The Lemon Fool

funduffer wrote:I have used at least 20% less gas every month this year compared to 2021. I have been struggling to understand why.

Yes, I have added some insulation, but this was in May, after the winter, so it can't be that.

Has it been a warmer than usual winter, well maybe. My thermostat settings have not changed.

I have a condensing combi boiler, and following some advice from my energy supplier (Octopus), in December 2021 I reset my boiler output temperatures to 55C for the radiators, and 50C for hot water. I can only assume this means the boiler is working much more efficiently at these temperatures than what I had previously. If so, that is astonishing.

In case anyone says this means the house is colder, I don't think so. The central heating is on longer, but the rooms still reach their target temperature.

FD

I'm not sure about the hot water side, but reducing the boiler temperature on the central heating side can make quite a difference.

The key is not the temperature of the water leaving the boiler, but the temperature of the cooler water returning to the boiler after completing it's circuit through the radiators.

If the returning water is above 54C or thereabouts, condensing will not occur, and it is this which makes a condensing boiler more efficient. If you have the central heating flow temperature set at 70C or so, there is a good chance that the return flow will be too hot to condense and therefore more gas will be used.

By having the flow set to 55C you can guarantee that the return will always be in the condensing range. I do this and prefer the lower radiator temperature. It may just be psychological but it seems to produce a more even temperature because it seems to reduce cycle of heating, subsequent overshoot before the thermostat reacts and the radiators cool, followed by the subsequent cooling, which then keeps repeating. Two possible downsides; first it obviously takes longer to heat up in the morning, so I have to set it to come on a bit earlier, and second, though I've yet to experience it, the setting might not be sufficient to keep the room at the required temperature if it's exceptionally cold outside.

Itsallaguess wrote:

funduffer wrote:
I have used at least 20% less gas every month this year compared to 2021. I have been struggling to understand why.

Yes, I have added some insulation, but this was in May, after the winter, so it can't be that.

Has it been a warmer than usual winter, well maybe. My thermostat settings have not changed.

I have a condensing combi boiler, and following some advice from my energy supplier (Octopus), in December 2021 I reset my boiler output temperatures to 55C for the radiators, and 50C for hot water. I can only assume this means the boiler is working much more efficiently at these temperatures than what I had previously. If so, that is astonishing.

Likely to be a combination of two beneficial factors -

1. Yes - we had a relatively mild winter last year

2. Combi-boilers work most efficiently around the lower temperatures that you've now been advised to set. This temperature range allows combi-boilers to operate in their most efficient 'condensing mode', recovering as much heat as possible from the system to help maintain that higher efficiency.

Cheers,

Itsallaguess

That's an interesting case. From memory I think radiators are typically sized for 70 degree C flow temperature. Dropping the flow temperature at the boiler to 55, buy the time it gets to a radiator it's nearer 50? I should think that to heat a house the way originally intended, the radiators would have to be rather oversized. The heat emitted to the room from each unit of radiator surface is going to be lower than intended. So, the case given here is perhaps depending on over sized radiators and/or a mild winter to maintain comfort?

There has to be threshold temperature for the water returning to the bolier where it is fully condensing. Let's say for arguments sake it's 60 degrees C to achieve fully condensing operation ***. Lowering the water return temperature to say 40 or 45 is not going to make any difference to the condensing mode since it was already fully condensing at the higher return temperature. Hope that makes sense.

*** That's a guess.

BullDog wrote:
That's an interesting case.

From memory I think radiators are typically sized for 70 degree C flow temperature. Dropping the flow temperature at the boiler to 55, buy the time it gets to a radiator it's nearer 50?

I should think that to heat a house the way originally intended, the radiators would have to be rather oversized. The heat emitted to the room from each unit of radiator surface is going to be lower than intended. So, the case given here is perhaps depending on over sized radiators and/or a mild winter to maintain comfort?

I agree - the flow and return figures we often see given are in the 70-degree-flow, 50-degree-return for efficient condensing mode on combi-boiler central heating, but as you say, radiator sizing could be influencing things where the earlier poster has been individually advised regarding his particular system.

