Posts by devman

Air Handling Unit

with PICV direct control

Function

The air temperature of the Air Handling Unit is controlled by a sensor in the outlet. When the control system calls for higher or lower temperature on the air outlet, the PICV opens or closes to increase or decrease the flow through the coil. The power output from the coil follows a parabolic curve where often an EQ% valve/actuator characteristic is chosen to have a direct relation between the input control signal and power output.

Benefits

•          The PICV ensures balancing of the primary flow and eliminates the use of both static balancing valves and differential pressure control valves.
•          Simple application as only a PICV is required to control flow, temperature and differential pressure.
•          At part load, the flow through the coil can be low leading to laminar flow and reducing the power output.
•          Larger coils can have different temperatures in different areas of the coil making precise temperature control difficult.
•          A metering station can be installed if additional flow verification is required.

Considerations

Air Handling Unit

with PICV injection circuit

Function

The air temperature of the Air Handling Unit is controlled by a sensor in the outlet. The secondary side of the injection circuit circulates a constant flow through the coil maintaining a uniform temperature throughout the entire coil.

When the control system calls for higher or lower temperature on the air outlet, the PICV valve opens or closes to allow heating or cooling water from the primary side of the injection circuit to enter the secondary side. The temperature in the coil then changes giving an almost direct relation between the temperature in the coil and the power output from the coil.

Benefits

•          The PICV ensures balancing of the primary flow and eliminates the use of both static balancing valves and differential pressure control valves.
•          AHU’s with a large coil area have a uniform temperature in all parts of the coil, providing a precise temperature control.
•          Direct relation between coil temperature and power output.

Considerations

•          Requires a small circulation pump on the secondary side of the injection circuit.
•          A metering station can be installed if additional flow verification is required.

Radiator System

with DPCV and dynamic balancing

Function

The room temperature is controlled by the radiator valve on each radiator.

The balance of the system is handled by the installation of a dynamic balancing valve on each riser/branch, controlling the flow rate through this section of the system.

The dynamic balancing valve is a flow limiter that prevents overflow in the part of the system controlled by the valve.

This will ensure that the design flow is always available in all parts of the system.

A DPCV controlling the differential pressure at each riser prevents from noise in the system and allows the radiator valves to regulate and close when required.

The temperature from the primary circuit is lowered to an optimal inlet temperature at the secondary side, with a heat PICV injection circuit connected to a controller.

Benefits

•         The flow rate through the dynamic balancing valve is independent of the differential pressure across it.
•         The flow can be set without the use of a manometer/commissioning device.
•         Only 1 dynamic balancing valve in series.
•         If the system is expanded, it will not need to be rebalanced.
•         No straight lengths of pipe before or after the dynamic balancing valve are required.
•         Prevents noise in the system and provides good modulation to the radiator valves.
•         All sections will have a defined DP available.

Considerations

•         Higher cost from both DP control valve and dynamic balancing valve
•         A metering station can be installed if additional flow verification is required by the witnessing authority.

Radiator System

with differential pressure control

Function

The room temperature is controlled by the radiator valve on each radiator.

The balance of the system is handled by the pre-setting of the radiator valves in conjunction with the pre-set differential pressure, controlled by the DPCV.

A DPCV controlling the differential pressure at every riser prevents from noise in the system and allow the radiator valves to regulate and close when required.

The temperature from the primary circuit is lowered to an optimal inlet temperature at the secondary side, with a heat PICV injection circuit connected to a controller.

The flow at the individual risers can be adjusted by the DPCV and verified on the metering station on each riser.

Benefits

•          Prevents noise in the system.
•          Provides good modulation for the radiator valves.
•          All sections will have a defined DP available.

With the correct radiator valve pre-setting, the flow will be controlled in every part of the system.

Low cost solution.

Considerations

If the radiator valves are without pre-setting or they are not set correctly, the flow in the system will not be in balance.

