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Old 10-26-2014, 02:23 PM   #1
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On Demand Electric Water Heaters

On Demand Electric Water Heaters

Anyone have or had one?
I've only seen them in homes in Europe, but was wondering??

Are there 12v systems??
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Old 10-26-2014, 02:48 PM   #2
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On Demand Electric Water Heaters

Anyone have or had one?
I've only seen them in homes in Europe, but was wondering??

Are there 12v systems??
We looked and talked about them but all I saw were 220v. Or propane, which we did not consider.

We've used tankless at home and love it, especially for showers. The ones I first saw years ago were mainly used in bathrooms, but then expanded to whole house.

Ultimately we decided wasn't worth it on our boat. It would seem to give a lot of instances per day of extra electricity required. Regular water heaters spread that requirement out more evenly over larger periods of time.

Now, we never have actually tried one on a boat. So this is just from looking. Hope someone here pops up who has used one on their boat. That will be the first person I've known to do so.
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Old 10-26-2014, 03:35 PM   #3
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Richard

We have a home single faucet unit for a lavatory sink far from the water heater. This was the smallest unit I found. Haven't measured the actual draw but the specs require a 60 amp 220 volt circuit breaker and appropriate wiring. This would be much too much for a boat
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Old 10-26-2014, 04:43 PM   #4
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My brain has been slow on the uptick, probably a result of all those solo voyages

So, just like my fridge and freezer which are now running on 220v shore power I just realized that my solution is a 220v system, which there are plenty of here in Europe.

I just need a system to have hot water and i am trying to come up with an alternative to using my 120v water heater with a 220v to 120v transformer, WHILE connected to 220v shore power.

Problem solved. thanks
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Old 10-26-2014, 04:58 PM   #5
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My brain has been slow on the uptick, probably a result of all those solo voyages

So, just like my fridge and freezer which are now running on 220v shore power I just realized that my solution is a 220v system, which there are plenty of here in Europe.

I just need a system to have hot water and i am trying to come up with an alternative to using my 120v water heater with a 220v to 120v transformer, WHILE connected to 220v shore power.

Problem solved. thanks
Yes, as long as you're on shore power, it could work fine for you.
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Old 10-26-2014, 06:29 PM   #6
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With your long run plans, consider an isolation transformer ($$$$). We have one on Bay Pelican and it allows me to plug into European 220 volt shore power and end up with North American 220 power. This allows me to run the 110v appliances.

For our members outside of North American, North American 220 volt shore power is made up of two legs each 110 volts. Bringing 220 volt North American into the boat,we can the physically split the two legs into 110 volt power as if there were two power sources, each 110 volts.
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Old 10-26-2014, 08:39 PM   #7
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The problem with on demand water heaters is having enough energy to heat up a given amount of water. The amount of energy needed is dependent on the starting temperature of the water and the set water temperature.

Quite a bit of electric power is needed to rapidly heat a given amount of water.

I looked at on demand water heaters for our house, and while they seemed really attractive, because of the extra cost in the on demand heater plus the limitations of electric power in this application, we went with a very efficient water heater.

Gas use in an on demand water heater is a different kettle of fish but I won't have gas in a house nor a boat.

Another issue, which with an on board water make would be minimized/nullified, is mineral content of the water. The minerals can clogged up the water heaters. About 8 years after building our house, I was talking to the plumber who helped build our house. He mentioned that he would no longer install instant hot water heaters because of problems due mainly to the mineral content of the water in my area. Not sure this would really be an issue on a boat but if using local water that was heavy in minerals for a long time it could be.

Later,
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Old 10-27-2014, 02:03 AM   #8
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Richard
With your long run plans, consider an isolation transformer ($$$$). We have one on Bay Pelican and it allows me to plug into European 220 volt shore power and end up with North American 220 power. This allows me to run the 110v appliances.

For our members outside of North American, North American 220 volt shore power is made up of two legs each 110 volts. Bringing 220 volt North American into the boat,we can the physically split the two legs into 110 volt power as if there were two power sources, each 110 volts.
That was the original plan, however at this point, I only have two items which need 110v, the water heater and Splendide washer dryer.

So my thought was get a 220v conventional water heater, but then I thought of the on demand type.

I'll be back for 4 weeks centered on thanksgiving. I'll have to think.
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Old 10-27-2014, 06:01 AM   #9
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Richard, for what it's worth, the Splendide probably won't run off a transformer converting the Euro power down to 110V. The reason is that a transformer, while it converts voltage very well, does not change the frequency of the AC power. So you end up with 110V 50hz, not 60hz. Something like a water heater won't care, but I'll bet dollars to donuts that the Splendide won't work properly. If you can keep running it off the inverter, that should work.

On the water heater, I can think of another possible solution. Depending on the heater, it probably has a removable heating element. You might be able to get a replacement element that is rated for 230V. If your boat is wired such that the 230V shore power is present at the water heater, then it should work fine. Just try to match the wattage of the heating element. A call to the manufacturer and/or a careful look through the parts manual should tell you if this is possible.
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Old 10-27-2014, 06:09 AM   #10
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Richard, for what it's worth, the Splendide probably won't run off a transformer converting the Euro power down to 110V. The reason is that a transformer, while it converts voltage very well, does not change the frequency of the AC power. So you end up with 110V 50hz, not 60hz. Something like a water heater won't care, but I'll bet dollars to donuts that the Splendide won't work properly. If you can keep running it off the inverter, that should work.
The cheapest solution, what has been called the poor man's voltage converter, is to have two inverter/chargers. One charging the batteries off of 220 volt European, the other providing 110 volt power for the appliances. Little tricky with a water heater at 1,500 watts but doable. Since the inverter will supply 60 hertz the Splendide will operate.

