On Demand Electric Water Heaters

[Wxx3]

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??

 

[BandB]

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.

 

[Bay Pelican]

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

 

[Wxx3]

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

 

[BandB]

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.

 

[Bay Pelican]

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.

 

[dannc]

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,
Dan

 

[Wxx3]

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.

 

[twistedtree]

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.

 

[Bay Pelican]

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.

 

[Billylll]

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.
Bill

 

[Robster_in_edmonds]

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?

 

[Larry M]

...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.

 

[BandB]

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.

 

[Chopperguy]

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!

 

[Wxx3]

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.

 

[Wxx3]

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.

 

[Wxx3]

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.

 

[twistedtree]

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.

 

[Billylll]

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.
Bill

 

[obthomas]

You guys with U.S. shore power using split phase power to get two feeds of 120 be careful with adding a 220 volt heating element. If you do you are connecting those phases that were separate and safe and creating a dangerous situation with breakers and hot plugs etc. 220 on these systems is not a good idea.

 

[JEP]

On demand water heater

You might want to look at a rheem prestige series 95 8.5 gal flow or a RTE 3 low flow which is a single fixture heater. All or 110v and the later is very water conscious. I have used both in home and office applications. They worked fine. As far as the scaling problem, all of them regardless of which one requires a yearly descaling. Very simple process which I do my on with vinegar and water. Takes about 30 minutes.
I rented a motor home a few weeks ago and it had a on demand water heater and it was awsome for a long hot shower. Maybe check the Rv centers. Hope this helps.
JEP.

 

[psneeld]

You guys with U.S. shore power using split phase power to get two feeds of 120 be careful with adding a 220 volt heating element. If you do you are connecting those phases that were separate and safe and creating a dangerous situation with breakers and hot plugs etc. 220 on these systems is not a good idea.

can't you just add a mini-220 sub-panel?...and even then....doesn't it wind up being the same thing?

 

[obthomas]

The problem is....once you are onboard the split phases are protected with 2 pole breakers that protect one phase and a neutral. These 50 amp two pole breakers are not linked giving you two independent pools of power. Now you bridge then with a heating element and you inadvertently re-connect the two phases. You can predict that if for some reason a short or maybe even maintenance, one of the pools of power is switched off and not being in lockstep with the other , you have left a very dangerous cross connect and the power you thought was off is still there coming across the 220 heating element. In addition if you have any boatside plugs that can be touched they are possibly live also. In summary it is a very good arrangement to use split phase power to provide two separate pools of power, it is not safe to then link them together using 220 volt loads.

 

[psneeld]

Isn't it that way in a house though .....if you went back to a sub panel with a double pole hot breaker??

 

[BobH]

Every house we have ever owned had a 220 VAC service split into two 110 VAC services. Appliances that were/are 220 VAC have a ganged two pole breaker. I have used the same arrangement on our last boat to power a 220 VAC watermaker. Obviously, if you have a 220 VAC appliance it needs to be protected with a two pole ganged breaker. It's not rocket science.

Bob

 

[Capt.Bill11]

In summary it is a very good arrangement to use split phase power to provide two separate pools of power, it is not safe to then link them together using 220 volt loads.

So how do you explain all the boats that have one 50a or one 100a 125v/250v cord yet run both 125v and 250v equipment off that single cord with out any issues?

 

[obthomas]

On a boat including mine the incoming phases are very often individually protected by a breaker that switches one hot and its neutral. A house on the other hand has both phases protected by a two pole breaker that is linked. When there is a fault in the house both phases are switched off every time. In a boat with the circuit breakers being independent and the second pole on each breaker switching the neutral it is different than a house. When you add 220 appliances to a boat it is dangerous if you do not re-arrange the main breakers to be interlocked like a house. If you can't see this problem I'm sorry but I have given the best explanation I can.

Please note that if your boat is wired like a house then the danger goes away. Most boats like mine are not wired like a house.

 

[obthomas]

So how do you explain all the boats that have one 50a or one 100a 125v/250v cord yet run both 125v and 250v equipment off that single cord with out any issues?

The boats you speak of are wired like a house and have the main incoming phases through the same two pole linked breaker.

I am speaking to adding a 220 appliance to a boat for example that has two 30 amp or 50 amp shore cords. You can do it same as the boats you speak of but it is not safe.

 

[FF]

Looked at it for our home and instant electric would have required a complete require 60A per LEG!!!


Our solution was a very high quality GRP inside and out tank, with great insulation that only looses 5deg C in 24 hours.

A super insulated tank might work if there is no dishwasher and washing machine.

Use the waste heat from your refrigeration as heat source. OTS