Brultech un-monitored loads

[dBeau]

I have three ECM-1240's watching over my breaker box. One channel monitors the load on the way into the breakers, then I have a CT on each of the 48 circuits leaving the box. The ECM-1240 Engine software has a cool feature where it subtracts all of outgoing loads from the incoming load and displays the result as "un-monitored".

In theory, this makes great sense. If the entire panel is monitored, this value should be zero. If not, it's an error either in the wiring of the CTs (ie something is not being monitored) or in the calculation of the total load. Watching the display reveals part of the problem as un-monitored spikes whenever a load that is monitored by a unit other than the one watching incoming load turns on. The time difference between polling the units creates an artificial imbalance between what is coming in an what is going out. That imbalance quickly corrects itself as soon and all units have been polled.

What I cant explain is the constant 100w un-monitored load I am seeing. I've checked and double checked all my connections. For each CT the monitored value goes up when a load comes on. So the wiring looks all good. Is a 100w error reasonable here? It's between 5%-10% of the typical load. Is anyone else monitoring all of their circuits and seeing something similar?

 

[damage]

do you have a zone that covers breakers on 2 different phases? (both legs of the oven for example) make sure the polarities of those CTs are correct (one CT facing the breaker, the other facing away, wiring the like colored leads together at the brultech)

 

[tenholde]

do you have a zone that covers breakers on 2 different phases? (both legs of the oven for example) make sure the polarities of those CTs are correct (one CT facing the breaker, the other facing away, wiring the like colored leads together at the brultech)

Have you tried turning off and then on each circuit one at a time to see if the total load coming in is changing the same amount as the breaker being toggled? Also, if all monitored circuits are off, is there still a load measured coming in?

tenholde

 

[dBeau]

The wiring is all correct. I've checked and double checked the polarity of the CTs. They are all fine. I've even verified each CT by watching the channel it was connected to while turning on a load. Each showed a reasonable increase on the appropriate channel.

I did try turning nearly all the breakers off and turning them back on one at a time. Each showed an un-monitored load. The reason I think it's an error is that it was cumulative. The more breakers that were on, the higher the reading on the un-monitored "channel".

The specs on the different CTs show different accuracies with the larger CTs being the most accurate and the micro 40s (what I have on most breakers) being the least accurate. Given this it would seem reasonable to expect an error. But, I'd expect some micro 40s to read higher than the split 200s and others to read lower (I'm just guessing though) and that should tend to cancel out the error overall. Oddly (or not perhaps) the unmonitored load floats around 100w +/- 20w while the main panel goes between 1000w - 2000w. With the exception of the spikes I mentioned earlier there is no clear correlation between the two.

All of this might be within expectations. I'm just not sure what to expect.

 

[BraveSirRobbin]

The error listed is +/- 1 %... If I'm doing my math right for a total load of 2000 Watt the error is 20 watt. For each of the 48 other current taps I assumed the load was evenly split for the point of discussion so that's 2000/48 = 42 watt each with a 0.42 watt error, or again around 20 watt. This could account for 40 watt if the errors generated by the individual CT's are the opposite end of the ones measuring overall power, so your 100 watt discrepancy sounds a bit high to me.