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10-15-2021, 10:08 PM
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#1
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Guru
City: Chattanooga
Vessel Name: Mishy Jean
Vessel Model: Helmsman Trawler 38E
Join Date: Oct 2020
Posts: 1,066
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Tankless hot water heater
Has anyone ever seen or heard of an electrical one built for a boat? I have seen some that go on RV’s but they are propane based. A friend asked if I had ever seen one, so I did a little research and thought I would ask here.
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10-15-2021, 11:22 PM
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#2
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Guru
City: Coupeville Wa.
Vessel Name: Pacific Myst
Vessel Model: West Bay 4500
Join Date: Oct 2015
Posts: 2,402
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I haven't seen one built for a boat. I've used many in the UK. I have experience with some installed on a boat. They aren't worth the trouble. They are prone to failure. The temperature is not well controlled if controlled at all.
__________________
Some things are worth doing simply because they are worth doing.
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10-16-2021, 08:08 AM
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#3
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Guru
Join Date: Oct 2007
Posts: 22,553
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Firs hassle with electric is a huge amount is required , many houses must be required to bring in 200A service , 60-80A at 240V is usually needed.
"The temperature is not well controlled if controlled at all.: (#2)
Same hassle as propane instant water heaters , off - on and no temperature stability.
Only cure is to hook the shower up is with a shower /tub selector valve , and send heater water back to tank for temperature stability.
There are RV propane units that will heat 6 or 10 gal of water , and can be operated on 120V power too.
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10-16-2021, 08:13 AM
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#4
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Senior Member
City: Cairns
Join Date: Jul 2019
Posts: 499
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I've never seen or used one on a boat but they are very popular in Asia houses and hotels. You need at least 3600W to get any sort of flow and temp rise. And that's in the tropics. If you have inlet water temps below 20°C, more power or less flow will be required.
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10-16-2021, 08:21 AM
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#5
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Guru
City: Chattanooga
Vessel Name: Mishy Jean
Vessel Model: Helmsman Trawler 38E
Join Date: Oct 2020
Posts: 1,066
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I thought that might be the case. The ability to “store” hot water for a little while after heating has its benefits also.
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10-16-2021, 09:16 AM
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#6
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Guru
City: Oconto, WI
Vessel Name: Best Alternative
Vessel Model: 36 Albin Aft Cabin
Join Date: Oct 2012
Posts: 3,145
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I don't like propane on boats, even though I carry it. I valve off both ends and disconnect the tank when I am done cooking. A "constant on' heater would give me nightmares. I guess I would consider a 110 volt home type model although this limits you to genny operation or plugged in.
I guess the bottom line would be..
No
pete
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10-16-2021, 09:56 AM
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#7
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Guru
City: Chattanooga
Vessel Name: Mishy Jean
Vessel Model: Helmsman Trawler 38E
Join Date: Oct 2020
Posts: 1,066
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Quote:
Originally Posted by Pete Meisinger
I don't like propane on boats, even though I carry it. I valve off both ends and disconnect the tank when I am done cooking. A "constant on' heater would give me nightmares. I guess I would consider a 110 volt home type model although this limits you to genny operation or plugged in.
I guess the bottom line would be..
No
pete
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The concern with a house unit would be the possibility of tied together neutral and ground wires. I agree with you on the propane. Many folks use it successfully, though.
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10-16-2021, 01:04 PM
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#8
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Guru
City: Between Oregon and Alaska
Vessel Name: Charlie Harper
Vessel Model: Wheeler Shipyard 83'
Join Date: Jun 2016
Posts: 3,021
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Some fishermen use propane tankless water heaters on deck. Not inside the hull. An electric version takes more power than most boats have or is available at a marina. Even those with generators.
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10-16-2021, 01:23 PM
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#9
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Guru
City: Seattle
Vessel Name: AZZURRA
Vessel Model: Ocean Alexander 54
Join Date: Aug 2017
Posts: 4,281
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My boat came with an electric hot water on demand faucet. It wasn’t really my thing so I removed it. It worked best on generator, you couldn’t use it on batteries. When on shore power you could use it but Then you had to balance it with other high high amp competing loads.
