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Thread: Combi Boilers

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    Combi Boilers

    Hello,

    I have a 3 bedroom house which is heated with radiators and a combi boiler. The house is always cold so most nights we have the radiators on.

    I work from home most of the day but just put up with the cold by putting on more clothes. My girlfriend told me though that it is probably cheaper (and more comfortable) to have the boiler on low all the time so the house is always at a nice temperature rather than having it on high for 3-4 hours a night.

    Can anyone confirm if this is the case or if she is just saying this so the house is always warm!

    Thanks

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    HEXUS webmaster Steve's Avatar
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    Re: Combi Boilers

    Hard to say.

    One think I would say, though, is that shifting temperatures cause issues such as condensation, depending on how well ventilated the property is.

    24/7 operation isn't likely to be very sensible, but I tend to have the boiler come on before I wake up for an hour or so, then just before lunch, then just before tea-time until nearly bed-time.
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    Re: Combi Boilers

    good question, keeping the CH warm all day would (relatively/time) use less energy than heating it up from cold every time.

    I imagine if you know the voume of water in your CH, the temp it starts at then the energy required to heat from cold & the energy needed to maintain X degrees then there's a start. Fairly simple if you have the figures I guess, try using calories (ie ignore actual energy use) to get a comparison of the two.
    See if this site helps? http://hyperphysics.phy-astr.gsu.edu...useenergy.html
    Last edited by Rob_B; 29-09-2008 at 08:32 PM.

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    Re: Combi Boilers

    if the house is always cold, consider ways of making it not so cold.

    Check the quality of your loft insulation, we had to re-do the stuff at my parents because the original stuff was useless (might of just been the Cornish for you, half the windows on the neighbours house don't even have planning permission).

    check:
    http://www.energysavingtrust.org.uk/
    you might even have a grant or something similar
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    Re: Combi Boilers

    supposedly it's more efficient to keep a house at 15C & then reheat to required temp rather than letting it fall below 15C but I suspect that it's 1 of these things with so many variables that every case is different.

    depending upon what controls you have it may not be a case of having the boiler on low all the time .

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    Re: Combi Boilers

    I'd say as long as you have a room thermostat, you should keep it on low all the time. I'm not so fortunate, so it's either on full blast, or off. If I ever have cause to get a new heating system installed, I'll be remedying that situation for sure.

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    Re: Combi Boilers

    I use a combi boiler and have the following setup :
    1) Thermostatic radiator valves on all radiators for setting individual room temperatures. Note that two radiators - one in the hallway, and the bathroom towel rail - do not have thermostatic valves, this is essential for safety.
    2) Main thermostat in hallway for switching boiler on and off depending on house 'core' temperature.
    3) Timer to set 'on' and 'off' times for each weekday and weekends. No point in having the heating on full if nobody is in the house, but it only needs to be on for half an hour to go from min to max, so it comes on half an hour before I get up, goes off almost immediately as I then go to work, comes on half an hour before I get home and goes off half an hour before bedtime.

    I run the system with minimum temperature set to 12° and max set to 18° but have the living room temp set to 20° on the radiator valve. The kitchen/diner is set a bit lower, bedrooms are set a bit lower still, the spare room is turned right down to 10°. The house has cavity-wall insulation although it could probably use more added to the loft.

    It initially took a bit of time to get everything nicely balanced, but now works well. I would recommend this sort of approach over just switching the whole system off completely during the day.
    (My running costs for the system are about £400 - 500/year for a 3-bed semi but I expect it to be more this year!)

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    Re: Combi Boilers

    Quote Originally Posted by greenalien View Post
    1) Thermostatic radiator valves on all radiators for setting individual room temperatures. Note that two radiators - one in the hallway, and the bathroom towel rail - do not have thermostatic valves, this is essential for safety.
    It's not for safety, it's for boilers without an internal bypass - in which case the system must be able to dissipate a specified minimum amount of heat to avoid the boiler overheating (which rather than be a safety issue, would be a "why has my boiler cut itself off?" issue).
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    Re: Combi Boilers

    Quote Originally Posted by greenalien View Post
    I use a combi boiler and have the following setup :
    1) Thermostatic radiator valves on all radiators for setting individual room temperatures. Note that two radiators - one in the hallway, and the bathroom towel rail - do not have thermostatic valves, this is essential for safety.
    2) Main thermostat in hallway for switching boiler on and off depending on house 'core' temperature.
    Quote Originally Posted by Steve View Post
    It's not for safety, it's for boilers without an internal bypass - in which case the system must be able to dissipate a specified minimum amount of heat to avoid the boiler overheating (which rather than be a safety issue, would be a "why has my boiler cut itself off?" issue).
    Also it's important to have the thermostat in a room without a Thermostatic valve (TRV).
    If you don't the TRV may kick in and throttle back the heat in that one room, leaving the main thermostat on unnecesarily

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    Re: Combi Boilers

    in September, in England, this is an issue for INSULATION, not the central heating.

    Get in the loft, take a photo with flash, and post it here.

    Ditto the windows and door.

    I bet your house is leaking heat all day and night. And it's really cheap to insulate your loft properly....but it's a hard effort. You can tell straight away though....I mean, immediately.

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    Re: Combi Boilers

    I would agree with ZAK . I am going to have to add more loft insulation as mine has been in for a long time and I think the recommended thickness is about 12 inches nowadays. B&Q used to do an 'ECO' one for about 9 pounds for 3 rolls but seem to have changed to a different type -3 rolls for 10 pounds at thickness 200mm , thats about 8 inches. It would be interesting if anyone could recommend an alternative reasonably prices supplier. P.S.(have not read that energy web link yet -going there now).

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