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Central heating facts and myths?

Discussion in 'Home Automation' started by ericmark, 13 Mar 2019.

  1. ericmark


    27 Jan 2008
    Thanks Received:
    United Kingdom
    The first house I lived in with central heating was gas fired hot air, in the street we all felt it was rubbish, and the latter houses in the estate had a water distributed system, which cost less to run, however this was late 70's, so no double glazing and not even sure if the ducts for the heating were sealed well, after fitting it was easy for some one to tread on the duct and as a result cause it to leak.

    I say single glazing as when circulating the air there were no cold spots, and with radiators there were many cold spots with glass getting that cold you would see it removing the humidity from air and allowing it to run down the windows.

    Our last house had a Myson fan assisted radiator, again no cold spots as air circulated, and fast warm up times, but we had higher bills there than here in spite being a semi rather than detached. Could also be due to boiler.

    So the big question, circulate the air or allow it to remain in the main static? There is no question mild circulation results in a more constant temperature which since it is constant can be set lower.

    This moves be on to second item, analogue or digital control, it would at first glance seem analogue is far better, the radiators modulate, the boiler modulates so you have a constant heat, however with digital speed can mean it alternates between hot and cold, or it is that fast that in real terms there is no difference between analogue and digital as far as room control goes, so only question is which releases the most energy to the outside.

    Clearly the home type will change results, but having a boiler run at most economic output then turn off for a time, or have boiler turn down to match demand, we are told every time a boiler turns off any heat in the boiler is lost through the flue, but heat is being lost through the flue all the time boiler is running, so does running a boiler at 25% output lose less to atmosphere than a boiler running for 25% of the time?

    To use TRV's to control temperature to each room independently requires the boiler to run for an extended time with low output, where having every room set as a proportion of whole output will some correction with the TRV's it can be run with a mark/space ratio.

    These all clearly impact on each other, when using hot air central heating from turn on to all rooms at temperature looking at around 15 to 20 minutes, that fast we would turn off heating when we left the house, and turn it back on when we returned. But the hot water and radiator system in this house, with a modulating boiler and electronic TRV on 4 of the 10 radiators it takes more like 2 hours to reheat the house, most of that time is due to the anti hysteresis software being careful not to over shoot.

    So first house did not need geofencing it heated up that fast turning it on as I arrived home was good enough, and this house geofencing does not work as it takes so long to reheat and stabilise the temperature.

    I have placed thermometers around this living room, depending on day, but can be over 10°C difference around the room, as to if good or bad, not sure, if in bay window is 15°C do I care when I am not sitting in the bay window, if my chair is at 20°C does it matter what temperature rest of room is at? Same when sun heats bay window to 28°C if my chair at 20°C do I care?

    I move into yet another house soon, so starting all over again, this time oil fired, so have to decide how far to take automation? So hope to start some debate on what is worth doing and what is OTT.

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