Most efficient way to fire oil boiler

tippgaafan

Just wondering what your opinions were on the different zoning options etc. for central heating. Which of the following is more efficient?
A) Fire the boiler when a stat calls for heat via the contacts on a zone valve. Keep the boiler cycling at its own thermostat setting and just open a zone valve when stat calls for heat.
All opinions appreciated..

sydthebeat

not an expert... but a boiler interlock is usually deemed best practise..

this is where the room thermostat calls for the boiler to fire....

cycling from its own stat is inefficient, as the boiler is firing when the room may not need it...

tippgaafan

By firing the boiler when there is a demand for heat, does that not mean that cold water is circulated through the rads (cooling them) until the boiler has brought the circulating water up to temp !

sydthebeat

tippgaafan wrote: »

By firing the boiler when there is a demand for heat, does that not mean that cold water is circulated through the rads (cooling them) until the boiler has brought the circulating water up to temp !

no
the water in the pipes heat the room to a certain temp. When this temp drops below the prescribed point it means that the heat has been drained from the water at the rad point..... generally the water between the rad and the boiler is incremently hotter... therefore when the boiler kicks back in and pumps again, the new water entering the rad is always hotter than the water it replaces.....

smashey

Moved to DIY.

JamesM

tippgaafan wrote: »

By firing the boiler when there is a demand for heat, does that not mean that cold water is circulated through the rads (cooling them) until the boiler has brought the circulating water up to temp !

Yes

Efficient in what way ? The less time the boiler is on, the less oil you will use - that's efficient.
But if you want a steady constant comfortable temperature in your living area, the boiler must be kept up to temperature with its own stat.

Unless the boiler is kept up to temperature, there will be quite a delay after the room thermostat calls for heat, before there is any rise in room temperature. So there will be quite a fluctuation of temperature in the room - the temp has to drop a few degrees before the stat calls for heat, and then there is a further delay while the boiler builds up the temp again.

The timer should be set to be on when it is anticipated that heat will be needed. This will bring the boiler up to temp on its own stat. Then, when the room stat calls for heat, there will be hot water available to the rads.

I'm sure that you could get modern controllers that will anticipate the drop in room temperature and have the boiler up to temp before the room stat calls for heat. You could have one room stat set 1 degree above the other - the 1st one would bring on the boiler and the second would then click in and open the valve when the room temp dropped below the required temp
Jim.

ennisjim

Not sure if this is of any help, but my system has a buffer tank which the heating engineer who designed the system tells me reduces cycling of the burner. There is also a delay switch which prevents the burner coming on for 30 minutes. He explained the reason for this some time ago but I've forgotten. May have been something to do with avoid the burner coming on the moment a stat calls for heat. I suppose in some cases the 30 minute delay might mean that burner doesn't come on at all if the room gets the extra degree or two it needs during the delay interval - but I'm just guessing.

We have underfloor heating by the way. In addition to oil burner the buffer tank is heated from solid fuel backboiler and solar (which heats DHW cylinder first and then switches to heat buffer tank - not much use in winter though :-).

Anyway, as I said - may be of no use...

ennisjim

I guess the other reason for the buffer tank might be that there is hot water available the instant a stat calls for heat. If the buffer tank is very well insulated it could be hot from day before for example.

Just guessing