First, let me clear up that there are techniques to use one or two CTs on any 240V circuit. Some involve the [voltage] “double” checkbox, and some involve passing two conductors through the CT. I prefer to distinguish 240V circuits by whether all of the current is carried in two conductors (true 240V) or whether some can also be carried in a third neutral conductor (120V/240V). This is discussed in the docs:
http://docs.iotawatt.com/en/master/CTbasics.html
http://docs.iotawatt.com/en/master/split-phase.html
There are exceptions, but generally the common true (two-wire) 240V appliances are:
- Hot Water Heaters (not some heat-pump types)
- Well Pumps
- Heat-pumps
- Electric baseboard heaters
- Some air-handlers
- EV chargers
Appliances that are usually 120V/240V
- Clothes Dryers
- Ranges and stove tops
- Ovens
- Some air handlers
- Sub-panels
They are probably 120V/240V requiring two CTs or both conductors passing through one CT in opposite directions. In the later case you would need a 100A CT for the Furnace, and probably the Range. The Dryer should be OK with a 50A.
Yes it is. See this post:
As explained, the CT is a current source, so the resistance of the extension should have no effect on the CT output unless it is excessive and causes the CT to be unable to drive the current. The other signal on the line is the CT DC bias, which is effected by resistance, but is constant and compensated by the IoTaWatt firmware.