Heat Pump – Plant Room

with PICV control

Function

The heat pumps are connected to the controller through the valve actuator which controls the flow through each heat pump using the PICV.

The controller measures the inlet and outlet temperature to maximize Delta T and regulates the variable speed pump to maintain the required pump pressure.

For optimal heat pump efficiency, the use of either cascade or unison control is recommended.

Benefits

•         The PICV ensures balancing of the flow and eliminates the use of both static balancing valves and differential pressure control valves.
•         Simple installation as only the PICV is required with no need for additional pressure or flow balancing valves.
•         Low total pressure loss in the system due to simple design.
•         The flow can be set directly on the PICV without the need of a manometer or a commissioning unit.
•         The differential pressure only needs to be checked at the PICV to set the required flow.

Considerations

•         A metering station can be placed on the main line if additional flow verification is required by the witnessing authority.
•         A minimum bypass flow can be required by the heat pump to secure instant heating or circulation of chemicals in the system. This should be placed at the most appropriate place in the system.

Fixed Speed Chiller – Plant Room

with PICV control

Function

The fixed speed chillers are connected to the controller which opens and closes the flow through each chiller by turning the PICV on and off.

The controller measures the inlet and outlet temperature to maximize Delta T and regulates the variable speed pump to maintain the required pump pressure.

For optimal chiller efficiency, the use of cascade control is recommended.

Benefits

•         The PICV ensures balancing of the flow and eliminates the use of both static balancing valves and differential pressure control valves.
•         Simple installation as only the PICV is required with no need for additional pressure or flow balancing valves.
•         Low total pressure loss in the system due to simple design.
•         The flow can be set directly on the PICV without the need of a manometer or a commissioning unit.
•         The differential pressure only needs to be checked at the PICV to set the required flow.

Considerations

•         A metering station can be placed on the main line if additional flow verification is required by the witnessing authority.
•         A minimum bypass flow controlled by a dynamic flow limiter is required by the chiller to avoid freezing as they are running at full capacity when switched on.

Radiator System

with dynamic balancing

Function

The room temperature is controlled by the radiator valve on each radiator.

The balance of the system is handled by a dynamic balancing valve on each riser/branch controlling the flow rate through this section of the system.

The dynamic balancing valve can also be installed at each apartment for a more localised balancing.

The dynamic balancing valve is a flow limiter that prevents overflow in the part of the system controlled by the valve.

This will ensure that the design flow is always available in every part of the system.

The temperature from the primary circuit is lowered to an optimal inlet temperature at the secondary side, with a PICV injection circuit connected to a controller.

Benefits

•         The flow rate through the dynamic balancing valve is independent of the differential pressure across it.
•         The flow can be set without the use of a manometer/commissioning device.
•         Only 1 dynamic balancing valve in series.
•         If the system is expanded, it will not need to be rebalanced.
•         No straight lengths of pipe before or after the dynamic balancing valve are required.

Considerations

•         Minimum differential pressure required for the dynamic balancing valve must be available at design flow.
•         The differential pressure in the different sections of the system cannot be controlled.

Underfloor Speed Chiller

with PICV control – single circuit

Function

The room temperature is controlled by a room thermostat connected to the PICV actuator.

The temperature from the primary circuit is lowered by a heat injection circuit down to a maximum of 30°C.

Due to the slow response time of an underfloor heating system, it is normally controlled by a weather compensated room controller with an outside sensor.

The control characteristic will normally be linear.

Benefits

•         The PICV ensures balancing of the flow and eliminates the use of both static balancing valves and differential pressure control valves.
•         Simple installation as only the PICV is required with no need for additional pressure or flow balancing valves.
•         Low total pressure loss in the system due to simple design.
•         The flow can be set directly on the PICV without the need of a manometer or a commissioning unit.

Considerations

•         Minimum differential pressure required for the PICV must be available at design flow.
•         A metering station can be installed if additional flow verification is required by the witnessing authority.