I have an Ideal Isar HE24. It lights for 2 minutes once an hour to warm the heat exchanger and 'optimise delivery time for domestic hot water to taps or showers'…
The problem is that this is burning a small fortune in gas for a function I use once a day in the morning for a shower – all of my appliances heat their own water and I'm out of the house 14 hours a day 5 days a week.
Is the normal functionality for a combi boiler? (first one I've lived with) if not it could actually be worth replacing the boiler as this appears to be adding £400 per year to my energy bills.
Best Answer
On page 5 of the boiler manual you linked to, it states:
So, you need to define some DHW "off" periods (most of the time, evidently) and a few DHW "on" periods when you expect to use it.
Programming those is described on Page 8.
The default is to run DHW "on" from 06:30 to 00:00 (page 11)
Edit: I have observed that most generalizations don't hold worldwide, so I did not start out with this one - but certainly the vast majority of North American "heating and domestic hot water" (what you presumably mean by "combi" - not a term we use) boilers simply run to keep themselves hot all the time - there may be a summer/winter switch which changes some setpoints, but the basic operation is to sit there being warm/hot as a default. So yes, I'd consider that "normal" operation for such a boiler, if it hasn't got the time controls as described. And @RedGrittyBrick's suggestion is a good one, if a newer control panel is compatible with an older boiler. The other change from older boilers we commonly see here is a LOT more insulation - according to the manual linked, your hourly burn is somewhat more frequent that expected, at least on the newer model - unless your boiler is located in a particularly cold place, that may well mean the newer models are better insulated (and/or, if you have not already done so, you may want to add insulation to the water pipes.) You might ask the manufacturer if there is a way you can add more insulation to (at least some parts of) the boiler itself without causing a hazard.
We had a period (not entirely extinguished, but somewhat tempered by observed results now) when "instant" hot water heaters, where only a pilot light, or sometimes not even that, was kept burning until water is called for, were all the rage. "Observed results" include far less savings (.vs. a well-insulated tank-type hot water heater) than claimed, and relatively delicate heat exchangers and control systems which become expensive to maintain after a few years. Some folks still love the things - they still hold a certain attraction for me, but being off the natural gas grid, not much - bottled/tank-trucked gas (propane) is far a more expensive fuel source.