"That's from your back bedroom radiator," said the engineer on Tuesday 15 September, holding up a jam jar of what looked like cold black coffee. I had been asked to hold the torch. I held the torch.
It was the second service on the boiler, £90, done by the same Gas Safe engineer Maureen uses, who has now seen the inside of our kitchen cupboard more often than I have. This time he also fitted a magnetic filter on the return pipe, £165. It's a white plastic cylinder with a magnet inside, and its job is to catch the black sludge that comes off the inside of old radiators and pipes. He had recommended one at the first service on 6 March last year. I said "not yet". I went on saying it for eighteen months, and that is the thing I'd change.
The service itself took about an hour and a half. He ran a gadget on the flue to check what was coming out of it, printed the numbers and showed me the slip, and I nodded as if I understood it. The word he used was "healthy". He also cleaned the condensate pipe, which was fine, and said the filter will need rinsing at each annual service, a job that takes him ten minutes and costs us nothing extra.
While he was in there he pressed the test button on the carbon monoxide alarm, the £22 one, and it screamed, as it should. He topped up the inhibitor, put the pressure back to 1.2 bar and asked whether we wanted to try the flow temperature at 50°C. We're staying at 55°C. Not this winter. The £255 was covered by the boiler pot (£135) and the house fund (£120).
The plan, written down
I bled the seven radiators on Saturday 12 September, top to bottom, and what follows is what we're doing from the middle of October. It's printed on one sheet of A4 and stuck inside the meter cupboard door next to Dennis's pencil notes, which seems the right neighbourhood.
- Office days (Monday, Tuesday, Thursday): heating on from 6.30 to 8am at 19°C, off while we're out, back on from 5.30pm with the thermostat in the front room at 18.5°C until we go up.
- Working-from-home days (Wednesday, Friday): only the box room radiator is open and the others are on 1 or 2, from 7.45am to 4pm with the thermostat at 16°C. The heated throw and the flask do the rest.
- The back bedroom goes on the frost setting unless somebody is staying, in which case it gets turned up the day before.
- The flow temperature stays at 55°C and the direct debit stays at £108.
The room we've stopped heating is the back bedroom, which feels like a confession. It's the one with the cold gable wall, but since May it has 6 cm of insulated board on that wall and the corner reads about 17°C on a cold morning, so the job now is to stop it freezing, not to warm it up. We will find out in January whether that's true, and I'll say so either way.
The numbers behind it
Last winter, from October to February, we used 6,850 kWh of gas. Over our first full year it was 10,420, against Dennis's estimate of 14,200 on the handover paperwork. This winter's soft target is 6,200 kWh, about 10% less. At 6p to 7p a kWh that's worth roughly £40, which is a poor return on a spreadsheet tab, but the target isn't there to save £40. It's there to tell me whether the filter, the wall and the schedule did anything.
One cold January makes liars of us all. Last winter's figure also had three days of broken heating in December in it, so this year's target is slightly harder than it looks. The smart meter will show me a gas reading every morning, and I have promised Matt I will not report it at breakfast.
Brew count: 2.
