Gas used running a boiler at different temperatures?

northernsoul

I have put Black and Red tape round my pipes. Better than pointing at the pipe itself.

thorganby

northernsoul wrote: »

Its only set at 55C (granted not far from your 60c) and stat set at 18C. Got to 18C at 12 , 4.5 hours after starting at 14C (helped by the sun ! ).
Your boiler is set about 60C, what about stat target temperature? Where roughly do you live ( only say roughly just to be safe , ) because if in Scotland that will make a fair difference.
Unfortunately non of the next 5 days are like my test days but may run boiler at 75C on one of the next 5 days. Will still for definate do it when/if the temps are the same.
After all "Thorganbuy" said "Only a fool would set the boiler flow temp to 50 degrees for a radiator system to try to save a few pence. This setting would only be used for a wet underfloor system" , so i must be very nearly a fool ! Haha

It sounds like you are another skinflint like Zither, I bet that he has never had his boiler on continuously for 4.5 hours ever!

Zither has previously posted "I barely use it on the mornings aside from weekends and maybe have it on for 1.5h in the evening"

Neither you or Zither have stated which boilers you have and with all of the variables e.g. property construction, glazing, drafts, insulation etc. the gas usage comparison figures are meaningless.

You have already stated that with a flow temp of only 55C degrees that it did not meet the target temp after 3 hours here and waiting 4.5 hours to raise the temp from 14 to 18 above, is unacceptable to me - you are not putting enough heat into the system with a flow temp of 55 degrees!

The objective of a properly commissioned central heating system is to reach the desired temp quickly and not to suffer low temps and long delays while the property slowly heats up!

There is money saving and there is stupidity!

Alex1983 wrote: »

On a correctly balanced radiator you will have a 20c difference across flow and return so the return should be around 20c below the flow temperature which is the temperature most boilers display.

Wrong - the temperature drop across each radiator should be about 20°F (12°C).

:eek:

bris

Norman_Castle wrote: »

Aren't the radiators balanced so they get an equal share of the available heat?

The water flows in one side at the same temp yes, but the trick is to balance the return so the heat from the flow isn't wasted.


You want the hot water in the radiators as long as possible without compromising the efficiency.


If the lock shields are all fully open then you have the hot water just doing a constant loop without giving it a chance to cool at the other end so you are at it's least efficient by just keeping everything at full temp constantly circulating.


By balancing the radiators starting from the furthest away radiator being fully open you slightly close the other lock shields down reducing the flow out the radiator which allows the heat to linger in the radiator slightly longer allowing the return to cool.


The ideal flow and return should be 75-55 but this is very hard to achieve in practice. Other factors that can affect this is having poorly sized radiators.


In smaller houses where the loop isn't so big it's also a factor as the water is looped to fast to achieve this drop.


Every house is different, room sizes outside temp all go against getting the ideal 75-55 so it's very rarely achieved. Even if you did get one day, the next it can be different.


Trial and error will get you a good system, but a boffin sitting in his office saying we need 75-55 is not living in the real world so don't worry if you cant get it.

Alex1983

I will not argue with you thronganby on that, I’ve always used 10-12c for standard efficiency boilers but since condensing boilers have come around have always used 20c as I was under the impression that was the standard because of the return needing to be under 55c to condense but if I’m honest and think where that came from I’m not sure.

northernsoul

okay, I'm a skinflint, you are not , well done. Why cant you use less aggressive language ? we are here to help. Lots of forums unfortunately now have people who criticise, look at electrical and plumbing forums, Its a shame its become like this.
It may be unacceptable for you to wait 4.5 hours to reach temperature but when did i say i was happy with this. I am just trying different things to find out what works. You may be rich enough to not try any money saving efforts, and there is nothing wrong with that, but some people have to look after their money or have different prorities.

Anyway, i thought i had been quite reasonable stating the variables. So here goes with more.

As stated, house is a terraced house
As stated, house is in northern England, near Leeds if you want to be more specific
As stated, outside temperature at start
As stated, it was a cloudy day, with no sun to warm up the house fabric
As stated, it was not windy
As stated, inside house temperature at start
As stated, target temperature
As stated, units are in metric m3
As stated, gas reading at start and at each secion of test
As stated, set boiler temperature
As stated, flow temperature, taken by IR gun on black tape wrapped once round pipe
Edit, As stated, flow and return temperatures.
Not stated, house is 100 year old with very little insulation, wooden floors, cellar under kitchen, 2 foot void under lounge, can be draughty. Stone outside and brick on inner wall
Not stated, 2 bedrooms and a bedroom attic with kingspan insulation on ceiling. Small condensation problems in attic. Due to change felt to breathable felt and put in ridge vents.
Edit, Not stated, double glazed through out and plastic upvc doors
Not stated, house faces southwest getting the sun in the afternoon in room the thermostat is in
Not stated, 8 radiators, total 47442 Btus or 13904 watts
And finally, not stated, boiler is a Vaillant Ecotec Plus 837, 28kW, 7 years old.
Before anyone says its too big, I did ask for a 24kW (I have a deluge shower which needs, of course, a lot of hot water). Unfortunately, the plumber made a mistake and fitted me this larger one. He says he did not charge me extra.
Cant think of any more varaibles, size of windows, type of doors maybe.

