Boiler firing up constantly during timed heating

Andy14690

My boiler is pretty old, its been checked and I was told that it works fine. However when the timed heating is on the boiler fires back up a lot, which I think is costing me a lot in gas?

Lord_Baltimore

Maybe the temp is set too high on the tank and the boiler is just doing its job of sustaining the (high) temperature?

Andy14690

It's has two dials on it on for heat numbered on to 9 and even with that turned to 5 still does it and the other is the hot water but even that it's turned down to about half as well

ajbell

Possibly a stuck motorised valve and hot water or radiators not getting to required temp.

molerat

How hot are the radiators getting ? Do you have TRVs on them ? The boiler fires to maintain the water temperature in the circuit, have those dials too high and it will fire too much. In the coldest periods my old boiler fires around 50% of the time but usually much less than that.

datlex

Andy14690 wrote: »

My boiler is pretty old, its been checked and I was told that it works fine. However when the timed heating is on the boiler fires back up a lot, which I think is costing me a lot in gas?

How accurately can you time when your boiler is on? Can you just set it to come on twice a day or can you specify for any given 15 minutes through out the day when you want it on or off? If you can specify every 15 minutes there is a little trick you can try. You simply have your heating on for 45 minutes out of every hour you want your home heated, then for the other 15 minutes you take advantage of the fact your radiators take time to cool and as such keep radiating heat. You shouldn't see or feel or reduction in temperature during those 15 minutes and your boiler will not be working during that time.

brianh

We used to have this problem with an old boiler. The engineer said it was "cycling" because of the amount of scale built up in the system.
Oddly I don't think our heating cost went up when it was in this situation.

Lord_Baltimore

Andy14690 wrote: »

It's has two dials on it on for heat numbered on to 9 and even with that turned to 5 still does it and the other is the hot water but even that it's turned down to about half as well

Presumably you have a combi boiler with no separate hot water cylinder? What are your room and radiator thermostats set at? Have the rads been bled recently and the system topped up?