Isotemp Water Heater Size

[Jammin']

I'm going down a rabbit hole with my electrical upgrade. I'm making space for a new battery charger and I'm replacing my large accumulator tank with a mini tank. "While I'm in there" I'm thinking of making more space for a second charger by replacing the hot water heater with either a 6.4 gallon or 8 gallon Isotemp hot water heater with an engine water coil. I like the 750 watt power usage, the engine water heat exchanger and the small size. I've never run out of hot water in the various campers I have owned and all of them had 6 gallon hot water heaters, and cheap ones at that. Is it really necessary to have a heater like the Isotemp larger than 6.4 gallons on a 43DC? I can get a hot water heater at Home Depot for $150. That's not what I want.

[Boatsb]

750 watts is 750 watts.

The better insulated ones hold the heat longer but dont really heat any faster. Having the engine circulate water to heat it is good if your running. Otherwise it's no benefit.

[oscarvan]

Is it really necessary to have a heater like the Isotemp larger than 6.4 gallons on a 43DC?

If my lovely bride is taking a Hollywood shower.... Yes, very much so. Discovered that on our first RV. Bunch of guys fishing? Probably not. So you answer(ed) the question based on your mission profile.

[jim rosenthal]

I have had very good service from a Seaward water heater for years. Not expensive, but has lasted quite a while.

[Jammin']

I took the plunge and ordered the Isotemp Basic 24 hot water heater. It's on sale at Defender right now and I like a number of things about it including that it will fit. Hopefully the way it works with storing hotter water and using a mixing valve to temper it, and better insulation will make up for decreased size, 10 gallons down to 6.4.

[jim rosenthal]

If you install the coolant loop, either from one of the drive engines or from the genset, you will have VERY hot water, at 175-180 degrees, which goes a long way. In my boat, it is plumbed to the port drive engine. I have used the electric element in the HW heater only a handful of times in the twenty years that water heater has been in there. And it isn't nearly as good quality as an Isotemp.

Make sure whoever is going to use hot water knows how hot it is when it's heated by the engine; a little goes a long way.

[Jammin']

I am planning to plumb the heat exchanger through the starboard engine. I also like that the hot water heater only draws 750 watts AC, although I'm not sure that it's really any tangible benefit.

I plumbed a radiant floor heating system on a house I built when I was a youngster back in the 80's and used a mixing valve like the one on this heater. Overly hot water shouldn't be a problem once adjusted.

[Photolomy]

750 watts on a 6.4 gallon tank is equivalent to 2300 watts on a 20 gallon tank. Power and volume of water are the two parts of the equation. My 20 gallon tank is only 1500 watt (because it is on a 110v circuit) and I haven't had issues. I have the thermostat up to 145 degrees which helps the hot water last longer.

6.4 gallon isn't a lot of water though. But with the engine running it probably heats up fast.

[jim rosenthal]

The water heaters with the coolant loop DO heat fast, and, because they are in the engine room, they stay hot even without the element switched on once you turn the engines off. Like for a day at least, because the engine room heat keeps it hot. It's the way to go. And like he said, that many watts in a small volume of water will heat up fast.

[Jammin']

Out with the old. In with the new. If I hadn't have been fooling with the thing I wouldn't have discovered the neutral wire was badly corroded and had been burning the insulation.