A heating and an Aga question

[Hzatph]

John,

You must have been reading my mind - A large cylinder is exactly what I have in mind so there is lashings of hot water and the Aga can reheat take all night to reheat it if it needs to. We have a normal size cylinder at the moment and if we a large amount of water it causes the Aga temperature to plummet which is annoying at the same time as one is trying to cook.

With regard to heat loss, I do have the Myson program but I have not run it. We do not have the cast iron pipes you encountered, but one of the boilers runs 18 radiators and struggles, plus the response time is slow. The other with only nine and a hot water tank (not all our water is from the Aga!) is more responsive. I am advised that they may install a smaller jet so the

240,000 BTU unit is throttled back a little - for example the Worcester Danesmoor Utility 50/70 can be configured from 170-240,000 BTU. I would also like to create some zones and the heating is configured so some can be fairly easy way to do

Thanks for your advice - it is much appreciated.

[Christian McArdle]

The requirement is for a "boiler interlock". This means that the boiler should entirely shut down when there is no call for heat. It isn't allowed to keep the circulating water hot. This is what would happen if you have TRVs on every rad and no signal to tell the boiler not to bother.

In 95% of cases, the requirement means that systems are designed to have one room without a TRV, with a room thermostat in this room. The room thermostat turns off the boiler completely, which is much more energy efficient. However, there is another solution suggested in the regs, which is to have a flow switch on the circuit. This detects when the TRVs are largely closed and turns the boiler off.

The regs are not prescriptive in any sense. Provided your solution prevents any gas being burnt at all when the rooms are up to temperature, then it would be acceptable. The room stat and flow switch solutions are only suggestions as to how to achieve this.

Speak to Aga. It may be that a reliable gravity circulation is required for safety reasons. This is commonly the case with solid fuel appliances. On gas/oil, secondary safety systems (i.e. manual reset overheat protection) may allow fully pumped operation. However, I'm not an expert on Agas, so don't know what systems they have installed.

Christian.

[Hzatph]

Thank you - that is great advice. In our case a room thermostat solution would not work as it would be a completely unreliable method of determining whether there would be a need for heat. Low flow does make sense - presumably it switches off the boiler but not the pump otherwise there is no means to generate a flow and switch heat back on when the TRVs open again.

[Christian McArdle]

Yes. However there are some possibilities to avoid the wastage of too much pump energy. Firstly, run the pump on a clock. Secondly, use a pump like the Grundfos Alpha, which reduces flow automatically and avoids noise and excessive electricity consumption. Thirdly, a device that pulses the pump every ten minutes or so could be good, although I haven't seen an out of the box solution for this.

Christian.