220V imbalance and Shared Neutral questions


  #1  
Old 02-29-20, 05:05 PM
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220V imbalance and Shared Neutral questions

Greetings, (2) unrelated questions, for a common cause:
I'm going to be ordering one of those TED energy monitors for my house, with the ability to check current on individual branch circuits. I guess they use little inductance coils that clamp around the hots where they connect to the breakers.

Question #1:
They say I only need a single coil to monitor a 240V circuit (the readings from one of the legs is doubled in the software program), but only IF the loads are balanced. I'd be monitoring the A/C and maybe the electric clothes dryer. Do these typically present balanced loads? I know any electronic circuit boards would likely be stepped down from one of the 120V legs, but that would be only a tiny difference. But what about, for example, the dryer's drum motor. That might be significant if it runs from a 120V leg. I'm pretty sure that with the A/C, the condenser fan motor is likely 240V, so probably no imbalance there.

Question #2:
Also monitored will be several "shared neutral" branch 120V circuits. I will ask the manufacturer if the readings might be off as result of shared neutral, as it has to do with their product, but for y'all, just generally, this is where a wire comes into the breaker box containing a ground, a neutral, a red and a black, with the red and black breakers side by side, so they connect to opposite 110V legs. My house was built in 1984. Is this acceptable practice nowadays? Seems I read somewhere that it could lead to current on the neutral, for good or bad, don't know. I have (3) " shared neutral pairs in the panel.

Thank You!
 
  #2  
Old 02-29-20, 05:19 PM
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You want a 120/240v current monitor.
Yes.... you can and will have current on the neutral.
 
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Old 02-29-20, 05:29 PM
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For the true 240v appliances like the oven, dryer, and AC, a one-coil/one-hot meter is fine. They will always be the same on each leg (like you said, other than fractions for 120v usage like the lightbulb and the control board).

For multi-wire branch circuits which are two 120v circuits on one cable, you'll want to use two separate coils/meters since they will always be different.
 
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Old 02-29-20, 05:30 PM
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Most ranges and dryers technically require 120/240v.
 
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Old 02-29-20, 06:17 PM
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The only true 240 volt loads in most homes are Electric water heaters and base board heat.
If you are a DIYer you could also have a compressor, welder or other power tool.
A dryer and a range are 120/240. Connecting to only one hot will not give a true reading especially on the dryer since the motor is usually 120 volts.
 
  #6  
Old 03-01-20, 02:30 AM
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At least 90% if not more of appliances that are 120/240 use L1 (black) as the side of the line that runs motor's etc in the unit so measure that side.

But probably still bets to check out a units wiring diagram.
 
 

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