Units With Hydraulic Module And Variable-Speed Pump - Temperature Differential Control - Carrier Aquasnap 30RB Series Installation, Operation And Maintenance Instructions

8 - WATER CONNECTIONS
8.5.1 - Hydraulic circuit cleaning procedure
Before proceeding, it is advisable to remove any possible
contamination from the hydraulic circuit.
• Start up the unit pump by using the override command.
• Set the frequency to the maximum value to generate a
higher flow rate.
• If there is a ''Maximum fow exceeded'' alarm, reduce the
frequency until an acceptable value is reached.
• Read the value of the flow on the user interface.
• Let the pump run for 2 hours continuously to flush the
system's hydraulic circuit (presence of contaminating
solids).
• Perform another reading of the flow and compare this value
with the initial value. A reducing value of the flow indicates
that the filters on the system need to be removed and
cleaned. In this case, close the shut-off valves on the water
inlet and outlet (item 19) and remove the filters (items 12
and 1) after draining the hydraulic part of the unit (item 6).
• Remove the air from the circuit (items 5 and 14).
• Repeat until all fouling is removed from the filter.
8.5.2 - Procedure for controlling the pressure
differential
Setpoint
Once the circuit is cleaned, place the hydraulic circuit in the
configuration for which the unit selection was performed generally
(all valves open and all cooling coils active). Read the value of
the !ow on the user interface and compare it with the theoretical
value of the range:
• If the value of the flow is greater than the specified value,
reduce the pressure differential setpoint on the user
interface to reduce the value of the flow.
• If the value of the flow is lower to the specified value,
increase the pressure differential setpoint on the user
interface to increase the value of the flow.
Repeat until the design pressure drop / flow rate is achieved.
Stop the forced operation of the pump and proceed to the
configuration of the unit for the required control mode.
Modify the control parameters:
- Set water flow control to 'pressure differential'
- Set the value of the required differential pressure
By default, the unit is factory configured at the minimum speed
(frequency: 50 Hz).
NOTES:
If during controlling, the low or high frequency limits are
reached before reaching the specified flow, keep the pressure
differential value to its lower or higher limit to enter in the
control parameters.
If the user already knows the pressure differential value to
be maintained at the unit outlet, this may be entered directly
as a parameter. However, the hydraulic circuit cleaning
sequence must not be omitted.
8.6 - Units with hydraulic module and variable-
speed pump - temperature difference control
The temperature sensors at the heat exchanger inlet and outlet
(items 8 and 9 in the typical hydraulic circuit diagram) are used
as means of control.
The system reads the measured temperature values, calculates
the corresponding temperature difference, compares it with the
user-selected setpoint value and modulates the pump speed as
necessary:
• If a higher delta T value than the set point is measured, the
flow rate is increased.
• If a lower delta T value than the set point is measured, the flow
rate is decreased.
This flow rate variation is realised, observing the minimum and
maximum admissible unit flow rates as well as the minimum and
maximum pump supply frequency values.
The delta T value maintained can in certain cases be different from
the set point value:
• If the set point value is too high (achieved for a lower flow rate
than the minimum value or a lower frequency than the
minimum value), the system settles at the minimum flow rate
or minimum frequency and this results in a lower delta T value
than the set point.
• If the set point value is too low (achieved for a higher flow rate
that the maximum value or a higher frequency than the
maximum value), the system settles at the maximum flow rate
or maximum frequency and this results in a higher delta T
value than the set point.
Contact Carrier Service to discuss the implementation of the
procedures set out below.
8.6.1 - Hydraulic circuit cleaning procedure
Refer to the procedure for cleaning the hydraulic circuit from chapter
8.3.1
8.6.2 - Procedure for adjusting the Delta T° setpoint
Once the circuit is cleaned, stop the forced start of the pump and
proceed to the configuration of the unit for the required control mode.
Modify the control parameters:
- Water flow rate control method (temperature differential)
- Set the value of the required differential temperature.
By default, the unit is factory configured at the minimum speed
(frequency: 50 Hz).
Combination of options for the periods when the unit is in
standby mode.
Ambient unit
without
temperature range
option 116
> 0 °C to 51 °C
-20 °C to 0 °C Option 41
Suitable
antifreeze
solution (such
as glycol)
(1) Allow the pumps to circulate. If there is a valve, install a bypass (see diagram
for winter position).
Product
With option With option
116
-
Option 42 Option 42B
(1)
or or
Suitable Suitable
antifreeze antifreeze
solution (such solution (such
as glycol) as glycol)
(1)
307
-
(1)
or
(1)
29