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Thread: Boiler coming on for just a few seconds

  1. #21
    Automated Home Legend paulockenden's Avatar
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    The system has calculated that the 35-40 seconds of heat every ten minutes is what's required to counter the heat losses.

    Would you rather than have that or a longer burst perhaps once an hour, with the subsequent bigger temperature swings in the house?

    The more of TPI I see the more I like it, I just think it needs to be made aware of how long a boiler takes to ignite!

  2. #22
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    Quote Originally Posted by paulockenden View Post
    The system has calculated that the 35-40 seconds of heat every ten minutes is what's required to counter the heat losses.

    Would you rather than have that or a longer burst perhaps once an hour, with the subsequent bigger temperature swings in the house?

    The more of TPI I see the more I like it, I just think it needs to be made aware of how long a boiler takes to ignite!
    I like the idea of TPI but it sounds like this 10 min / 1 min cycle if preprogrammed and not calculated on the actual house/room requirements.

    Anyway, I need to try and accept this system and "let it do its thing". Weather warming a bit now, so will turn off until heating the autumn and see how I get on with it through our first winter together. It'll either stay, or end up on eBay (I hope they get a good resale value )

  3. #23
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    the TPI in itself is fine. But being able to control minimum-on-time and amount-of-cycles-per-hour is pretty important.

  4. #24
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    Quote Originally Posted by paulockenden View Post
    The system has calculated that the 35-40 seconds of heat every ten minutes is what's required to counter the heat losses.

    Would you rather than have that or a longer burst perhaps once an hour, with the subsequent bigger temperature swings in the house?

    The more of TPI I see the more I like it, I just think it needs to be made aware of how long a boiler takes to ignite!
    That's like getting up and starting your car every half hour in the winter just to make sure it's warm inside when you need to drive for work...

    The amount of water running through your radiators is so low it should take a modern boiler no more than 5 minutes to heat up from scratch...Let alone a T° difference of a few degrees when you're in need of heat...
    So this firing-up is totally useless and a complete waste of energy...
    But I'm no expert...and the more I read the experts advice and comments...Evohome IS rocket science !!!

  5. #25
    Automated Home Legend paulockenden's Avatar
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    Quote Originally Posted by Wallyİ View Post
    That's like getting up and starting your car every half hour in the winter just to make sure it's warm inside when you need to drive for work...
    Imagine if that same car didn't have a variable accelerator. It simply had a binary on/off.

    How would you do a steady 70MPH on the motorway?

    You'd apply little dabs of power at regular intervals.

    I think that's what TPI is trying to do. As opposed to traditional heating controls which are like allowing the car to slow down to 60, then accelerating to 80, then letting it slow back down to 60, etc. etc.

    There's good logic there, and if you have a boiler relay you can set parameters so that your boiler cycles aren't wasted.

    The problem is that those of us with S Plan don't get to do that.

    P.
    Last edited by paulockenden; 7th May 2015 at 09:20 PM.

  6. #26
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    Quote Originally Posted by Wallyİ View Post
    So this firing-up is totally useless and a complete waste of energy..
    If the system was totally cold, I would agree. However, once your system and room is at temperature, it only takes a very little amount of extra energy to maintain that temperature (especially if your house is insulated). Just a minute of turning ON can easily be enough to maintain requested temperature.

    In my case, the 1 minute of heat requested by Evohome actually added TOO MUCH heat to the system. And because it continued to go ON for 1 minute every 10 minutes, regardless of rising temperature and already being above setpoint, Evohome would build up huge overshoots in my house.

    My old wired Honeywell Round uses TPI as well and also uses 10 minute cycles once temperature is reached (temperature within the proportional band). However, it sometimes skips a 10 minute cycle. For example: it will go ON for 1 minute, stay OFF for 10 minutes, go ON for 1 minute, stay OFF for 20 minutes, go ON for 1 minute, go OFF for 10 minutes, go ON 1 minute, stay OFF 30 minutes, go ON 1 minute, etc. This keeps the temperature almost perfectly on setpoint.

    So the point I'm trying to make: 1 minute of heat per X minutes does not have to be a waste. It can easily be enough to maintain, or even raise room temperature.
    Last edited by erik; 8th May 2015 at 12:05 PM.

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