thelonious

Website Name: Midsummer Energy Website URL: http://www.midsummerenergy.co.uk Website Description: Solar panels, wind turbines, regulators, batteries... tons of stuff for the eco friendly narrowboater! Any other comments: Check out the PVL peel and stick solar panels, perfect for narrowboat roofs.

Hi, can anyone help with a Webasto problem? I have just installed a second-hand thermotop C. On the first couple of tries it went through the start up process but didn't fire, I think the diesel was not getting through. On the third try it worked perfectly. A little later I fired it up again but after 15 minutes it cut out again, and now it is totally dead. When you turn it on nothing at all happens, neither pump nor the fan make a noise and I get an "F" on the timer screen after about one minute. Any ideas? I don't know where to start to be honest. But I do have a multimeter and know how to use it! Thanks, Theo

Hi everyone, I'm halfway through my second fit out (www.offwidth.co.uk/easytiger) and really need to get on top of all this RCD bureaucracy. The boat was a brand new shell, and the builder supplied an "Annex A" RCD certificate, which both the council and the EA seemed to like. I have also got an HIN number. The engine and windows came with their own compliance certificates. That is as far as I got. I have been reading up on the official sites but getting very confused. It seems we have to decide which written standards we should follow, then self-certify that we have followed them? Sounds a bit bonkers to me. And do I need to get it surveyed at the end or not? I would really really appreciate it if someone who has gone through this process already would be kind enough to give me a copy of their finished documentation. Thanks for any help. Jeremy

There are obviously a lot of plus points to this system, not least saving on incredibly expensive pump-out fees. But what are you supposed to do with all the pee? My mooring is nowhere near any toilets, and it would need doing at least once a week. Tip it in the river? Is this legal, is it environmentally acceptable? If it is, then a separate urinal could be the answer (for men anyway!)... Theo

Interesting, I hadn't heard about that. It's all explained here: Peukert's equation Basically, the capacity of a battery depends on how fast you discharge it. Apparently, batteries are rated at a '20 hour rate', meaning if you discharge them linearly over 20 hours you get what it says on the tin eg. 110 Ah. Faster, and you get less out. At high currents, this loss becomes quite high. Interestingly, if you run them as less than the 20 hour rate (for a 110Ah battery this is 5.5A), you can actually get more than the rated capacity. The calculator provided on the website above indicates that a 220Ah battery bank discharged at 160A will last about 0.6 hours (36 mins). If you are only taking half, then you end up with just 18 minutes, as you correctly pointed out. Effectively you only have 95Ah capacity at this current. Increasing the battery bank to 440Ah gives you about 240Ah to play with. Not as bad, but still a big loss. Steve would need a lot of batteries to get 2kW with any kind of efficiency. Theo

Hi Pete, A convection circuit certainly has its attractions - simplicity and no electricity required. But there are problems with having a calorifier on the same circuit. It might drain all the heat out of the cylinder when the stove is cold. And if the cylinder is hot, it might not circulate at all. I don't think it would have the 'go' to push open an non return valve either. Plus you need massive pipes, which are hard to conceal, they seem tricky to set up, and the length of the boat (60') might be a problem. I'm not sure whether you could set up a secondary heat source to heat the rads. This is becoming one of those open-source design projects I keep hearing about! Theo

Chris - I think you've found the achillies heel. If the transfer of heat between the coils and the hot water is not efficient, it's not going to work at all. 1kw is not enough to keep the diesel heater even turned on, and the efficiency will drop even more as the water in the cylinder gets hotter. Looks like the only sensible approach is to put the cylinder and the rads in series in order to make best use of the heat source.Here is another design: Heating Design 2 This is simpler, in that there is only one pump, one circuit and a single coil cylinder.The engine and the diesel heater will heat the radiators before the cylinder, and the back boiler will do the opposite. This is all fine. However, there's no way to prevent the back boiler getting heated by the engine or diesel heater. It's not safe to fit a cut-off valve in case someone lights the fire with the valve shut - big bang or at least lots of steam! On the plus side this will act as the required heat sink, but in the height of summer when I just want hot water it will be a pain. There is the possibility of fitting a solar heating circuit to the second coil for summer use, which could be done at a later date. Thanks for all the great feedback. Theo I was thinking of fitting a thermostatic mixer where the hot water leaves the cylinder to regulate the maximum temperature of the hot water to the taps down to 40 or so. I just left it off the drawing because it was getting messy. This does not solve the mineral issue though. Very hard water around here too. Theo

