how do you experts balance a large CH system that is ErP

Discussion in 'Plumbing and Central Heating' started by old duffer, 24 Oct 2021.

  1. old duffer

    old duffer

    Joined:
    16 Oct 2021
    Messages:
    62
    Thanks Received:
    4
    Country:
    United Kingdom
    I have experienced a number of issues with rads being cold then warm on alternate days/times.
    I balance the system and then the next day its out of balance once again.
    On recording the data (rad temp in/out Dt etc) I concluded that this is a function of the ErP compliant system I have. It will increase/decrease the speed/hp of the pump according to flow/return temps at the boiler. Now this is a common feature on all boilers that are at least 5 years old so I can't be the only one to experience this.
    So how do you experts balance a system that has variable pump speed/hp/flow rates?
     
  2. ericmark

    ericmark

    Joined:
    27 Jan 2008
    Messages:
    18,913
    Thanks Received:
    1,778
    Location:
    Llanfair Caereinion, Nr Welshpool
    Country:
    United Kingdom
    I am looking forward to replies, not a problem now since moved to oil boiler, but had a real problem with late mother's house. In the past I simply turned off the lock shield and slowly turned it on again until I felt a little warmth in the feed pipe. But speed is so important, I found with the TRV on the supply side it reacts faster to on return side, and the important thing is the radiator heats up slow enough for the TRV to have time to react, even with electronic TRV heads open to closed looking at around 3 minutes, so looking at around 10 minutes for radiator to heat up or it over shoots.

    So I used the temperature report, I have 5 temperatures reported to my PC, Heating not keeping up.jpg one the boiler must be running, no good adjusting if boiler not running, and the TRV report shows target and current, Flat Battery TRV.jpg so if current over target I close the lock shield a little, but when target under current opening the lock shield a little may not be the right move, as one does not at least with mother's boiler know if the boiler is running at full output or throttled back (modulated) so I only opened the lock shield when it repeatedly showed target under current.

    In the end with 6 TRV's of which 4 were electronic I was able to adjust the lock shields so temperature was spot on, I moved one of the electronic TRV's from radiator to radiator to set, and once set returned it to an important one.

    This house 9 electronic TRV's and 5 mechanical TRV's and one radiator without any, and after a year since boiler finally stopped cutting out, and have not been able to set the lock shields to work well. Boiler switching on/off rather than modulating does not help, but as said if lock shield is open too far then the current exceeds target so easy close a tad, but with reverse one can only open a tad if sure boiler has be running long enough.

    I tried aiming a thermostat at the pipes thermometer.jpg theory seemed sound, set to 15°C difference, practice the readings jumped up and down like a jo-jo, no way could I set them using that, some where I have a differential thermometer and I suspect that is only way?

    So looking forward to your replies.
     
  3. Sponsored Links
  4. old duffer

    old duffer

    Joined:
    16 Oct 2021
    Messages:
    62
    Thanks Received:
    4
    Country:
    United Kingdom
    I have spent most of the day reading into this and it turns out it is incredibly well documented and understood in engineering circles so why do the expert heating engineers never mention this phenomena when referring to balancing a domestic heating system?
    Variable speed pumps mean there is no such concept as balancing for optimum performance using lock shields and the pump curves data are in effect meaningless as a point of reference.

    Shame on you professional expert heating engineers for misleading us mere mortals....you really should have know better.
     
  5. muggles

    muggles

    Joined:
    28 Oct 2005
    Messages:
    13,431
    Thanks Received:
    3,104
    Location:
    Daventry
    Country:
    United Kingdom
    I use IMI Eclipse TRVs, which are much easier to balance with than messing about with lockshields ;)
     
  6. Sponsored Links
Loading...

Share This Page