Tankless hot water heater.

[86Hat41]

Has anyone ever installed an on demand tankless hot water heater in their boat? They are less than $500 at Home depot and those I’ve spoken to with them in their homes seem to like them with no complaints.

Removing my current 10gal. heater will provide me with MUCH easier access to the outboard side to my engine and vacuflush vacuum generator, not to mention taking about 125lbs out of the boat.

 

[Tim Powell]

Has anyone ever installed an on demand tankless hot water heater in their boat? They are less than $500 at Home depot and those I’ve spoken to with them in their homes seem to like them with no complaints.

Removing my current 10gal. heater will provide me with MUCH easier access to the outboard side to my engine and vacuflush vacuum generator, not to mention taking about 125lbs out of the boat.

I hear the electric ones are not very good. I have a gas one in my home all well so if you have propane on board go for it. I am sure some more will chime in....

 

[Boatsb]

How much power do you have aviable on the boat. Small ones for a shower and sink draw about 50 amps.

 

[RonNP]

I've had one in my home and didn't like it. You turn on the water and have to wait a few minutes for the gas to warm up the hot water and for it to go through the pipes to reach you. My overall gas bill went down marginally but my water bill went up marginally as well. I would think on a boat with limited water storage capacity this would be a losing proposition as too much water would be wasted unless you have a water maker on board.

 

[krush]

How much power do you have aviable on the boat. Small ones for a shower and sink draw about 50 amps.

Damn that power vs energy thing.

 

[Boatsb]

How many amps of 240 volt 60 htz alternating current would be available on your vessel during its time of intended use?


Is that better Jay?

 

[SEVEN]

This is been discussed on previous posts, most everybody indicates there's too much power draw and unless you're plugged to an electrical cable at your dock you have to fire up your generator each time you want to take a shower or wash the dishes etc.

 

[Boatsb]

This is been discussed on previous posts, most everybody indicates there's too much power draw and unless you're plugged to an electrical cable at your dock you have to fire up your generator each time you want to take a shower or wash the dishes etc.

Having installed many inverter systems I have not included the draw of a hot water heater in my lead calculations. Then again I'm sure someone has tried it.


Most docks have a 240 50 amp service for boats under 65 feet or so. If you were to use that just for the wate heater you will have to wash dishes in the dark without air conditioning.

 

[MikeP]

Waste of time and money and you will end up converting back to a conventional HW heater. Don't do it. The advantage it MAY provide in the home does not apply on a boat due to both reasons mentioned - very high power draw and waste of water.

FWIW, we have had them in several houses and my opinion is mixed. IF you get one sized for a single bathroom (for example) and locate it in or adjacent to that bathroom, they work great. OTOH, I have NEVER had a whole-house version that was satisfactory. We are fighting that battle even as I write this - trying to get a new whole house tankless to perform. It was already in the house and it just can't do the job.

One problem is that a tankless requires X amount of water low to activate. A whole house (or whole boat) tankless may not see enough flow to activate if just a sink faucet is turned on.

Again, if you have three bathrooms and put a small tankless in each, they really DO work well. Otherwise...not so much

 

[krush]

How many amps of 240 volt 60 htz alternating current would be available on your vessel during its time of intended use?


Is that better Jay?

I was agreeing with you 100%. Both tank and tankless water heater will use the same amount of energy, but tankless requires much more powar!!@#

 

[jim rosenthal]

However, there IS a way to get essentially "free" hot water- buy a marine water heater with a coolant loop in it. This diverts some of the flow from the engine's cooling system (the fresh water or antifreeze side) through a pipe in the water tank, and heats the fresh water in the tank. Some advantages:

1) VERY hot water- 180 degrees, meaning you don't need much of it for showering and doing dishes, as hot as you can stand.
2) no cost to you. The energy that is heating the water heater would just go out through the cooling system otherwise.
3) available as long as the engine or generator it is hooked to is running.
4) stays hot a long time. Since most water heaters are located in the engine room anyway, when you are running the boat, it is hot in there, so the water heater loses heat a lot more slowly than you'd think.
5) heating element is always available for when the engine/genset is off.

Disadvantages:

1) water is HOT. REALLY HOT. It can burn you. And you can't turn the temp down- although you CAN get a tempering valve which will mix in some cooler water as it comes out of the water heater, and bring it down a bit.
2)more plumbing (a problem at least in theory, although I have not had problems with it.)
3) people will think you are a cheapskate.
4) people will think you are a sailboater or trawler owner. See item #3 just above.

Seriously, I have had this setup for a long time and it works VERY well. Incidentally, the recovery time for the water heater is VERY quick with the engine or genset running. Evidently there are a lot of BTUs in the engine cooling system just waiting to help you take a Hollywood shower on your boat.

 

[Walter P]

My experience with tankless heaters was less then good. Back in The Netherlands, (Holland) they were quite common and as prior posts state it, they are slow recovery and IMO not very efficient. I don't have any experience with them here in the US but almost everything I hear from folks who have had them has been negative.

Dr. Jim's suggestion to use the engine hot water to heat the domestic water supply is very good as long as you're careful not to burn yourself.

Walt

 

[Boatsb]

My 41c has an engine heated hot water tank. Run a few hours and there's nothing but hot water. My tanks between the engines in the er.

 

[BOATER BOB]

I would look at relocating tank or maybe a different style like a Horizontal round one mounted up out of the way of engine .
Bob

 

[Finalee]

Take a look at the Bosch water heaters. Very compact and quick recovery. Plus a glass tank and changeable zinc.

 

[Glory]

How much power do you have aviable on the boat. Small ones for a shower and sink draw about 50 amps.

50 amps, where the heck are you gunna get that?

 

[rwappleton]

What Jim said. My hot water heater stays hot for 18 hours or more after shut down

 

[jim rosenthal]

Right, and if the AC element has to boost it a bit, it doesn't take long at all. And, if you are on the hook, running your genset, and the genset engine feeds the coolant loop, you will always have hot water from that.

 

[krush]

Incidentally, the recovery time for the water heater is VERY quick with the engine or genset running. Evidently there are a lot of BTUs in the engine cooling system just waiting to help you take a Hollywood shower on your boat.

say 136,000 btu per gal diesel. figure about 1/3 ends up in the coolant. that's 45,000 btu per gal potentially for your shower pleasure....quite a bit!

 

[steve c]

This past summer I replaced the water heater on my 1987 41C. It was located outboard of the port engine and was in a very difficult place to service. My boat is a galley up configuration and I found space under the sink drain trap to relocate. I wa able to easily re-
plumb and wire the unit using the existing set up. Less than $250 from Defender and much easier to service. I still haven't found a way to remove the old unit short of cutting it up. Ballast for now I guess. I originally considered a tankless unit but because of the current draw it wasn't feasable for my application. The new heater has the ports for using the engine coolant but I did not configure it that way.Sorry about the late response.