Operating Instructions
29
WattNode Basic Configuration
●
Set the
CtAmpsA
,
CtAmpsB
, and
CtAmpsC
objects to the correct rated CT amps of your
current transformers. For example, if you are using 100 A CTs, write 100 to all three objects.
●
If you are planning on using demand measurements and you don’t want to use the default 15
minute interval, you should set the
DemPerMins
as well.
Verify Operation
You should be able to read several objects to check that the meter is correctly installed and
measuring power and energy. Verify objects in the following sequence:
●
(power line frequency)
: should be near 50 or 60 Hz.
●
: should match your line-to-neutral voltage.
●
: should be positive (unless you are measuring something that
can generate power like a PV system) and in a reasonable range for the load being measured
(make sure your load is ON).
●
: these will return 0 if there are no errors. If you see any non-
zero values, write them down and check the
determine the problem.
If you don’t get reasonable results, check
Measurement Troubleshooting (p. 25)
above.
Measurement Overview
The WattNode meter makes measurements every second to update three types of variables
(objects):
●
Energy measurements
: These accumulate up (or sometimes down) based on the consumed
energy during each measurement period. Energy values are preserved across power failures.
●
Instantaneous measurements
: These are non-accumulating values, like power, volts, cur-
rent, etc. These are not preserved across power failures.
●
Demand measurements
: these accumulate data continuously, but only report updated
demand values at the completion of a demand interval (or subinterval), which is typically every
15 minutes. Only the peak demand values are preserved across power failures.
Operating Instructions
Quick Start
To start communicating with a WattNode BACnet meter using a PC or host device, you’ll need to
complete the following steps:
●
Set the BACnet address and baud rate using the DIP switches (see
●
If you are using a PC:
○
Find and install BACnet software for your PC. For a list of some programs, see the
website article
BACnet Software
.
○
Find and install an EIA RS-485 interface for your PC. The RS-485 USB interfaces are gen-
erally the best choice, because they are USB powered, don’t require a serial port on your
PC, and automatically handle switching bus directions for the half-duplex bus.
●
Configure the BACnet software or host baud rate, COM port, BACnet MS/TP, N81 parity (no
parity, eight data bits, one stop bit), and the WattNode meter’s BACnet address.
Now you should be able to send messages to the WattNode meter and receive responses. A
good starting point is to try to self-discover the meter and the objects. If this works, try reading the
frequency object. You should see the AC line frequency, generally 50 or 60 Hz. If you don’t get a
good response, check the section
BACnet Communication Diagnostics (p. 27)
.