Do I still need a pressure tank with a Franklin constant pressure system?
Variable Frequency Drive systems including Franklin’s MonoDrive and SubDrive still use a bladder tank but are typically much smaller than one sized for a standard system.
In a SubDrive or MonoDrive installation the tank’s role is to capture water turbulence, not store water. The MonoDrive and SubDrive systems are designed to hold water pressure to plus or minus one psi of the set point. With a switch this sensitive, any water turbulence around the pressure sensor would cause wider pressure swings. The tank’s job is to capture any wave action in the plumbing coming from the pump side, so the water moving around the pressure sensor is smooth and steady.
The gallons per minute, or gpm rating of the pump, determines the size of the tank needed. The tank’s air pre-charge is also different than a conventional system. Please see your installation manual for complete instructions.
See previous frequently asked questions on our FAQ page.
Franklin Electric offers many different constant pressure systems. What are the differences?
Different models for different horsepowers.
Different horsepowers for different water needs.
MonoDrive is for Franklin 3-wire, 230-volt, single-phase motors, ½, ¾ and 1 hp.
MonoDrive XT is for Franklin 3-wire, 230-volt, single-phase motors, 1 ½ and 2 hp.
SubDrive 2W is for Franklin 2-wire, 230-volt, single-phase motors ½, ¾ and 1 hp.
SubDrive 75, 100, 150 and 300 are for Franklin 230-volt, three-phase motors 1 ½ hp, 2 hp, 3 hp and 5 hp respectively.
Franklin’s SubDrive and MonoDrive systems have both red and green lights. What do they do?
The green light is the power light. When green is on steady, it means the unit has electricity and is waiting to run. Not unlike sitting on the sidelines waiting to play in the big game. Once the pump and motor are activated, the green light begins to blink. A blinking green light tells you everything is “good” and your system is running. When the red light is on, it means the SubDrive or MonoDrive has found something it does not like. It is like the “check engine” light on your car. While it may continue to operate, the red light means something is not quite right and your system is calling for help.
Due to the volume of calls we have received about SD75, this issue will answer several of the most frequently asked questions we have fielded. To begin, SubDrive75 is a variable speed system that provides constant water pressure and a host of other benefits to the homeowner. The entire system consists of a pump/motor assembly, the SubDrive75 controller, a pressure switch unique to SD75, and a pressure tank. The SD75 system uses a standard ¾ Hp pump mounted to a standard 1½ Hp Franklin motor (3-phase, 230V), allowing flexibility in component selection. Following are answers to some of the most frequently asked questions about this system. Continue reading