Yes - good point! The cylinder would need to be small enough to heat up fast, but still big enough for a shower. From experience, showers seem to use 25-30 litres a go. Though at about 40C, quite a lot would be coming from the cold supply. For the sake of argument, say I had a 30 litre cylinder. To get it from stone cold (~10C) to hot enough for the rads (~60C) with a 4kW heater would take (60-10)*30*4200 / 4000 = 1575 seconds, or nearly half an hour. Damn. Though as I live aboard, it would rarely be starting from stone cold. Hmmm, needs more thought. Just to liven things up, has anyone thought about or tried evacuated-tube solar water heating? Eco-nomical for example do them amazingly cheaply. I've done several installations on houses, but never seen one on a boat before!

I've got a pretty good idea of the way narrowboat heating systems are normally set up, but I haven't seen any that can heat either just the water (summer) or the water and the radiators (winter) from any one of their heat sources. This would mean no gas boiler needed for hot water - that's what I'm aiming at. If it won't work that's fine, I can go to a more tried and tested set up, but there's no harm in trying. Theo

Thanks for your helpful replies everyone, I like this forum! Hi Chris, If the manual heating switch is turned off, then yes, the diesel heater will quickly heat the cylinder then shut down. This is intentional and allows you to get hot water quickly in the summer when you fancy a shower. But if the heating switch is on, once the cylinder gets hot the the circulation pump on the rad circuit will kick in and start to take heat away from the cylinder to the radiators. Hopefully, it will do this fast enough to keep the diesel boiler alight. Most diesel heaters seem to have an automatic high and low setting, but I have to confess I'm not sure if they will switch off entirely once a certain temperature is reached. Anyone know? I haven't chosen a heater yet, but the Webasco ones seem significantly cheaper than the Eberspacers. Anyone know if they are equally good? Theo Yes that's true, the pump will have to run whenever the stove is hot enough to prevent boiling. There are some nice 'magnetic' 12V circulation pumps out there that consume as little as 11W which should be fine. I'm planning to have around 200W of solar panels connected to the battery bank. As far as I know, a pump is the only option for back boilers if you are not using a 'gravity' circuit - probably not feasible due to the length required. And I don't like the large amount of high-flow pipework that would need to be on show. I take your point about complexity though, it may well be overcomplicated. But I do find that the solid fuel burner usually produces far more heat than you actually need, so connecting it to the hot water system is very attractive. In an insulated cylinder, the water should stay hot overnight for the morning shower. Yes, indeed it will! But I think this is OK - the back boiler should just function as another radiator on the system. It looks like a lack of heat capacity in the engine/diesel boiler circuit might be a problem. It doesn't matter for the engine, as the skin tank will take the excess heat. But the diesel heater might be unhappy just with the cylinder coil when in 'summer' mode (see above). Theo Keep them coming!

Hi, Can I pick the brains of the boat building folks here? I've been trying to decide the best way to set up the heating & hot water systems for my new boat. The tricky bit is trying to effectively connect three heat sources (engine, diesel heater and back boiler) so they heat both the hot water and the radiators. The solution I have come up with uses a well-insulated twin-coil cylinder both as a source of hot water and as a heat exchanger. Something like the 'thermal store' approach you see with solar set-ups. You can see my proposed set up here: Proposed heating setup (PDF) It LOOKS like a quite elegant solution, but it may have a major flaw! A virtual pint to anyone who can spot one. One potential problem that I have already noticed is that running the engine and the stove at the same time could actually heat up the water exiting the engine, putting more strain on the skin tank. But only if the water in the cylinder is hotter than the water leaving the engine, which is unlikely I think. Thanks, Theo

You can discharge lead acid batteries very quickly without harm, this is one of the reasons they are used for starting engines. In this application, you might be able to flatten one completely in only a minute or two. The important thing is not to let them get too flat, and not to leave them flat for long. The voltage should not be allowed to go below 12v and preferably 12.2V, though you can only get an accurate reading after leaving them to stabilise for a while. Your 2kW drain at 12V gives a current of 167 amps. Say you had two fully charged 110Ah batteries that would be 80 amps each which is fine (assuming your wires are HUGE) but you couldn't do it for long. Half the batteries' capacity would be gone in about 45 minutes. If you use more than half, the batteries will start getting very flat and may eventually suffer damage, particularly if it is not quickly recharged. If I've got any of that wrong, I'm sure we'll soon hear! Theo