Help W/water tank pump pressure switch

Re: Help W/water tank pump pressure switch

Hi "Swamp",
Several things - -
You ask "what PSI should my tank be at?" That depends on where you want it to be and what your pump is capable of. You state that your pump is rated 60 PSI, I would suspect that to be the max if one is to expect a reasonable length of life for that pump. If that be so, than I would run it at a lower pressure, perhaps 20 to o40 PSI, or even lower if you don't need that much pressure. Lower pressure would also mean lower power consumption, assuming this is a positive displacement type pump.
Second: "Will there be any problem with the pumps internal switch and another working together?" - - - No, as long as the pressure settings of the external pressure switch is set lower than the pumps internal switch. That way, the internal switch will always stay on, and power to the pump will be controlled by the external switch.
Third: "I seem to remember a post on here talking about a AC rated Square D switch that would work with DC". This switch is likely the one spoken of: http://www.acehardware.com/product/index.jsp?productId=29000596 This switch has a very fast acting toggled mechanism that, depending on the amps demanded by your 12 volt pump, should result in the contacts lasting a long time. Since the double contacts in this switch open far enough and very fast, and with only 12 VDC to control, unless the pump's current draw is relatively huge, arcing won't be a problem. These switches have been known to withstand terrible abuse in 120 and 240 VAC service for years and still keep on working. While it may not be RATED for DC operation, I'd have no concern using it in your application if pump draw is less than 10 or 15 amps @ 12 VDC. It's also very easy to change it's pressure settings for much lower pressures, just adjust the nut that pre-loads the spring pressure exerted on the internal mechanism.