Using a CT with an early Immersun

My searches have identified the thread about successfully using a CT to monitor the energy diverted via an iBoost. To help with deciding which options to choose when buying an emonPi, I would like to find out if anyone has achieved a similar result of using a CT to monitor energy diverted via a Mk1 Immersun (circa 07/2013: I’m assuming the Immersun circuitry may well be different to that of the iBoost). In particular, if the figures collected from the CT closely match the figures shown on the Immersun display i.e. instantaneously, daily, monthly etc.
I apologise if this has already been dealt with and I have missed it in the wealth of information available. If so, a push in the right direction would be appreciated. Thanks in advance.

One commercial diverter - I can’t remember which one - rectifies the mains and supplies the immersion heater with d.c. The manual gives that away (not in so many words) by telling you not to put a c.t. on the immersion heater wire downstream of the unit. If yours says that, there’s the trap. (Transformers don’t work on d.c.!) Otherwise, you are probably safe putting a c.t. on the immersion wiring.
But to be certain, you could put the c.t. upstream of the unit. It would measure then the operating power/energy of the diverter itself as well as the diverted power, but the additional parasite power should be relatively constant and small, which you could allow for.