Application

Sequence of Operation

Alarms

Siemens Industry, Inc.

BACnet LCM-OAVS, Application 6754

140-1325

2015-07-07

WARNING

To ensure that VOL DIF ALM turns on before the pressure in the room changes sign,

DIF ALM DBD must be less than the absolute value of VOL DIF STPT.

For example, if negative pressure is desired and VOL DIF STPT equals 70 cfm and

DIF ALM DBD is 200 cfm, then the room could go positive by almost 130 cfm without

the pressure alarm turning on. In this case, if you want the alarm to turn on before the

room changes sign, then you must set DIF ALM DBD to be less than 70 cfm.

The pressurization alarm point is turned off when all of the following conditions occur:

 VOL DIFFRNC has a status of Normal.

 VOL DIFFRNC stays above VOL DIF STPT – DIF ALM DBD for a time at least

equal to DIF ALM DEL.

 VOL DIFFRNC stays below VOL DIF STPT + DIF ALM DBD, for a time at least

equal to DIF ALM DEL.

 DIF ALM DBD and DIF ALM DEL can be configured to prevent nuisance alarms.

Local Annunciation

ALARM ENA is an analog point whose value determines whether or not a particular

alarm activates ALARM DO7.

For ALARM ENA, the terms enabled and not enabled do not mean that a particular

alarm is enabled or not. It means whether or not a particular alarm will or will not

activate ALARM DO7. For example, if ALARM ENA is set to

1 (Vent Alarm Enabled)

and a ventilation alarm occurs, then both VENT ALM and ALARM DO7 will turn on.

However, if ALARM ENA is not Vent Alarm Enabled and a ventilation alarm occurs,

VENT ALM will turn on, but ALARM DO7 will not.

ALARM ENA Values.

ALARM ENA

default

No alarms are enabled.

Vent Alarm is enabled.

Alarm Switch is enabled.

Dif Alarm is enabled.

Vent Alarm and Dif Alarm are enabled.

Alarm Switch and Dif Alarm are

enabled.

Vent Alarm, Alarm Switch, and Dif

Alarm are all enabled.

NOTE:

If ALARM ENA is set greater than 7, it will default to 0.

ALM ENA is additive. For example, if ALM ENA equals 5, then either a ventilation or a

pressurization alarm will activate ALARM DO7, but the alarm switch will not.