Balancing Radiators

Discussion in 'Plumbers' Talk' started by Pollowick, Apr 17, 2019.

  1. Pollowick

    Pollowick Well-Known Member

    WillyEckerslike and KIAB like this.
  2. KIAB

    KIAB Well-Known Member

    Got a differential digital thermometer, makes it easy to see the drop on flow & return to radiator.:)
  3. Severntrent

    Severntrent Active Member

    Usually its when a couple of radiators are not heating up that people are directed towards flow balancing and as the above guide assumes all radiators are heating up extra steps will be required.
  4. MGW

    MGW Well-Known Member

    I thought mine were balanced OK, until I fitted a TRV that actually is set to degs C not *, 1, 2, 3, 4, 5, 6 and I found radiators over heating, careful notes realised the TRV was turning off, it was the heat stored in the radiator that was causing the over heat, which in turned caused by the speed at which the radiators heated up.

    It was compounded by some one fitting the TRV on the return, but setting temperature difference takes no account of heat up speed, any TRV needs time to close, also of course to open, but it is the closing which causes the problem, once the radiator is hot it takes a lot of cooling.

    I roughly set, i.e. close completely then open bit at a time until inlet gets warm set all TRV heads to temperature required, if room over temperature close a little if under open a little, once set it stayed at temperature what ever the weather does.

    However with a TRV with *, 1, 2, 3, 4, 5, 6 that is not going to work, as you have no idea if it's the TRV that needs trimming or the lock shield valve. And without using electronic heads on the TRV it would be impossible.
  5. sam spade

    sam spade Active Member

    Step 2: "Remove the lockshield valve". Really??
    Step 6: Why 12°C? Condensing boilers usually require a differential of about 20°C. Low differentials result in much higher head loss and need more powerful pumps.
    Step 7: Opening a lockshield valve more than 1½ turns rarely makes any difference.

    What about setting the pump (if possible)?
  6. Heat

    Heat Well-Known Member

    It meant just remove the lockshield covers from the valves.
    Just worded badly.
    Crazy that it isn’t for modern condensing boilers systems
    The Teach likes this.
  7. The Teach

    The Teach Well-Known Member

    That balancing guide has been floating around the internet for many years and is just a rough guide for boilers with constant gas consumption & non modulating pumps.

    Condensing boilers,modulating gas boilers,modulating pumps,some designer heat emitters all need a different approach to balancing. radiator balancing is done during initial installation/commissioning and system alterations cant see why they would further balancing

    These do not need any calibration ;) bra.jpg
  8. sam spade

    sam spade Active Member

    Simple answer: the balancing was not done correctly.

    I have read the following advice from pros on forums: "set all ground floor rads to one turn open and all first floor rads to fully open" (or similar words); "TRVs are self balancing, so balancing is unnecessary". If that is typical of how balancing is done by the "experts", no wonder many house-owners decided to have a go themselves.
  9. Heat

    Heat Well-Known Member

    I rarely would have the time to balance every heating system that I have worked on, adding or replacing radiators, new boiler install, etc.
    A quick attempt at turning the lockshields to where I think they approximately need set, gets the system roughly balanced and all rads heating fully.
    Customers will not pay for the extra time required.
    Almost all systems I go to are not balanced and often all lockshields are full open.
    The public tamper with them anyhow, as to decorators and builders
    The Teach likes this.
  10. Baxi Boy

    Baxi Boy Member

    It it possible to achieve a 12degree difference with small radiators and a small house,with say a total of 20,000 btu? I find the most I can get in this case is 7 degrees,and 8-9 degrees on the boiler flow and return pipes.
  11. The Teach

    The Teach Well-Known Member

    Thats the problem :)

    With gas boilers able to supply variable heating loads,to avoid variable gas burn ramp up or down during balance its an idea to set the gas boiler to a constant low temporary fire rate and get the required balance. It has to be done fairly quickly ;)

    Getting a gas condensing boiler & system to work as economically as possibly will need considerable onsite adjustments during initial installation,any further diy interference can reduce the gas boiler efficiency and boiler life :(

    System balancing and trv's is another circumstance to consider.

    Diy :p
  12. Baxi Boy

    Baxi Boy Member

  13. sam spade

    sam spade Active Member

    If a system has not been correctly balanced, does it comply with the Commissioning requirements laid dowin in Approved Documents L1A and L1B?

    This defines commissioning as follows:

    Commissioning is the advancement of a fixed building service after all or part of the system has been installed, replaced or altered. The system is taken from a state of static completion to working order. Testing and adjusting, as necessary, ensure that the whole system uses no more fuel and power than is reasonable in the circumstances, without compromising the need to comply with health and safety requirements. For each system, commissioning includes the following: setting-to-work; regulation (that is, testing and adjusting repetitively) to achieve the specified performance; calibration, setting up and testing of the associated automatic control systems; and recording of the system settings and the performance test results that have been accepted as satisfactory

    The relevant part is that about "regulation", which obviously includes balancing.

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