Cheers,

Itsallaguess

Itsallaguess wrote:

BullDog wrote:
That's an interesting case.

From memory I think radiators are typically sized for 70 degree C flow temperature. Dropping the flow temperature at the boiler to 55, buy the time it gets to a radiator it's nearer 50?

I should think that to heat a house the way originally intended, the radiators would have to be rather oversized. The heat emitted to the room from each unit of radiator surface is going to be lower than intended. So, the case given here is perhaps depending on over sized radiators and/or a mild winter to maintain comfort?

I agree - the flow and return figures we often see given are in the 70-degree-flow, 50-degree-return for efficient condensing mode on combi-boiler central heating, but as you say, radiator sizing could be influencing things where the earlier poster has been individually advised regarding his particular system.

Cheers,

Itsallaguess

Thanks for the point about radiator size. When we moved into our house we put in a new combi boiler and a number of new, almost certainly oversized, radiators. This probably explains why I have not noticed any real difference in reducing the boiler output temperature to 55C.

FD

funduffer wrote:

Itsallaguess wrote:

BullDog wrote:
That's an interesting case.

From memory I think radiators are typically sized for 70 degree C flow temperature. Dropping the flow temperature at the boiler to 55, buy the time it gets to a radiator it's nearer 50?

I should think that to heat a house the way originally intended, the radiators would have to be rather oversized. The heat emitted to the room from each unit of radiator surface is going to be lower than intended. So, the case given here is perhaps depending on over sized radiators and/or a mild winter to maintain comfort?

I agree - the flow and return figures we often see given are in the 70-degree-flow, 50-degree-return for efficient condensing mode on combi-boiler central heating, but as you say, radiator sizing could be influencing things where the earlier poster has been individually advised regarding his particular system.

Cheers,

Itsallaguess

Thanks for the point about radiator size. When we moved into our house we put in a new combi boiler and a number of new, almost certainly oversized, radiators. This probably explains why I have not noticed any real difference in reducing the boiler output temperature to 55C.

FD

Exactly. With hindsight it was a good idea to do so. Good luck over the winter months to come. Let's hope it's a mild but windy one. We need the wind generation next winter to reduce the gas demand from CCGT power generation.

One fairly easy hit for us is that our electric shower, that gets used three times most days, has an 'Economy' setting which only uses one of the two heating elements, so after a couple of test-runs that turned out better than we expected, the two adults in our house are now using that cheaper option to help shave some kWh off our future electricity bills.

The water flow does drop fairly noticeably, and it's not yet clear how comfortable it might be when the incoming water temperature drops quite a bit during the colder months, but for now it's an easy hit to help reduce the electricity bill during the current turmoil in the energy markets.

Cheers,

Itsallaguess

Itsallaguess wrote:The water flow does drop fairly noticeably

It will always take the same amount of energy to heat a volume of water; would you get the same savings by just turning down the tap when you're in the shower?

I guess it might change the efficiency of the exchanger a bit.

But I think the key to any cost change would be not putting unecessarily heated water down the drain

It can be helpful (but not as easy as one would expect) to compare the actual cost per kWh of energy being purchased in the various fuels available for us to use.

Here is a chart I've compiled for my own circumstances giving this info. A lot of assumptions have been made so YMMV.

Prices per kWh:
0p Logs gathered in the woods out the back of my house
7p Kiln dried hardwood logs delivered
7.5p Natural gas
7.6p oil
8p Homefire smokeless fuel
14.5p LPG in 47kg bottles
19p Economy 7 mains electricity
25p LPG in 13kg bottles
35p Daytime mains electricity


Edit to add:
The natural gas and mains electricity prices above are current prices, before application of the new higher price cap announced on Friday 26th August 2022.

servodude wrote:

Itsallaguess wrote:
The water flow does drop fairly noticeably

It will always take the same amount of energy to heat a volume of water; would you get the same savings by just turning down the tap when you're in the shower?

I guess it might change the efficiency of the exchanger a bit.

