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Old 26-10-2015, 11:07   #31
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Re: Heating water without shore power?

How will you keep your batteries charged up? If you have refrigeration just run the engine once daily with a hot water heater in the loop.
I guess if you are not running your engine, an on demand propane water heater is the most economical. Careful installation, monitoring in use etc and they seem to be safe, although not marine approved.
I would use it by turning it on like the propane cooking range and turning it off when not used.
$120 new. The last one I bought was a camping device and was superior to my old Paloma I had years ago.
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Old 26-10-2015, 11:14   #32
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Re: Heating water without shore power?

Quote:
Originally Posted by AFKASAP View Post
How do you heat your water for showers etc when staying aboard long term? I am staying aboard my Beneteau Oceanis 40 for the European winter months.

What are my most cost effective options for heating water? In spring next year I will be heading to the Med.

I guess any practical wind or solar power devices will not generate sufficient electricity to power my boiler.

I do have shore power at the moment, but I am looking for self sufficient alternatives (if any).

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We heat water from the engine cooling, the generator cooling loop and via a heat exchanger at the outlet of our espar diesel heater.

The generator is by far the most used water heating option. We run the gennie late in the afternoon.

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Old 26-10-2015, 11:22   #33
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Re: Heating water without shore power?

If your at the dock, the facilities available at the dock will always be cheaper than any other option you have, unless of course they are crooks and way overcharging. They will also be the lowest maintenance.
You just can't generate a watt of power cheaper than you can buy it from the grid. The day that you can, will be the day you see Solar becoming popular for residences.
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Old 26-10-2015, 11:27   #34
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Re: Heating water without shore power?

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Originally Posted by Dockhead View Post
In my opinion, electric heat powered by shore power is always going to be cheaper in the end than heating with diesel fuel, although of course the marginal cost vary depending on fuel cost, cost of power, etc
It's possible to estimate a pretty good comparison. One Gallon of oil produces 140,000 BTU. Assuming 75% efficiency, the minimum allowed in the US for RV warm-air furnaces, that's 105,000 BTU of usable heat from every gallon burned.
(Sorry for the US measurements, I found them faster than metric.)

105,000 BTU is equivalent to 30.8 kWH, or 9.24 Euros (assuming .30/kWH).

So, in this example, if you pay more than 9.24 Euros per gallon (or 2.44 Euros per liter), electric is cheaper. Otherwise, oil is.

You can plug in different costs per kWH and per gallon or liter for other locations.

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Originally Posted by Dockhead View Post
But the other beautiful thing about electrical heat is that you can produce it with a $50 Chinese fan heater which has zero maintenance.
Or a $10 Chinese fan heater. It really doesn't matter for the sake of this comparison, since electric resistance heat is 100% efficient.

Sorry for the thread drift. I know this doesn't help the OP with the question about heating only domestic water. But it makes the thread more complete for others contemplating heating issues.
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Old 26-10-2015, 11:30   #35
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Re: Heating water without shore power?

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Originally Posted by Mikado View Post
I haven't seen anyone post who's 120v water heater runs on their inverter when off shore power and generator power? My hot water system is well insulated so only runs for a few minutes every couple of hours unless we use a lot of hot water. It's just another component as part of our power consumption plan.
That's going to be my eventual plan. I'm hoping that with a 400AH lithium bank and ~600 watts of solar I'll be able to keep my hot water tank running easily.
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Old 26-10-2015, 11:54   #36
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Re: Heating water without shore power?

So I checked out what boiler I have. It's 25L Nautic Boiler 1200 watt.

I really appreciate all the comments. There is a lot for me to take in.

I get the feeling I am best off just using the shore power.
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Old 26-10-2015, 11:58   #37
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Re: Heating water without shore power?

There are marine rated tankless water heaters, search on Google and you can find them. They are $$$$$ however. I know only one person who went this route. The heater is in the lazarette, has an air intake from outside, and vents outside, has lots of safety shutoff sensors, and his wife LOVES it. The whole bill came to around three boat-units.
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Old 26-10-2015, 13:08   #38
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Re: Heating water without shore power?

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I meant space heating, not water heating. Do you have some kind of space heating on board?
Sorry I misunderstood you. I have an Eberspächer diesel heater for space heating.

