14
Network Communications—N2 Communications Bus
•
Move the LCPs and DX9100s to a separate N2 Bus, as described in the
Dual N2 Bus Application Note (LIT-6363145) in the Metasys Network
Technical Manual (FAN 636).
If problems occur with throughput once the system is operational, monitor
the N2 network traffic using N2/L2/S2 Statistics. This gives an estimate of
the network activity to help you to determine if additional steps are
required.
The number of messages allowed on the N2 Bus differ depending on the
ASC firmware revision.
A maximum of 1100 messages per minute are allowed on the N2 Bus
unless it is connected to one of the following controllers (in which case
900 messages per minute are allowed):
•
Air Handling Unit (AHU) Version C02 or lower
•
One Unitary (UNT) Controller Version B02 or lower
•
Variable Air Volume (VAV) Controller Version A02 or lower
Refer to the following steps to determine the average rate at which
messages are traveling over the N2 Bus:
1.
Using the N2/L2/S2 Statistics window, track the number of polls,
commands, and offline polls for a five minute period during peak
usage.
To do this, clear the statistics and reread them after the five minute
period. (Refer to Using Diagnostics in the Operator Workstation
User’s Manual [FAN 634] for detailed instructions on using the
Statistics window.)
2. Using the statistics from the five minute period, multiply the number
of offline polls by four (since offline polls take four times longer to
complete), add it to the total number of commands and polls, and
divide the total by five to calculate the total number of polls per
minute.
commands + polls + 4 (offline polls)
= number of polls per minute
5
Monitor Your
System’s
Improvement
Estimating Your
System’s N2
Traffic
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