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    Can any plumbers / gas engineers answer me this question please?

    On my boiler (Baxi 60/100 system boiler) I can set it so the hot water and central heating come on independently or both at the same time.............

    So I was thinking today, if they both come on at the same time does it still use the same amount of gas or does it use more or just take more time to heat both of them up?

    Hope this makes sense and you can understand my way of thinking........i.e. I may as well heat the water every time I put the central heating on to save doing it independently in the early hours prior to when I get up for work :-)

    22 Comments

    I'm not a plumber but think I can answer this one for you..

    Won't save any energy or any saving will be negligible. At the end of the day, a boiler just transfers energy from gas to heat so it will use as much energy as needed.. I.e it won't save energy to heat the water whilst it's heating the central heating

    Hope that makes sense

    Hi, The answer is simple, when you turn on the tap the water the boiler is heating is sent in a loop by a diverter valve, and this takes priority over the heating. So in short when the hat water is on the heating is not. So no gain

    Original Poster

    big_chris24

    Hi, The answer is simple, when you turn on the tap the water the boiler … Hi, The answer is simple, when you turn on the tap the water the boiler is heating is sent in a loop by a diverter valve, and this takes priority over the heating. So in short when the hat water is on the heating is not. So no gain



    That's a combi isn't it? I've got a system boiler, so when the hot water is on the water in a cylinder is heated. Once the cylinder is at the correct temp or the hot water is turned off, the hot water then sits in the cylinder until it is required

    big_chris24 you are referring to a combi-boiler which heats up water on demand.

    The question was referring to a system boiler which has a hot water cylinder for supplying the hot water.

    And quite rightly if it the heating is on it may as well he's the hot water as well.
    The cylinder should be pretty well insulated anyway so topping up the heat won't take long then once it is heated it will go to heating only anyway.

    So yes, if the heating is set to come on on, the hot water may as well be heated as well. From cold you should be looking at a maximum of 45 minutes to heat a full cylinder of water, unless you live in a mansion with a massive cylinder.

    Original Poster

    mrdmorris

    big_chris24 you are referring to a combi-boiler which heats up water on … big_chris24 you are referring to a combi-boiler which heats up water on demand.The question was referring to a system boiler which has a hot water cylinder for supplying the hot water.And quite rightly if it the heating is on it may as well he's the hot water as well.The cylinder should be pretty well insulated anyway so topping up the heat won't take long then once it is heated it will go to heating only anyway.So yes, if the heating is set to come on on, the hot water may as well be heated as well. From cold you should be looking at a maximum of 45 minutes to heat a full cylinder of water, unless you live in a mansion with a massive cylinder.



    170 litre cylinder.

    So heating both would use the same amount of gas as just heating one (Water or Central Heating?)

    Why don't boilers also heat the water automatically every time people put their central heating on, it would save everyone (with system boilers) a fortune if this was the case

    It would use a bit more bit gas but it is pretty minimal, as it would be heating up to heat the radiators anyway, and if you are keeping your cylinder heated it takes less energy to keep it topped up than it would to heat it up from cold every time.



    This is assuming you use your hot water regularly....
    And it's well insulated....

    If you only use hot water say once a week then you will be better off just heating it once a week when you need it.

    Original Poster

    mrdmorris

    It would use a bit more bit gas but it is pretty minimal, as it would be … It would use a bit more bit gas but it is pretty minimal, as it would be heating up to heat the radiators anyway, and if you are keeping your cylinder heated it takes less energy to keep it topped up than it would to heat it up from cold every time.This is assuming you use your hot water regularly....And it's well insulated....If you only use hot water say once a week then you will be better off just heating it once a week when you need it.



    Once a week oO lol

    Its used numerous times a day, everyday, showers, baths, washing pots, cleaning etc

    Original Poster

    The tanks well insulated as well, Megaflo Cylinder............Think i'll try and do what we've been talking about and see how it goes

    Then do as you were....
    If it's heating radiators then heat the water....
    It may only be heating water for 15 minutes if the cylinder is pretty warm anyway just topping it up. Then all heat will go to radiators.

    The scientific way would be to try one way for a week then time hot water differently for a week... and take meter readings to compare.
    But you would need the weather to be the same for two weeks.

    If it's a Megaflo the heat loss from that would be very minimal.

    Original Poster

    Haven't got the time or the inclination to go to that depth.

    I'll just put the hot water on every time I put the central heating on and see how hot the water gets. If it heats it adequately then i'll stop putting the water on separately every morning.

    Cheers for the info

    It should only take 33 minutes to heat that cylinder from cold, so depending on hot water used the energy to keep it topped up will be pretty minimal.

    Original Poster

    mrdmorris

    It should only take 33 minutes to heat that cylinder from cold, so … It should only take 33 minutes to heat that cylinder from cold, so depending on hot water used the energy to keep it topped up will be pretty minimal.



    Cheers pal

    They already have this technology. It's called a thermal heatstore. Brilliant if you heat it with the energy from solar panels as it's free. Mains powered hot water in seconds.

    cons is it's not as cheap as a combi to run

    Original Poster

    kester76

    They already have this technology. It's called a thermal heatstore. … They already have this technology. It's called a thermal heatstore. Brilliant if you heat it with the energy from solar panels as it's free. Mains powered hot water in seconds.cons is it's not as cheap as a combi to run



    I've had free hot water all summer...........I have got solar and I use a Solar iBoost that feeds any excess electric I'm not using into the immersion heater in my cylinder. Trouble is its now winter and there's not much sun :-/

    I think it's better to have both going at same time as you will be using the heat generated by boiler more efficiently. Can't say how much you will save over a year though.

    Original Poster

    wayners

    I think it's better to have both going at same time as you will be using … I think it's better to have both going at same time as you will be using the heat generated by boiler more efficiently. Can't say how much you will save over a year though.



    Any saving is better than no saving, especially if the central heating is on anyway.

    Original Poster

    chocci

    The boiler can't heat both at the same time. The diverter valve just … The boiler can't heat both at the same time. The diverter valve just switches them over. It wont save you anything.



    On the cylinder its self (Megaflo) there is a 3 port valve position A = Hot water, Position B = Central heating and mid position is both hot water and central heating together

    Original Poster

    What happens inside the boiler if I select hot water and the central heating at the same time?

    not a plumber but surely its going to be roughly the same
    you are heating a given mass of water from a given temp to a new temp, depends on efficiency of transfer and heat losses and temperatures used/needed
    Edited by: "brilly" 10th Nov 2016

    Original Poster

    brilly

    not a plumber but surely its going to be roughly the sameyou are heating … not a plumber but surely its going to be roughly the sameyou are heating a given mass of water from a given temp to a new temp, depends on efficiency of transfer and heat losses and temperatures used/needed



    I'm not really sure how the boiler works either. But if its just a single flame (pilot light) and the water for both the central heating and hot water passes through a coil over this flame, then if they both pass over at the same time why would it use any thing extra?

    Original Poster

    So can any gas engineers so for sure either way?
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