Twistedtree raises a good point and that is the hertz. An isolation transformer will not convert the hertz and the Splendide likely will not operate. When I use European 220 volt shorepower I operate my Splendide off of the inverter.
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Old 10-27-2014, 09:40 AM   #11
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AC powered on demand water heaters are power hogs. You might be able to run it while plugged in or on a 220VAC generator. They do make Propane versions but then you have to deal with all the safety features required when installing Propane on a boat.
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Old 10-27-2014, 09:43 AM   #12
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When we added diesel heat to our boat we bought a combination unit that also heats our water. Maybe that is a possible solution for you?
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Old 10-27-2014, 10:57 AM   #13
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...On the water heater, I can think of another possible solution. Depending on the heater, it probably has a removable heating element. You might be able to get a replacement element that is rated for 230V. If your boat is wired such that the 230V shore power is present at the water heater, then it should work fine. Just try to match the wattage of the heating element. A call to the manufacturer and/or a careful look through the parts manual should tell you if this is possible.
When we were in NZ/OZ a few cruising boats did this. Raritan and Torrid both offered 120/240 volt heating elements.
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Old 10-27-2014, 12:37 PM   #14
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Something like a water heater won't care, but I'll bet dollars to donuts that the Splendide won't work properly. .
I bet two donuts to your thousand dollars? lol

I wouldn't bet the Splendide won't work properly. In manufacturing we ran thousands of machines built for 60 on 50. With test equipment we could measure slight declines in performance but as a user couldn't tell the difference. I don't know about the Spendide and the other options are probably better than trying it, but you'd be surprised at the equipment that has no problem with 50.

It is something one could discuss with the manufacturer. Not with a distributor or retailer.
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Old 10-28-2014, 10:59 PM   #15
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My sister has one that they use on their 5th wheel trailer, that we borrowed not long ago. It works great, it's small, runs on propane and uses 2 D batteries for power. I was shocked that it works so good. I can't recall the name brand off the top of my head but have considered installing one on our boat. Some simple flex plumbing and exterior mount with a small propane bottle and you are set!
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Old 10-29-2014, 12:34 AM   #16
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Richard, for what it's worth, the Splendide probably won't run off a transformer converting the Euro power down to 110V. The reason is that a transformer, while it converts voltage very well, does not change the frequency of the AC power. So you end up with 110V 50hz, not 60hz. Something like a water heater won't care, but I'll bet dollars to donuts that the Splendide won't work properly. If you can keep running it off the inverter, that should work.

On the water heater, I can think of another possible solution. Depending on the heater, it probably has a removable heating element. You might be able to get a replacement element that is rated for 230V. If your boat is wired such that the 230V shore power is present at the water heater, then it should work fine. Just try to match the wattage of the heating element. A call to the manufacturer and/or a careful look through the parts manual should tell you if this is possible.
Thks Peter,

Yes, having lived in Europe for 10 years, I do understand the different cycles issue and on fact, the Splendide did work of my Chinese transformer, but now, after our rough trip from Horta, the drum does not turn, (running off the gen, 110v, 60 cy) though the machine seems to think everything is normal.

Makes me think a belt slipped off.

As for the water heater.
I spent some time with the U.K. Wallas distributor. That time spent confirmed the decision to go with the Wallas, as my top criteria are: boat heating and drying, efficiency and quiet operation. The Wallas satisfies all three.

But that still leaves me with cold water.

Changing the heating element is a good idea, but then I couldn't use it with the gen anymore. So it's back to square one.

I think the best solution was my first one, transformer for both, but that still entail isolating both, so they are not connected to the boats' 110v system.
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Old 10-29-2014, 12:39 AM   #17
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Richard
With your long run plans, consider an isolation transformer ($$$$). We have one on Bay Pelican and it allows me to plug into European 220 volt shore power and end up with North American 220 power. This allows me to run the 110v appliances.

For our members outside of North American, North American 220 volt shore power is made up of two legs each 110 volts. Bringing 220 volt North American into the boat,we can the physically split the two legs into 110 volt power as if there were two power sources, each 110 volts.
Yes, this in fact is what Dave Arnold suggested and will be my long term solution.
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Old 10-29-2014, 12:41 AM   #18
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When we were in NZ/OZ a few cruising boats did this. Raritan and Torrid both offered 120/240 volt heating elements.
Yes, this would also work. I'll look into it.
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Old 10-29-2014, 07:10 AM   #19
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Speaking of replacement heating elements, you might be able to find one that id dual rated, i.e. one that can run off 120V or 240V without rewiring. It will be 1/2 or double the power depending on which voltage you run, but might solve you wiring challenge. This might be what Larry M was suggesting, but I don't know if he was referring to one that has to be hard wired one way or the other.
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Old 10-29-2014, 07:41 AM   #20
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Since we are talking about heating elements if you have a wind generator and or solar panels there are 12 and 24vdc heater elements you use instead of your dump load.
I know they are limited from 300 to 600 watts. Also the heater could be plumbed into your primary engine then there would be no power issues.
In addition I looked at a 2 panel solar water heater system for complete off grid use the only power needed is a 12-24vdc low current circulating pump.
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