My electric shower works the way I described earlier - there's two separate heating elements, with only one of them used in 'Economy' mode, and both used in the full-power mode -



Source - https://www.tritonshowers.co.uk/media/custom/upload/File-1439285024.pdf

When electricity was cheaper, we have been happy to use full power mode to achieve a better flow of water for a similar temperature that can be achieved by using 'Economy' mode, but where the economy mode needs to reduce the flow of water to enable an improved heat-transfer from the single element then being used.

Using 'Economy' mode in the above 'single-element' heating situation will clearly save me by using a lower power-rating whilst the shower is being used, and like I said in my earlier post, it feels like a relatively easy hit given the current spike in those electricity costs.

Cheers,

Itsallaguess

Itsallaguess wrote:Using 'Economy' mode in the above 'single-element' heating situation will clearly save me by using a lower power-rating whilst the shower is being used, and like I said in my earlier post, it feels like a relatively easy hit given the current spike in those electricity costs.

Agreed.
I was pondering if a similar savings could be made for those who don't have the opportunity to change the power rating of their shower - by e.g. just controlling the flow?

servodude wrote:

Itsallaguess wrote:Using 'Economy' mode in the above 'single-element' heating situation will clearly save me by using a lower power-rating whilst the shower is being used, and like I said in my earlier post, it feels like a relatively easy hit given the current spike in those electricity costs.

Agreed.
I was pondering if a similar savings could be made for those who don't have the opportunity to change the power rating of their shower - by e.g. just controlling the flow?

Perversely no you can't. On a basic fixed power electric shower, the temperature of the water is controlled by a flow rate adjuster, usually a needle valve of some sort. The higher the flow rate, the lower the temperature and vice versa.

There are one or two more sophisticated and expensive electric showers around where electronics modulate the power fed to the element. I dunno how exactly but I suspect some PWM going on. So if you have one of these, yes reducing the flow and holding the temperature would reduce the power consumption.


(Edit to add the last sentence.)

Mike4 wrote:Here is a chart I've compiled for my own circumstances giving this info. A lot of assumptions have been made so YMMV.

Prices per kWh:
0p Logs gathered in the woods out the back of my house
7p Kiln dried hardwood logs delivered

Thanks Mike for taking the time to post that info, very useful.

We have been getting quotes for a wood burning stove. The installers are being inundated with enquiries and lead times for supply/install are into next year. As demand increases I wonder how long the kiln dried hardwood will be available at 7p.

I think there is a lot in favour of a balanced flue gas stove. As suggested else where, gas will "probably" always be available, a simpler fuel to use, a good backup heat source if the electric goes off (Battery Piezo ignition), you can also turn the kWh rate down and it might just turn out cheaper than dried logs if loads of wood burners are installed.

servodude wrote:But I think the key to any cost change would be not putting unecessarily heated water down the drain

And recover the heat from water down the drain.

scotview wrote:....might just turn out cheaper than dried logs if loads of wood burners are installed.

I think that once people who never ran a fire before have a year of lugging logs and ashing out and chimney sweeping, for many the novelty will wear off.

We only get through about 3 tons a year, we buy it locally, a mix of 10" and 15" lengths for efficient use of the stacking area, some lumpy pieces have to be selectively chopped to thin them down, then stacked in the purpose-built woodstore I made where it's dry but well ventilated, then lugged up a long flight of steps and stacked in the fireplace, then the stove itself needs keeping an eye on every 20-30 minutes to make sure it doesn't burn too hot or cold, the fire has to be ashed out and made up every morning... kindling that I chop/glean myself but which otherwise has to be bought, newspaper when many people don't even have a proper newspaper... and then there's finding a reliable supplier of truly seasoned wood which took us three false starts.
Then there's the ashes, one can only grow so many onions....
And that 3 tons just does two woodburners which are only lit in the evening, and sometimes we run out and I have to order more and it's a tossup whether one can even get more by January when it's apparent it's going to run out.

Yes, the novelty will wear off.

V8

scotview wrote:

Mike4 wrote:Here is a chart I've compiled for my own circumstances giving this info. A lot of assumptions have been made so YMMV.

Prices per kWh:
0p Logs gathered in the woods out the back of my house
7p Kiln dried hardwood logs delivered

Thanks Mike for taking the time to post that info, very useful.