It really depends on how you use your boat and why you would be adverse to using a traditional hot water tank.
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10-16-2021, 02:23 PM
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#10
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Senior Member
City: Cairns
Join Date: Jul 2019
Posts: 499
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Quote:
Originally Posted by Helmsman
The concern with a house unit would be the possibility of tied together neutral and ground wires. I agree with you on the propane. Many folks use it successfully, though.
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If you don't like propane nor electric, the only other practical option is some form of calorifier or heat exchanger. These are available as instantaneous (very popular with the camping/4WD crowd here) or storage. You don't mention how often you motor nor how much hot water you want??
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10-16-2021, 03:27 PM
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#11
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Moderator Emeritus
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 21,129
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We had one in a previous house that ran on natural gas and it was great. But for a boat, no way.
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Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
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10-16-2021, 04:09 PM
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#12
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Guru
City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
Join Date: Jul 2016
Posts: 5,482
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Looked into all methods for when our 180 litre 240v electric dies.
Came to the conclusion that a $400 25 litre 240v electric will the the most viable and cost effective way to go as I can swap that out myself.
1800watt elements are about $40 extra
https://www.bunnings.com.au/dux-prof...ug-in_p5104137
__________________
Everything on a boat is broken, you just don't know it yet
Full time cruising is repairing boats in exotic locations
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10-16-2021, 04:16 PM
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#13
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Guru
City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
Join Date: Jul 2016
Posts: 5,482
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Quote:
Originally Posted by GoneDiving
If you don't like propane nor electric, the only other practical option is some form of calorifier or heat exchanger. These are available as instantaneous (very popular with the camping/4WD crowd here) or storage. You don't mention how often you motor nor how much hot water you want??
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Only practical if you use the big motor every day
I thought one could run off the Genset but likely not
In the thread below a 38hp didn't work so our 21hp certainly won't
But it'll pump out plenty of juice to run an electric like I posted above
For us, solar currently gets us there most days
https://www.cruisersforum.com/forums...-152072-5.html
__________________
Everything on a boat is broken, you just don't know it yet
Full time cruising is repairing boats in exotic locations
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10-16-2021, 04:17 PM
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#14
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Guru
City: San Diego
Vessel Name: SEA WOLF
Vessel Model: 1979 CHB 41 Trawler
Join Date: Feb 2020
Posts: 996
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I’ve looked at the propane units and understand the concerns. I’ve been contemplating one on the swim step as part of a transom shower but don’t think I’d want one in the hull either.
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10-16-2021, 04:56 PM
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#15
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TF Site Team
City: Jacksonville
Join Date: Nov 2008
Posts: 11,670
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Quote:
Originally Posted by Helmsman
Has anyone ever seen or heard of an electrical one built for a boat? I have seen some that go on RV’s but they are propane based. A friend asked if I had ever seen one, so I did a little research and thought I would ask here.
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Not built for a boat but you can always modify it. We spent a season in Brazil and these shower heads were in the majority of the houses. The water temperature to the head was probably 70 degrees which helped. It took a while to get over the idea that you are standing in water with less than code wiring. We never did got shocked though.
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10-16-2021, 05:39 PM
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#16
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Guru
City: Seattle
Join Date: Jun 2012
Posts: 3,305
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Quote:
Originally Posted by Simi 60
Looked into all methods for when our 180 litre 240v electric dies.
Came to the conclusion that a $400 25 litre 240v electric will the the most viable and cost effective way to go as I can swap that out myself.
1800watt elements are about $40 extra]
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Simi, what are you going to do with only 6 gallons of hot water??? By the time it gets mixed down with incoming cold water you're likely to obtain about 3-4 gallons of hot. 2 people living full time, showering, washing dishes, etc.
I like the idea of a huge residential heater, say 160-200 liters, with a 240V element and a 24VDC-900watt element also, so it can run off the generator, load dump from solar, and have enough heavily insulated capacity to last several days.
