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Old 01-11-2019, 05:38   #1
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Tankless water heaters

I have been considering a 110v/120v Tankless electric hot water heater for my sailboat for in port use. I would like to remove the 6 gallon hot water tank for some storage space.
Has anyone else tried this and are there any recommendations on which work best?
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Old 01-11-2019, 06:56   #2
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Re: Tankless water heaters

Didn’t know these can be found for 120VAC. That should exercise your amp meter...

Unless it’s a dock queen, you still need a heater capable of running off engine heat so why have 2 heaters when your stated objective is to save space?
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Old 01-11-2019, 07:28   #3
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Re: Tankless water heaters

Hot water at the dock is handy.

But hot water from motoring into the anchorage after a long day's cruise... priceless!
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Old 01-11-2019, 10:14   #4
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Re: Tankless water heaters

Yes instant style at only 120V would be a lot of amps, and likely only handle a slow flow rate if the water starts out cold, might need to recirculate, so back to a tank of some sort.

OP link to the ones you're looking at?
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Old 01-11-2019, 10:20   #5
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Re: Tankless water heaters

Propane tankless heaters work very well, but need a hot exhaust vent. These can be quite small:
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Old 01-11-2019, 10:40   #6
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Re: Tankless water heaters

If you are looking for a hot shower yeah, there are plenty out there. Can even run on battery if you are willing to live with a very low flow shower head (0.5gal/min) and shut off flow when lathering.

Draw is about 20amps at 120v at 0.4gal/min for 41F temp gain. $210

Would need a 3kw inverter.

https://www.mscdirect.com/product/details/69592004
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Old 01-11-2019, 11:08   #7
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Re: Tankless water heaters

We installed a Titan (out of Florida) tankless 110v water heater in our camper and was impressed with the output. The entire unit was slightly smaller than a motorcycle battery.
140°F water that never ended, if I can work out the amps we will be adding one to Adeline.
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Old 04-11-2019, 19:33   #8
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Re: Tankless water heaters

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Propane tankless heaters work very well, but need a hot exhaust vent. These can be quite small:
Though effective, be aware that propane heaters can cause problems or have problems under way when the boat heels.
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Old 04-11-2019, 20:06   #9
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Re: Tankless water heaters

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Though effective, be aware that propane heaters can cause problems or have problems under way when the boat heels.
What kinds of problems? The only thing that comes to my mind is some sort of heel induced failure in flow switches.
The ones I have cursory looked at in failed (land installation) propane tankless heaters seemed pretty resistant to partial tilting.
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Old 05-11-2019, 14:38   #10
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Re: Tankless water heaters

Every manufacturer’s instruction manual for tankless propane heaters seems to call for installation that is both level and plumb. Using the unit on a heel, with the heat not going directly “up” as designed, is likely to cause problems. Some boats heel more than others, and some heaters may be more susceptible than others. Propane heaters need to be vented or mounted outside. Improperly installed units have killed people with carbon monoxide poisoning. Non-condensing designs have hot exhaust gases that require steel chimneys. Ask your insurer what they think before installing one.
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Old 05-11-2019, 14:50   #11
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Re: Tankless water heaters

A diesel engine produces a great deal of waste heat compared to the useful power delivered.


The potentially simplest tankless water heating system is a plate-type heat exchanger plumbed into the fresh water cooling circuit of the main engine or genset engine.
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Old 05-11-2019, 15:43   #12
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Re: Tankless water heaters

Sounds like sound advice to me
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Old 05-11-2019, 16:00   #13
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Re: Tankless water heaters

Quote:
Originally Posted by psk125 View Post
Every manufacturer’s instruction manual for tankless propane heaters seems to call for installation that is both level and plumb. Using the unit on a heel, with the heat not going directly “up” as designed, is likely to cause problems. Some boats heel more than others, and some heaters may be more susceptible than others. Propane heaters need to be vented or mounted outside. Improperly installed units have killed people with carbon monoxide poisoning. Non-condensing designs have hot exhaust gases that require steel chimneys. Ask your insurer what they think before installing one.
We have 34 years experience with propane instant water heaters on board WINGS. They have been reliable and generally trouble free. We are on the fourth one. We use it every day for dishes, showers, washing etc. We use it at the dock, at anchor, and at sea. They work on all angles of heel without issue. We first installed our Paloma (in 1986) with a hatch over it in the head compartment. Since then we deemed the hatch unnecessary and have moved it. Now there is no direct exhaust vent or inlet vent. The heat 4 inches over the top of the heater is only warm, not hot.

The biggest problem is that the water temp for dishes is too hot for the shower.

It uses a lot of propane, We use a 10 lb tank every 21 days, on the average but that also covers cooking and we cook virtually every day.

In Mexico they are available for about $125
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Old 05-11-2019, 21:50   #14
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Re: Tankless water heaters

I have been using a propane tankless water heater for three years, two years as a full time liveaboard. My heater is vented through the cabin top using SS vent tube. Something told me that old toilet paper roll inserts probably weren’t a good idea for hot exhaust. I sail in Mexico so fresh makeup air isn’t a problem as all my hatches and portlights are usually open. Besides I have CO and smoke detectors in various places on my boat, despite it being only a 38 footer.
I can’t say that I have used it at much of any angle of heel, as I mostly singlehand or sail with eyecandy. I don’t go below and shower if it’s blowing, and I don’t use hot water often for washing dishes.
I was genuinely curious if people had experience with poor performance at angles of heel since I consider myself quite safety conscious.
I may have to replace my heater due to cosmetic rust problems- some salt water can come down the exhaust stack when it is open. I found a tiny Rheim heater here in Mexico for less than $100 US.
Glad to hear that actual long term users are happy with their choices.
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Old 05-11-2019, 23:20   #15
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Re: Tankless water heaters

All the AC tankless heaters I have seen are 240v and draw 30 amps or more. Many dive and fishing boats have an on deck shower powered by propane. And electric tankless doesn't heat as high as a conventional water heater. Usually to about 110°F.
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