Has anybody tried fitting the whale pressure switch into the negative wires instead of the positive. If the switch led earth is connected to the pump side earth the light in theory should work as before ? Will this cause any problems?
Whale pressure switch
- Thread starter guy55
- Start date
It is unconventional to use the pressure switch in the 0V side of the wiring, so I have to ask why are you considering it? Convention suggests means of control should where possible isolate the appliance from sitting at elevated potentials - This is not just good practice from the safety point of view, and there is a practical reason, in the event of the pump developing a fault to ground, the means of isolation would leave the fault passing current, and that could start electrolysis of the the water producing hydrogen which is of course highly flammable.
In relation to the indicator lamp/LED it cannot be assumed the 0V side of the indicator will be connected directly to the pumps 0V terminal, In fact its far more likely to have its own 0V connection in the control panel, so it would not continue to work as intended.
If you could explain why you want to do this we many be able to suggest an alternative solution.
Thanks for the response. I understand the worry about electrolysis but how could the pump earth other than though the wire which will have an open switch.
I am trying to replace the surge damper switch on an older Coachman and still retain the warning led on the switch which only illuminates when pump is pumping. Others have this permanently lit and have fitted a second led on the pump side of the switch ie positive feed when pump is working. Any help much appreciated.
When it's working properly, it can't "earth" other than through the -ve - but electrics should be fail-safe and allow for "earthing" in fault conditions.
From what you tell us you want an indicator lamp that only illuminates when the pump is running, but the indicator you have is in the pump isolator switch.
By far the simplest way to achieve a pump active indicator would be to have an LED (with voltage dropping resistor) or a small bulb connected in parallel across the pump's electrical connections. This avoids unconventional wiring.
With reference to electrolysis issue, using your 0V pump switch, when the switch opens it does stop the current flow for the pump, but the pump remains connected to the +12V. This means the whole pump remains at the elevated potential. If the pump develops a fault it might allow water to reach the motors electrical parts and thus the 12V potential.
The water will almost certainly find other parts of the water system such as the hot wate rheater's tank will be at 0V potential and thus between the pump and hot tank the water could see the voltage potential and begin to electrolyse.
It's far better to truly isolate the pump from the power supply as per the conventional wiring.
By far the simplest way to achieve a pump active indicator would be to have an LED (with voltage dropping resistor) or a small bulb connected in parallel across the pump's electrical connections. This avoids unconventional wiring.
With reference to electrolysis issue, using your 0V pump switch, when the switch opens it does stop the current flow for the pump, but the pump remains connected to the +12V. This means the whole pump remains at the elevated potential. If the pump develops a fault it might allow water to reach the motors electrical parts and thus the 12V potential.
The water will almost certainly find other parts of the water system such as the hot wate rheater's tank will be at 0V potential and thus between the pump and hot tank the water could see the voltage potential and begin to electrolyse.
It's far better to truly isolate the pump from the power supply as per the conventional wiring.
I think that is wise, because it mean it will make sense to anyone who may have the caravan after you.
Good luck
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