We have been getting quotes for a wood burning stove. The installers are being inundated with enquiries and lead times for supply/install are into next year. As demand increases I wonder how long the kiln dried hardwood will be available at 7p.

I think there is a lot in favour of a balanced flue gas stove. As suggested else where, gas will "probably" always be available, a simpler fuel to use, a good backup heat source if the electric goes off (Battery Piezo ignition), you can also turn the kWh rate down and it might just turn out cheaper than dried logs if loads of wood burners are installed.

I'm feeling very smug as I had a woodburner installed a few weeks ago, ordered back in June in anticipation of this fuel crisis Probably going to get a single room air-to-air heat pump installed as they are cheap as chips compared to air-to-water, and deliver cooling in summer too. So apart from cost of the fuel, availability is just as important. I'll have a choice of heating my hovel with oil at 8p/kWh, wood for free if I can be bovvered, wood delivered at 7p/kWh, or leccy at 10p (given the 3.5 COP of the heat pump). But the leccy will be broadly doubling shortly with the new price cap so even writing this makes me think perhaps I won't. But then I prolly should for professional reasons - ought to be able to talk to customers about them from personal experience!

Bear in mind a balanced flue gas-fired stove will be perhaps only about 60% fuel-efficient, if that. Check before buying...

88V8 wrote:

scotview wrote:....might just turn out cheaper than dried logs if loads of wood burners are installed.

I think that once people who never ran a fire before have a year of lugging logs and ashing out and chimney sweeping, for many the novelty will wear off.

We only get through about 3 tons a year, we buy it locally, a mix of 10" and 15" lengths for efficient use of the stacking area, some lumpy pieces have to be selectively chopped to thin them down, then stacked in the purpose-built woodstore I made where it's dry but well ventilated, then lugged up a long flight of steps and stacked in the fireplace, then the stove itself needs keeping an eye on every 20-30 minutes to make sure it doesn't burn too hot or cold, the fire has to be ashed out and made up every morning... kindling that I chop/glean myself but which otherwise has to be bought, newspaper when many people don't even have a proper newspaper... and then there's finding a reliable supplier of truly seasoned wood which took us three false starts.
Then there's the ashes, one can only grow so many onions....
And that 3 tons just does two woodburners which are only lit in the evening, and sometimes we run out and I have to order more and it's a tossup whether one can even get more by January when it's apparent it's going to run out.

Yes, the novelty will wear off.

V8

This is where solid fuel wins hands down. 10% of the volume of wood for the same amount of energy, and 10% of the ash.

Interested that you buy wood by the tonne. All the suppliers I can find sell it by the cubic metre and are dead coy about the weight. Probably because since the law came in requiring a max water content of 20%, it is all a lot lighter than it ever used to be.

Do you happen to know the approx weight of a cubic metre of cut logs, 20% moisture content? I estimated 250kg for my calcs. Thanks if you do!

88V8 wrote:

scotview wrote:....might just turn out cheaper than dried logs if loads of wood burners are installed.

I think that once people who never ran a fire before have a year of lugging logs and ashing out and chimney sweeping, for many the novelty will wear off.

V8

Thanks V8, very useful, real info. I think a balanced flue gas stove is maybe the way to go (for our circumstances). Primarily as a Christmassy treat but mostly as a backup heat source, some stoves are even rated as high as 5 kW , with turn down to 2kW. Instant back up heat source, with piezo & remote control. Moisture exited to outside unlike LPG.
Thinking about it, when electric is off nearly all gas boilers will be off, so plenty of gas supply for folkies with piezo ignition gas stoves.

Mike4 wrote:I'm feeling very smug as I had a woodburner installed a few weeks ago, ordered back in June in anticipation of this fuel crisis Probably going to get a single room air-to-air heat pump installed as they are cheap as chips compared to air-to-water, and deliver cooling in summer too. So apart from cost of the fuel, availability is just as important. I'll have a choice of heating my hovel with oil at 8p/kWh, wood for free if I can be bovvered, wood delivered at 7p/kWh, or leccy at 10p (given the 3.5 COP of the heat pump). But the leccy will be broadly doubling shortly with the new price cap so even writing this makes me think perhaps I won't. But then I prolly should for professional reasons - ought to be able to talk to customers about them from personal experience!

