Results 1 to 6 of 6

Thread: Latch open a 4043?

  1. #1
    Automated Home Jr Member
    Join Date
    Mar 2015
    Posts
    45

    Default Latch open a 4043?

    I had an S-plan heating system that has been upgraded to full Evohome with HR92s on every radiator. At the time we simply latched open and electrically disconnected the existing heating zone valve as the boiler is now under control of the OpenTherm bridge.

    But I vaguely recall reading somewhere recently that latching open the valve using the lever on the motor head doesn't fully open the valve, but only partially opens it to allow filling/draining of the system.

    My system has been working brilliantly, so the latching has worked, but I am now curious as to whether the valve is indeed fully open or not, and whether it would matter either way. I can see that if it was partially open then it introduces an extra pressure loss over the valve in addition to the losses over the radiators etc.

    I know that in the long run I could remove the valve completely, but means more work, so I'm quite happy with the valve in situ but open. I'm more curious about what goes on in the valve when it is latched!

    Thanks!
    Last edited by StuartG; 27th November 2016 at 06:24 PM. Reason: Fix typo.

  2. #2
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    1,800

    Default

    Hi Stuart

    I've posted about this in several threads now but the short answer is the filling latch opens the valve about half way whereas under motor power it opens fully. So the flow resistance will be a bit higher in this half open state, but whether this causes you any noticeable issue or not will depend on your system, and whether your system already has a low or high flow resistance.

    The other thing to consider is the possibility that it might seize if left permanently in one position. This would probably take many many years though on a good valve. Personally if I was in your situation and wanted the valve disabled I wouldn't go to the bother of removing it (especially if you decide you want it again later) but just wire it to the same power as the pump, that way it will open fully whenever the pump is running but close at other times to save power but also ensure there is a little daily movement to prevent it seizing over the years.

  3. #3
    Automated Home Legend
    Join Date
    Jul 2014
    Posts
    995

    Default

    And the above is exactly what I did. It now serves me two purposes. Opens the CH valve whenever the pump is running, even during over run. And also in the summer will get my non TRV towel rails warmed when the HW only kicks in.

  4. #4
    Automated Home Jr Member
    Join Date
    Mar 2015
    Posts
    45

    Default

    I hadn't thought of that - I'm using the boiler's internal pump, but I think I saw in the installation manual that there is an output to run an external device. That said, all my radiators have thermostats on so the valve doesn't have to move. I've never disassembled one, but if I took the valve head off could you manually open the valve and leave it fully open that way. It wouldn't matter if it seized up as it is effectively redundant.

    It's somewhat academic as the system is performing beautifully in the cold weather. Boiler is modulating down, and trending is showing that the system is starting, stopping and maintaining with great control.

  5. #5
    Automated Home Jr Member
    Join Date
    Nov 2016
    Posts
    38

    Default

    I'd thought about removing the head as well. I can't see why it wouldn't work. All the springs, etc are in the head, so the stopper part should just stay where you leave it.

  6. #6
    Automated Home Guru
    Join Date
    Nov 2015
    Posts
    143

    Default

    As You say yourself "My system has been working brilliantly,"

    In that case I would leave it as it is

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •