Circuit For Recovery For Heating - Danfoss AK-PC 781A User Manual

Circuit for recovery for heating

Application
This regulation can only be carried out when the selected refriger-
ant is CO 2 , which makes it possible to supply hot gas for heating a
receiver vessel.
Regulation can be carried out using one of the following three
principles, when the circuit calls for heat:
- 1. Basic control (no HP offset).
- 2. Offset of the condensing pressure (HP offset)
- 3. Offset and regulation of the gas cooler and pump (max. hr)
Generally, for all three principles:
Valve - V3hr
When heating of the circuit is required, the gas valve will change
over and route the gas in through the heat exchanger.
When the temperature goes above the reference plus half the
band, the gas will be routed outside of the heat exchanger.
Pump - Pump hr
It is recommended to use a pump with variable speed, so that the
regulation flows and does not display great fluctuations in the
condensation pressure.
Flow switch - FShr
A flow switch should be installed for safety reasons, in case of
pump failure. The controller will then disconnect the entire recov-
ery circuit.
Sensors - Shr2, Shr3, Shr4 and Shr8 (Stw2/Sd)
All sensors must be installed due to safety reasons:
Shr2: The controller must know the temperature of the gas that is
sent for condensation.
Shr3: Heat exchanger cold access. Used for temperature regulation
Shr4: Heat exchanger hot outlet Used for temperature regulation
Shr8: Receiver temperature and in relation to the reference.
Stw2 or Sd: The regulation must know the temperature of the gas
that is sent into the heat exchanger.
114 Capacity controller RS8HE202 © Danfoss 2017-07
1. Basic control (no HP offset).
Reference
Regulation is done using a receiver temperature of e.g. 40°C, the
value is adjustable. A temperature sensor Shr8 is installed in the
receiver, and the temperature is maintained in a band around the
selected value.
Reference
Band
When the temperature goes above the reference plus half the
band, the gas will be routed outside of the heat exchanger.
The reference can be displaced variably using an external 0-10 V
signal. 0 V results in no displacement. 10 V results in a displace-
ment indicated by the set value.
Regulation
The following can be used as a regulation sensor:
- Shr8
- Shr4
- Delta T via heat exchanger (Shr4-Shr3) of e.g. 4K, but still using
Shr8 as a reference.
The pump can be controlled on/off or variably. For Shr4 or DeltaT
regulation it must be controlled variably. During variable opera-
tion the pump will stop when the regulation desires a lower
capacity than the selected min. speed capacity for the pump.
AK-PC 781A