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Thread: Evohome problems - assistance please!

  1. #1
    Automated Home Jr Member
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    Default Evohome problems - assistance please!

    Hi there,

    Have been experiencing issues since Monday. When HW failed to heat.

    My boiler is an excellent NBE RTB Biomass boiler. (Built like a tank, monitored online - highly recommended!)

    My Evohome setup has separate BDR91's for CH and HW.

    Boiler not firing up is unusual. It can send me an email if the pellet hopper is blocked (and has done before!) but is pretty much rock solid.

    Did some tests and although BDR's were lighting up contact wasn't getting to the boiler. Suspected the CSR92 batteries had failed so swapped them for a fresh set.

    Speaking to installer we suspected that the two port valve might have failed. I'm no expert but I ordered a replacement powerhead and it was a straightforward swap out.

    Afterwards I called for HW and everything ran as it should.

    Today though, the timed event programme happened but there was no HW heating.

    During the morning, I could see (from the boiler event log) that there were a few calls for heat between 11am and noon. I was out at work.

    Came home and got on the phone with Honeywell. Spoke to a very patient chap in Bucharest and we attempted to diagnose the issue.

    We re-bound the BDR's. And then went again from the top doing the CS92 first, then the other two.

    That call finished just after 4pm. I called for heat and my HR80 opened and green light on the BDR.

    But I noticed that when I cancelled the heat demand the green light on the CH BDR did not extinguish.

    I set a test programme for HW and the HW BDR lit but no signal got through to the boiler after waiting fifteen minutes.

    The support number is now closed for the weekend. My system has worked pretty much flawlessly for the past four or so years. Had an HR80 issue recently but that was solved.

    Can anyone shed any light on where the fault may lie?

    Is this a binding issue still? Or are both of my two port valves playing up? If so, can anyone help diagnose a faulty two port valve?

    All help gratefully appreciated.
    Last edited by ericd; 1st September 2017 at 05:59 PM.

  2. #2
    Automated Home Ninja Dan_Robinson's Avatar
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    If you have an s plan, what are the hr 80's doing?

  3. #3
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    Is that incorrect then? I am not familiar with the terminology on the system.

    Am trying to work out why the green light on the CH BDR is not extinguishing despite heating set to OFF.
    Last edited by ericd; 1st September 2017 at 06:17 PM.

  4. #4
    Automated Home Legend paulockenden's Avatar
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    Quote Originally Posted by ericd View Post
    Did some tests and although BDR's were lighting up contact wasn't getting to the boiler.
    Can you expand on that please. "BDRs lighting up" sounds like the on/off signals are being received properly.

    If that's the case, it's an electrical problem between the BDR and the boiler.

    P.

  5. #5
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    Thanks for responding Paul.

    With my Honeywell support call we reset and rebound everything to make sure things were good from the Evohome side.

    When I ask for CH the green light appears on the CH BDR and vice versa with HW.

    I suspect the issue lies with the 2- port valves at the moment.

    I just called successfully for CH and contact was made at my boiler.

    But when I call for HW, the BDR for HW lights, I can see the switch move on the 2port valve powerhead - but then nothing else happens.

    Apparently (like the Evohome 4 minute ping) it can wait five minutes at the boiler from receiving a contact to beginning the ignition sequence. But it just happened after 1:20 for CH.

    Not the best way to spend a Friday afternoon I have to say. But then, glad it isn't the middle of winter.

  6. #6
    Automated Home Legend paulockenden's Avatar
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    I think you might be right with the 2 port valves. The microswitches inside can fail.

    You can replace the heads without replacing the valve (wet part) itself.

    P.

  7. #7
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    Yes I replaced one of them yesterday (HW) - although could not spot the difference between new and old. Tested and all worked fine. But that was yesterday.

    Just now, the CH BDR just came on of its own accord and triggered ignition at the boiler.

    Any clues?

  8. #8
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    Quote Originally Posted by ericd View Post
    Thanks for responding Paul.

    With my Honeywell support call we reset and rebound everything to make sure things were good from the Evohome side.

    When I ask for CH the green light appears on the CH BDR and vice versa with HW.

