"Geoff Schultz" wrote

You can get elements that have both 120V AC and 12V DC feeds. See
http://www.svhotwire.com/divert_loads.html


That's great, but:
- how is the water temperature controlled? Temperature should not exceed
49C to prevent scalding (used to be 60C)
- Once water reaches maximum temperature, what do you do then?

Seems to be of limited value if engine is also used to heat water. Our hot
water gets up to about 45C after an hour of motoring at low speed. It is
self limiting because of engine thermostat.

GBM

"Geoff Schultz" wrote

You can get elements that have both 120V AC and 12V DC feeds. See
http://www.svhotwire.com/divert_loads.html


GBM wrote:
That's great, but:
- how is the water temperature controlled? Temperature should not
exceed
49C to prevent scalding (used to be 60C)
- Once water reaches maximum temperature, what do you do then?

Seems to be of limited value if engine is also used to heat water. Our
hot water gets up to about 45C after an hour of motoring at low speed.
It is self limiting because of engine thermostat.

Just curious because I'm not familiar that with them - do marine water
heaters have any sort of provision whereby you can insert a temperature
sensor, which can then be hooked up to a limiting circuit?

Sailaway wrote:
"Geoff Schultz" wrote

You can get elements that have both 120V AC and 12V DC feeds. See
http://www.svhotwire.com/divert_loads.html


GBM wrote:
That's great, but:
- how is the water temperature controlled? Temperature should not
exceed
49C to prevent scalding (used to be 60C)
- Once water reaches maximum temperature, what do you do then?

Seems to be of limited value if engine is also used to heat water. Our
hot water gets up to about 45C after an hour of motoring at low speed.
It is self limiting because of engine thermostat.

Just curious because I'm not familiar that with them - do marine water
heaters have any sort of provision whereby you can insert a temperature
sensor, which can then be hooked up to a limiting circuit?

Marine water heaters typically have two heating devices in one package.

The first is a standard 110V electrical heating element, connected thru
a thermostat mounted on the tank, more or less just like your standard
domestic water heater.

The second heating device is a coil of tubing inside the tank thru which
you can circulate your engine coolant. There is no thermostat in the
water heater for this circuit. But the engine has a thermostat which
controls the temperature of the engine coolant which is circulating in
it. This means that the hot water temperature will approach the engine
thermostat set temperature with prolonged engine run times.

bob

bob wrote:
Marine water heaters typically have two heating devices in one package.

The first is a standard 110V electrical heating element, connected
thru a thermostat mounted on the tank, more or less just like your
standard domestic water heater.

The second heating device is a coil of tubing inside the tank thru
which you can circulate your engine coolant.

Hi Bob,
Actually I was curious about the 12 volt heating device someone had
mentioned they had in theirs - would that one come with, or have
provision for inserting a thermostat or temperature sensor? Thanks

Sailaway wrote:
bob wrote:
Marine water heaters typically have two heating devices in one package.

The first is a standard 110V electrical heating element, connected
thru a thermostat mounted on the tank, more or less just like your
standard domestic water heater.

The second heating device is a coil of tubing inside the tank thru
which you can circulate your engine coolant.

Hi Bob,
Actually I was curious about the 12 volt heating device someone had
mentioned they had in theirs - would that one come with, or have
provision for inserting a thermostat or temperature sensor? Thanks

I followed the link posted by others and looked at the elements - they
look more or less exactly like standard 110V or 220V elements do - that
is, they do not have an integral thermostat. If your plan was to
install the 12V element in addition to an existing 110V element, then
you would need another thermostat as well. And perhaps even more
importantly, you would need another threaded tank penetration into which
to screw the element.

bob

You could use a home water heater 120/240V AC thermostat on 12V DC. I just
needs contact with the inner tank. If the water heater has a 120V
thermostat, disconnect all the 120V wires and use it for 12V.
Lee Haefele
"Sailaway" wrote in message
...
"Geoff Schultz" wrote

You can get elements that have both 120V AC and 12V DC feeds. See
http://www.svhotwire.com/divert_loads.html


GBM wrote:
That's great, but:
- how is the water temperature controlled? Temperature should not
exceed
49C to prevent scalding (used to be 60C)
- Once water reaches maximum temperature, what do you do then?

Seems to be of limited value if engine is also used to heat water. Our
hot water gets up to about 45C after an hour of motoring at low speed. It
is self limiting because of engine thermostat.

Just curious because I'm not familiar that with them - do marine water
heaters have any sort of provision whereby you can insert a temperature
sensor, which can then be hooked up to a limiting circuit?

"GBM" wrote in news:5vvzg.53527$Uy1.48756
@read1.cgocable.net:


"Geoff Schultz" wrote

You can get elements that have both 120V AC and 12V DC feeds. See
http://www.svhotwire.com/divert_loads.html


That's great, but:
- how is the water temperature controlled? Temperature should not exceed
49C to prevent scalding (used to be 60C)
- Once water reaches maximum temperature, what do you do then?

Seems to be of limited value if engine is also used to heat water. Our hot
water gets up to about 45C after an hour of motoring at low speed. It is
self limiting because of engine thermostat.

GBM

I would say that if you have large enough panels to worry about this, then
you should use the controller in PWM mode. Solar panels don't require a
load. Wind generators do. I use 1 controller for both.

In real life I rarely have problems with the batteries being completely
charged while cruising. I only have 2 panels that output 68W *peak* each.
The only time that I have the luxary of fully charged batteries is when it's
been blowing 15-20+ for a day or two and my wind generator is cranking.

Remember, this is a boat and there's no one-size-fits-all solution. You can
always buy a resistive load such as the one at
http://www.svhotwire.com/divert_loads.html, but then you have to do something
with all of that heat. I can always find something to do with my "extra"
power such as making more water and washing down something on the boat.
Don't go crazy solving a problem that probably doesn't exist in real world.

-- Geoff