Bell & Gossett 176R0649C Technologic 502 Series Pump Controller - Manual (Page 25)

25
Installation of 70X Series Drives and
Pumps
A 70X configuration consists of one variable speed
pump (lead pump) connected to the 70X controller,
and from 1 to 3 constant speed pumps connected
to mains through a contactor controlled by the 70X
controller. (See Figure 3-15.)
The 70X controller monitors system pressure and
stages on and off constant speed pumps as needed
to maintain system pressure. Parameter 27-20,
Normal Operating Range % is used to define the
acceptable deviation from the setpoint before staging
or destaging takes place. This parameter is defined
as a % of parameter 3-03, Maximum Reference.
(See Figure 3-16 for customer connection schematic
diagram.)
Staging:
When the system demand increases the 70X
controller will increase the speed of the lead pump
until it reaches its maximum speed. If the system
demand continues to increase, it will no longer be able
to maintain the desired system pressure. Once the
pressure drops below the Normal Operating Range for
the time set in parameter 39-11, Stage Proof Timer,
the controller will stage on a constant speed pump
and ramp the lead pump to its minimum speed.
De-Staging:
When system demand decreases, the 70X controller
will decrease the speed on the lead pump until it
reaches its minimum speed. If the system demand
continues to decrease, the pressure will exceed the
Normal Operating Range. If this continues for the time
set in parameter 39-14, De-Stage Proof Timer, the
controller will destage a constant speed pump and
ramp the lead pump to maximum speed.
Alternation:
Since timed alternation only applies to changing the
lead pump, it is not part of a 70X system which has
only one lead pump. It is possible however to manually
alternate constant speed pumps using the right and
left arrows on the LCP.
Pump Running Order:
Parameter 39-33, Pump Running Order can be used
to determine the sequence with which constant speed
pumps are staged on and off.
AFD Failure and Fixed Speed Only mode:
Parameter 39-40, AFD Fail Proof Timer is active
in the 70X configuration. If the AFD fails, the 70X
system will switch to Fixed Speed Only mode.
In this mode, the controller will stage on and off
constant speed pumps if the system pressure
deviates from the setpoint more than parameter
27-22, Fixed Speed Only Operating Range. Setting
27-22 to zero disables this mode.
Pump Failures:
The DP switch inputs can be used in the 70X
configuration. If a failure is detected in the lead pump,
the controller will switch to Fixed Speed Only mode as
described above. If a failure is detected in a constant
speed pump, the controller will alternate to a different
constant speed pump and mark the pump as failed.
Zone Failure Detection:
All of the normal Zone Failure detections can be used
in the 70X configuration. The loss of a single sensor will
disable that sensor. The loss of all sensors will pump
the system into jog mode. 70X jog mode will run the
designated number of pumps at full speed by default.