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Thread: Radiator balancing woth HR92s

  1. #1
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    Default Radiator balancing woth HR92s

    Hi,

    Would like to check/balance my system. I have 12 zones (14 rads), all with HR92s on.

    In practise only half of these zones are used heavly (Spare rooms etc are set to low heating) Therefore should i balance my rads as if some of the zones are not calling for heat (A typical morning/evening) or just whack all zones to 25c?

    Thanks

  2. #2
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    If you're balancing your radiators by adjusting the lockshield valves you should always do this with ALL radiators in the house turned on.

    So just schedule all the rooms to 25+ degrees during the balancing. (It helps to start from a cold house doing this so you don't roast everyone alive in the time it takes to do the balancing. )

  3. #3
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    Quote Originally Posted by DBMandrake View Post
    If you're balancing your radiators by adjusting the lockshield valves you should always do this with ALL radiators in the house turned on.

    So just schedule all the rooms to 25+ degrees during the balancing. (It helps to start from a cold house doing this so you don't roast everyone alive in the time it takes to do the balancing. )
    Once agian DBmandrake you have answered my question helfully! Thank you.

    An odd question but is the best way to get a room to heat up quickly to set the temp much higher than desired, and thus get over the 1.5c threashold of evo. For example i want the batheroom to be much warmer in 1 hours time for a shower- was set to 19.5 and i wanted it at 22c, all i saw happend was valve open slightly more and boiler contiune to modulate at 37C, so took a long time to get to new temp. Is there an in built target time when a room is set to a new target temp?

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    Quote Originally Posted by Norfolkboy View Post
    An odd question but is the best way to get a room to heat up quickly to set the temp much higher than desired, and thus get over the 1.5c threashold of evo. For example i want the batheroom to be much warmer in 1 hours time for a shower- was set to 19.5 and i wanted it at 22c, all i saw happend was valve open slightly more and boiler contiune to modulate at 37C, so took a long time to get to new temp. Is there an in built target time when a room is set to a new target temp?
    From this and comments in other posts of yours it really doesn't sound like opentherm is modulating properly for you.

    If the current room temperature is 19.5 degrees and you turn it up to 22 degrees that is a 2.5 degree change - which should result in "full" boiler demand. On a BDR91 relay this would be 100% duty cycle (continuously on) and on an OpenTherm system I would have thought it should raise the flow temperature to the maximum (user set) flow temperature, and remain there until the room temperature got to at least 20.5 degrees before it started to back off the flow temperature. If its just staying at 37 degrees that is just not right.

    I use a relay instead of opentherm but if I was to make the same adjustment in my bathroom I know for a fact the radiator would come on full blast and be piping hot very quickly.

    As I don't use OpenTherm I don't have any suggestion for how to find what the problem is though, hopefully an OpenTherm user with a similar boiler to you can help out, or perhaps you need to contact Honeywell support directly.

    Does it still remain at a flow temperature of 37 if you turn your bathroom up to a really high setting like 25 or even 30 ? If it does, something is definitely wrong.
    Last edited by DBMandrake; 29th November 2016 at 03:09 PM.

  5. #5
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    Quote Originally Posted by DBMandrake View Post
    From this and comments in other posts of yours it really doesn't sound like opentherm is modulating properly for you.

    If the current room temperature is 19.5 degrees and you turn it up to 22 degrees that is a 2.5 degree change - which should result in "full" boiler demand. On a BDR91 relay this would be 100% duty cycle (continuously on) and on an OpenTherm system I would have thought it should raise the flow temperature to the maximum (user set) flow temperature, and remain there until the room temperature got to at least 20.5 degrees before it started to back off the flow temperature. If its just staying at 37 degrees that is just not right.

    I use a relay instead of opentherm but if I was to make the same adjustment in my bathroom I know for a fact the radiator would come on full blast and be piping hot very quickly.

    As I don't use OpenTherm I don't have any suggestion for how to find what the problem is though, hopefully an OpenTherm user with a similar boiler to you can help out, or perhaps you need to contact Honeywell support directly.

    Does it still remain at a flow temperature of 37 if you turn your bathroom up to a really high setting like 25 or even 30 ? If it does, something is definitely wrong.

    I agree, something isnt right with the Opentherm bridge, i witness this morning when zone came on, the boiler firing on/off 3 times in 1 minutes, and one of these times shutting the boiler right down and the pump switched off as well, even though there was a big demand for heat

  6. #6
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    Just asked Viessman if they have had any problems with Opentherm, and the response:

    I would not use Opentherm myself, it's a bit like fitting a BMW automatic gearbox to a Mercedes-Benz.

    Looks like it might be 85 down the drain buying the Opentherm Bridge for me!

  7. #7
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    Going out on a limb here to try and help, so potentially adding confusion and don't do anything based on it yet .

    I took a look at the Veissmann installation docs, and read the Wikipedia page on OT to look for clues.

    Wikipedia describes two or three implementations of OT, one using a digitally encoded level, and one using pulse width modulation.

    The manual suggests that jumpering the OT contacts will bring boiler on, making me think that is more likely to suggest PWM control, unless permanent high low is processed as digital override. It might also make some sense to what you're seeing if a suitably coded digital signal can sometimes trip the PWM level, so it might come on / off / on fairly quickly.

    In short, could there be a mismatch between OT styles?

    Given that NL link I previously posted I suspect not, but having thought of it I thought I'd throw it in.

    EDIT: And the reply in the other thread also suggests the components should work OK together.
    Last edited by Little Tinker; 29th November 2016 at 06:31 PM.

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