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Thanks for your replies. It just makes me uncomfortable the idea of taking the batteries right down to 12V. I remember someone telling me if you have your batteries below 12.4V then you're damaging them. The switch will disconnect at 12 then reconnect at 13. I'm getting the impression though that disconnecting at 12 under load is not nearly as bad as the batteries sitting at 12V SoC? If I used the switch like this in reality it wouldn't switch the fridge off much I don't think, i've never seen it go down to 12V while I've been checking it with the fridge on. The batteries are 3 x 110ah. I'd rather lose some food/milk than damage the battery bank of course..

Hi, I've bought a Red Flash LVD10 low voltage disconnect to install on my fridge wiring to safeguard the batteries from being damaged. I run the whole boat on a 245W solar panel. It was sold as 'programmable' and I foolishly took this to mean I could program whatever disconnect voltage I wanted, which I was going to make 12.6V to stay on the safe side of protecting my batteries. Now unfortunately I find that of the preset programs this switch will disconnect at the lowest is 12V. I've phoned DMS technologies who sell the unit and they insist their programs will protect 12V batteries and I'm now wondering if my caution with my battery voltage is naive and over the top. Does anyone out there have views on this? I would expect the fridge to take the battery voltage below my low voltage setting at night, and then reconnect in daylight when the solar panel starts feeding it 13V or so. I could buy another switch I've seen which has a 12.5V disconnect setting, but I wonder whether I should just use the one I've got

Great answers thanks. I have a pretty good voltmeter which of course measures amps, if I simply put this across my wires while a load is on will I get an accurate reading of the current ? And do you have an idea what the startup current is to your fridge?

Hi, I'm seeking views on how much solar I need to run my 12v fridge. It's not a modern one, it's an oldish Lec. I plan to switch it on in daytime only, and it'll be used prob April - September only. I know there are many factors involved but I am looking for views on how many W of solar will do to run a fridge, personal experiences would be great, finger in the air job is fine but please try and put a figure on it. Many thanks

Hi, I've been looking at this calorifier for sale on Ebay: http://www.ebay.co.uk/itm/321670257974?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT The seller doesn't know anything about calorifiers, and can't tell me if it's single or twin coil. I want a twin coil. It does look to me like it has a second coil on the opposite side capped off with red caps, I can't think what else this would be, but I'm not feeling sure enough to bid. The cylinder is made by the Stone Boat Company in Newcastle and they do do a 50 ltr twin coil cylinder, as well as a 50 ltr single.So any opinions from those with more experience of calorifiers than I appreciated, do you think this is a twin coil cylinder? Thanks

Thanks for the info, yes the cylinder is very domed almost a full hemisphere at top and bottom. So with an Essex boss I basically need to cut the right size hole and go for it? Is this safe when you've got an unvented cylinder which will have a back boiler going into it as well?

On further research I think these bosses may be for 12v immersion heaters - hard to find by the looks of it but they seem to have been smaller than 240 elements, I've found mention of one that fits 3/4 BSP but no longer available

Thanks, I will post a picture of it if I can work out how, can anyone tell me how to upload a picture here I can't see an option for it anywhere

Hi I need a 240 immersion heater for my hot water whilst on shoreline. The Calorifier on my boat is a double coil, which has previously just been hooked up to the engine, and it appears to also have bosses for an immersion heater in the top and at the bottom. However measuring the threads on the caps of these bosses they are about 26mm which the internet tells me means they're 3/4"BSP. Every immersion element I've seen is bigger than this so my question is does anyone know of an immersion element going on such a small connection? Or are these connections for something else? Thanks for reading

Thanks Pete yes they are male 28mm BSP out of the boiler, was just wondering about the malleable iron fittings as they have quite a few swept bends and a kind of swept T as well which would be good for assisting the thermosyphon. I can do it all with compression fittings and a pipe bender but would have to use a regular T, but I'm probably over doing it worrying about that. The T could be arranged so the Calorifier takes the straight branch Now to make this dream into reality, thanks for all your advice folks

Been firming up the design- please excuse my plumbing ignorance but can anyone tell me how you plumb in the threaded fittings- like the malleable iron fittings recommended on this forum from bes? They do 'nipples' which are pipes with threaded ends but the longest ones are just 18". I can handle compression, and you could couple raw pipe to these threaded fittings using it but that would add up to a big knot of fittings. Am I missing something?

Thanks for your advice everyone, to be honest I have been coming round to the idea of a pump for the Calorifier. At £18 for a 12v pump you can afford to have a spare on board in case of failure, but I have seen that jabsco do a very nice looking circulator with variable speed settings that goes down to 0.25A on minimum. Not cheap though, over £200! But I think I will take a risk and try and make it work on gravity. I was thinking if I included a stop cock in the Calorifier pipework I could close it down over night or once it was up to temperature to stop any reverse flow happening. The radiator gravity circuit would take any further heat so no problem doing that.

Hi , already had lots of useful advice from Bengo, smileypete & mike boilerman on my back boiler system thanks guys. Any advice on the following much appreciated: On further investigation of my back boiler hot water/radiator gravity system design I've found that having my calorifier right behind the stove in a cupboard - under worktop height, I will only get a rise of 140mm on the flow from back boiler to the coil inlet. This will be about 300mm behind the stove, connected by 28mm copper and I can have a custom calorifier made with a 28mm coil. So this doesn't look like much of a height difference to try & get a thermosyphon flowing through the calorifier. Think I may be able to get the manufacturers to stretch the coil a bit and have the inlet a bit higher on the cylinder but it won't be by much. I'll have an air release valve at the calorifier inlet. Alternatively I could put the cylinder back in the engine room at a higher level, with a rise of about 250mm from the back boiler but this could be increased to about 500mm by building a higher platform for the calorifier. This would be at about 5m away from the stove, with the pipe rising shallow & continuous to a radiator and then sharply up to the calorifier for the last bit, again in 28mm pipe. I know it's tricky to get a gravity system to flow through a calorifier so my question is am I better off having the calorifier close by the stove with a low pipe rise (or will this likely not work at all?) , or far away but higher up in the engine room? I'd been planning on having it right behind the stove as I've seen this work quite nicely on gravity in another boat, but the pipe rise was higher there.

I am reassured, but a bit surprised by what you say about pipe rises /falls Mike, seems a bit counter to most of the stuff I've read on gravity systems. The flow at least needs to rise to encourage hot water to flow through it? I will have 28mm pipework, rising continuously from boiler to vent for the flow. But I wonder whether I can have the return go lower than the boiler and then rise to connect to the boiler inlet? The Calorifier will be directly behind the boiler with 22mm coil, then the heat dump rad will be approx 4m down the boat with about 35mm rise per metr. . I'm a bit worried the thermosyphon won't be strong enough to reach along to the rad and back. Also not sure as to best layout for pipes on connection to the rad - flow could continue straight up to the vent, with a T off to a falling pipe to the rad. Or I could have the flow go straight into the rad and take the pipe up to the vent from the other end of the rad. Sorry I've not worked out a way to upload sketches on here yet hope this is clear.

Also I'm potentially looking at a pipe run rise of 35mm per metre on the flow, accounting for the trim of the boat. Any thoughts on whether this is an adequate rise?