Instrument condensate pump

My impression is that float switches mostly contain a magnet, and they used to be monitored by dry-reed switch capsules, where the contacts closed if the magnet got close enough. Today a Hall effect sensor could do the same job with a cheaper and more compact sensor.

Putting the coil of a relay in series with the pump's (AC?) power supply might not be a good idea. Again a Hall sensor could do the same job with a cheaper and more compact sensor. You might want to separate the live and neutral leads and wrap them (in opposite directions) around gapped ferromagnetic toroid and put the Hall sensor in the gap in the toriod, but this might be an over-kill.

Use a current transformer, not a series relay. Ed

I was trying to be cheap and simple. Make a little plastic box with a plug on one end, outlet on the other and a contact closure that the HVAC tech could wrap his head around. Nothing potentially exposed to the user/tech by this device.

Current transformer needs a burden to keep the potentials "safe" if my kit is disconnected (or, not YET connected). I'd have to build that into the "device" to ensure it doesn't present any issues to installers/users.

I figure most condensate pumps tend to be of similar capacity and, thus, present similar loads (~100W).

Or use a current sensing relay which is designed for exactly this kind of application. Some of them contain active electronics and extract their operating power from the circuit being measured.

John

This should do what you need, maybe with a few turns of wire through the opening if your pump is very low power. No power supply is needed.

It would give me the functionality for a prototype but would likely be too expensive in a production deployment. The condensate pumps are in the $50-100 range. Something like the part you mentioned -- packaged into something with plug and receptacle on each end -- would be a significant fraction of that amount.

Most pumps have a pair of "microswitches" mechanically driven by the floats. Replacing the one that controls the pump with another that has a second pair of contacts would be dirt cheap -- but, would put me in the condensate pump business.

The information I can garner from the "pump float" is more diagnostic than performative, in nature:

- a pump running continuously is likely broken or obstructed

- a pump never running could indicate a bad float switch (assuming the safety float eventually signals)

- a pump never running can indicate a mains failure/disconnect (assuming the safety float eventually signals)

- a pump never running can indicate an ACbrrr not dehumidifying

- a pump cycling but running for longer periods of time could indicate an impending check valve failure

The performative data I could obtain would represent the amount of moisture removed from the air, per time interval (the assumption being that the float and its hysteresis represents a relatively constant volume of condensate)

None of these things are worth much in terms of cost. But, could add value "if the price was right" (which is the reason for my "cheap" focus)

The units I mentioned are much cheaper from Ali Express. Even cheaper at around 1 USD from Ali Express are isolated hall effect current sensor modules based on the ACS712 chip.

John

Safe, sure they make current relays. An opto-coupler may be a better choice here.

Use a finger, a solenoid, or other motor, to lift the float.

Some use a magnet and a reed switch, some detect tilt by movement of a steel ball, some detect tilt using a mercury tilt switch, some use a lever to operate a switch...

Off the shelf hall current sensors are definately a valid option.