nicknorman

Less than that I think. The double blanket takes about 140w on max when it is heating up, but over night it has to be shut well down otherwise you get hot and sweaty. Maybe 50w max, probably more like 30w. We do have a memory foam mattress which is very “insulative” so virtually no heat escapes downwards.

I would add to the bedding list an “all night” type electric blanket. The bedroom in our boat is at the back and a long way from the stove and we didn’t really want multiple duvets for different seasons. So we have a fairly light duvet and an “all night” thermostatically controlled electric under blanket that keeps us cosy all night and the Li batteries shrug off the power consumption.

No not really. With twin wall the air in the flue will be hotter, but slower moving. Because it is hotter it is lighter and creates more suction, so the air vent on the stove has to be more closed. Because lots of cold air isn’t being sucked into the stove, much of which would not actually be used for combustion, it burns hotter. So the stove body will be hotter, the flue outside surface cooler. Bottom line is that a twin wall flue makes the stove more efficient. This means that for a given amount of fuel, more heat goes into the room and less heat is lost up the flue. You do make an interesting point about ventilation but having thought about it, most boats have the stove at the front and there is normally fixed ventilation at the front eg in the front door. So without twin wall, there will be more air flow in the boat but this is likely to follow the shortest path ie from the nearest fixed ventilation to the stove inlet, so I doubt it would have much effect on general dampness in the boat.

Yes it will be hotter. Which gives a much better combustion. This is why stove thermometers have an optimum operating temperature range - if the stove is too cool the burn is inefficient. If a slightly hotter stove causes the boat to go on fire, it wasn't very well installed! If you are going to install a new stove with a twin wall flue it would be sensible to install it properly so it doesnt set fire to the boat!

The flue is warmer, yes. The flue is warmer because there is a fast stream of hot gasses going up the chimney and heating the world. Unless there is a fast flow of hot gasses going up the chimney, the gasses cool too quickly, there is no draw and the fire goes out. With twin wall, the gasses can go up much more slowly whilst retaining the draw, and consequently less heat is sent up the chimney and more goes into the cabin. I know it seems somewhat counter-productive and I didn't really believe it until we replace the stove at the gliding club with a similar sized one - but with a twin wall flue. The difference was very noticable. Less wood used and more heat into the room.

So in summary does any bit of Victron kit have a high current relay or FET switch that could isolate the batteries and yet allow say 500A bidirectional current? I ask because currently I am using a TE Connectivity Tyco bistable relay rated at 190A as the battery emergency shut off. Even though the 190A is at 85C and the small print says 260A at 23C, I am not clear if this is ambient temperature or its own temperature. It gets quite hot when pushing a lot of charge current in so I am reluctant to use the full 200A or so charge capability for long periods as I don't want it to melt and disconnect the alternator in full flow!😱 Edit: Yes I can see the Lynx BMS does have a contacter but it uses over 200mA continuously (as opposed to my bistable relay that uses zero unless it is switching) and it costs three quarters of a grand!

No, you don't understand the issues.

It is not techno babble, it is correct. However the issue of less air moving through the boat is an interesting one I hadn't previously considered. In that case the stove is undersized for the space it is heating. But in most narrowboats the stove is more than capable and it spends most of its time shut right down, building up gunge on the inside of the flue (which at least provides some insulation!)

Im confused by this. As far as I can tell, the Victron Lynx shunt doesn't have any sort of relay or switch to isolate the supply. It just has a fuse.

It rather depends on which "concentrate" you buy. I was looking at this recently for another engine and noticed that some "concentrate" antifreezes weren't that concentrated, to be used neat for very cold temperatures or 2:1 (concentrate to water) for not very cold temperatures! Traditionally I would suggest 33% antifreeze to 66% water. Down to about -15C should be fine because with the boat in the water and the engine area below the water line, it never gets exceptionally cold, just a few degrees below freezing. The general rule was not more than 50% concentrate, as the ability to carry away heat is reduced with excessively strong mixtures. But that was when "concentrate" was concentrated!

Yes. Telemachus is just on my avatar picture. Not to worry!

It might be worth considering why it has failed. The engine coolant should of course have antifreeze in it, and the antifreeze function doesn’t degrade over time (unless you dilute it) but the antifreeze also contains a corrosion inhibitor which does degrade and really should be changed every couple of years. When was yours last changed? If not for a long time, probably the heat exchanger has corroded through from the coolant side and it would be advisable to completely change the coolant (including what is in the skin tank) when you replace the heat exchanger.

Well to be accurate, I was nicknorman here long before I was Telemachus over there!

