From: jrwalliker@gmail.com   
      
   On 24/11/2025 23:05, Don Y wrote:   
   > On 11/24/2025 3:13 PM, ehsjr wrote:   
   >> On 11/23/2025 11:54 PM, Don Y wrote:   
   >>> These tend to be mains powered with an internal float switch   
   >>> to engage the pump.   
   >>>   
   >>> A separate float switch provides a volt-free contact to   
   >>> cause the demand for cooling to be interrupted in the event   
   >>> the pump fails.   
   >>>   
   >>> I can monitor the "safety" switch and implement a similar   
   >>> interface to the plant -- including *commanding* the AC off,   
   >>> if it is currently calling for cooling (otherwise, a   
   >>> smart system may signal a cooling failure).   
   >>>   
   >>> I don't want to modify the actual pump appliances (they   
   >>> are varied).  But, if I *assume* they all are effectively   
   >>> just power-gated pumps, I think I can monitor the internal   
   >>> float switch by sensing when the pump calls for power.   
   >>> (If I could monitor that float switch directly, I would just   
   >>> turn around and power up the pump).   
   >>>   
   >>> How safe to just put the coil of a relay in series with   
   >>> the pump's power (mains) and use that to indicate the   
   >>> state of the pump?   
   >>   
   >> 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).   
      
      
   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.   
      
   https://www.amazon.com/Current-Sensing-Normally-Adjustable-SZC23   
   NO-AL-CH/dp/B07N1P6TWL   
      
   John   
      
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