svsonora wrote:I have a [RULE 2000-GPH] pump for my sailboat. ...my sailboat's bilge hose has something like 6 feet upward travel before it hits the transom drain.
For an application in which a pump must lift its output more than six feet vertically, there will be a substantial reduction in the output of a centrifugal pump from its rated output. The RULE pump specification sheet shows their model 2000-GPH pump produces an output flow of 2000-GPH only when the pump output lift is zero-feet. That is a useless specification unless the pump is intended to pump water downhill. If you need to pump water uphill, that is, to lift water out of a sump area on a boat and overboard into the sea, the rating of RULE centrifugal pumps must be decreased significantly. For the 2000-GPH model, an output lift of 3.3-feet reduces the pump flow to 1,620-GPH, a derating of 380-GPH or 19-percent. An output lift of 6.6-feet reduces the pump flow to 1,300-GPH, a derating of 700-GPH or 35-percent.
A further problem with the rated flow of RULE centrifugal pumps is the operating voltage needed to produce those ratings. RULE uses an operating voltage of 13.6-Volts. The nominal terminal voltage of a fully-charged 12-Volt battery is only 12.8-Volts. RULE uses an operating voltage that is far above the voltage of a 12-Volt battery, unless the battery is being charged by a battery charger and has its terminal voltage forced to be much higher.
The model 2000-GPH 12-Volt pump is also rated to be drawing 12-Amperes at 13.6-Volts. That is 163-Watts of electrical energy. If the pump is run on 12.0-Volts, it only draws 8.4-Amperes, or 101-Watts. This represents a significant decrease in electrical power by a factor of 0.617, and there must be a corresponding significant decrease in output flow. Also note that the voltage decreased only 1.6-Volts from 13.6-Volts, a reduction of 0.88, but the electrical power consumed dropped by a factor of 0.617. This is a very non-linear reduction, more like an exponential reduction by a factor of almost 4.
A further problem is providing the electrical power to the pump. For a circuit drawing 12-Amperes, in order to reduce any electrical voltage drop in the wiring to the pump, and assuming the conductors will be at least 12-feet long, the wire gauge needed to limit the voltage drop to not more than three-percent would be 10-AWG. I suspect that there are almost NO installations of a RULE 2000 pump with the wiring to the pump done with 10-AWG conductors. This means the actual voltage at the pump is inherently going to be even lower than expected.
In summary, for a centrifugal pump that uses an unusually high voltage (13.6-Volts) as the operating voltage, uses a value of 0-feet as the amount of head on the pump output, is powered from a 12-Volt battery that is not under heavy charging current, and is connected by conductors of smaller than 10-AWG to the power source, the pump's rated output flow will never be obtained in practice.
Going back to the cited example of a 2000-GPH pump with a nominal 6.6-foot head being operated from 12-Volts at the pump (allowing for voltage drop in the conductors and a battery not under heavy charging current), the expected pump flow is going to be around 1,300-GPH (the rating for the vertical lift at 13.6-Volts) and derated of 0.617 (for the reduced electrical power) for a best-case output of about 800-GPH. That is only 40-percent of the rated pump flow volume. This reduction is clearly indicated in the manufacturer's specifications and by the physics of work and electrical power.
I suspect that some of the uncomplimentary remarks made about RULE centrifugal pumps that are read in anecdotal reports about them are due to the owner of the pump being unaware of how a centrifugal pump must be de-rated for any vertical lift on the output and how sensitive the pump is to reductions in electrical power available to operate the pump.
The mention of applications in sailboats with deep sumps is completely unrelated to use in Boston Whaler boats. In Boston Whaler boats the cockpit sump area is generally no more than a few inches below the level of the sea. Water to be lifted from the sump to the sea is generally only lifted about 1-foot or less. The de-rating of a centrifugal pump for an output for lift is shown by RULE to be linear. We can interpolate from their data that if a 3.3-foot lift reduced the flow by 0.12 the reduction is then at 0.036 per foot, and thus a lift of 1-foot would reduced flow by 0.963. A rated 2000-GPH pump would deliver 1928-GPH flow in a typical Boston Whaler boat.
For removing water from the cockpit sump of a Boston Whaler boat, the use of a RULE centrifugal pump is an excellent choice.
As for the notion that there are "old" RULE pumps that are superior to "new" rule pumps as other websites have published (somewhere unspecified in this entire discussion), I am not particularly concerned or surprised. Most websites are poorly moderated and often carry completely contradictory and unverified information. The goal of continuouswave has been to collect and organized reliable and accurate information and to debunk nonsense.