Yes there is normally a heat exchanger between gearbox oil and engine coolant. It has sprung a leak by the sounds of it. Normally it is a tube shaped thing, trace the hydraulic hoses coming from the gearbox, they will terminate in the heat exchanger. It probably looks something like this (this is from a Beta 43)

We are just a holiday boat but we have about 7kWh of Li batteries. No solar though. We are fairly profligate with the power, electric kettle and air fryer (we hardly ever use the gas oven these days) but we have a gas hob. We sometimes run the washing machine from the batteries and even the immersion heater😱. We have a decent alternator and travelpower which means we can charge at about 200A(12v system). We use around 200-250Ah a day (say 2.5 to 3.25 kWh) Lithium batteries are fantastic, just a bucket full of electricity that you can pour electricity in and out of. Unlike lead acid which is sulky, grumpy and resistant to doing anything much! But a proper Li battery installation is expensive and technically complex to get right. With a roof full of solar you will have enough power in the summer. You don’t need heating in the summer! You do need heating in the winter but the solar will be pants, so you will definitely want a solid fuel or diesel stove (gas heating is too expensive).

Regarding 3, it is better to have the expansion vessel on the inlet to the calorifier just after the NRV. If it is at the outlet, then it fills with water when the calorifier is heating. Then several hours later it has cooled down. When you turn on the tap, this cold water comes out of the hot tap and you have to run off more water to get it to come hot, than if you had the vessel at the calorifier input. But in neither case is there a legionella risk because water is flowing in and out of the expansion vessel routinely and the expansion vessel spends most of its time empty.

Several people did, but the questioner decided to ignore them.

Jump leads yes, if you can find someone to jump from . Solar probably not because I don't think the solar controller will do anything unless it is connected to a battery showing enough volts to operate the controller. Maybe depends on the specifics of the controller. And in winter...

Jolly good. Now kindly disappear off back under your bridge. You can't say anything useful until an incoherent question is made more coherent. If your view is that no-one should post anything except a useful answer, then 90% of questions will go unanswered. It is a bit of a silly attitude.

Well thank you for admitting you are a troublemaker. But of course we already knew that! Why not put everyone on ignore except LadyG and they you would be happy. Oh sorry, I forgot that being happy is not something you seek.

Who is Telemachus? (on this forum!)

A starter motor rating is just a figure on paper. And kw rating is not relevant, it is the current that is relevant. The actual current taken will vary massively with the load and the speed and the battery voltage. I think the peak current for our engine is around 450A but probably the first 100 milliseconds is much higher than that. If a house Li battery bank can cope with that, then fine. But you still have a single point failure (accidentally letting the battery go flat) which renders the entire boat dead.

(Sorry but the pedant in me forces me to mention that kW is not a measure of energy!) 99.9% of boats have separate starter and leisure batteries. This is to ensure that the engine can be started if the leisure batteries are flat. Otherwise you are totally stuck! With Li I would agree that it is much less likely that this would happen, since a suitably rated Li battery at say 20% SoC could still start the engine. But accidentally leaving something on when away from the boat and totally flattening the battery is a foreseeable event. The main concern would be whether the Li battery system could supply the necessary surge current. The cells themselves almost certainly could. However the battery requires a BMS and some sort of switch that the BMS can open to isolate the batteries. It is this switch, which might be FETs or a contactor, whose rating might be less than the peak current of the starter on a cold morning. And set against that, an LA starter battery is totally suitable for the task at hand and is the much easier and more reliable solution.

HaHa I guess the irony is totally lost on you! Anyway, I think you have made a typo above. I am not trying to show them how superior THEIR canal knowledge is! But seriously, people are coming on here and asking for other people's time to answer technical questions "by remote control" which is quite difficult. It is reasonable to expect an attempt to ask the question in a way that it can be answered and if they don't do that and are asked for additional information, it is reasonable to expect that to be forthcoming to the best of their abilities and for them not to get sulky when it is asked. I think you will be struggling to find any occasion when I have dissed a questioner before they get all sulky and/or have declined to offer any further information beyond an initial and totaly vague, unanswerable question. If you are going to reinforce the behaviour of these sorts of posters, you are not doing them a favour because they are never going to get their questions answered - if indeed they actually do want their questions answered, which I sometimes doubt. I don't need to read them - I wrote them! Duh!

You will notice that I didn't engage with him at first. I realised the question was carelessly written and unanswerable, so bad in fact that I suspected it was a wind up. It was only when he came back all sulky and entitled that I got pissed off with him.