On 11 May 2020 at 17:51 Steven Bode - SV Intention 1994-SM#117 <steve@...> wrote:
FRESH WATER SAFETY SHUTOFF SYSTEM REQUEST FOR COMMENTS
Amelians, I believe that there is a serious issue with the fresh water pump system on the Super Maramu and I would like your input.
The problem: In the event of a failure of the pressurized freshwater system — a break anywhere in the water plumbing, the entire freshwater supply could be drained overboard resulting in (a) loss of critical freshwater, (b) overuse of the freshwater pump (killing it) and (c) over use of the main bilge pump (killing it, too). Don’t ask me how I know.
Situational description: The freshwater pump may be left on. This is often the case when people are onboard, for example overnight or sometimes when they are ashore (off the boat).
The pump will pressurize the water system and remain off as long as the system remains pressurized. The pump will activate automatically any time there is a drop in water pressure.
If there is a break in the pressurized water system — a fault, then the pump will activate and run continuously until it is switched off, draining the entire fresh water supply into the bilge where it will be pumped overboard by the main bilge pump. This is a costly occurrence or possibly a safety issue if fresh water can not be resupplied, for example if the boat is off shore and there is no water maker.
A Proposal: A safety mechanism is needed to prevent this. A simple solution would be a timer that is activated every time the pump is activated. When the timer expires the pump is automatically deactivated until the system is manually reset. By determining the average time the pump is running each time it is activated, the timer could be set to shut off the system whenever above average run time is encountered. For example, if the pump typically runs for an average of 60 seconds, then the timer could be set for five minutes. If the pump runs for five minutes, then the timer turns off the power to the water pump, functioning like a breaker. The pump must be reset manually like a breaker.
Resetting the breaker: Ideally, this timer circuit would reset automatically once water pressure is restored, but that is much more complicated as it would require the deactivated pump to be turned on again or some other system employed.
This is a request for comments from those of you out there who have either considered this issue or who would like to develop a solution. I propose that a timer circuit be introduced between the breaker and the pump to serve as a safety device. It would be unobtrusive as long as the water was not to remain open for more than the timer duration. I am not a circuit designer, but I have been researching homebuilt circuits that might work.--
Steve Bode, Sailing Vessel Intention
Amel Super Maramu #117 (1994)
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