Operating Instructions

Applications 651–Operating Mode
Siemens Building Technologies, Inc. 4-3
Alarm limits
The FHM contains low and high face velocity alarm limits, LO ALM LMT (Point 13)andHI
ALM LMT (Point 10). These points apply to LOW ALM (Point 5) and HIGH ALM (Point 6).
When the face
velocity is…
……
…
Then…
……
… The FHM displays…
……
…
lower than LO ALM LMT (Point
13) for a time greater than
ALARM TIME (Point 96)
LOW ALM (Point 5) will toggle
to ON.
LOW FACE VELOCITY
greater than HI ALM LMT
(Point 10) for a time greater
than ALARM TIME (Point 96)
HIGH ALM (Point 6) will toggle
to ON.
HIGH FACE VELOCITY
Fail-safe operation
The FHM has the following fail-safe operation:
When…
……
… Then…
……
… The FHM displays…
……
…
the FHM detects a hardware
failure (such as a failed sensor
or an internal start-up failure)
the status of ALARM STATUS
(Point 7) will change to ALARM.
FFF and GENERAL FAILURE
NOTE:
If
FFF
and
GENERAL FAILURE
display on the FHM, then call your Siemens
Building Technologies, Inc. representative.
External alarm and notification
When power to the FHM is OFF, the contacts of ALARM RELAY (Point 41) will be open.
If the alarm relay
contacts…
……
…
Then the FHM will…
……
…
After the FHM is powered
up and conditions are
normal…
……
…
are connected to a centralized
control system and the power
is OFF
send an ALARM condition to
the centralized control system.
the contacts of ALARM RELAY
will close, indicating a NORMAL
condition to the centralized
control system.