34
10.7.17 Stop function (4.3.1)
Fig. 43
Stop function
Description
This function makes it possible to stop the last pump if there is no
or a very small consumption. The purpose is to
•
save energy
•
prevent heating of shaft seal faces due to increased mechani-
cal friction as a result of reduced cooling by the pumped liquid
•
prevent heating of the pumped liquid.
The description of the stop function applies to all Hydro MPC
booster sets with variable-speed pumps. Hydro MPC-S will have
on/off control of all pumps as described in
Fig. 44
On/off band
When the stop function is activated, the operation of Hydro MPC
is continuously monitored to detect low flow rate. When the
CU 351 detects no or a very low flow rate (Q < Q
min
), it changes
to on/off control of the last duty pump.
Before stopping, the pump increases the pressure to a value
corresponding to H
setpoint
+ 0.5 x on/off band. The pump is
restarted when the pressure is H
setpoint
– 0.5 x on/off band.
As long as the flow rate is lower than Q
min
, the pump runs on/off.
If the flow rate is increased to above Q
min
, the pump returns to
normal operation, H
setpoint
.
H
setpoint
is equal to the current setpoint, see section
.
Detection of low flow rate
Low flow rate can be detected by means of
•
direct flow measurement with a flowmeter or flow switch
•
estimation of flow rate by measurement of current pressure
and speed.
If the booster set is not connected to a flowmeter or flow switch,
the stop function will use the estimating function.
If the detection of low flow rate is based on flow estimation, a
diaphragm tank of a certain size and with a certain precharge
pressure is required. The tank size and precharge pressure must
be as follows:
Recommended minimum diaphragm tank size:
Precharge pressure:
Hydro MPC-E, -ED, -ES, -EF, -EDF and -F: 0.7 x setpoint.
Hydro MPC-S: 0.9 x setpoint.
During each flow estimation (every 2 minutes) the estimating
function will disturb the discharge pressure by ±10%. If this
disturbance is not acceptable, the stop function must be based on
direct flow measurement with a flowmeter or flow switch.
•
The flow switch is set in the menu
Go to setting of digital
input
, see
10.7.18 Overview of digital inputs (4.3.7)
10.7.19 Functions of digital inputs (4.3.7.1 to 4.3.7.12)
.
•
Flowmeters are set in the menu
Go to setting of analog
input
, see
10.7.20 Overview of analog inputs (4.3.8)
,
10.7.21 Setting of analog inputs (4.3.8.1 to 4.3.8.7)
10.7.22 Functions of analog inputs (4.3.8.1.1 to 4.3.8.7.1)
When the setting has been made, Q
min
can be set, i.e. the flow
rate at which the booster set changes to on/off control of the last
duty pump.
If both a flowmeter and a flow switch are connected, the
changeover to on/off control is determined by the unit first
indicating low flow rate.
Setting range
Setting via control panel
System without flow switch or flowmeter
1. Mark the
Settings
menu with
.
2. Mark
Secondary functions
with
or
and press
.
3. Mark
Stop function
with
or
and press
.
4. Mark
Active
with
or
and press
.
The activation is indicated by a check mark in the box.
5. Mark
On/off band
with
or
.
6. Set the on/off band with
or
and save with
.
T
M
03
23
55
40
05
TM
03
16
92
27
05
H
Q
H
setpoint
Q
min
On/off band
On/off
control
Normal operation
Pump type
Recommended diaphragm tank size [gallons]
-E
-ED
-ES
-EF
-EDF
-F
-S
CR(E) 3
4.4
4.4
4.4
4.4
4.4
4.4
20
CR(E) 5
4.4
4.4
4.4
4.4
4.4
4.4
34
CR(E) 10
10.2
10.2
10.2
10.2
10.2
10.2
62
CR(E) 15
34
34
34
34
34
34
211
CR(E) 20
34
34
34
34
34
34
211
CR(E) 32
44
44
44
44
44
44
317
CR(E) 45
86
86
86
86
86
86
528
CR(E) 64
132
132
132
132
132
132
1056
CR(E) 90
-
-
-
132
132
132
1056
On/off band:
5 to 30%
Min. flow rate:
2 to 50% of the nominal flow rate (Q
nom
) of one
of the pumps. (Can only be set if direct flow
measurement by means of flowmeter has been
selected.)
www.motralec.com / [email protected] / 01.39.97.65.10
