"Larry" wrote in message
...
"Neil" wrote in :

Heater is a 12v 100watt ceramic heater

Make a little test before going farther down this slippery slope.....

Put a 100W lamp in the boat at dusk. Measure the temperature when you
start. Come back in the morning and see how hot it is inside the boat
from
this 100 watt heat source. I doubt it will raise the boat 1 degree. That
will make it 11F inside when it's 10F outside....unless the wind is
blowing
through any hatches not hermetically sealed.

If you can't try this on the boat, try it in your garage WITHOUT parking
the warm car in there. Set a 100W lamp on the center of the floor at dark
and check it in the morning. The boat isn't insulated like the garage,
either.

--
Larry

The ceramic heater is not a lamp, it will in 15 minutes defrost all the
glass in a Mercedes Estate car and raise the interior temperature to
acceptable before starting. Trying to source an appropriate thermostat to
operate it in the boat's water tank compartment.

Neil

"Neil" wrote in :

The ceramic heater is not a lamp, it will in 15 minutes defrost all the
glass in a Mercedes Estate car and raise the interior temperature to
acceptable before starting. Trying to source an appropriate thermostat to
operate it in the boat's water tank compartment.

Neil



100 watts is 100 watts is 341.29 BTu/hr no matter what the resistive
element looks like. The bulb does convert a small amount of it to light
because it gets hot enough to incandesce, but the heat from that light is
absorbed by anything it lights up.

In spite of the ad hype, the BTU output of a cheap nichrome heater is
exactly the same as the same wattage amazingly expensive ceramic heater.
Buried inside the ceramic, by the way, is a nichrome wire, which is what
heats it. The ceramic heater does concentrate its BTu output into a nicer
stream of hot air, making it feel like it's putting out more heat, which
it's not. My old "milk house heater" has a metal case that gets warm, but
it heats the room just as good.

Oil heaters that look like old radiators heat the same, too, once the oil
get warmed up. Go figure...nostalgia?

All these heaters with open thermostats will make a boat explode in the
presence of gasoline or propane fumes in explosive concentrations.
Luckily, I've seen some upper-end heaters coming out with solid state
thermostats that have no contacts, but triacs to control them.

To convert watts to BTu, the formula is:

BTu/hr = Watts x 3.4129

Find other interesting conversions on:
http://www.simetric.co.uk/sibtu.htm

Any heater whos outlet gets hot enough to ignite cotton, like those damned
radiant heaters, should be BANNED with the kerosene heaters. People are
too stupid to use these heaters.

The leakage from the boat is lots more than 341 BTu/hr, I'd bet raising the
temperature only slightly and just killing the batteries.

--
Larry

"Neil" wrote in message
...

"Larry" wrote in message
...
"Neil" wrote in :

Heater is a 12v 100watt ceramic heater

Make a little test before going farther down this slippery slope.....

Put a 100W lamp in the boat at dusk. Measure the temperature when you
start. Come back in the morning and see how hot it is inside the boat
from
this 100 watt heat source. I doubt it will raise the boat 1 degree.
That
will make it 11F inside when it's 10F outside....unless the wind is
blowing
through any hatches not hermetically sealed.

If you can't try this on the boat, try it in your garage WITHOUT parking
the warm car in there. Set a 100W lamp on the center of the floor at
dark
and check it in the morning. The boat isn't insulated like the garage,
either.

--
Larry

The ceramic heater is not a lamp, it will in 15 minutes defrost all the
glass in a Mercedes Estate car and raise the interior temperature to
acceptable before starting. Trying to source an appropriate thermostat to
operate it in the boat's water tank compartment.

Neil

Granted your ceramic heater puts out more heat than a 100 watt light bulb I
still think Larry has a point. You'd never warm up a whole boat with this
but I guess you might raise the temp above freezing in a smaller
compartment. How often is it going to cycle on though? Might end up
running almost continuously. A real nuisance as you don't have AC to
recharge your batteries.
Why don't you just pump out the water tanks, add some RV-type antifreeze
(pink stuff, propylene glycol) and pump that through the system. Now you
don't have to worry as much about the charge of your batteries, about high
currents periodically running through wires or the whole system failing and
the water freezing.

In article NvIgf.127275$S4.46489@edtnps84,
"Gordon Wedman" wrote:

Granted your ceramic heater puts out more heat than a 100 watt light bulb

On what planet do your Laws Of Physics, reside...... 100 Watts is 100
Watts.... it doesn't matter if that comes from a light bulb or a ceramic
heater.....Ok now you say that the light output must be subtracted from
the 100 Watts, BUT, so does thew glow from the ceramic heating element
as well. Both are RESISTIVE Loads, both produce 100 Watts of energy
into the enviorment...Again 100 watts is 100 Watts...... back to High
School Physics for you.....

Me

On 2005-11-21, Neil wrote:

Thanks for the replies.
Heater is a 12v 100watt ceramic heater, power supply 4x120AH leasure
batteries (shore power will not be installed at my berth this side of
Winter).
Trying to raise temprature a few degrees in a compartment contaning water
tank and pipes, for ice protection (nowhere near any diesel).

hmm, if for example in cold wether heater was to run full time it'd deplete
those batteries in only 57 hours...

anyway it's be approximatley an 8 amp load, so a relay (eg automotve headlight
relay) would be a good idea to save wear on the expensive thermostat
contacts.

something like a refrigerator thermostat would probably cover the temperature
range you're interested in, but the contacts are backwards (open when cold)

the easiest fix would be to use an automotive horn relay anstead of a
headllight relay, but this would waste a small amount of electricity
(15ma - about what a LED uses) holding the relay contactts open.

If it's possible to attach heating wire to the pipes and then insulate
them that may use less electricity...

--

Bye.
Jasen