inside the boiler unit, the radiator circulator pump (red Grundfos) and the thermostat inside the water tank.
    Valve-pump inside boiler unit.jpg

    Quote Originally Posted by DBMandrake View Post
    It's possible you might also need to trace the wiring from the BDR91's to see where it goes. The cover pops off a BDR91 fairly easily with a small flat blade screwdriver at the bottom (it hinges at the top) but turn the boiler power off at the switchboard first of course and verify it's dead before doing so.
    LHS BDR wiring.jpgRHS BDR wiring.jpg

    I have taken the pictures of the BDR's and the file names show which is on the left and right. Hopefully this is enough for someone to say which at least was intended to be the CH / DHW.


    Quote Originally Posted by DBMandrake View Post
    Having a boiler relay bound is probably wrong if you have only 2 relays, but it does depend on the plumbing and wiring configuration, so nailing that down first would be advisable.
    Thanks again for your help.....
    Attached Images Attached Images

  10. #10
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    And here's a couple more piccies to help show what I've got...

    Front view cover off.jpg
    Spaghetti behind control panel 1.jpg
    Spaghetti behind control panel 2.jpg

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