Back Boiler Gas Usage Between Hot Water and Central Heating

[alton]

We currently have New World Stowaway back boiler fitted, which is attached to a Randall programmer that offers either hot water and heating on, off, on twice, only hot water, etc.

My question is (and please forgive what seems like a stupid question) does the boiler use less gas to heat just the hot water, than it would to heat both the hot water and the heating/radiators?

The question seems like a silly one, but I ask because surely if the boiler is on and burning and heating up, then it is using a certain amount of gas whether it is heating just the hot water or whether it is heating both the hot water and radiators. The flame underneath seems the same size whether it was heating both hot water and radiators, or just hot water.

Secondly, if the boiler is set to hot water only, but there is no hot water cylinderstat fitted, why would the boiler keep firing up and going off? It is doing so like the water is reaching a certain temperature and then cutting out the boiler, but surely if there is no cylinderstat fitted this would not apply? Or is there a thermostat within the boiler somewhere?

 

[mrgas]

There is a stat on the boiler which makes the flame come and go.
Whenever the boiler lights it should have the same size flame no matter if hot water/heating selected.
You might find that immediattly after lighting the flame is a bit smaller and then increases to a larger flame. This would be normal.
You can control your hot water temperature with the stat on the boiler.
Hope this is clear enough and helpful

 

[alton]

Yes the boiler does have the same size flame, regardless of whether it's just hot water or both heating and hot water. So, given that the size of the flame is the same, does that mean the same amount of gas is used regardless?

 

[Agile]

Unfortunately you are missing the point!

Running the boiler for heating and the hot water is provided at the same time.

To just heat your water the boiler cycles on/off all day and this is VERY inefficient. Probably less so than it would be to use the electric immersion heater during the cummer.

Thats why proper controls pump the heating coil to warm it quicker and then turn off the boiler when the cylinder is hot enough.

Tony

 

[macfudd]

My question is (and please forgive what seems like a stupid question) does the boiler use less gas to heat just the hot water, than it would to heat both the hot water and the heating/radiators?

It uses the same amount of gas regardless of whether you have the H/W or the C/H and H/W on.But,on most systems it will use less on H/W because it will shut off sooner due to the cylinder stat kicking in.You don`t have a cylinder stat,which is why it`s cycling on and off and using more gas.

If you can`t afford a modern boiler,which is way more efficient get a good plumber in to upgrade the H/W side.