Water Pump Fusing

[Richard_5067800]

I have just tried to connect the external Whale water pump and the 10 amp fuse keeps blowing.

Is it likely to be the external Whale pump which is faulty or a more serious problem inside the van.

Thanks for your help.

 

[rayc]

Richard, If the fuse only blows when the taps are turned on with the pump fitted then it is most likely the pump itself. If you remove the pump and connect a load such as a stop lamp bulb in its place does the fuse blow?

If the fuse blows without the pump or load fitted then something in the van.

 

[ProfJohnL]

Hello Richard,

Like Ray C I believe that you will find that your pump is faulty. Submersible pumps are vulnerable to failure if they have been allowed to run dry.

The pumps are usually of a dual concentric construction, where the motor sits inside the inner tube, The motor shaft points downwards through a shaft seal into a lower chamber where the impeller sits. The outer tube provides an annular passage for water to flow when the pump runs.

The motor is hermetically sealed into the inner chamber, to prevent water from getting inside. If either the shaft seal or the power cable seal fails then the motor will eventually fill with water.

Typically these motors use about 3 to 4A when running, so by simple maths (Volts x Amps = Watts) 12 x 3 = 36 Watts or more power is being used. This causes the motor to get hot. Normally the water flowing through the pump dissipates the heat, but if you run out of water, then the temperature in the motor housing will rise.

As it gets hot, any air inside the motor housing will increase in pressure, and eventually it will overcome the shaft seal and vent a little. If the motor continues to run, they can get hot enough to cause the breakdown of insulation in the windings, resulting in short circuit.

If the pump is turned off, then it cools down. The air pressure in the motor housing drops and becomes slightly negative. This can encourage the induction of water through the shaft seal. Ultimately this action can cause the motor housing to fill up with water.

The moral of this, is always ensure the pump is fully submerged in water to keep it cool, and also when you have finished always disconnect the pump, to prevent it unintentionally being turned on whilst towing.

It could be wise to carry a spare.

 

[Damian]

Richard, the pump needs replacing as it is causing the fault.

If it is the Watermaster, you can get a new pump alone and replace just that , without having to replace the whole thing, if you are handy with a screwdriver.

However, when you remove the old pump and pull the wires through the sleeve, you may well be disgusted by the slime and black "gunge" that comes out!!!, but with a bit of time and a "pull through" made of wire and a small piece of cloth with bleach on it will soon clean it all out.

A new pump will cost something around