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