High gas usage for boiler.

[Chuck]

The new meter has clocked up 4560 m^3 since 07-Sep-2020. That's a total of ca 10.8 kW hr m^{-3} * 4560 m^3 = 49,250 kW hr over 16 months, which I make 37,000 kW hr / yr. This includes one summer and 1.5 winter seasons so your annual consumpt is more like 30,000 kW hr, roughly half the 58,000 kW hr quoted in post #1. Hence, I think that the 58,000 kW hr must be the total for two years, i.e. 29,000 kW hr.

If I'm right, we're looking for a way to explain an extra 19,000 kW hr per annum, i.e. 52 kW hr / day, or the equivalent of 2 kW continuous loss.

The easiest way to waste this amount of heat without really noticing is to have a hot water leak. This would be quite significant, I make it about 0.62 litre per minute.

Anyway, try comparing the consumption with the cold feed to the hot water cylinder off vs on. Do you have any unbalanced mixer taps/showers? Any applicances fed with hot water? If you look at your water meter, is there an unexplained 0.62 litre per minute of consumption? Did your water consumption jump (by ca 320 m^3 per annum!) at the same time as your gas bill?

(Someone should check my figures and reasoning, I'm pressed for time right now so the above was a bit rushed.)

 

[John.g]

That seems quite high IMO, its a boiler output of 12kw, would have expected around 50% of this.
Is this whole house heating or just one zone like downstairs, room stat setting also affects usage, I average 4 to 5kwh with downstairs at 20C and upstairs at 16/18C for 16 hours/day, oil firing, 50 year old house.
Have you any bills (personal details redacted) for any summer periods, like the past summer and any summer when the consumption averaged 10,000kwh/annum and ditto for any winter periods?.
Is there very high HW usage like teens continuously showering?.

 

[John.g]

The new meter has clocked up 4560 m^3 since 07-Sep-2020. That's a total of ca 10.8 kW hr m^{-3} * 4560 m^3 = 49,250 kW hr over 16 months, which I make 37,000 kW hr / yr. This includes one summer and 1.5 winter seasons so your annual consumpt is more like 30,000 kW hr, roughly half the 58,000 kW hr quoted in post #1. Hence, I think that the 58,000 kW hr must be the total for two years, i.e. 29,000 kW hr.

If I'm right, we're looking for a way to explain an extra 19,000 kW hr per annum, i.e. 52 kW hr / day, or the equivalent of 2 kW continuous loss.

The easiest way to waste this amount of heat without really noticing is to have a hot water leak. This would be quite significant, I make it about 0.62 litre per minute.

Anyway, try comparing the consumption with the cold feed to the hot water cylinder off vs on. Do you have any unbalanced mixer taps/showers? Any applicances fed with hot water? If you look at your water meter, is there an unexplained 0.62 litre per minute of consumption? Did your water consumption jump (by ca 320 m^3 per annum!) at the same time as your gas bill?

(Someone should check my figures and reasoning, I'm pressed for time right now so the above was a bit rushed.)

Rushed or not, you are right on the ball, annualizing the new meter its ~ 33,231kwh/annum or 91kwh/day, 10,000kwh/annum = 27.4kwh/day, shortfall 64kwh/day. if HW leak then 0.76LPM or 400M3/annum.

So suggest shutting off cold feed to HW cylinder and take another set of hourly readings.
Is the HW cylinder heating controlled by programmer and cylinder stat?.

 

[stevedurban]

ok, so here is a bill from May/June last year when the heating was off. Water was on constant as it always is (Notice the estimation on the right)

Rushed or not, you are right on the ball, annualizing the new meter its ~ 33,231kwh/annum or 91kwh/day, 10,000kwh/annum = 27.4kwh/day, shortfall 64kwh/day. if HW leak then 0.76LPM or 400M3/annum.

So suggest shutting off cold feed to HW cylinder and take another set of hourly readings.
Is the HW cylinder heating controlled by programmer and cylinder stat?.

Yes - There is a cylinder stat - and the hot water Isn’t overly hot so it seems to be controlling it.

For reference, we have all tank fed showers and baths.

 

[stevedurban]

Water usage looks relatively static - although i cant go back any further than 2020

And this is an over view of Gas Usage

Also, something that may help. Octopus take half hourly readings on the smart meters. You can see here in the report i got that, when the heating turns off at 9pm, no gas is used over night until the heating turns on again at 6am. If there was a water leak, would i not expect to see usage over night as well? it also tells me that my tanks is relatively efficient at keeping the heat in.

on the 9th, it seems like the boiler did fire in the middle of the night

 

[John.g]

Somethings not adding up now anyway Steve. (maybe good)
You used 1257kwh of gas, apparently for HW heating. This equates to 43.4kwh/day for that 29day billing period. This equals to 36.9kwh/day at a boiler efficiency of 85%.
Assuming cold water at 12C heated to 60C, Litres of hot water = 36.9*860/(60-12), 661Litres.
This would equate to 1133 LPD at 40C.
Your actual water usage for both May and June was 460LPD for each month so ????.