    I suspect the issue lies with the 2- port valves at the moment.

    I just called successfully for CH and contact was made at my boiler.

    But when I call for HW, the BDR for HW lights, I can see the switch move on the 2port valve powerhead - but then nothing else happens.
    Assuming that you have a typical S-Plan system where the switches on both zone valves are wired in parallel to fire the boiler, I think you've answered your own question. If the HW zone valve is moving but the boiler won't fire for HW demand the problem is not with the BDR91 or Evohome, it's one of:

    1) The zone valve jamming before it moves all the way (the switch in a zone valve only contacts at the very end of the valve travel)
    2) The switch in the zone valve is faulty (it moves/clicks, but the contacts are faulty or possibly intermittent / burnt out)
    3) There is a wiring fault between the zone valve switch and the boiler

    Should be pretty easy to diagnose with a multimeter, if the wiring is readily accessible with a multimeter for example in a wiring centre. (Be very careful of the mains voltages though, they are deadly)
    Apparently (like the Evohome 4 minute ping) it can wait five minutes at the boiler from receiving a contact to beginning the ignition sequence. But it just happened after 1:20 for CH.
    Not quite correct. There is a delay of up to about 4 minutes between when you turn CH on or off with Evohome before the CH relay will react - this is because set point updates are only sent to HR92's about every 3-4 minutes. So if you turn off the heating it might be up to 4 minutes before HR92's start closing and only after they all close will a signal be sent back to the controller and then onto the CH BDR91 to switch it off.

    However there is no delay with HW - when you override HW to be on or off the HW BDR91 will switch instantly, provided that the temperature is below the HW set point minus HW differential.

    By the way you can press the button on a BDR91 to temporarily override the on/off status of the relay for testing purposes. (It will go back to following commands from the Evotouch automatically within 20 minutes or so) If you think the fault lies between the BDR91 and the boiler, just press the button on the relay to toggle it on and off for your testing - no delays, no confusion. That's what the button is for. (Aside from binding)
    Last edited by DBMandrake; 1st September 2017 at 09:12 PM.

  9. #9
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    Thank you DBMandrake for assisting also.

    Whilst grabbing food I was trying to think of what was causing seemingly random demand (during the night before last and during the morning whilst out) so decided to investigate what temps my HR80's were showing. Sure enough in my room there was one at 20 and it's lost sync with the Evohome controller. Doesn't want to SYNC right now either but will deal with that another day.

    Thanks for the specific instructions. I don't own a multimeter (just ordered one on Amazon) and an electrician friend is popping over to help investigate.

    It's all worked flawlessly for years (along with my Hometronic controller before that) so I'm keen to find where the fault lies.

    ***UPDATE***

    OK - closer investigation reveals I have probably fitted the powerhead on the two port valve slightly incorrectly.

    I uncoupled it and moved the lever watching the microswitch. It shows that the little brass piece is *just* falling short of touching the microswitch thus failing to make a connection.
    This explains why my boiler is asleep on the job. It's not receiving its wake up call.

    ***UPDATE 2***

    With the powerhead uncoupled I pressed the BDR button and watched what happened. The microswitch was pressed, and I watched my boiler wake up.
    All was well until the boiler was told to stop somehow and then the switch reset itself.

    *** 3 ****

    Just tested CH side of things. All worked fine. Call for heat, switch worked, boiler got contact, ignition began and boiler fired up for the past fifteen minutes. Rules out faulty relay on rear of boiler then.

    Now back to the HW 2 port valve.
    Last edited by ericd; 1st September 2017 at 10:37 PM.

  10. #10
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    Went to sleep quite peeved that solving this problem had consumed all of my spare time since coming home early from work.

    Figured the issue *HAD* to be a bad connection somewhere in the junction box - rather than stuck valve, failed switch, failed motor etc.

    Took the morning off, turned the power off after lunch and undid and remade all the connections.

    Powered up and left the casing off the powerhead. Called for heat via the BDR and contact was made. However, it stopped as the boiler began its ignition sequence.

    Tried again using the Evohome Controller and worked fine! Have just let the boiler run for an hour and heat my hot water. Am going to run three test this evenings. Not counting chickens yet.

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