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View Full Version : How much heat...? Kw etc..



Ifraser
07-09-09, 09:45
Hi again, further to my last post about how best to heat a boat that is not on shore power.. I've now put down a deposit on a c-kip 40 trawler yacht which I should take delivery of late october. I've narrowed down my heating options but does anyone know how to work out roughly how much heat I need... ie if I buy a relfleks or similar do i need 4, 5 or 6 Kw ( I'd rather be over than under as one thing I dont want is to be cold ). Also interested in people with similar sized boats as to the rating of appliances that they already use. I'm not really into turning the heating down and wearing more jumpers ( sorry I know thats not very eco but I will have a solar panel if that helps my carbon footprint!!) The one thing I want for a life afloat and am prepared to splash out on is to be snug and warm... think I must be a bit of a wimp really..! thanks in advance of any help... Iain

Manuel
07-09-09, 15:36
Where are you going to be moored? Are you living aboard 24/365? Do you require overnight heating in the sleeping quarters or just in the living areas? Will you be on shore power all the time? Is your source of electricity going to be at a reasonable price or heavily uplifted by the supplier? The easiest and most convenient winter heating is electric convection heaters and in southern England you would want two 2kW heaters with thermostats and one fan as a top-up. A small 500W/750W oil filled for the sleeping quarters would be nice at some times. If you are going diesel you need to consider blown air, wet, or drip (radiant/convector).

The most direct answer to your question is that you will need 5kW or 6kW but you must be able to reduce the power. If it is wet or blown then you will need to budget for the electricity either from the shore or your own generator.

Ifraser
08-09-09, 08:20
Manuel, thanks for your reply. The vessel currently has an ebarspacher hydronic running a radiator system and for my first winter I will be in a marina in Poole but as time goes on I want to cut costs to a minimum so will be unlikely to be in a marina after winter number one. At the moment I dont think of eberspacher as a full time heating solution so am considering augmenting it with a drip feed diesel heater with back boiler. I've seen small 12v circulating pumps that are rated at about 1ah and I'm planning to have at least 120w solar panels to provide some charge for the batteries. Hopefully with that system I could run for several days without any need for external power. I will have a genny to top up every few days as required. Hopefully with a bit of clever plumbing and changeover valves I can choose drip feed or eber and just hot water or hot water and heating to suit the time of year etc. The above is all from what I've read.. although I have thousands of hours boating I don't have any experience of living aboard 24/7 365 so welcome any comments on my plan above... from what I've read it would seem that a drip feed heater alone in the saloon might leave the cabins a bit cold as they are lower than the saloon. My other thought was to use a stand alone drip feed and duct air gently around the boat using low current computer type fans but that doesn't heat the water and as the boat I am buying has a radiator system already in place it seems sensible to use it.. any thoughts greatfully received.. cheers Iain

Manuel
08-09-09, 09:27
Iain, for your first winter check the cost of electricity kWh versus diesel and the wear on your heating system. Electric convectors - I mean convectors - are a good option and very cheap if the electricity is cheap. You can afford to throw them away when you leave for warmer places they are so cheap compared with the cost of the fuel. We always found dehumidifiers good in the UK living aboard and leaving the boat. By bringing the humidity down it reduced the fuel needed and saved mildew.

The drip feed idea sounds good for the main saloon and I know many people who do only that. Plumbing it into the Hydronic sounds good on paper but I think it will be so complicated and unreliable it is not worth doing. I was planning to take the waste hot water from my generator to the calorifier until I worked out what was involved. You will also lose space by fitting a drip feed as they get hot and you cannot sit on top of them.

I suggest you do nothing yet. Live on board and find out the cost of fuel. Buy electric heaters if that makes sense when you know the prices. Then during the winter think about whether the drip feed idea would make sense. You won't know until you have experience of where you like to sit and what you like to do in the evenings. Before fitting one make up a cardboard replica and put it in place for a few days. You might find you would rather not go ahead.

Ifraser
08-09-09, 14:45
Manuel, thanks again for your sound advice which makes entire sense. I have identified a corner cupboard in the saloon which could be removed to make way for the drip feed heater. You are quite right in that I don't have a clue until I have done it. Like I say year one will be in a marina and if I find electric heating affordable and can manage marina prices for the second winter then that may indeed be the way to go.. cheers Iain

Manuel
08-09-09, 20:19
Manuel, thanks again for your sound advice which makes entire sense. I have identified a corner cupboard in the saloon which could be removed to make way for the drip feed heater. You are quite right in that I don't have a clue until I have done it. Like I say year one will be in a marina and if I find electric heating affordable and can manage marina prices for the second winter then that may indeed be the way to go.. cheers Iain
Iain, before going for the drip feed whip the door off and fake up a mock heater. You will need to think how the flue is going to pass up and how you will terminate it during use and outside the heating period. And the fuel supply either tic-tic pump (noisy) or gravity (where?). If in a cupboard you will need to put some shielding round the heater, polished stainless? Parabolic? You will lose all that storage space and that could be a problem. There is no single solution that is ideal for every situation but cheap electricity is the best!

Sandyman
09-09-09, 00:33
Iain, can I ask where you will be berthed in Poole ???

We liveaboard a 43' steel ketch on the South Coast coming towards our third winter.
Our only heating is a D1L Eber but from experience we have learnt that the key to keeping warm is the amount of insulation you have to the hull below the waterline.
The problem was finding material usable in a marine enviroment, other than the type of stuff they put in landlubbers lofts, which would form and shape itself to the hull profile. We found the answer in Trago Mills, Falmouth who sell large rolls of waterproof plastic backed foam carpet underlay.(its advertised as posh underlay for the knobs with expensive carpets, but well worth it) About 40 quid a shot. We used 2 rolls & it increased our comfort 10 fold. I would suppose it must be available from most carpet shops.
I am not sure how to explain its composition, only to say that it is made up of hundreds of small bits of foam stuck together, rather than a single sheet of flat foam. This seems to give it strength.
Without going into great detail about efficiency/cost/fuel type, etc etc and taking into account maintenance costs, I am yet to find any source of heat onboard better than diesel. But then I do my own maintenance/repairs/servicing so my comments maybe bias.

Ifraser
09-09-09, 09:55
Sandyman, thanks thats interesting.. thats the first time anyone has mentioned hull insulation...I'm wondering if that is specific to steel boats? but definately something to consider. I haven't finalised my berth yet but its likley to be Poole town quay marina for the winter then swinging mooring in Holes bay for the summer. The second winter will depend very much on how the first goes and on finance as to whether I feel the need to get back into a marina for the winter. Boats I know very well but I'm very much on a learning curve with regard to the living aboard. cheers Iain