Float Switches Explained
While you’re looking for submersible pumps to buy, there would be many types of pump switches that you would see. The following blog post covers the basic terminology and mechanism of functioning of the three most commonly used pump switches, along with their pros and cons.
Float switch
The float switch’s job is to keep a check on the tanks/sump’s water levels. Within the float switches, there are contacts that complete electrical circuits when they close. They are used to send signals to pump, timers or alarms to be activated or deactivated when needed.
For direct control, a pump switch is used, and it can be directly connected to the motor or in the pump’s power cable. Alternatively, a small plug can be used for plugging it into a switch. The pump’s full amperage is supplied to the pump switches, so make sure the pump switch you opt for meets the amperage of the pump you have.
Normally Open Vs. Normally Closed
When the float is in an empty tank / at rest electrical circuit state is called normally open and normally closed. When the float is hanging freely, there is no passing of electricity in a normally open float. The contact will close, and power will pass when the water level rises, and the float rises as well. Mostly in the sump, sewage and dewatering pump, this kind of float is used.
On the other hand, the normally closed float functions in the opposite manner. When the float is hanging, there are closed contacts. The contact opens, and the power supply is stopped when water is supplied, and float is raised. In an application where a pump fills cistern or any other filling mechanism such kind of float is used.
In short, in an application where pump fills the tank the normally closed switch is used, and in applications where pump empties tanks then normally open switches are used.
Kinds of Pump Switches
· Tethered
· Diaphragm
· Vertical
These can be purchased individually or with an automatic pump. The float option you have is dependent on the diameter the basin has.
Before purchasing any float, check out the minimum basin diameter suggested by the manufacturer.
Tethered switch
The installation of tethered pump is done either on the pump or the discharge pipe. In these pipes, there is a 7-36 inches pumping range.
Some pros and cons are:
· Largest adjustable pumping range
· High reliability
· Replacing is convenient (in case of only piggyback plugs)
· For functioning correctly, the basin should be large (at least 14 inches).
· Annual cleaning might be needed since float can weigh down since it collects debris and scum.
Vertical switches:
The installation of vertical switches is on the basin, discharge pipe or on the pump. The pump has a 0.75-6.5 inch pumping range. Some
The pros and cons of the pump are:
· Basin should be at least 10 inches so it can be used in smaller space where tethered switch cannot be used
· The pumping range is adjustable
· Quite reliable
· With piggyback plugs, replacement is very convenient
· It can be adjusted to few inches since the float moves up and down on a fixed rod
· There might be rapid cycling issues to the small pumping range
· Annual cleaning might be required as float collects debris and scum, which weighs it down.
Diaphragm switches
The installation of diaphragm switches is generally on a pump or basin. When operating normally, the switches are entirely underwater.
On reaching a particular height, the contact in switch closes, and the pump starts or shuts. Depending upon the manufacturer, the pumping range may vary, but it is typically between 3-5 inches. Some pros and cons are:
· As compared to others, it requires the smallest basins.
· They just occupy some space on the pump and need no additional area.
· With piggyback plugs, it is very convenient to replace
· Chances of malfunctioning are comparatively greater since they are easily plugged.
· Cleaning is a bit hard
· Reliability is not that high
· May have an issue of rapid cycling since the switch has a small pumping range
Selecting a Pump Switch
For current installations: if your pump uses a piggy bank plug, then in case of a fault, it can easily be taken out. However, if it is wired into the motor, the motor would need to be disassembled and rewired.
It is recommended to replace it with a pump switch of the same kind when replacing an existing pump switch.
For installations in future: Pump switches can connect using a piggyback plug or have a direct connection with a motor. Remember this key that buy a tethered switch if the basin’s diameter is 14inches or greater if you want a longer life expectancy of the pump. Otherwise, buy a vertical switch if the basin’s diameter is lesser than 14 inches if you want a longer life expectancy of the pump. Only in a unique situation where vertical and tethered switches cannot fit, then diaphragm switches are used.
If you have any queries related to choosing a float switch, contact us by calling at (760) 440-8520.
