On demand propane water heater

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AussieCraig

AussieCraig

Senior Member
Joined
May 16, 2013
Messages
179
Location
USA
Vessel Name
The Salty Swallow - named by wife
Vessel Make
Private builder - 50' Trawler
Looking to replace the old electric hot water heater on our boat and given the price, ease of installation and cost of running I am considering on demand propane...any experiences or advice Gents ?
 
None of these units can be installed in accordance with ABYC standards ... even the ones that say they can. Some of them even come with warnings in the installation instructions not to install in a boat or RV. Your insurance company might take issue with it, if its mentioned on your next survey.
 
The big hassle is showering , Navy Style.

If you shut off the water to scrub , the heater shuts off from no water flow , so when you resume showering the water will be cold for a while.

One solution is a bath tub/shower valve , where the tub feed simply sends the heated water back to the FW tank.

Costs a bit of propane , but is comfortable.

Second solution is a RV propane water heater which does have a tank holding a few gallons , and most can be ordered with an electric element for dockside or noisemaker operation.

These are easy to winterize , should that be required.
 
boatpoker said:
None of these units can be installed in accordance with ABYC standards ... even the ones that say they can. Some of them even come with warnings in the installation instructions not to install in a boat or RV. Your insurance company might take issue with it, if its mentioned on your next survey.
Click to expand...

Yep, that's a pretty big downside. I don't worry so much about the insurance company, my goal is to wake up the next morning in one piece.
 
Well that sucks LOL...back to the drawing board then...cost is the prohibiting factor in most 'marine' systems I have seen so far...
 
AussieCraig said:
Well that sucks LOL...back to the drawing board then...cost is the prohibiting factor in most 'marine' systems I have seen so far...
Click to expand...

You can buy a marine water heater that uses 120 volts AC and/or waste heat from the engine to heat water. They start at a two or three hundred dollars and work quite well. After a day's cruise my wife and I can take showers and still have reasonably hot water the next morning. That's just from the engine's waste heat.
 
Simplest is the stock marine unit , with added insulation to get an extra day from it.

Solar (electric or water ) heat sources can be added , if you have outside flat space to loose.
 
I an electric residential

I use a residential 30 gallon 240 volt that always gives me plenty of hot water. I cook with electricity and charge batteries in the morning with the generator. The water heater runs for an hour or so at night and maybe two to three hours in the morning. No problem with hot water ever. Maybe the insulation on the tank is enough. This is a fairly inexpensive solution.
 
Craig

If you are in a large RV sales repair area, used/new electric water heaters can show up locally at dealers or on Craig or Amazon. But as Scary indicates, Home Depot or Lowes works too.
 
Many ABYC, etc rules I think are somewhat BS. But not the ones regarding propane. I would not want a propane system on the boat that comes on automatically. Too much opportunity for a failure to cause gas buildup in the cabin. A stove still has risk, but that is usually being monitored by whoever is doing the cooking.

Electric water heating makes the most sense on a boat provided there is a gennie. Better yet if there is a heating loop from an engine.

I went without the engine heating loop. Gennie has to run periodically for other uses, so in about 15min I get hot water for very low cost. And system is drop dead simple.
 
All propane RV water heaters have the flue exiting downhill. That means you would have to install it about deck height to have enough clearance above the waterline, so not in the bilge

My buddy installed a solar heating panel to supply heat to his marine hot water heater. The package (about $400) included a small solar electric panel that powers a small circulating motor. It works ok, adding 30 degrees or so to the water tank temp during a sunny day.

I agree with Ski, stay away from non approved propane devices on a boat.

David
 
I had 2 different on demand heaters on boats. Both worked well. They were plumbed with electric solonoid just like a range would be. To use you would flip the solonoid on, to supply propane, to waterheater. Propane at water heater, controlled by another solonoid, that would be energized by you opening the tap, which allow propane to flow and igniter would then ignite and you have almost instant hot water. Turn the tap off, propane shuts off. Is it possible to have troubles, certainly. Water on a boat is something that is generally used conservatively, and user is generally near the tap when either cold or hot is flowing. Some older units had pilot lights, which needed propane flowing all the time, not so good. There are some out there that are ventless. I have always had propane on my boats since the 70's. I take care of it, and it takes care of me.. I had an electric range on a boat, swapped it for propane. Could not get used to cranking and running generator every time I needed to cook something. It was a 110vac unit, and you could not run oven and top burners at same time. I guess the propane could blow you up, or the AC, might electrocute you. DS
 
