--- In [email protected], "dave hearnden" <[EMAIL PROTECTED]> wrote: > > Help. > > My Surflow pump has started to leak after about 5 years. > > So have gone for a Johnson of similar spec but this does away with the > accumalator and I have removed a seperate pressure switch which was also in > the system. (from days of old) > > The new pump does say it should not be run with an accumalator. It should > sense the water pressure and turnoff etc as if one is fitted > > My problem is: > > If you now switch on the new pump, the pressure tank Similar to a cars > expansion tank with raditor cap starts to overflow it has now split the > tank! spraying water everywhere. This is feed from a feed at the top of the > hot water tank. > > I also have a tank that is filled from the main water tank and is controlled > by a ball valve for the central heating > > The pump is at the front of the boat and the expansion tank and the tank > with water supply are at the bank with the hot water tank. > > The question is do I need this pressure tank? what's its purpose?
Bloody silly electronic pumps - why complicate things? To answer the question. That "car type" tank was used to save buying a pressure relief valve - probbaly cheaper in some long gone past. Your pump is delivering too much pressure for the pressure cap. The tank prevents the calorifier splitting when the water inside it expands. Fit a sutable PRV anywheer in the system a slong a sits on the hot side of any non-return voaves. It pressure must be above the maximumm pump pressure. Pipe the PRV outlet over the side or into the stern bilge. Alternatively refit the pressure swithch and adjust os it cuts the motor's electricity off just before the tank starts leaking. Unfortunatley no one has explained to me how those pumps deal with the pressure drop associated with the cooling water in the calorifier at night without an accumulator, or how they deal with very slight weaps and back leakage through their valves. I think most of them will do the "alarm clock thing" at about 03.00 in the morning unl;ess you turn the system off at night. If I was forced to have obne of those pumps I would keep teh accumulator - I do not see how it can cause the pump any problems. FWIW I know that last spring a shipment ha dbeen received with faulty pressure switches that either did not turn off or turned off at too high a pressure. Tony Brooks
