Central Heating Boiler stays on for too long?

[David_W]

Last Summer British Gas installed a Glow-worm HE 330 Condensing Boiler to replace our ageing Potterton Netaheat boiler. The main reason we decided to upgrade was because we were told that we would save around 33% on our gas bill. However, since then I have calculated that the savings have only been around 15% even after taking into account the rise is gas prices and I'm trying to find out why. One of the things I have noticed is that the new boiler seems to stay on a lot longer than the old one. Over a 3 hour period it normally shuts down and starts up again only once (this is not triggered by the room thermostat as the temp hasn't got that high). Our old boiler used to cycle on and off at regular intervals. If the boiler is on for longer periods doesn't that result in more gas being consumed or am I missing something?. Would be grateful for any thoughts/advice. Thanks. David.

 

[chrishutt]

we were told that we would save around 33% on our gas bill

They lied. What else did you expect from a bunch of greedy corporate suits - the truth?

Look, standard efficiency boilers are around 80% efficient, condensing boilers around 90%. So the improvement in efficiency is about 12%. Of course other improvements to a CH system like fitting TRVs might bring further efficiencies, and in the most extreme situation imaginable (i.e. existing system very old boiler with no controls whatsoever and poor insulation) the total improvement might be in the order 30%, but this is of no relevance to normal situations.

 

[meldrew's_mate]

....If the boiler is on for longer periods doesn't that result in more gas being consumed or am I missing something?....

The new boiler modulates the burner so it doesn't burn gas at the same rate all the time; as the system water comes near to temperature the burner "wick" is automatically turned down. This promotes higher efficiency and less cycling....remember, every time it clicks the relays to start the ignition it wears out moving components on the PCB.

 

[Agile]

Your new boiler will be a lot more efficient than the old one.

I usually find that people with new efficient boilers keep it on for longer hours and sometimes to a higher temperature just because its cheaper to run. The effective saving is thus very much reduced.

Like my old big car. I use it rarely because its so thirsty. The small car I use it a lot because its economical! The petrol bills come to the same ( but I go twice as far in the small one! )

Tony