Bear in mind a balanced flue gas-fired stove will be perhaps only about 60% fuel-efficient, if that. Check before buying...

Now that's interesting. My son is in an 11th floor apartment and he uses a 3kw + 1kw wall mounted electric panel heaters to warm his living room/kitchen area. Would it be practical to install an air to air heat pump in his apartment? He has a balcony where the compressor and fan unit could stand. But I imagine there's going to be all kinds of obstacles put in his way to actually install a 4kw output heat pump? Having to pass a pipe through the external wall and somewhere to drain condensate (plus condensate freezing issues in winter) seem to be the most obvious issues? Thanks for any input, running a 4kw heat output heat pump would maybe reduce his electricity bill by anout 2/3. He works from home so having a cold apartment isn't really an option.

88V8 wrote:(snip)
Yes, the novelty will wear off.

V8

Thanks for the insight.

I'm going to light the wood burner for the first time this year. It was already in the house when we moved in 7 years ago and I've never had cause to light it but I don't need the heat. We have the invoice from the previous owners chimney sweep from a few months before we moved in and I've had a peer up the flue with an endoscope it looks fairly clean - to be sure I booked the sweep for a couple of weeks time. I bought 1m³ of seasoned hardwood which is under a tarp by the back door. The new regime including some of V8's list of jobs is currently a novelty but I can see them becoming chores.
In general I'm able to live a low temperature, we have the thermostat set to 14°C overnight, 20°C for an hour in the morning ready for getting up and 17°C tick over when we're both in the house in the evenings. SO has an oil filled portable heater in the spare room/office as they have been increasingly working from home. I reckon they boost the CH when I'm not here and they're in all day.
This is the test year as I'm lucky to be on a fixed rate until December 2023. We're planning on setting aside some of the deferred costs for future inevitable increases. I've a few friends with wood burners in the living room and I do find them hot such that I have to remember to sit far away from the heat and bring my summer clothes to their houses in winter. Those same friends bring jumpers when they visit me.

Mike4 wrote:

88V8 wrote:

scotview wrote:....might just turn out cheaper than dried logs if loads of wood burners are installed.

I think that once people who never ran a fire before have a year of lugging logs and ashing out and chimney sweeping, for many the novelty will wear off.

We only get through about 3 tons a year...

Interested that you buy wood by the tonne. All the suppliers I can find sell it by the cubic metre and are dead coy about the weight. Probably because since the law came in requiring a max water content of 20%, it is all a lot lighter than it ever used to be.

Sorry, lapsus lingus. I meant three metres... which comes in ton bags... But it's still plenty of work, if one regards it as work.

Mike4 wrote:This is where solid fuel wins hands down. 10% of the volume of wood for the same amount of energy, and 10% of the ash.

.
You're right. And I could burn solid fuel in one of our stoves. The limitation is not the stove, they're both the same, it's the flue liner. Needs to be 316 stainless. One of them is, one probably isn't.

Also, solid fuel burns much hotter. Or at least, it can. We have thermometers on our stoves so I can keep an eye on the temp, but even so... and with thatch you don't want too much heat in the chimney, at least I don't, not even with an insulated liner.

The truth is, I like burning wood.The rustic thing.

kempiejon wrote:I'm going to light the wood burner for the first time this year. It was already in the house when we moved in 7 years ago and I've never had cause to light it but I don't need the heat. I bought 1m³ of seasoned hardwood which is under a tarp by the back door.
In general I'm able to live a low temperature...

Good with the low temperature. 6iF (16C) vs 70F makes a gigantic difference in energy usage when it's cold, and 16C is perfectly livable if suitably dressed.

Wood under a tarp, that's the arrangement we inherited from the PO... especially over earth, it will sweat and become soggy and recalcitrant. Buying seasoned wood and keeping it that way is like buying fine wine and storing it in the boiler room.... even an open-front lean-to would be better.

I went to buy some wood yesterday, I needed it to raise the floor in the attic so I can insert more insulation. Ye gods and little fishes, the price of constructional wood!

V8