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  • FIRST POST
    • s00tie
    • By s00tie 12th Feb 18, 6:55 AM
    • 7Posts
    • 1Thanks
    s00tie
    Heating Sense Check
    • #1
    • 12th Feb 18, 6:55 AM
    Heating Sense Check 12th Feb 18 at 6:55 AM
    Could someone tell me I'm not going crazy please?

    Last year we moved into a rented 3 bed detached bungalow - suspect built in the 60's. Although it's not the best insulated house in the world, it's not the worst either.

    The heating is run from a Baxi Duo Tec 40 and whilst it seems to manage ok, I've become very concerned with it's gas consumption since November (ironically when it was last serviced).

    I've been keeping a track on both electricity and gas usage since a smart meter was installed in September and whilst the electricity feels about right, the gas bill seems a little on the high side to me.

    We're consistently using over 120kwh of gas per day with some peaks over 140kwh. I haven't got the benefit of seeing the warm weather usage to bring this average down but don't think we've experienced a cold winter this year which is worrying. In November, prior to the 'service' the average usage was 60kwh which is what has me concerned.

    The system runs from a Nest thermostat, most Rads have TRVs installed - they are pretty well balanced and all get evenly hot with about a 12 degree drop from flow/return.

    I've tried different thermostat temps (currently 20.5 from morning to night with 17 overnight) - I've tried boiler ch temps from 50 up to 75 (usually settling back to the 63 degrees which coincides with what I think is the eco mark on the boiler) with no real difference in cost just a difference in speed reaching the set temp and I've experimented with the Nest from fully automatic to simple manual mode. None of which seem to have much of an impact on the usage.

    I got up this morning at 6:15am - the heating came on at 6. It had already consumed 14.5kwh according to the smart meter. According to the nest, with a set temp of 17 overnight it perhaps fires up the heating once for around 15 mins to maintain the 17 degrees.

    Whilst I know costs are subjective depending on supplier we're currently paying about £160 per month for combined usually drawn from about a £6 per day average cost, electricity about £1.50 and Gas about £4.50. Tariff is elec/gas standing 22p/22p unit 12p/3p which I know will be going up in the summer.

    I accept that this could be the smart meter and happy to pursue that too - but before I start talking to both the landlord and the energy supplier, wanted to make sure I'm not going nuts

    Apologies for the wall of text and happy to answer any further questions or try any other suggestions I haven't thought of so far.
    Last edited by s00tie; 12-02-2018 at 6:58 AM.
Page 1
    • Cardew
    • By Cardew 12th Feb 18, 8:29 AM
    • 27,181 Posts
    • 13,290 Thanks
    Cardew
    • #2
    • 12th Feb 18, 8:29 AM
    • #2
    • 12th Feb 18, 8:29 AM
    IMO for a 3 bed, 60's built, bungalow, consumption of 120kWh a day is quite reasonable.

    120 x 3p + 22p = £3.82 a day.
    • s00tie
    • By s00tie 12th Feb 18, 8:46 AM
    • 7 Posts
    • 1 Thanks
    s00tie
    • #3
    • 12th Feb 18, 8:46 AM
    • #3
    • 12th Feb 18, 8:46 AM
    Thanks @Cardew - exactly why I posted. Will see what others have to say
    • Hengus
    • By Hengus 12th Feb 18, 9:47 AM
    • 5,163 Posts
    • 3,162 Thanks
    Hengus
    • #4
    • 12th Feb 18, 9:47 AM
    • #4
    • 12th Feb 18, 9:47 AM
    Could someone tell me I'm not going crazy please?

    Last year we moved into a rented 3 bed detached bungalow - suspect built in the 60's. Although it's not the best insulated house in the world, it's not the worst either.

    The heating is run from a Baxi Duo Tec 40 and whilst it seems to manage ok, I've become very concerned with it's gas consumption since November (ironically when it was last serviced).

    I've been keeping a track on both electricity and gas usage since a smart meter was installed in September and whilst the electricity feels about right, the gas bill seems a little on the high side to me.

    We're consistently using over 120kwh of gas per day with some peaks over 140kwh. I haven't got the benefit of seeing the warm weather usage to bring this average down but don't think we've experienced a cold winter this year which is worrying. In November, prior to the 'service' the average usage was 60kwh which is what has me concerned.

    The system runs from a Nest thermostat, most Rads have TRVs installed - they are pretty well balanced and all get evenly hot with about a 12 degree drop from flow/return.

    I've tried different thermostat temps (currently 20.5 from morning to night with 17 overnight) - I've tried boiler ch temps from 50 up to 75 (usually settling back to the 63 degrees which coincides with what I think is the eco mark on the boiler) with no real difference in cost just a difference in speed reaching the set temp and I've experimented with the Nest from fully automatic to simple manual mode. None of which seem to have much of an impact on the usage.

    I got up this morning at 6:15am - the heating came on at 6. It had already consumed 14.5kwh according to the smart meter. According to the nest, with a set temp of 17 overnight it perhaps fires up the heating once for around 15 mins to maintain the 17 degrees.

    Whilst I know costs are subjective depending on supplier we're currently paying about £160 per month for combined usually drawn from about a £6 per day average cost, electricity about £1.50 and Gas about £4.50. Tariff is elec/gas standing 22p/22p unit 12p/3p which I know will be going up in the summer.