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Old 26-10-2015, 13:21   #39
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Re: Heating water without shore power?

In the calculations of efficiency of Diesel vs electric, don't forget to amortize the purchase cost of the equipment, installation and maintenance.
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Old 26-10-2015, 13:23   #40
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Re: Heating water without shore power?

I read somewhere the cost of us to make electricity with the cost of batteries etc was about 20 times the cost of buying it off the grid.
Of course we are forced into that as extension cords are only just so long
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Old 26-10-2015, 13:28   #41
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Re: Heating water without shore power?

Quote:
Originally Posted by CaptTom View Post
It's possible to estimate a pretty good comparison. One Gallon of oil produces 140,000 BTU. Assuming 75% efficiency, the minimum allowed in the US for RV warm-air furnaces, that's 105,000 BTU of usable heat from every gallon burned.
(Sorry for the US measurements, I found them faster than metric.)

105,000 BTU is equivalent to 30.8 kWH, or 9.24 Euros (assuming .30/kWH).

So, in this example, if you pay more than 9.24 Euros per gallon (or 2.44 Euros per liter), electric is cheaper. Otherwise, oil is.
Thanks

Diesel here in Amsterdam is EUR 1.249 per liter.


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Old 26-10-2015, 13:33   #42
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Re: Heating water without shore power?

My coil of black hose on the dock always is full of extremely hot water. Not sure how it gets that way though...
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Old 29-10-2015, 12:48   #43
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Re: Heating water without shore power?

Quote:
Originally Posted by CaptTom View Post
It's possible to estimate a pretty good comparison. One Gallon of oil produces 140,000 BTU. Assuming 75% efficiency, the minimum allowed in the US for RV warm-air furnaces, that's 105,000 BTU of usable heat from every gallon burned.
(Sorry for the US measurements, I found them faster than metric.)

105,000 BTU is equivalent to 30.8 kWH, or 9.24 Euros (assuming .30/kWH).

So, in this example, if you pay more than 9.24 Euros per gallon (or 2.44 Euros per liter), electric is cheaper. Otherwise, oil is.

You can plug in different costs per kWH and per gallon or liter for other locations.



Or a $10 Chinese fan heater. It really doesn't matter for the sake of this comparison, since electric resistance heat is 100% efficient.

Sorry for the thread drift. I know this doesn't help the OP with the question about heating only domestic water. But it makes the thread more complete for others contemplating heating issues.
Thread drift is natural, and in this case I think interesting for most here.

What you've done here might be right as a calculation of fuel cost versus electric cost, in one particular case, but for total marginal cost you have to consider maintenance too. A hydronic heating system can easily cost as much in maintenance per hour of use, as it uses fuel during that hour, doubling the total cost. Your $10 Chinese fan heater, obviously, is maintenance free.

I don't mention depreciation of the oil-fired heating system because I assume you're going to have it anyway (as I do), but if you were deciding between oil heat and electric without oil backup, you would need to consider that, as well. Mine probably cost close to $6,000.

In our case, I guess the choice of electric heat at the dock is not so much cost (although for us it is far cheaper since unlimited electrical power is almost always included in berthing around here), but to avoid timing out the furnace, whereupon you have to have it serviced at the cost of several hundred dollars. When you're out cruising, you've also got to find someone who can do it, which can be surprisingly difficult. BT, DT.


Another form of heating we haven't discussed is reverse cycle A/C. That's the only heat I had on my previous boat. This is extremely efficient if the water is warm-ish. But of course you need power, and we didn't have a genset on that boat, so in cold weather on the hook our only heat was our own body heat in a warm sleeping back
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Old 29-10-2015, 13:07   #44
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Re: Heating water without shore power?

12 volt heating element in water heater plus 500 watts of solar panels?


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Old 29-10-2015, 13:21   #45
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Re: Heating water without shore power?

Planning to install a boiler myself the coming spring. We have a bulkhead mounted propane heater in a closet (air intake and exhaust to outside) with radiators around the boat. Should be a breeze to connect the boiler coil to the heating circulation. This would eliminate the need to run the engine for hot water when at anchor and am leaning towards this option. Then again, propane use will go up somewhat whereas if the boiler is connected to engine cooling system we would get a "free" load of hot water every time the boat is moved. If in a marina would still absolutely use the electric element.
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