Marine vs House electric water heaters

[Kotheof]

Hello everybody, I would like to hear your opinions about the differences between an electric water heater with a built in heat exchanger that is made for use in a house and a marine one.
Is the first one even suitable for a long term use on a boat or will it corode in the first month?

Some water haters use some kind of glass to store the water, is that too fragile for a sailing boat?
Anybody tried it?
One obvious difference I can spot is in most designs is that the marine ones are smaller and have more options for installation in titled surfaces in order to to fit in a boat locker etc.
Here in Greece where I live the marine water heaters cost 5 times more than the house ones and I am trying to understand why....
Thanks in advance!

[Lepke]

I have a 50 gallon house electric water heater that's about 15 years old. It's not rusting away. I did replace the heating element about 7 years ago.

[rslifkin]

A glass lined tank shouldn't be an issue. Raritan makes marine water heaters with glass lined tanks that hold up fine.



If you don't have a gas powered boat or have a non-fuel-containing space to mount the heater in, you don't need ignition protection. So I can't think of much that a marine specific heater would offer you.

[Franziska]

I take it you talk about the electric type with a reservoir.

In case of the gas driven ones you do absolutely need a very well vented space, no matter if there is fuel stored in the space or not. If not any you have a leak everyone will have a huge fireworks display.
If you get one like that it has to have a completely separated off burn chamber, without test flame. You also need it connected directly to a exhaust and vent chimney.
Btw. These are not fully legal in Europe if installed in a boat. Not sure about a cockpit installation.

Regarding the electric ones with reservoir, make sure it's not to big.
About 40l is plenty. You do want to have a volume which requires more often reheating to prevent germs, funghi and so on.
House ones will run with 220v, so you need to be able to supply that, or be able to add a suitable 12v heating cartridge.
The other issue is that the domestic ones may be geared towards starting heating automatically not sure if that creates issues.

[mikecambrai]

Domestic water tanks are usually low pressure as they have the header tank in the loft of the house and only get the pressure from the head of water. Marine water tanks will be designed to take the pressure probably up to 7 bar and hence the material will be much thinker. You can buy high-pressure domestic ones in France I think. See what the local rating is in the DIY shop selling the tanks.

[Clivevon]

Always the "Anchor Factor" for anything boaty. I was going to suggest a caravan hot water cylinder but that wouldnt have connections for engine heating. I did find this one which was about the smallest I saw:
Domestic:
https://www.heatandplumb.com/acatalo...2:298-0&sort=2
Or this marine one - not that much different in price.
Marine:
https://www.asap-supplies.com/produc...-litres-520140

Maybe browse around those 2 suppliers websites? ASAP do say they can supply Greece.

[RigBig]

What hasn't been mentioned yet is the AC wiring of a non marine hot water heater. A box store unit will more than likely have the ground and neutral wires connected at the hot water unit. You don't want that on a boat. The ground and neutral wire should only be connected at the dock pedestal and NOT anywhere on a boat.

[GinTonic]

I have an Excel VentFree Tankless water heater , it is an advanced version of the Paloma from a few years ago. Starts up with only 2 psi. of water pressure. Holds up to 150 psi. All other tankless gas water heaters require at least 20 psi to start up due to their outdated technology. Electronic Ignition: no standing pilot required ODS Vent-Free technology:ODS is to gas what a circuit breaker is to electricity. Bought it at https://excelonlinestore.com/product...-ventfree-lpg/

Originally Posted by Kotheof

Hello everybody, I would like to hear your opinions about the differences between an electric water heater with a built in heat exchanger that is made for use in a house and a marine one.
Is the first one even suitable for a long term use on a boat or will it corode in the first month?

Some water haters use some kind of glass to store the water, is that too fragile for a sailing boat?
Anybody tried it?
One obvious difference I can spot is in most designs is that the marine ones are smaller and have more options for installation in titled surfaces in order to to fit in a boat locker etc.
Here in Greece where I live the marine water heaters cost 5 times more than the house ones and I am trying to understand why....
Thanks in advance!

[Franziska]

Ventfree is not an option on a boat in Europe. Even with a completely to the inside of the boat sealed burning chamber, and a exhaust and air inlet stack it is very much a debate if that is permissible. Safest solution would be most likely an on deck installation.

