Meters are calibrated together with CTs for 1% accuracy. They are available in Amperage ratings of 80A, 120A, 300A, and 600A. The CTs are non-shunted, and produce 200mA @ full scale. The CT cables can be disconnected for installation, but different size CTs cannot be used, as the meters are calibrated in hardware (perhaps you could re-scale in post-processing if you were really determined to swap -EJG).
There are 5 voltage leads for a 3-phase meter, including both a neutral and a ground. The node is line-powered by either line-line or line-neutral so it can be used with both delta and wye circuits. It can handle 0-600V gracefully, but needs a separate power source for the node above that (you would also need an electrician with medium-voltage certification).
The nodes can report at up to 1-min frequency over the ZigBee Pro network to the gateway, and the gateway can sync to the server at 1-min frequency. The nodes transmit true power, power factor, and other detailed metrics, but only store an accumulated kWh value (meaning that you would not miss any of the total energy consumption, but would lose the trending activity during the period f lost communication.) On the other hand, the gateway has 160GB of storage, and it archives all data during periods of network outage, then syncs with the server when possible.
The nodes do not have any troubleshooting indicators other than connectivity, and the interface to check the network status and view live data is through the server, meaning that the gateway must be connected before you can effectively start checking an installation. However, there is no licensing fee to run the server software yourself (requires Windows and SQL Server) so I'm hoping it would be possible to run the server environment on a laptop in order to monitor the installation, then connect the gateway to the "real" server if possible and when convenient. I believe there is an annual fee for using their hosted server.
Costs:
$1,000 - gateway
$750 - node @ qty 1 (300A 3-phase ZEM)
$675 - node @ qty 10 (next break @ 100)
$150 - air temp node (also use as repeater)
Brendan also explained that they have seen an increase in sales since Arch Rock stopped offering their (nearly identical) wireless sub-metering product line. Consequently, there is a 6-8 week lead time for their products, as they are struggling to keep up with demand.
My take: as an audit tool the ZEM gains some flexibility over Arch Rock's WattNode-based IPpower meters, as it can handle a diversity of voltage inputs. On the other hand, it looses flexibility by disallowing CT swapping (and spare CTs are much cheaper than extra meters!) The lack of an admin web interface on the gateway is annoying, but might be solved by the local-server hack. Data storage on the gateway is a huge advantage, as it means they can be installed in locations with no network access. I'll need to check out the server interface to get truly excited about it, but it sounds like a fairly useful system.
