Metasys N2, Technical Manual

Page: 18 / 67

18 N2 Dialer Module—N2 Dialer Module (NDM)
Table 4: Disconnect Delay Control
Value Description
0 Default (10 minutes)*
1 240 minute delay
2 Never hang up automatically
* Configured in HVAC PRO for Windows using the disconnect delay parameter
Together the disconnect delay and the disconnect delay control parameters control how
long the connection between the remote and local NDMs is maintained before it
automatically breaks the connection.
The disconnect delay parameter sets the default time that the local NDM uses when
maintaining a connection to a remote facility. The disconnect delay control point controls
whether the NDM uses that default delay, uses a four hour delay, or disables the
automatic disconnect delay feature all together.
Each time a connection is established, whether the remote dials in or the local dials out,
an automatic disconnect timer is started and the disconnect delay control point is set to
zero. This causes the local NDM to use the default disconnect delay time (10 minutes)
configured in HVAC PRO for Windows. When the timer expires, the local NDM
automatically breaks the connection.
The operator can extend the automatic disconnect delay time to four hours by overriding
the disconnect delay control parameter to a value of 1. Overriding the disconnect delay
control point to a value of 2 disables the automatic disconnect delay feature altogether.
Remember that when this is set to 2, the phone connection is maintained indefinitely until
the dial command point is manually overridden to hang up the call. Care should be used
when disabling the automatic disconnect function, especially on long distance phone calls,
as there is a potential for high phone bills should the user forget to hang up the
connection.
The disconnect delay is defaulted to ten minutes in HVAC PRO for Windows. Adjusting
the default may be necessary to assure that all the remote N2 devices come on line and
can report any alarms in the event of a dial in from the remote site. If the disconnect
delay time is set too low, the connection will be made, but there may not be time for the
FMS to poll all the remote devices before the connection is broken. This would cause the
remote NDM to make unnecessary additional phone calls until the alarm condition was
reported.