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Duel fuel towel rail trips circuit

Discussion in 'Electrics UK' started by ax222s, 18 Oct 2021.

  1. SFK

    SFK

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    Don't just watch. Ask the plumber to show you how to do it (watch a few Youtube videos first).
    I feel a good plumber will be more than happy to show how to bleed a radiator and re-presurise system.
    SFK
     
    Last edited: 22 Oct 2021
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  2. ericmark

    ericmark

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    To re-pressurise easy, if you have the filling loop, not required if you have a header tank, balancing is very different however, you have already turned the lock shield valve so will be required.

    The idea is every radiator when the TRV heads are open will have the same temperature drop across the radiator. And the speed any radiator can heat up is slower than the speed the TRV can close, yes I know no TRV on the towel rail, but still needs to match the rest.

    With an oil boiler it does not really matter that much, as long as every radiator gets warm, with gas the boiler will normally modulate (reduce output) to ensure if gains the latent heat, it will still work if not set right, but not as economically. Normally plumbers set the radiators so temperature drop with all running is around 15°C, however I tried with an inferred thermometer thermometer.jpg theory should work, practice the recorded temperature jumped up and down like a yo-yo.

    So I set by turning off all radiators and then turning back on until could just feel a little heat on supply side, then I used the computer TRV report TRV_report.jpg until target and current matched, but it took some time, and clearly you need TRV heads linked to PC to do it. I actually at first only had two, and swapped them radiator to radiator to set lock shield, once set put the mechanical one back on, but adjusting between 2 and 3 until room at 20°C is easy with a TRV marked *123456 once lock shield set, but until lock shield set you simply don't know which one needs adjusting.

    I do wonder how the plumbers set the lock shield I would think with a differential thermometer, but never seen it done. Know mother house when I came to it all lock shield valves were wide open, clearly the system had never been commissioned.

    Central heating has changed over the years, early systems had no TRV on the towel rail, either as a by-pass when all other TRV's closed, or as a balance between the hot coil so the towel rail heats up even when central heating is turned off, it heats up with the domestic hot water, clearly that can't happen with a combi-boiler.

    Water from the mains contains oxygen or fish could not live, but that is released when it is heated, so all central heating systems need bleeding after they have been run for a time as the gas collects in top of radiators. Often one finds one radiator tends to get most of the gas, you hope that is not the towel rail as if the element is not covered it will burn out.
     
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  4. ax222s

    ax222s

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    Im running a Mistubishi Ecodan powered by a Mitsubishi air source heat pump.

    I found this useful video . Ill go out to the garage later (where the system is) and investigate.
     
  5. ax222s

    ax222s

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    Yesterday I checked the pressure on the system. It was 0.5 bar. I increased it to 1 bar and then bled the towel rail (the whole height of the towel rail gets nice and warm now!).

    I then went back outside to check the pressure, and it had dropped. I was expecting this to happen, so I topped it back up to 1 bar

    IMG_0189.jpg IMG_0190.jpg

    Ive just checked on it again this morning and it seems to have lost a little pressure. So now its at 0.9 bar. Would you expect this? How often should I check the pressure? Does the pressure affect the efficiency of the Ecodan? Perhaps I should increase it to 1.5 bar?

    Thanks
     
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  7. EFLImpudence

    EFLImpudence

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    Yes.

    If it is working then it is alright.

    No, it won't work if the pressure is too low.

    Doesn't really matter.
    If you do and there is a leak, it will take longer to drop to low enough to stop it working.
     
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