26/04/2025
HOW A SOAKER HOSE CAN POTENTIALLY CAUSE DAMAGE TO A SUBMERSIBLE PUMP
Electric motors convert electrical energy into mechanical energy, making it possible to move things, like water. In the process, electric motors produce heat, and that heat must be displaced. Otherwise, the heat will build up in the motor and cause motor failure. Motors that are located above ground use the air around them for cooling, sometimes with the assistance of a fan. In the case of a submersible motor, the water being pumped is used to cool the motor and provide a long, reliable service life; therefore, a minimum cooling flow is required depending on the size of the motor & the size of the pump sleeve over the motor. Whether you have a FRANKLIN, GRUNFOS or LOWARA pump, the cooling principle of submersible motors is the same.
🍀Most domestic/semi-commercial submersible pumps that come assembled with a pump sleeve are 4" motor with either a 5" or 7" pump sleeve. According to FRANKLIN a 4" motor with a 7" pump sleeve in operation needs a minimum of 76lpm of cool liquid to flow pass the motor. A soaker hose has a flow rate between 0.5-1.5l per meter per minute which means the flow rate of a 30m soaker hose is 15-45lpm. This means if you have a pump with a 4" motor & 7 " pump sleeve & you run a soaker hose for long enough you will cook the pump motor. It's like running your car with not enough coolant in the cooling system, you will overheat the engine eventually. With a submersible pump, the amount of coolant moving pass the pump motor to cool it down is determined by the total water consumption which is determined by you. We can put a flow control valve in to stop problems caused by over pumping, but there's nothing we can add to the system to stop you from under pumping.
🍀Every time we install a submersible pump we always tell our customers multiple times to be careful using soaker hoses, drips & micro sprays because of this very reason.
🍀If you want to use a soaker hose make sure you turn a row of pop-up sprinklers or something else on at the same time to give the motor the minimum cooling flow it needs. With a system that has a VFD check the screen to make sure motor is not running under 30Hz.
🍀A submersible pump is very reliable & gives you great performance, but there are rules we have to follow & giving it the enough flow rate for cooling of the motor is one of them.
🍀Overheating of submersible motors are primarily caused by 3 things: bad power, wrong application or not enough flow through the motor which are why it's not covered under warranty by any pump manufacturer. There are submersible pumps in the market that have a thermal overload built into the motor which helps with (not eliminate) overheating issues of the motor, but they come with other issues so they are not always recommended.
