Electric circuits

[samphire]

This is my third season with my 272LE and I finally decided to do something about the leaky joints in my water system and the taps that would never turn off completely (We had to switch the water on and off at the distribution board each time we used the faucets). After several failures I thought that perhaps the Sureflo 7.5 amp pump was too powerful. So I put a 2.5 ohm resistor on the earth side of the pump and the result was miraculous. No more leaky taps. However I find the resistor is rated 50 watts and heats up more than I like. Can any one confirm that I should be using a resistor with, say, wire of three times the present guage and three times the length? Would that give the same resistance but less heat? The resistors cost about 20.00 a shot and I do not want to get the next purchase wrong. I'd appreciate some advice on this.

 

[Russ20666]

An alternative

Assuming that the DC resistance of the motor is about the same as the resistor, I don't doubt that your resistor is getting really hot. You're having it dissipate about 45 watts (P=6v x 7.5amps). Not to mention that you are throwing away a ton of power in the form of heat.If I were in this position I would rather opt for an adjustable water pressure regulator and take out the resistor. Then you could dial in the pressure on the taps but leave the higher pressure available for say a deck wash hose.

 

[samphire]

Thanks Russ

Thanks Russ. I shall investigate a water pressure regulator. Never heard of that before. It sounds like the best answer. However, I'm not sure I agree about "throwing away a ton of power". Doesn't the power consumption remain the same? What the resistor uses in heating-up the pump is being deprived of -- that's why the water pressure is lower with the resistor in the circuit. Also, it occurs to me the resistor is heating only when the pump is pumping. Maybe the risk from over heating is therefore not as serious as I thought.

 

[Russ20666]

What I meant was..

that battery power is being used to generate heat. That heat is doing no useful work and thus is being wasted. Since battery power on a boat is precious I always try to find the most efficient use of it.After thinking about your situation some more, I'm wondering if your system wouldn't benefit with the addition of an accumulator tank. This way the excess pressure would get stored in the tank and be available for the next time you turn on the faucet. Maybe enough would get stored that the pump won't need to run every time and save some power.Just a thought.