Multiple feeds on one breaker/CT

[cedartubs]

I have just moved into a house and the panel is maxed, there are a few 120 VAC 15 amp breakers that have 2 feeds coming off them going to different devices/circuits.  Can i put one CT around both wires being fed by the same single pole breaker and get accurate results?

D

[Lynoise]

Yes and you likely should if you want to measure the power usage of both circuits.

It will accurately measure both circuits together.

[cedartubs]

Thanks, one of the reasons i asked is i have at times aobut 100-250 watts in the “Balance” classification.

 

Every circuit is being metered and my 240 VAC are set to 2.

 

Any ideas how to test where this other is comming from?

 

Dan

[engineerdad]

I have a similar question and problem.  I have a 42 position main panel.  I have all the sensors installed, but obviously several circuits are not individually monitored.  I have all the big items monitored (heatpump, well pump, kitchen, washer, dryer), but I still regularly get a balance of 20-60% at the end of the day.  I have been moving some of the extra non critical sensors around to find where the extra draw is coming from, but only find those circuits pulling less than a percent.  My plan is to turn off all breakers that don’t have their own sensor and see if the balance goes to zero, but I have to wait for a time when my family will not be bothered by Dad’s project.

My main question is that I do have some sensors monitoring multiple circuits.  For example, my heatpump and air handler have independent 240v circuits, but I ran a leg from each through one sensor with a scale factor of 2.  I made sure to use the same leg from each dual pole breaker.  My multimeter was dead last night so I couldn’t check, but does it sound like I’m doing something wrong?

 

thanks,

 

Tom

[jj613]

It’s hard to tell from your description if you are doing something wrong, but I would think that if 60% of your usage is “missing” the most likely scenario is that one of your CTs is backwards or something along those lines.  You are not likely to just be unable to account for 60% of your usage.  One breaker at a time is the right approach to finding the problem, whether it’s your installation or your memory.

A suggestion: Don’t combine your big 240V loads.   Those will account for the vast majority of your overall electric usage and it’s useful to be able to distinguish problems that are specific to the device, i.e. the pump or the blower.    I think it’s better to combine the “uninteresting” loads.  If you have dedicated lighting circuits for example you can combine ALL of them.  Their combined usage will still be very small and nothing interesting will ever happen, or if it does, you’ll have to do a lot of detective work regardless to find the source of the problem.

[waterboyz]

Again, JJ613 makes perfect sense.

[dr_zerocool]

I recently rewickered my Vue2 setup to combine multiple feeds like how you described so that I could reduce more of the “balance” category. One thing I learned while doing this (which was also confirmed by tech support a few days later) is in order to do this, you can only combine load wires from breakers that are on the same 120V phase. So for most panels that have a 2-phase L1-N-L2 configuration, it will be every other breaker (i.e. none side-by-side). Side-by-side/Adjacent breakers will subtract from each other instead of sum together. Hope this helps someone else!

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