    I accept that this could be the smart meter and happy to pursue that too - but before I start talking to both the landlord and the energy supplier, wanted to make sure I'm not going nuts

    Apologies for the wall of text and happy to answer any further questions or try any other suggestions I haven't thought of so far.
    Originally posted by s00tie
    Nest is a TPI thermostat which is designed to maintain temperatures within a fixed set range (usually +/-1C). Whenever there is a heat demand to get the property back up to the set temperature, your boiler will normally go to maximum boiler flow (ie; it will use a large amount of gas)

    That said, 14.5 kWs in 15 minutes equates to 58kWs in an hour which just isn't possible unless you have a monster of a boiler. What your smart meter is actually telling you is that your total consumption since midnight is 14.5kWhs. I suspect that part of your problem is the high 17C overnight temperature. To maintain this temperature, your boiler is firing up more often than you might think. Do you really need to maintain 17C?

    If you actually want to monitor your gas usage throughout the day then a smart meter is about as much use as a chocolate fireguard in my opinion. I have a gas monitor that graphs usage every 15 minutes which has over the past few months has provided me with empirical data on how best to run my condensing boiler. For example, so far today, my boiler has consumed 2.75 cubic metres of gas. 0.62 cubic metres was consumed to re-heat the hot water cylinder to 60C; 1.58 cubic metres of gas was consumed to get the house up to its day target temperature and approximately 0.48 cubic metres of gas is being consumed per hour (5.4kWhs) to maintain the set temperature. All that said, the key message that comes out of this data is that once the house is at temperature, it is best just to let it run even if I am out of the house for 3 hours. The gas used to get the property up to temperature far exceeds that gas used to keep it there. I do turn the house set temperature down to 10C overnight ( 10 to 7 am): the rest of the time, I just let it run.
    • s00tie
    • By s00tie 12th Feb 18, 9:55 AM
    • 7 Posts
    • 1 Thanks
    s00tie
    • #5
    • 12th Feb 18, 9:55 AM
    • #5
    • 12th Feb 18, 9:55 AM
    Thanks for the reply Hengus. You're absolutely correct in that it is since midnight, but I did state:

    "According to the nest, with a set temp of 17 overnight it perhaps fires up the heating once for around 15 mins to maintain the 17 degrees."

    I see in the history that the Nest usually calls for heat once or twice overnight to maintain the 17 degrees.

    As for whether we need to maintain that, we don't from a comfort point of view. When I've got the CH heat on the boiler set at about 70 (still suspect the return is generally cool enough for condensing) then it takes around an hour for the temp to climb from 17 to 20.5 - what I was assuming is that if the house cools much further than that overnight, the energy needed to regain the set temp would be higher and possibly even more than the 15 - 30 mins of overnight energy needed to hold at 17.

    Happy to drop this to test of course, but not convinced that this is the main issue.

    I've just checked our smart meter (one shower has been had in addition to the heating on since 6am) and we've now consumed 45.11kwh (total of about 4 hours elapsed) and as I'm currently running at 55degrees for testing, the set temp has only just been reached.
    • matelodave
    • By matelodave 14th Feb 18, 5:39 PM
    • 3,362 Posts
    • 2,054 Thanks
    matelodave
    • #6
    • 14th Feb 18, 5:39 PM
    • #6
    • 14th Feb 18, 5:39 PM
    The thing about monitoring is that you've got to do it continuously so you can see whats happening and to get a baseline, ideally with some that logs the data a regular intervals - as Hengus does so you can see trends.
    The problem with suddenly starting to do it, especially at this time of the year you are getting confused by too many variables, the main one being the outside temperature which can vary by 10-15 degrees from one day to the next and even between night and day.

    At the very least you should be rcording your meter readings at the same time every day and trying to put them into context with the outside weather and what else is going on in the house.

    I've also got an energy monitor that logs my consumption so I can see exacly what's happening and when it happens (mine logs every six seconds and produces a continuous graph - http://www.energyhive.com/dashboard/dave look at the bar chart and see how the daily consumption varies). I've also got seven years worth of weekly data which allows me to monitor my consumption against my averages and this year is roughly the same as last although it doesn't track it week by week.
    Last edited by matelodave; 14-02-2018 at 5:45 PM.
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    • s00tie
    • By s00tie 14th Feb 18, 5:55 PM
    • 7 Posts
    • 1 Thanks
    s00tie
    • #7
    • 14th Feb 18, 5:55 PM
    • #7
    • 14th Feb 18, 5:55 PM
    I'm taking the data from the smart meter as this is what will be feeding into the supplier. Also, I take the actual meter readings at 10pm each night and log them into a spreadsheet I created which correlates to the smart meter.

    I think at this point I'm just looking for reassurance that others don't believe the Gas usage I'm seeing of 120khw+ per day on average is not that far out that it suggests either a boiler or meter fault. I know the house could be better insulated, but we don't feel cold and it doesn't feel like the heating is on constantly. Nest reports heat calls of between 4 and 8 hours per day (although because we've got the heat relatively low, I know this doesn't mean continuous burn from the boiler) out of a possible window of 15 hours. The variance is down to the weather, this is for sure.
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