"The objective of a properly commissioned central heating system is to reach the desired temp quickly and not to suffer low temps and long delays while the property slowly heats up!" Slightly disagree with this comment if I am allowed to be picky. If all someone wanted was to heat up quickly, just put it up to max and don't bother about the cost, but people are bothered about cost, so its a compromise for most people.
I agree its not great to wait 4.5 hours to reach target temperature.

Its just a test. In time I will run it how I like it, and I wont criticise anyone for running theirs differently.

northernsoul

I , after looking at boiler (theoretical) condensation graphs, would say to not get too bothered about the be all or nothing magical 55C return temp (from an efficiency point of view). The reason is as follows
At 71C return efficiency is (theoretically) about 86.1% (i know its unrealistic at 71C)
At 65C return efficiency is (theoretically) about 86.3%
At 60C return efficiency is (theoretically) about 86.7%
At 55C return efficiency is (theoretically) about 87% (at which temperature it statrs to condense)
At 49C return efficiency is (theoretically) about 89.8%
At 43C return efficiency is (theoretically) about 92%
At 37C return efficiency is (theoretically) about 94%
Please look at Boiler condensing graphs
What you may notice is for example :
The difference in efficiency between return temperature of 55C and 43C (5%), is much more than the difference between 55C and 65C (about 1%). So having a return temp above 55C does not become so disasterous for efficiency (at least according to the graphs - please search 'boiler condensation graphs).

northernsoul

To give an example of how much it can (should ? ) cost to run this house, next door, with 1 more person (should make little difference to heating a house), in a house exactly the same as mine, pay £70 a month for gas (do not know their tariff but obviously they have it hotter than me). This house costs £30 a month on a 3 year fixed isupply tarrif of 2.574/kW inc VAT + 15.5p per day standing charge.

*j*

Radiator temperature drop; let's have a look at it.

A choice of two scenarios:

One is a radiator with an inlet temp of 70 degrees C and an output temp of 50 degrees C. That means an average temp of 60 C across the whole rad.

Second is an inlet temp of 70C and an outlet temp of, say, 60C. That means an average temp of 65C across the whole rad.

Which rad will heat the room more quickly?

The one which has the higher overall temperature, isn't it?

A 65C object will heat a room more quickly than a similar 60C object.

shortcrust

This whole balancing radiators thing is new to me. Is suspect that water is just rushing through mine. However, my house is warm and my gas bills are relatively low so I think I'll just leave things alone! Admittedly not very MSE.:o

Zither

thorganby wrote: »

It sounds like you are another skinflint like Zither, I bet that he has never had his boiler on continuously for 4.5 hours ever!

Zither has previously posted "I barely use it on the mornings aside from weekends and maybe have it on for 1.5h in the evening"

Neither you or Zither have stated which boilers you have and with all of the variables e.g. property construction, glazing, drafts, insulation etc. the gas usage comparison figures are meaningless.

You have already stated that with a flow temp of only 55C degrees that it did not meet the target temp after 3 hours here and waiting 4.5 hours to raise the temp from 14 to 18 above, is unacceptable to me - you are not putting enough heat into the system with a flow temp of 55 degrees!

The objective of a properly commissioned central heating system is to reach the desired temp quickly and not to suffer low temps and long delays while the property slowly heats up!

There is money saving and there is stupidity!



Wrong - the temperature drop across each radiator should be about 20°F (12°C).

:eek:

Have to agree with northernsoul pal. Your post might have been well intended, but it just comes across as aggressive and unhelpful.

From my perspective unfortunately I don’t have the income to run my heating for as long as I would like to. If I could run it for several hours per day then I would - but I can’t so I’m just trying to work out how to use the boiler most effectively and looking for other people’s experiences.

Northernsoul has kindly taken the time to do some investigation and then take the time again to write up and post his results. Of course there are lots of variables to comparing gas usage - but I didn’t ask for a scientific paper on the subject - just different experiences and northernsoul shared, in my opinion, some excellent detailed observations on heating their own house. Thanks northernsoul!