From: jrwalliker@gmail.com   
      
   On 24/11/2025 22:13, 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.   
      
   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   
      
   > Ed   
   >   
   >>   
   >> Any ideas as to how I could *force* the pump on in cases where   
   >> there is NOT enough condensate to trip the float switch?   
   >   
      
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