Central Heating Done (ish)

The remaining pipework for radiators was quickly finished this morning, including tidying up some of the existing piping in the hall (that used to be under the stairs). As I said yesterday, the radiators in the unplastered rooms have not been fitted but the pipework has been capped off so that the whole system could be pressure tested.

This just left the boiler change as the remaining task. This too is now done, though things did become a little hectic and fraught.

The biggest disappointment is that the flue could not be channeled using the same route as the old boiler. This used a vertical flue up through an old chimney void to a terminal on the roof. In the days when the original boiler was fitted a flue was for exhaust gas only, and comprised a flexible stainless steel liner that could be threaded through a confined space. A modern flue for a condensing boiler is "balanced" and has exhaust gas output through a central tube, with fresh air pulled in through a concentric pipe around the outside. The flue itself is constructed from combinations of rigid components, either straight lengths or 45 degree angles. If the old chimney had been straight we might have stood a chance, pre-assembling the straight lengths with their clamp bolts and dropping them down from above, with just an awkward operation to connect up the 45 degree bend at the bottom. However, aligning the new boiler with the old hole in the wall soon showed that the chimney above was not straight. You can see it in this photo, by comparing the new flue terminal (which goes horizontally straight out through the wall) with the old terminal tower on the roof :

The other option we had was to run the flue vertically upwards through the airing cupboard and out through the roof in a different place. This is something perhaps to consider for the future if we really don't get on with the wall terminal. One of the problems with the latter is that we have a table and chairs in the area adjacent to this wall and often use it for summer eating al-fresco (though we may use this area less now that we have our deck).

Jan was particularly disappointed in not being able to re-use the existing channel - she considers chopping a hole in the wall as wanton vandalism of the old part of her house.

You may have noticed in the above photo that the boiler was actually running. I was testing out the central heating which seems to work fine. There is a small leak from somewhere under the boiler, but not related to the CH circuit, so when they come back to fix up the wall and a few other finishing tasks I will ask them to attend to this too.

I was surprised by the amount of condensation (pluming) from the exhaust flue as I though these boilers were supposed to recover the heat. The exhaust was reasonably hot, though I could put my hand in front of it, so I suppose it is not excessive. I did note that with the central heating running the gas meter was running more slowly that it used to, so there is an early indication of the improved efficiency.

Of course, the fluid that does get condensed out of the exhaust has to drain off somewhere, so there is an additional plastic pipe leading through the wall that will eventually be connected (I assume) to the kitchen waste pipe :

This has to be done in plastic because the condensate may be slightly acidic and react with copper. Note that there is also a copper pipe lower down which is connected to the pressure relief valve, just in case something blows. Apparently our old boiler had one of these (I guess all pressurised systems do), but it was never connected up ! This new one still needs to be shortened and terminated with something.

At the moment the boiler electrics are simply connected to a 3 pin plug in a 13A socket. This is largely because the existing wiring for the old boiler proved to be a spaghetti mess with 6 cables leading to the master switch and timer :

The new boiler has the timer on-board, so most of this complexity will go, though apparently we still need to connect at least one room thermostat, despite all radiators having TRVs (Thermostatic radiator valves) - this is a building regulation.

The electrics here are a bit of a grey area - we have not asked the electrician to deal with this, but the plumbers won't touch it. I guess we will have to work out what all those wires are for ourselves.

So here is a view of the resplendent new boiler, nicely lined up with the old flue hole, now filled with expanding foam :

Incidentally, the foam was mine, as they "didn't have any on the van", as were the plasterboard fixings for one of the radiators and the 3 pin plug for the boiler. I even found, after they had left, that they had used my claw hammer and snapped it off at the head. Grrrrrrrrr.

One last view of the boiler shows an additional device that we needed. This is the red cylinder at the bottom which is a secondary expansion vessel. There is a primary on-board the boiler but because of the large number of radiators and long pipe runs, the water volume in our system is quite high, thus necessitating additional expansion capacity :

Curiously this vessel is not mounted in any way, it is just lying on the floor. I queried this and was told it was standard practice, though they can get me a bracket and mount it on the wall if I like. It seems a little susceptible to damage to me, so I think I will get them to move it when they come to fix the remaining radiators.

It was interesting to hear the comments on plastic piping from both of the fitters that have done most of the work on this job. They were unanaimous in that they prefer to fit it because of it's flexibility and ease of connection, but wouldn't have it in their own houses. They have known seals to come undone when inadvertently under tension, and have both been called out to jobs involving leaks as a result of rodents chewing through pipes. Also, even if the pipe used is "top quality barrier pipe" (there I go again Ian !!!), the fittings are not made of the same stuff and are therefore susceptible to air ingress. On the whole I think we were right to stick with copper - largely down to Jan being adamant that she should not have to compromise when spending a large amount of money.