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10-16-2021, 05:48 PM
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#17
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Guru
City: San Diego
Vessel Name: SEA WOLF
Vessel Model: 1979 CHB 41 Trawler
Join Date: Feb 2020
Posts: 996
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Quote:
Originally Posted by Mako
Simi, what are you going to do with only 6 gallons of hot water??? By the time it gets mixed down with incoming cold water you're likely to obtain about 3-4 gallons of hot. 2 people living full time, showering, washing dishes, etc.
I like the idea of a huge residential heater, say 160-200 liters, with a 240V element and a 24VDC-900watt element also, so it can run off the generator, load dump from solar, and have enough heavily insulated capacity to last several days.
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Yeah your HW tank is just another form of energy storage - and a lot cheaper than batteries! Tankless really doesn’t make much sense if you’re using electric.
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10-16-2021, 06:29 PM
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#18
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Guru
City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
Join Date: Jul 2016
Posts: 5,482
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Quote:
Originally Posted by Mako
Simi, what are you going to do with only 6 gallons of hot water??? By the time it gets mixed down with incoming cold water you're likely to obtain about 3-4 gallons of hot. 2 people living full time, showering, washing dishes, etc.
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Maybe the 50 litre one
But we sure as hell don't need 180 litres
Washing up once a day uses probably 5 litres
A shower every second day uses a few more in winter
In summer we dont need hot water for showers at all
Quote:
I like the idea of a huge residential heater, say 160-200 liters, with a 240V element and a 24VDC-900watt element also, so it can run off the generator, load dump from solar, and have enough heavily insulated capacity to last several days
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Reality is with a normal Resi system if you miss a day of charging it up it takes twice as long the next day.
By day 3 it's pretty much cold, so better off with a smaller system with shorter charge times done daily imho
Not sure how you'd get dual elements in an off the shelf HWS.
__________________
Everything on a boat is broken, you just don't know it yet
Full time cruising is repairing boats in exotic locations
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10-16-2021, 07:05 PM
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#19
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Senior Member
City: Cairns
Join Date: Jul 2019
Posts: 499
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Quote:
Originally Posted by Simi 60
Only practical if you use the big motor every day
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There, sort of. 😁. Or the OP could install sufficient storage. Or have light usage to not run out. That's why I asked his usage and cruising requirements.
Quote:
Originally Posted by Simi 60
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Why didn't this work? I would have thought a smaller engine is likely to run hotter and be able to do the job. Sure longer run times may be needed but it's hard to see it not working at all on any engine with coolant at ~80°C.
25l may work for you but on vessels our size (I don't know the OP's) I'd side with the bigger, the better mentality: solar banking; extra storage for SNAFUs or greedy guests and minimal marginal costs. Given the OP's dislike of propane and electric I'd want as much buffer as possible.
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10-16-2021, 07:30 PM
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#20
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Guru
City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
Join Date: Jul 2016
Posts: 5,482
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Quote:
Originally Posted by GoneDiving
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25l may work for you but on vessels our size (I don't know the OP's) I'd side with the bigger, the better mentality: solar banking; extra storage for SNAFUs or greedy guests and minimal marginal costs. Given the OP's dislike of propane and electric I'd want as much buffer as possible.
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Greedy guests are never onboard our vessels
And as I said, a big HWS takes a long time to charge and is brutal on the amps or seems that way to me.
If keeping on top of ours, doing it daily from around 10am it takes 1.5 hours + or - pulling 80 amps @ 24v and that's with us not using much hot water, if we did it would surely take a lot longer.
Ok on a sunny day as we cover that and the rest of the boat running most of the time
But when a cloud goes overhead I freak out a bit seeing the spike
I would like to think a new 50 litre unit would take a lot less time to charge up.
More time for smashing amps into the LFP bank.
BUT.......as we don't have the LFP yet my views might well change when we've had in in for a month or three to access.
__________________
Everything on a boat is broken, you just don't know it yet
Full time cruising is repairing boats in exotic locations
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