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Old 10-29-2014, 08:41 AM   #21
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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.
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Old 10-29-2014, 09:15 AM   #22
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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.
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Old 10-29-2014, 11:11 AM   #23
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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?
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Old 10-29-2014, 12:41 PM   #24
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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.
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Old 10-29-2014, 05:14 PM   #25
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Isn't it that way in a house though .....if you went back to a sub panel with a double pole hot breaker??
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Old 10-29-2014, 06:28 PM   #26
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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.

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Old 10-29-2014, 08:35 PM   #27
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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?
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Old 10-30-2014, 07:39 AM   #28
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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.
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Old 10-30-2014, 08:06 AM   #29
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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.
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Old 10-30-2014, 12:27 PM   #30
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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
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Old 10-30-2014, 03:23 PM   #31
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can't you just add a mini-220 sub-panel?...and even then....doesn't it wind up being the same thing?
That is sorta where I am right now, but even simpler.

I've cut the 120v wires just before they go into the water heater and inserting a male and female plug, make on the heater side.

That way the water heater is totally isolated but still protected through the ground fault of the 220v shore power system.

The cord coming from the transformer ends in a female plug also. That way WH can only be connected to one power source at a time.

I'm using the German plugs, since I have them and I'll remember it's 220!
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Old 10-30-2014, 03:32 PM   #32
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Having the fridge and freezer already on 220v shore power, means that if I am not in the boat using lights and stuff, the solar panels produce enough to keep the batts up, even on rainy days.

Once I get an auto radio, I'll hook it up to the auto pilot and I won't have to worry about a constant lookout, as I won't even be on the boat.

It could be the first Kadey Krogen drone:-)
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Old 10-30-2014, 03:52 PM   #33
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What did you do for the water heater?
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