cheapest way to use the heating

[tonybhoy]

Cycling or hunting is the main cause of money wasted. If the gas valve is open for long periods-cold house-and off for long periods-toasty house then you will save money however if the gas valve is constantly on off on off then you are wasting about 20% of the volume of gas on each cycle cause you can't ignite 100% volume of gas so about a fifth of it when gas valve opens goes out the flue unburnt.

If that is happening 50 times an hour then that is an awful lot of unburnt gas simply wasted. Among the worst culprits for cycling are combi boilers with not roomstat and a house full of TRVs. And,an old cast iron boiler with 28MM gravity primaries and no cylinder stat which you can't have anyway ,only way to control the hot water temp is by turning down the boiler stat (more cycling) or fitting a Cytrol valve/Danfos tapstat on the return at the cylinder which is worse than useless.

 

[oilman]

T
Donkey simple question can you give me a link to any energy site that will confirm less gas is burnt under these conditions . I have heard both sides of this arguement for 25 years and never been shown proof on either side it is a case of it sounds like it makes sense so it must .

You have been told time and time again this is basic physics. The hotter it is, and the longer it is hot, the more fuel is required to do it. Why would you believe any internet site over any other?

 

[DursleyDonkey]

Thats who the kiddy was spacegas but its not everytime it all depends on various probables .
Which is much the same about what is the cheapest way to heat a house, There are far to many probables to give a proper answer and the biggest probable is every customer is different and use the house in different ways so what works for one does not work for others.
Donkey simple question can you give me a link to any energy site that will confirm less gas is burnt under these conditions . I have heard both sides of this arguement for 25 years and never been shown proof on either side it is a case of it sounds like it makes sense so it must .
Much the same if you asked a hundred people if a glass of hot water froze quicker than cold one 90% would prob think what a stupid question the cold one of course 5%would think it a trick question and say the hot and the other 5% like me and spacegas would be sad gits and know such trivia

Unless you live in a small glass of water in a freezer then the mpemba effect is irrelevant. A house is a large warm body in a current of air (the wind). Under those conditions, rate of cooling is propotional to excess temperature. On a still day it might be slightly more complex, but would still be a good approximation. Sit by your boiler with a stop watch all day to see how much gas it uses "ticking over".

 

[Watchmaker]

"cast iron boiler with 28MM gravity primaries and no cylinder stat which you can't have anyway ,"

I have this type of installation and was intending to fit a cylinder stat, ie, via a 12/230 volt relay which would switch the boiler control. This control would, of course, only be used when the central heating is not required and my reasoning is that I might get a finer control over the domestic hot water temperature and avoid excess boiler firing. In view of Tonybhoy's very informative and helpful posting, have I overlooked something? Any comment or advice would be appreciated.

 

[spacethegas]

"cast iron boiler with 28MM gravity primaries and no cylinder stat which you can't have anyway ,"

I have this type of installation and was intending to fit a cylinder stat, ie, via a 12/230 volt relay which would switch the boiler control. This control would, of course, only be used when the central heating is not required and my reasoning is that I might get a finer control over the domestic hot water temperature and avoid excess boiler firing. In view of Tonybhoy's very informative and helpful posting, have I overlooked something? Any comment or advice would be appreciated.

convert the system to fully pumped.

 

[Watchmaker]

Thanks for the comment and advice. Yes, I could fit a solenoid operated two way valve and allow the pump to operate in the primary circuit but, what would be the advantages of a fully pumped system? I have quite long primary pipework anyway (from a Baxi back boiler) but, the gravity system seems to work quite well, and the hot water rise, to the cylinder entry elbow is quite quick after the initial boiler start up. Would a pumped primary system be more economical, ie, boiler running for less time? Any advice or comment much appreciated.

 

[oilman]

IMO it would be worth putting a 2-port valve in the primary to stop convection when the tank is at temperature. I doubt a pump is worth putting on, as you will have to restrict the flow to the tank, so negating the benefit of the pump.

 

[spacethegas]

IMO it would be worth putting a 2-port valve in the primary to stop convection when the tank is at temperature. I doubt a pump is worth putting on, as you will have to restrict the flow to the tank, so negating the benefit of the pump.

but you would only be halting convection the b/stat would still have power.+ this is not a sufficient upgrade to comply with regs.

if converted to fully pumped in hw only once the c/stat was satisfied power to the b/stat would be removed.

 

[D_Hailsham]

Ok if that equation is right what freezes quicker a hot glass off water or a cold glass of water

Newtons Law of Cooling: the rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings, or environment.

i.e. Delta T(t) = Delta T(0) e^-rt

 

[D_Hailsham]

And,an old cast iron boiler with 28MM gravity primaries and no cylinder stat which you can't have anyway

I have this type of installation and was intending to fit a cylinder stat, ie, via a 12/230 volt relay which would switch the boiler control.

If you don't want to go fully pumped, the solution is Honeywell C-Plan

View media item 827 View media item 73

 

[oilman]

but you would only be halting convection the b/stat would still have power.

Wrong. The tank stat controls the 2-port valve. The 2-port valve controls boiler. Normal boiler interlock.

 

[spacethegas]

but you would only be halting convection the b/stat would still have power.

Wrong. The tank stat controls the 2-port valve. The 2-port valve controls boiler. Normal boiler interlock.

understand. aka semi-gravity control installation.

 

[Watchmaker]

Thanks for the most interesting comments, ideas, plans etc. A lot to consider but, one last query. Is a valve, manual or solenoid operated, allowed in a primary circuit? I had always thought that this was considered dangerous practice. Again,any comment appreciated.

 

[spacethegas]

http://www.heatingcontrols.org.uk/site/downloads/TACMAGuide.pdf

this should contain all you need to know.

 

[Watchmaker]

Many thanks for the link