gas usage by hot water query

aay1987

hey people.

in a day we use 1.2units of heating and 1.6 units for hot water. ( i tried to work it out roughly ..when we didnt have hot water on how much gas was consumed in an hour etc)

i think the one for hot water is high. we have a meter which says cu ft. the conversion factor for KwH is arnd 31(thts what soutern electric does while charging me)

i have a combi boiler (new ..got it fixed lat april). it has a button which says 'eco' on it. it is for preheat and when eco is on ..there is no preheating of hot water. i take it that eco stands for economy ...and hence i have it on all the time tryin to save gas.

we are 4 people in the house. does 1.6 units of hot water sound correct?we are using arnd 2.8 units per day and our heating is on for arnd 10 hrs a day. (we the boiler is on all the time ..but the thermostat is at 0 for arnd those 14 hrs)

further we lower the thermostat to 2 whn we go for a shower ....and it is on 4 the other times. hence keepin in mind we dont have preheat on ...is this actually saving any gas?

do reply guys. i'll be very grateful for ur input.

Cardew

I don't know how you determine that you use 1.6 units(approx 50kWh) for hot water and only 1.2 units(38kWh) for heating per day.

The total for heating and hot water is quite reasonable at about £16 a week in winter; but hot water will never use that amount.

notbritishgas

Aay Aay, I see you have a combi boiler, as far as I know that only uses gas for hot water when a hot tap or shower is turned on, it does not store hot water in a cylinder. I do not see how you can determine your hot water gas usage in one hour as it would depend on how often you ran the tap.
As Cardew says your weekly usage for winter is quite reasonable considering your heating is on 10 hrs a day. My usage is between 18 and 20 units (cu feet meter) a week.

aay1987

with regards to hot water - i noted that on the meter we use .12units per hour when hot water tap/shower is not turned on. hence given the fact we use 1.2 units. in a day i noted 2.8 was the average. therefore 1.6 was used by hot water when tap/shower was turned on. is that logic wrong?

i think i have a combi junior boiler.

also people could you clarify the meaning of 'eco' button. its to do with pre heating. if pre heating is on all the time, does that mean more gas consumption?

Cardew

aay1987 wrote: »

with regards to hot water - i noted that on the meter we use .12units per hour when hot water tap/shower is not turned on. hence given the fact we use 1.2 units. in a day i noted 2.8 was the average. therefore 1.6 was used by hot water when tap/shower was turned on. is that logic wrong?

i think i have a combi junior boiler.

also people could you clarify the meaning of 'eco' button. its to do with pre heating. if pre heating is on all the time, does that mean more gas consumption?

Yes the logic is complely wrong.You might measure the gas consumption for 1 hour(when HW is off) and it will not have used any gas. Measure over a different hour and it might read 0.6 unitsSo using the logic in your earlier calculations(where you multiplied 0.12 units by 10) your CH uses either no gas or 6 units a day!!!Heating HW is generally a fairly small proportion of your overall gas bill - generally between £100 and £150 a year for the average family.

Cardew

There is a recurring fault with this website that puts any post into a solid block of text, with no spaces between sentences or paragraphs. Has anyone else found this?

aay1987

dear Cardew,

i still didnt understand your post clearly. let me just explain a little more.

my heatin is turned on 5 - 8 am in the morning and 7pm to 2 am in the evening. that makes it 10 hours. yes if i mesure gas consumption at say 1 pm (and no hot tap/shower) there would be 0 gas consumption.

but i measured it between 10pm and 11pm. and we used .12 units then (whn hot water/shower was not on). i re checked it a few times and the avg was still .12.

hence now keeping this in mind, could you expand a little bit more on as to why this reasoning is wrong. thanks cardew.


when we have hot tap/shower on the last digit of the meter turns pretty fast .03 units every 2 minutes. (it is slightly faster initially and then moves slightly slowly). this is without central heating on (i.e. arnd 1 pm ) and could u craify the 'eco' button and gas consumption aswell?

Cardew

aay1987 wrote: »

dear Cardew,

i still didnt understand your post clearly. let me just explain a little more.

my heatin is turned on 5 - 8 am in the morning and 7pm to 2 am in the evening. that makes it 10 hours. yes if i mesure gas consumption at say 1 pm (and no hot tap/shower) there would be 0 gas consumption.

but i measured it between 10pm and 11pm. and we used .12 units then (whn hot water/shower was not on). i re checked it a few times and the avg was still .12.

hence now keeping this in mind, could you expand a little bit more on as to why this reasoning is wrong. thanks cardew.

The gas consumption of your boiler is not constant. The boiler switches on and off as the water in the radiators reaches the set temperature, or the rooms are at the correct temperature as set by the thermostat.

So even if you have your heating 'on' the amount of gas it uses in any given period varies hugely. When it first switches on in the morning, after the house has cooled down overnight, it will use far more heat to bring the house up to temperature and then it will use far less to maintain it at that temperature.

I suggest you check the consumption between 5am and 6am and 7pm and 8pm(e.g. the first period after your heating is put on)

aay1987

so will a thermostat of 4 will consume less gas to maintain a temp of 25 degree? when we compare it to a thermostat of 2? i.e. say between 1pm and 11pm?

is that the case with hot water aswell? say while having a shower we reduce the thermostat to 2?is that saving any gas had i left the thermostat on 4 for the shower?

so why do they say using low thermostat lowers your gas consumption.

notbritishgas

I would say the only really accurate way to measure your hot water gas used is to switch off your heating for one complete day and then go through your normal routine of showering , use of the taps etc. Measure the gas used and hey presto thats your water usage. Of course if you cook by gas you may have to live on salads or go out and treat yourself.:rotfl:

aay1987

cheers notbg. you said you have a combi boiler. do you have ur eco button on? it if for pre heating. what does it mean? anything to with using less gas?