Here’s another piece of commercial gear, from an industrial air conditioning unit. These pumps are used to drain the condensate from the evaporator unit, so water doesn’t end up raining down from the ceiling.
This is a peristaltic pump, with a silicone hose forming the pumping element.
The test switch & electrical connections are on the back, along with the data label.
The electrical connections are all on a single 5-pin socket. Along with 240v AC mains, there are a pair of thermistors connected to the unit, which switch the pump on when a 5°C temperature difference across the evaporator coil is detected. When air is cooled, it’s capacity for moisture drops, so the water condenses out on the coil.
Here the front cover has been removed from the pump, showing the silicone tube & roller wheel. The wheel was originally Cadmium-plated, but exposure to the elements has oxidized this into highly toxic Cadmium Oxide.
Here you can see the rollers. These pinch the tube at the inlet, and the rotation carries a slug of liquid through the tube to the outlet side.
Here’s the tube itself, the main wearing part of the pump. This is replaceable as a spare part.
Inside the casing is a shaded-pole motor, connected to a large gearbox, to give the slow rotation for the pump head. The rated speed is 51RPM.
There’s not much to the control PCB. The large resistor forms a voltage dropper, to reduce the mains 240v to a more suitable level for the logic. There’s a TL062C Low-Power JFET Op-Amp & a CD4060BCM 14-stage binary ripple counter forming the logic. The set point is adjustable via the potentiometer.
The pump motor is switched via this Z7M SMD triac, not much switching power is needed here as the motor is only a very small shaded-pole type.
