XPost: alt.home.repair   
   From: no@never.com   
      
   On Wed, 02 Jul 2014 15:05:12 -0500, amdx  wrote:   
      
      
   >   Hi Neon,   
   >I was slow in reading your response, but it is very good. The prices   
   >on the site you referenced are very reasonable, and the boxes to mount   
   >the meter are also cheap.   
   >   I'm perplexed about your use on 120V, I don't see where it   
   >is wired any different, two leads in, two leads out, except on 120V,   
   >one lead is neutral instead of hot.   
   >  Maybe you could educate me on why that connection works on 120V.   
      
   Sure, no problem.  The meter responds to volts * amps * cos(theta)   
   with cos(theta) being the power factor.  for this discussion let's   
   assume a PF of 1 so that part drops out.  Now the meter is simply   
   volts * amps.   
      
   So the meter would rotate the same RPM with 120 volts and 2 amps as it   
   would with 240 volts and 1 amp, because in both cases the power is 240   
   watts.  I exploit that fact in my connection.   
      
   With 240 volts the potential coil has 240 volts on it and the current   
   passes through the current coil only 1 time for 120 volt loads.  The   
   current returns through the neutral.   
      
   On 120, the potential coil has only half voltage, 120 volts.  BUT, the   
   current passes through the current coil TWICE, once going out on the   
   hot lead and once returning on the neutral.  Internally, the coils are   
   arranged so their fields add.  So we have 1/2 the voltage but twice   
   the current and multiplied together they equal 1.  No calibration   
   factor nor adjustment necessary.   
      
   The only time this fails is if some of the current returns through   
   ground - leakage, for example.  Thus, this would not be suitable for   
   revenue metering where people could cheat by using a ground rod but IS   
   fine for energy surveying.   
      
   The connection scheme that Hialeah shows remedies that flaw but at the   
   cost of having to run a wire from the potential coil's calibration   
   link to the hot line.  The meter is no longer plug'n'play and could   
   not be removed or installed without killing the power source.  Or   
   working the aux wire hot.   
      
   I prefer my method because the meter IS plug'n'play.   
      
   John   
   John DeArmond   
   http://www.neon-john.com   
   http://www.fluxeon.com   
   Tellico Plains, Occupied TN   
   See website for email address   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)