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Old 07-14-2020, 10:59 AM   #1
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Need hot water!

Hello Everyone!
Hoping to pick the mighty brains of Trawler forum.
My wife and I, as a team, are new to ocean boating. I have a few years of experience, however my wife not so much. For the past 2 years, she has really taken to boating, however her one wish would be; to have hot water for more than 1 1/2 days when on the hook.
Our trawler has the following;
- Force 10 (411011 model) hot water heater. Water is heated through engine coolant lines when running or when on shore power.
- New Espar (large, but sorry no model number)
- there is a water to water heat exchanger in the lower part of the hull of the boat, with in and out lines coming from both the Espar and the Force 10. There is no recirculating pump on the hot water side so I am assume the water just passively flows through?? Either way in the winter with Espar running to heat cabin, the water does not get hot with this method.

My 2 options;
1) Use two 3way valves to tap into the coolant lines coming from the engine at the hot water tank. Connect these to the two Espar lines going to the heat exchanger in the lower part of the hull, thus taking the heat exchanger out of the “mix”. The fans on the fan coil units can be turned off so we aren’t heating the cabin during summer time. This method would allow us three different methods of heating water; shore power/ engine/ Espar
2) Put a small recirculating pump on the hot water side of the small heat exchanger in the lower part of the hull. This would then make better use of the heat exchanger and potentially heat the water.

I think option 1 is the best as it would heat the water faster than option 2.
What does the group think?
Any advice on the How To on either option?

Thanks

Brent
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Old 07-14-2020, 12:00 PM   #2
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Sounds like a recuic pump would solve the problem.


When on the hook, I'll typically run the Genset for an hour in the morning and evening to charge up the batteries, make coffee, and heat water. We never seem to run out. If we have run the boat anywhere, the water gets hot anyway. We seem to have plenty for dishes and showers in the evening.
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Old 07-14-2020, 12:37 PM   #3
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Thanks for the reply. I should mention to everyone, we do not have a genset, only solar, which so far works very well, except for the hot water.

Brent
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Old 07-14-2020, 01:02 PM   #4
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Yeah, OK. Well then I think a recirculating pump from your heater would be the best option. Mine doesn't have that but would be great in the colder times when we run the furnace.
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Old 07-14-2020, 01:05 PM   #5
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How large is your water heater?

Ted
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Old 07-14-2020, 02:49 PM   #6
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I used a similar water heater on a commercial boat. Using engine heat to heat your water saves a lot of diesel compared to Espar or others. The engine heat is a waste produce and costs nothing.
Something that will make the hot water last longer is set your water heater on 1" or better foam and surround it with foam. The heaters are not that well insulated. Also insulate the lines, to and from the heater. They bleed heat while sitting.
The current water heaters I use are insulated with 2" foam and hot water, enough for a shower, lasts 2 days in cold weather. All the lines are insulated, even the cold for 6' after the heater.
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Old 07-14-2020, 02:49 PM   #7
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Thanks Dave. That would be the easiest option, just wondering about the time to heat. I would think having a feed and return line directly from the Espar to the water heater would be more efficient, however I am then integrating the Espar coolant with the engine coolant to some degree.
The Force 10 Model 411011 is 11 gallons Ted.

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Old 07-14-2020, 02:52 PM   #8
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Lepke
Absolutely. Insulating the heater and the lines is on the “to do” list. Simple way to make the water stay hot/warm longer.

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Old 07-14-2020, 03:08 PM   #9
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You could check out 12 vdc solar hot water. It would beat the cost of a generator.
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Old 07-14-2020, 03:42 PM   #10
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Lepke and Brent get my vote.
Another thing to consider is to install a mixer valve at the hot/cold water outlets from your hot water tank. Either buy one or use a shower mixer unit to set the temperature and it helps to conserve your hot water.
I have one installed on Snow Mouse and they are very effective and also prevent scalding.
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Old 07-14-2020, 04:42 PM   #11
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The engine is by far the best way to heat your water as has been said, but if you’re not cruising someplace, you need a second source. A circulator on the Espar sounds like the way to go with your current setup.

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Old 07-14-2020, 04:52 PM   #12
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I have about a six gallon electric heater. I have the temp set pretty high, hot enough to burn you if you use straight "Hot" water. The tank heats up in less that ten minutes and will stay usable warm for eight to ten hours. After that I run the genny for a few minutes.

