Then we gradually learnt how much wood to put on (more than that... no, even more) and how to control the air flow using the ash flap, and we're now pretty good at getting the tank up to temperature. I should point out that using the ash flap to manage air flow is not the recommended means of controlling a stove, in fact some would say it's downright dangerous, but we keep a pretty close eye on it and haven't seen any sign of overheating. This may have something to do with the fact that this is a multifuel stove but we're only using wood on it. We went through the whole design process working with the nominal heat output for this stove then right at the end, as a passing remark, the plumber said,
Of course, if you're just using wood, you'll only get about half that.Now he tells us!
It's possible that our system is somewhat under-sized, but we got used to using it. Even after we'd learnt how much wood the thing eats, we still had to adjust our habits. We'd been used to lighting a fire at about 4pm, and it took quite a big adjustment to get used to lighting it in the morning. We had to remind ourselves that the specification of this system was to give us a couple of hours of heating in the mornings, so we'd be able to get dressed and breakfasted in some comfort before lighting the fire. As we got better at managing the fire, the time we needed to light it varied between about 9am and 4pm. We have two thermometers on the tank, one at the top and one in the middle, so we have a pretty good idea of how much stored heat we have at any one time. One of these days we'll get round to putting the doors back on the airing cupboard and then it won't be quite so convenient to check!
The system consists of three circuits. The first, stove to tank, is as simple as can be; stove back boiler - pipe - tank - pipe back to boiler. Hot water rises, creating a current round the circuit, taking heat from the stove to the top of the tank, and cooler water from the bottom of the tank back to the stove. Something we hadn't anticipated, but which is obvious when you think about it, is that this circuit flows in reverse when the tank is hot and the stove is cold. This isn't a big problem, as it just takes some heat back to the sitting room, but it reduces our level of control a little.
The hot water circuit is only slightly more complicated. There is a coil of pipe immersed in the middle of the tank through which mains water flows. When the tank is hot, the flowing mains water absorbs some of that heat and emerges hotter than it was when it went in. The slight complication is the thermostatic valve that mixes in a little cold water if it's too hot when it comes out. Actually, I have my doubts about how thermostatic that really is - hot water temperature seems to be heavily dependent on tank temperature. Apart from that, I love the simplicity of this system. There's no waiting a few seconds for a valve to notice that you've switched the tap on before it starts to deliver hot water, nor even a valve to wear out, like there is with combi boilers.
In contrast, the underfloor heating is very high-tech. Each room has a separate loop of heating pipe (apart from loo, bathroom and hall, which are all on one loop) and each loop is controlled by its own electric actuator valve. These sit in a row in the airing cupboard so we can see the little buttons pop up on the tops when they're open (you can tell why we haven't put the doors back on, can't you? It's not just because I've lost the screws.) These valves are controlled by a little computer, which receives information from these:
Each room has one of these fancy wireless, programmable thermostats. Learning how to use these was a challenge in itself. I felt sorry for the guys plumbing the system in, because they had to set it all up but they'd never seen this system before. They also felt they had to explain to the customer how to use it but I let them off that bit as the customer (me) had, after all, chosen the system in the first place!
We can choose between manual mode, in which we just set the desired temperature, and program mode, which toggles between
nighttimedesired temperatures at the programmed times (variable by day of the week, if you like). The fact that there is no
offin the programme confused us at first, until we realised that
offis replaced by
comes on only when it's very cold, so you set the
offtemperature to the minimum you want the house to get down to.
We thought we had a problem with one of these when the bedroom heating started coming on at unexpected times. Eventually we realised that this was the
auto onfunction, which starts the heating before the programmed time, so that the room gets up to temperature by the time you've asked it to come on. We soon turned off that function because the rooms were never getting up to temperature. We also pretty quickly changed the night/day temperatures from the pre-programmed 18/21 deg C. We were quite surprised by how low the temperature is that we find comfortable in the house: Between 14 and 16 deg C. I've heard that underfloor heating feels warmer at any given temperature, so that may be it.
So there we were, getting used to the fancy-pants electronic controls as well as coming to terms with just how much wood a wood burning stove will eat, and generally keeping quite comfortable, when the weather changed. We've been lucky to have a very mild winter so far, but the last few days have been very cold. We'd get the house up to a toasty 16 or 17 deg C and the tank full of hot water before going to bed, then by morning it's dropped to 11 or 12 and the tank has used up all its heat. This morning I started the fire at 7am and by about 9 it looked like this:
I'd built the fire up nicely, though it was still struggling to keep up with the demands of the heating. Shortly after this the temperature in the tank suddenly shot up. I'm guessing this was the effect of the outside temperature going up. This house is obviously far too affected by the temperature outside: We need better insulation.
And another thing... you may notice that those stove windows are filthy. This is an old stove and it does not have Clearview/Airwash/insert-trademark-of-your-choice technology, so the windows need cleaning frequently - every other day, ideally. This doesn't happen because by the time I remember that they need cleaning I want to get the fire lit, and cleaning them when it's hot is not a good idea. I have learnt about an excellent cleaning paste, though: Vinegar and ash. Do try to avoid contaminating your best spirit vinegar with ash, though, as I did. D'oh!
Nearly forgot to mention: Warm floors are looooovely!