Rebel112r said:
I had 2 different on demand heaters on boats. Both worked well. They were plumbed with electric solonoid just like a range would be. To use you would flip the solonoid on, to supply propane, to waterheater. Propane at water heater, controlled by another solonoid, that would be energized by you opening the tap, which allow propane to flow and igniter would then ignite and you have almost instant hot water. Turn the tap off, propane shuts off. Is it possible to have troubles, certainly. Water on a boat is something that is generally used conservatively, and user is generally near the tap when either cold or hot is flowing. Some older units had pilot lights, which needed propane flowing all the time, not so good. There are some out there that are ventless. I have always had propane on my boats since the 70's. I take care of it, and it takes care of me.. I had an electric range on a boat, swapped it for propane. Could not get used to cranking and running generator every time I needed to cook something. It was a 110vac unit, and you could not run oven and top burners at same time. I guess the propane could blow you up, or the AC, might electrocute you. DS
Click to expand...

If you can find a propane water heater that's ABYC approved for installation on a boat and you hire a qualified installer or think you are qualified to install it according to ABYC requirements, it might be an option for some folks. I have never seen one in a marine catalog but that doesn't mean there isn't one out there somewhere.

I am not against propane, it just has to be installed and used safely.
 
On demand propane systems would not be something I would use. At one stage I think Aquabelle was going to install an on demand diesel system, but not sure if that eventuated.

I use a 'summer loop' on the diesel fired Webasto hydronic heating system to heat the Torrid water tank. Or use the engine heat loop, or dock power. I don't have a gennie, other than a Honda 2000 for emergencies. I can always get hot water in under 30 minutes if it isn't warm enough already.
 
I doubt any builder recommends them. I think if you understand the systems and maintain them they are as safe, as a factory installed propane range. I have a regular 10 gal electric with exchanger on the NP. I do have a Base Camp Aquacube, that is a portable, on demand heater, in the lazerette, that works well for showers and dishes. It is great, if you have been on the hook for awhile and don't want to wait, the 1/2 hour or more for the electric to heat water. It was a gift. Runs on 1 pound bottles.
 
Whale now makes a 3 gal HW heater that runs on 12v.

Mostly made for outboards , but it might solve your problem.
 
AYBC aside, I had a buddy look pretty hard into these for his boat, and he could not find one that the manufacturer did not very emphatically warn against installing in boats. Being a somewhat cold weather boater to begin with, he went with a Hurricane diesel hydronic system and was very happy with it. A Grand Banks we chartered once had the same system, seemed pretty slick to me.
 
I had two propane demand hot water systems on a 41' Island Trader ketch. One for potable water, and one for raw water. Premise was that I could take a long hot shower with raw water, then rinse off with hot potable. Worked OK, but had to keep the sensors clean, clean, clean.

The demand hot water systems require power, water flow, and propane to ignite. The propane and power were there whenever the system was energized. In theory, only when you opened a hot water valve, did you have flow. - And there's the danger. If the sensing unit is dirty, corroded, got a speck of junk in it, then it senses flow, and the heater lights. - No flow... superheated water, steam, and BOOM! - I was lucky that the hoses just got hot, softened, and slipped from under the hose clamps. No injuries or damage, just some water spraying around the cabin.

I am replacing the water heater on Last Tango with a 120 VAC / heat exchanger system. Much less worry and risk. Save the propane for the Barbee.
 
Last Tango said:
I had two propane demand hot water systems on a 41' Island Trader ketch. One for potable water, and one for raw water. Premise was that I could take a long hot shower with raw water, then rinse off with hot potable. Worked OK, but had to keep the sensors clean, clean, clean.

The demand hot water systems require power, water flow, and propane to ignite. The propane and power were there whenever the system was energized. In theory, only when you opened a hot water valve, did you have flow. - And there's the danger. If the sensing unit is dirty, corroded, got a speck of junk in it, then it senses flow, and the heater lights. - No flow... superheated water, steam, and BOOM! - I was lucky that the hoses just got hot, softened, and slipped from under the hose clamps. No injuries or damage, just some water spraying around the cabin.

I am replacing the water heater on Last Tango with a 120 VAC / heat exchanger system. Much less worry and risk. Save the propane for the Barbee.
Click to expand...

A bad washer in the hot water tap can get you too.
 
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