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Old 07-14-2020, 07:57 PM   #13
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Hi Pete
Thanks for the reply, however no genny on this boat. We are solar.
Irish Rambler
Your mixing valve idea is a good one I think, once we can get the H2 and O heated.
Ken
When you say a circulator on the Espar are you thinking more of my option #2? This is by far the more simple solution as we already have a water to Espar coolant heat exchanger low down in the hull. To put a very small recirculating pump on the water side of the heat exchanger, then this would allow the pump to circulate the water from the HWT through the exchanger and back to the HWT. The question is; how efficient would this be?
Thanks everyone so far who have chimed in!

Brent
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Old 07-14-2020, 09:11 PM   #14
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Yes, I’m referring to your option #2. How efficient? Well, almost anything would be more efficient than running a main engine JUST for hot water. A small taco circulator will run forever and they use less than 75 watts. Easily handled by your inverter.

You’d just have to figure out the thermals and a way to shut it off when it got the hw up to temp.

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Old 07-14-2020, 09:45 PM   #15
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The water coming out of a Force ten, must be pressurized, going to water to water exchanger. The water thru the Espar is pressurized going to water to water exchanger, seems like cranking the Espar and opening a tap should give you hot water, as long as the line from Force ten is on the hot water output side. I have one of these plumbed in and it works very well.
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Old 07-14-2020, 10:06 PM   #16
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You could move to Florida. The water in my tank is 90F right now. No water heater needed. Of course, then she might want cold water....
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Old 07-14-2020, 11:28 PM   #17
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I've a 30k btu Hurricane hydronic heater with the heater loop going through the heat exchanger of a 6 gal. Kuuma water heater. Starting the Hurricane from cold it'll get the water heater water hot in under a half an hour. I also have the same water/water heat exchanger that Rebel has in the loop. This will give continuous hot water as long as the Hurricane is running. Having the water heater in the loop lets me have stored hot water when the Hurricane is not running. It also unburdens the water/water heat exchanger a little. Also have an engine coolant/heater loop heat exchanger so with the heater circ pump running will heat the water heater water and give me house heat without the Hurricane running.
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Old 07-24-2020, 01:26 PM   #18
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So I have done some more inquiring, using the tips provided by the forum group here. We had a marine tech stop by our boat to do an assessment as we are about an 18 hour drive away from the boat.
His assessment came back with a solution very similar to Sean's, only he suggested using a stainless manifold with valves to control;
- heating water with main engine
- heating cabin with main engine
- pre-heating the engine coolant with Espar
- heating the hot water tank with the Espar
- he also feels moving the hot water tank from the lazarette into the engine room would be a good idea for heat retention

This system seems more elaborate than initially plan, however he's done this before and feels its the best way to go.
Here are my possible concerns;
- valves would need to be in an accessible area
- engine coolant would mix with Espar heater coolant. This alone shouldn't be an issue but then there would be more failure points for engine coolant.

Thoughts from the group?

Thanks again to everyone who has given their opinions thus far

Brent
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Old 07-24-2020, 01:46 PM   #19
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My boat is almost done refit, complete gut job and new everything other than hull and superstructure. When it came time to discuss hot water and my new Mercruiser engine, my refit guy said it would be cheaper not to hook up the hot water to the engine.

For me here in the PNW & North, heating the boat is priority number one which I have done, I think with Espar but I've lost track as we were going to go with Wallas only to discover it wouldn't heat water so I forget what's in there now. My refit guy said that he could heat a water tank with the kerosene (diesel) heater used for boat heating and not to hook up to the engine to save money. You need to burn a lot of fuel heating hot water to break even with hooking up to the engine.

My boat is gas propulsion so the reason I'm going to use kerosene for my fuel instead of diesel is that if the fuel sits for a long time, I don't want to deal with sludge and other issues that befalls old diesel. So I have a small dedicated tank for the boat/water heater. The kerosene is definitely pricier than diesel but I expect to use maybe twenty gallons in a "heavy use" year.
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Old 07-24-2020, 02:02 PM   #20
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Change the routing so that the espar coolant runs directly through the force 10, and the engine coolant only runs through the heat exchanger. This way the Espar heats the water during winter and on the hook.



This is what I do, and I hooked up my diesel heater circulating pump to a separate 12v switch so I can turn it on when the engines are running without turning the diesel heater on. It's pretty cool because it allows me to heat the cabin or the hot water with the engines. And the diesel heater can be used to heat the cabin or the hot water.
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