Originally Posted by GinTonic

I have an Excel VentFree Tankless water heater , it is an advanced version of the Paloma from a few years ago. Starts up with only 2 psi. of water pressure. Holds up to 150 psi. All other tankless gas water heaters require at least 20 psi to start up due to their outdated technology. Electronic Ignition: no standing pilot required ODS Vent-Free technology:ODS is to gas what a circuit breaker is to electricity. Bought it at https://excelonlinestore.com/product...-ventfree-lpg/

[GinTonic]

Originally Posted by Franziska

Ventfree is not an option on a boat in Europe. Even with a completely to the inside of the boat sealed burning chamber, and a exhaust and air inlet stack it is very much a debate if that is permissible. Safest solution would be most likely an on deck installation.

ODS technology originated in Europe, and has been widely used in European gas heating appliances for more than 45 years with an outstanding record of safety and then adopted by U.S. manufacturers for all vent-free gas products such as logsets and camper heaters.

Consumer Product Safety Commission (CPSC) accident/incident data accumulated since 1980 show an unparalleled 100% safety record on ODS-equipped vent-free gas heating appliances. Industry engineers say the ODS pilot is to gas what a circuit breaker is to electricity.

[Franziska]

Shoreside you are right, but on boats it's a different subject.

Boats heel, have spaces in the bilge which can not be properly vented and boats are not connected to permanent electrical currents.

I'd love to use a Propane on demand water heater on our boat, but, as far as I know and have researched they are not fully legal to be used on boats in Europe.
Old installations are permitted under a grandfathering rule.

Vent free is definitely forbidden on boats in Europe (Vent free = the burning chamber has openings towards the interior of the boat).
Even with the full enclosed and directly via a chimney to the exterior vented burning chamber the installation of any such equipment below on a boat in Europe is not fully legal to my knowledge.

Originally Posted by GinTonic

ODS technology originated in Europe, and has been widely used in European gas heating appliances for more than 45 years with an outstanding record of safety and then adopted by U.S. manufacturers for all vent-free gas products such as logsets and camper heaters.

Consumer Product Safety Commission (CPSC) accident/incident data accumulated since 1980 show an unparalleled 100% safety record on ODS-equipped vent-free gas heating appliances. Industry engineers say the ODS pilot is to gas what a circuit breaker is to electricity.

[joelhemington]

Originally Posted by GinTonic

I have an Excel VentFree Tankless water heater , it is an advanced version of the Paloma from a few years ago. Starts up with only 2 psi. of water pressure. Holds up to 150 psi. All other tankless gas water heaters require at least 20 psi to start up due to their outdated technology. Electronic Ignition: no standing pilot required ODS Vent-Free technology:ODS is to gas what a circuit breaker is to electricity. Bought it at https://excelonlinestore.com/product...-ventfree-lpg/

Bookmarked this for when the time comes - especially like the fact that it's ventless. Supplying a stainless steel vent up through the deck would be a PITA. For $200 how can you lose? Thanks

[Franziska]

"Boom", is what you can lose. Actually it's what it will make.

Originally Posted by joelhemington

Bookmarked this for when the time comes - especially like the fact that it's ventless. Supplying a stainless steel vent up through the deck would be a PITA. For $200 how can you lose? Thanks

[boat driver]

electric hot water tank with or without dual heating capability is fine. Material construction and configuration is your choice. Install configuration in boat may be the challenge that returns focus to the marine units. Logical approach to your install will dictate the materials as in corrosion concerns.
The diesel fired units in trucks are often the most compatible and often robust, but it really comes to your choice of labor vs price.
The insurance company becomes involved when gas is introduced.
A/C voltage source is standard and connections to unit standard. Ground wire may need investigating depending on voltage and design.

[GinTonic]

Originally Posted by Franziska

Shoreside you are right, but on boats it's a different subject.

Boats heel, have spaces in the bilge which can not be properly vented and boats are not connected to permanent electrical currents.

I'd love to use a Propane on demand water heater on our boat, but, as far as I know and have researched they are not fully legal to be used on boats in Europe.
Old installations are permitted under a grandfathering rule.

Vent free is definitely forbidden on boats in Europe (Vent free = the burning chamber has openings towards the interior of the boat).
Even with the full enclosed and directly via a chimney to the exterior vented burning chamber the installation of any such equipment below on a boat in Europe is not fully legal to my knowledge.

If vent free is prohibited in Europe , than does this mean you cannot have a gas range / stove in your boat in Europe ? As far as I know the burning chamber of a gas stove has openings towards the interior of the boat...and these water heaters are 38,000 Btu , very similar power to a gas range.