Paul, I've got a couple of questions about the CT's and I'm hoping you can help me.
First, as a bit of background, I have 200A electrical service to my house. As a test the other day I tried to turn on pretty much all of the electrical devices in my house - my two heat pumps, the electric water heater, the range and the drier and many of my lights and other appliances. Then I put a clamp on ammeter on each leg of my electric service and discovered that with pretty much everything on I was only drawing about 60A on each leg.
Now, it's my understanding that the 100A CT's have a bit better accuracy on the low end than the 200A CT's. Given that it's highly unlikely that I'll ever draw more than 100A - it was all I could do to draw 60A with everything on - would I be OK getting 100A CT's? Or do I need to get 200A CT's because I have 200A service? If I do get 100A CT's and I somehow manage to draw 110A or 150A at some point would that damage anything or would I just get bad readings during the periods of high current draw?
Also, are the solid core CT's any more accurate than the split core CT's or are they just a little cheaper because they're easier to make? I have a somewhat unique situation in that my main breaker is in a box on the outside of my house, which feeds a panel with the rest of my breakers inside the house. So it would be fairly easy (and safe) for me to shut off the power at the main breaker outside, then temporarily disconnect those feeds on the box inside (which would then have no power in it) to slip a solid core CT on. It's certainly worth a little extra trouble for me to do that if I might get slightly better readings, but if the difference really is only cost, then I may as well pay a few dollars more and have the ease of just clipping the split core CT's on.
Thanks much,
Brett
Brett,
It is not uncommon to have an over rated panel. This leaves the option for house
expansion, hot-tub, pool etc without having to upgrade the electrical service. You could in
theory use a SPLIT-100 current transformer however your limitation would lie with the
conductor diameter. Our SPLIT-100 CTs will accept a maximum diameter of 0.61" while our
SPLIT-200 CTs are good to 0.98" wire diameter. I think the SPLIT-100 will just make it
if your wiring is copper.... don't take my word on this, check first. The other
limitation would be the maximum continuous current the CTs can handle. If this is
exceeded for an extended period of time, the CT could get warm due to excessive current
in the CT winding and Core saturation. The ECM-1220's readings would also become
in-accurate, although it would not damage the unit.
I just checked the specs on our SPLIT-200s and it it very linear down to 1A which is
the lowest data point taken. I suspect that it still performs well below that. I know
that my panel at home rarely, if ever drops below one amp (roughly 120 watts).
I can find more if you wish.
Typically, solid core CTs are less expensive than split-core CTs for an equivalent
accuracy. There is little demand for solid core CTs for use with our ECM-1220, since it
is mostly installed in existing electrical systems and removing the line wires require
disconnecting incomming power to thread the wire through the center of the CT. Not
recommended!
Since the demand for solid core CTs is small, the lower quantities we would purchase would make the cost
comparative to that of the split-core CTs which we have manufactured in large quantities. We
therefore have opted to stay with split-core CTs only. We do stock some donut-type CTs
if you preferred.
(Remember.... this should only be done by a qualified person or electrician... )