Don't know how they came up with a estimated gas usage of 60550kwh/annum

 

[John.g]

Water usage looks relatively static - although i cant go back any further than 2020

View attachment 72749



And this is an over view of Gas Usage

View attachment 72751


Also, something that may help. Octopus take half hourly readings on the smart meters. You can see here in the report i got that, when the heating turns off at 9pm, no gas is used over night until the heating turns on again at 6am. If there was a water leak, would i not expect to see usage over night as well? it also tells me that my tanks is relatively efficient at keeping the heat in.

View attachment 72753


on the 9th, it seems like the boiler did fire in the middle of the night

View attachment 72755

You can see from the above that your "present" hourly usage is ~ 0.7M3/30min = 1.4M3/hour=15kwh/hr. or 13kwh/hr useful heat. Are you heating the whole house??.
Maybe turn the cylinder stat down from 60C to its very minimum and use the electric immersion say from 0900 to 1500 hrs tomorrow and monitor gas meter readings.

 

[Chuck]

Water usage looks relatively static - although i cant go back any further than 2020

Er, it was ca 300 litres per day in Feb & Mar 2020 and then jumped up to >550 litres per day and has been slowly declining since then. When do you think that the increased gas consumption started?

 

[stevedurban]

Somethings not adding up now anyway Steve. (maybe good)
You used 1257kwh of gas, apparently for HW heating. This equates to 43.4kwh/day for that 29day billing period. This equals to 36.9kwh/day at a boiler efficiency of 85%.
Assuming cold water at 12C heated to 60C, Litres of hot water = 36.9*860/(60-12), 661Litres.
This would equate to 1133 LPD at 40C.
Your actual water usage for both May and June was 460LPD for each month so ????.

Don't know how they came up with a estimated gas usage of 60550kwh/annum

thanks for much for the detailed response john.g!

Ill try the Immersion Tomorrow and see if it makes a difference.

Does the immersion have a thermostat on it or will it just keep heating the water?

Er, it was ca 300 litres per day in Feb & Mar 2020 and then jumped up to >550 litres per day and has been slowly declining since then. When do you think that the increased gas consumption started?

is hard to pinpoint because the bills were 6 monthly back then, and now monthly.

Im trying to get hold of the orignal bills but Avro went bust - so i cant get them so easily!

Guys i really appreciate everyones input! thanks for taking the time to help!

 

[John.g]

Yes, The immersion will have its own thermostat, probably set to 60/65C. Make a note of the cylinder stat setting before turning down to minimum, it looks like (and should be) set to 60C.

 

[Chuck]

Assuming cold water at 12C heated to 60C, Litres of hot water = 36.9*860/(60-12), 661Litres.
This would equate to 1133 LPD at 40C.
Your actual water usage for both May and June was 460LPD for each month so ????.

I wonder if the flow temperature being used to heat the DHW tank too low for the tank 'stat setting. E.g. if the flow temperature is 60°C and the tank stat is 65° then the boiler will cycle on and off all day keeping the heating loop that supplies the tank hot and, given there seems to be no insulation visible on the photo perhaps the losses from that would be enough to waste 2 kW.

Is there a programmer that limits the periods that the DWH tank is being heated for? It shouldn't need to be actively heated for more than an hour or two per day.

IME, the flow temperature needs to be a minimum of 5°C above the thermostat-determined setpoint.

 

[stevedurban]

I wonder if the flow temperature being used to heat the DHW tank too low for the tank 'stat setting. E.g. if the flow temperature is 60°C and the tank stat is 65° then the boiler will cycle on and off all day keeping the heating loop that supplies the tank hot and, given there seems to be no insulation visible on the photo perhaps the losses from that would be enough to waste 2 kW.

Is there a programmer that limits the periods that the DWH tank is being heated for? It shouldn't need to be actively heated for more than an hour or two per day.

Is there any way to confirm that?

The hot water is on permanently 24x7

 

[John.g]

There is a motorized valve+cylinder stat but apparently HW is on "all day".

 

[Chuck]

Is there any way to confirm that?

Measure the DHW temperature from the closest tap with a 0-100°C thermometer. Check the flow temperature the boiler is delivering, which is shown on on its LCD display.

I don't like the way your cylinder stat appears to be away from the side of the cylinder. It should be secured in place with a strap. If the sensor is not in good contact with the pocket you'll have the boiler running continuously and will waste a lot of heat because the circulation loop will be hot 24/7.

The hot water is on permanently 24x7

Why? How much hot water do you use over the course of a day, and when. A programmer gives a good measure of protection from the above issues.

 

[ShaunCorbs]

Measure the DHW temperature from the closest tap with a 0-100°C thermometer. Check the flow temperature the boiler is delivering, which is shown on on its LCD display.

