Help working out my gas usage....

QrizB

weehamish said:

So the 1 rad is in my bedroom, the room has a 2 windows but it has curtains and the door is always closed. 
The rad thermostat is set to max, which is 5 it doesnt have temps on it, the house thermostat is set to 20c.

The net effect of this - having your radiator in the bedroom turned on, but with the TRV set to MAX and the only control being the house thermostat - is that the house 'stat will always be calling for heat and the radiator will always be hot. This is not a very efficient way of running things.

Somewhere in the house there is likely to be another radiator without a TRV and which is always on.

The boiler is set to economy mode which is 70c but drops to 58c once its heated up.

Is that the flow temperature? If so that's not very "economy", your flow temp could be 55C permanently and you'd not notice a difference in heating but your boiler would be moore efficient.

I didnt know boilers had a minimum usage? whats the point in that? SO 17khw is the minimum i can use but it could heat more rads for the same usage?

I think this comment was a red herring. Modern gas boilers will modulagte their output down to low levels and will cycle on and off if the return water is too warm.

weehamish said:

I will test with more rads on to see if the usage goes up but either way, what can i do to get things checked to see why its using so much gas for 1 rad? 

My advice:

1. Ideally, heat more of your house, and have the boiler on for longer.

2. Turn the TRV in your bedroom down from MAX to maybe 4.

3. Turn the flow temperature on your boiler down to 55C.

4. You haven't said yet whether the boiler also heats your hot water?

weehamish

I can try turn it down to 4 to see if that helps, 58c is the flow its just 70c until it heats up its, its the eco mode on the boiler but i can turn it down more if needed.

Yes the boiler heats the water but the test i did wasnt heating any water, it was just for the heating.

Still with all the above, doesnt explain why some people are saying its hard for 1 rad to use 17khw of gas in 4hrs?

QrizB

weehamish said:

Still with all the above, doesnt explain why some people are saying its hard for 1 rad to use 17khw of gas in 4hrs?

There will be heat coming out somewhere else. Either your bredroom is a long way from the boiler and the heat is being lost from the pipes, or (more likely) there's a small radiator that is always on. The "always on" radiator is intentional; it ensures that if your TRVs are all closed but the thermostat is still calling for heat, there's somewhere for the water to go.

You could go round the house and find out which one is unexpectedly hot.

Have you got a tape measure? How big is your bedroom radiator?

GunJack

The "hot" rad is likely to be the bathroom or hallway one..if all your other rads have TRVs, it'll normally be the one without a TRV.

markin

The manual will say what the boiler can modulate down to, what make and model is it?

theoretica

weehamish said:

I didnt know boilers had a minimum usage? whats the point in that?

Think of a normal gas stove - it has a maximum and you can turn the flame down quite far, but then at some point you have to turn it off - there is a gap between the minimum heat it will output and off, it can't work at barely on.   There will be some minimum number of kW the boiler is running at when it is on - even with it switching on and off repeatedly to not overheat it is not at its most efficient.

https://www.heatgeek.com/what-is-boiler-modulation/

weehamish

Yeah i understand the thermostat rad is always on, its at the bottom of the stairs near the thermostat for the house, i understand thats to gage the house temp but thats irrelevant as thats always gonna be on? The rads i have on by choice i only have 1 on.

I tried 5hrs at a lower temp yesterday and it used 2m3 of gas which is like 22khw of gas... so lower temp for longer is not saving money and in fact looks as if it made zero difference, maybe costing more? I dont get none of this...

Going off the usage graphs the boiler is mostly even, i seen a spike yesterday but normally its totally even from start until finish, looks like around 0.2m3 per 30 mins.

I will test multiple rads tomorrow as its too late to do the test today but i think its guzzling way more gas than it should be and the house is mostly freezing... if some of you are heating 7 rads for about the same usage... !!!!!! is going on in this house?

markin

The bricks and plaster will take in a lot of heat the first time its heated well which will mess the data for just 1 day, a forum member that worked away 5 days a week and would have to heat all day on Friday and had a cold house tried heating all week and had the same or less gas usage heating all week on low and had a warm house when he got home.

The stairwell is a lot of volume to heat and it just keeps raising up, why its usually the coldest part of the house and the heat will always escape into the rooms and out the ceiling, so like it or not you are trying to heat the hole house just very slowly so it probably clicks on and off all the time when its on.

wild666

weehamish said:

Hi, im not sure im being charged properly for my gas usage... it seems very high for what i use.

I only have data from the past few days as octopus site has not been tracking gas usage for a while... it seems the new stats also show usage in m3 instead of khw... which is where im struggling to get my correct usage!

So for 4hrs heating, 2 in the morning and 2 in the afternoon im using 1.511m3 of gas at 6.22p per khw... googling m3 , 1 unit of m3 = 10.55khw so roughly i should be using 16khw? If thats how its actually worked out, so to me thats £1 roughly per day? 

So my heating should only be £30 a month and then my cooking and showers on top and then my standing charges.

Im not sure im doing the maths correct here but thats how i look at it? 

But my bills are not adding up to that, they are way way more... it seems if i have my heating on for a full 7 hours straight my gas bill is the same too, so trying to save money by not using my heating is not even working, some days i wasnt even having my gas on or only using 2hrs of heating and nothing seems to be adding up properly.

1 unit can be anything from 10.96 kWh to 11.39 kWh. If you want to air on the side of caution use 10.96 kWh as the reading for one unit of gas but if not that fussed use 11.39 kWh. It all comes down to the calorific value of the gas used. These figures are worked out using CV's of between 38.6 and 40.1, the difference is 0.43 kWh per unit so if you use 10 units and the bill is using a higher CV than you used, say 40.1 compared to your 38.6 and the kWh price is 6.22p you will be 6.88p out on the bill. The more gas used the higher the total you will be out on the bill.

wild666

weehamish said:

Okay just an update for this so i dont keep people hanging if any of you were haha... Octopus worked out its 17khw so i was 1khw off! which seems pretty accurate for a bodge attempt.

SO my next question is does 17khw seem like normal usage for 4hrs heating? i know its based on my house which is unique to me but on average does 17khw seem about right for 4hrs heating? My boiler is brand new only fitted in october and its set to economy mode! 

It could depend on what temperature the heating and hot water temperatures are at on the boiler the installer or person who services it will probably turn it up to 60 plus degrees when you can have the heating down at 55 degrees and the water at 50 degrees. This will use less gas but the heating would take longer to get up to the temperature setting on the thermostat.