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Radiator Balancing - Drayton TRV4's - Some on flow, some on return...

Discussion in 'Plumbing and Central Heating' started by Rhothgar, 26 Oct 2020.

  1. Rhothgar

    Rhothgar

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    Hi,

    Been scratching my head on this one for a few days.

    I've just replaced all the rads in my house bar a few which I'll do later this week.

    System fully bled and it's running on an Intergas Rapid 32.

    What I cannot get my head around is this:-

    1) I was looking for some cheap rad thermometers but it's a case of you get what you pay for with some buyers on amazon claiming they are like 20degC out!!! The guy in the Drayton TRV4 video uses a Jet thermometers but they are £80 a piece! No way I want to pay that.

    Anyhow, I have a Draper Laser Thermometer so I think I'll have to make do with that on the bottom channel of either side of each rad as I reckon that's probably more accurate than trying to get an accurate reading off the pipes.

    2) It seems I've fitted some TRV4's on the return side. Do I need to change these to the correct side?

    I'm thinking not as they are listed as bi-drectional and I saw over the weekend that you can buy a Drayton TRV4 balancing key? But I'm thinking, "OK. So I can adjust the flow on the TRV side even if it is on the return pipe but that it might affect the accurate operation of the TRV itself?

    Still got loads of floorboards up so I could go around and map out which pipe goes where to gain a better understanding of what goes where exactly or is this not really umportant?

    I know which radiators heat up first.

    Thanks in advance.
     
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  3. oldbuffer

    oldbuffer

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    1. With TRV4's it doesn't matter whether the TRV is on flow or return.
    2. With a laser thermometer its a good idea to put a bit of black tape on each measuring point, and use that as the target. They aren't all that good with shiny surfaces.
    3. You don't have to use the TRV4 balancing option, you can still use the lock shield valve on the other end.
    4. Make sure all the TRV4's are fully open when you do the balancing.
    5. Are the radiators sized for a return temperature of around 55 degrees, or the older 70 degrees?
    5a. If for the newer standard, look for a flow / return differential of 20 degrees.
    5b. If for the older standard, look for a differential of around 11 degrees. However, your boiler won't work in condensing mode as much, if at all.
    6. A good starting point for lock shield valves is:
    6a. Furthest from the boiler, 2/3 to fully open.
    6b. Nearest the boiler, 1/8 to 1/4 open.
    6c. In between, in between.
    6d. Count the turns to fully open each lock shield (the valves differ on no. of turns) and calculate 1/2, 2/3 etc based on that. Not totally accurate as the flow doesn't increase linearly with turns, but as close as you can reasonably get.
    7. Its a long and boring job. If you have TRVs on all radiators, you can get away with an approximate balancing, which the TRVs will make up for as they open / close.
     
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  4. Rhothgar

    Rhothgar

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    Hi oldbuffer

    Thanks for the prompt reply and advice.

    Great idea about the black tape.

    I've done a cursory balance to within 11 deg although all I've done is replace radiators with a like for like size. In some instances, I've gone slightly larger but the old rads were just double panel, I've now gone for Type 22's through bar the odd P+.

    So technically the radiators haven't been sized. I didn't want to have to rummage through all my old college notes and try and redesign the system from scratch. It would be an interesting exercise. The U-value side of the calculations is easy but I can never remember how to account for air changes per hour!

    What actually happens if I turn the lockshields down to create a 20 deg differential? Do they radiate less heat?

    I should perhaps check the flow temperature. Factory default is 80 degrees. The nearest radiator to the boiler is receiving around 65 degrees. Pipes are currently uninsulated below floor as I stripped it all off for amending the pipework.

    Can't believe cost difference between Byelaw 49 and just plain 15mm thick walled insulation! 3 x the price!!!
     
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