I don't like the way your cylinder stat appears to be away from the side of the cylinder. It should be secured in place with a strap. If the sensor is not in good contact with the pocket you'll have the boiler running continuously and will waste a lot of heat because the circulation loop will be hot 24/7.


Why? How much hot water do you use over the course of a day, and when. A programmer gives a good measure of protection from the above issues.

Unvented so pocket stat with sensing bulb set to 50dc

 

[stevedurban]

i was told (rightly or wrongly) when it as fitted that they are so super efficient, that it can be left on all the time because they will only really heat when you use the hot water, because the thermal loss is so negligable.

However, your point is very valid that if there are issues, it could be heating all day!

The house would have 2 baths and 1 shower in an evening normally - so from a quick google, thats maybe 90L? tank is 210 - so if we just have the water on tomorrow for 2 hours at 12pm tomorrow, that should cover the day?

 

[John.g]

What is the cylinder stat set to now and what is the boiler temperature (set point) now, does this setting be changed in summer/winter?.

Two baths at 88 Litre/bath? and 45C is equivalent to 123 litrs of cyl HW at 60C so ~ 77 litres at 60C remaining = 128 litres at a showering temp of 40C = 10 min shower at 13LPM.
12kwh required to heat tank from cold so 2 hours should be fine as cylinder stat will cut out boiler anyway??.

 

[Chuck]

Another couple of faults that need to be ruled out:

1. The CH zone valve were letting by when it should be closed. The CH radiator system would then act as a bypass for the DHW cylinder and waste a lot of heat in the process.

2. An incorrectly set automatic bypass valve (ABV) opening when the cylinder is heating.

P.S. Sorry if these ideas have already been discussed; I'm not able to read most of the posts at the moment because everything is covered in adverts.

 

[stevedurban]

What is the cylinder stat set to now and what is the boiler temperature (set point) now, does this setting be changed in summer/winter?.

Two baths at 88 Litre/bath? and 45C is equivalent to 123 litrs of cyl HW at 60C so ~ 77 litres at 60C remaining = 128 litres at a showering temp of 40C = 10 min shower at 13LPM.
12kwh required to heat tank from cold so 2 hours should be fine as cylinder stat will cut out boiler anyway??.

cylinder stat:


Boiler is on 6



We don’t generally touch them all year round.

 

[stevedurban]

Another couple of faults that need to be ruled out:

1. The CH zone valve were letting by when it should be closed. The CH radiator system would then act as a bypass for the DHW cylinder and waste a lot of heat in the process.

2. An incorrectly set automatic bypass valve (ABV) opening when the cylinder is heating.

P.S. Sorry if these ideas have already been discussed; I'm not able to read most of the posts at the moment because everything is covered in adverts.

1) any way to prove this option?
2) here is the external abv




Is there an internal one in the boiler that may need checking.

 

[ShaunCorbs]

Turn the cylinder stat down boiler should go off if it’s heating the hot water

 

[stevedurban]

I’m pretty sure the house is calling for heat almost all day - and just no longer able to get up to temperature. Tado shows in the heat graphs as follows. The darker area shows when the boiler is firing constantly. The medium grey means it’s coming on and off a few times an hour apparently - and the light colour is off (this is heating only!)
The house is relatively well insulated, loft conversion to regs 5 years ago. Cavity wall insulation installed 10 years ago. Double glazed throughout.

When I discussed the issue with tado - they said looking at the graph for how the temperature drops from when the heating is off over night, the house only looses about 3 degrees over night - which he said was relatively good!

So could Chucks opinion that maybe something like a bypass not working properly - causing the water to go round and round instead of to the radiators be an issue?or something along those lines? Pump not pushing hard enough?

 

[John.g]

Can you see the actual boiler temperature from the boiler display to confirm that the high setting 0f 6+ is actually reflected in the boiler temperature.
Also, as suggested above, turn the cylinder stat up if the motorized valve is shut and ensure it opens and turn it down if the motorized valve is open and ensure it shuts.
If the boiler temperature is as high as it might be, 75C+, and if the DHW temperature doesn't feel scalding then a fair indication that its temperature is being controlled to its setpoint of 50C. (should really be 60C, for legionella protection).

 

[stevedurban]

Can you see the actual boiler temperature from the boiler display to confirm that the high setting 0f 6+ is actually reflected in the boiler temperature.
Also, as suggested above, turn the cylinder stat up if the motorized valve is shut and ensure it opens and turn it down if the motorized valve is open and ensure it shuts.
If the boiler temperature is as high as it might be, 75C+, and if the DHW temperature doesn't feel scalding then a fair indication that its temperature is being controlled to its setpoint of 50C. (should really be 60C, for legionella protection).

I tested the boiler stat - the valve was closed - I turned the boiler stat up and the valve opened. As soon as I turned it back down - the valve closed again.

Unfortunately the boiler doesn’t have a display - only the dial.

 

[John.g]

Ok then, the flow pipe from the boiler should be absolutely scalding and you should only be able to touch it for a very short time.