Danfoss HRU Operating guide
Classified as Business
Operating Guide
HRU – Heat Recovery Unit
controlled with ECL Comfort 310 – P501.12 application
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Contents
HRU Unit with ECL Comfort 310 – P501.12 ........................................................................................ 3
Primary function .............................................................................................................................. 4
Function description P501.12 ............................................................................................................. 5
Operation ......................................................................................................................................... 5
Control ............................................................................................................................................. 5
ECL operating mode .................................................................................................................... 5
Regulation ....................................................................................................................................... 6
Flow temperature ........................................................................................................................ 6
Sale of excess heat ....................................................................................................................... 6
Energy monitoring ...................................................................................................................... 6
Alarms .......................................................................................................................................... 7
Sensor overview .............................................................................................................................. 7
Configuration guide: ........................................................................................................................... 8
Heating circuit: ................................................................................................................................ 8
REMEMBER ................................................................................................................................... 8
Flow meter F1, F2 and F3 configuration ......................................................................................... 9
Configuration parameters for flow temperature from the HRU unit (S3) ................................... 10
Configuration parameters for the return temperature controller............................................... 11
Configuration parameters for optimisation ................................................................................. 12
Reg. parameter 1 applies to M1 controls ...................................................................................... 13
Reg. parameter 2 applies to M2 controls ...................................................................................... 14
Circuit 1, heating circuit ................................................................................................................ 15
Circuit 1, schedule 1 ...................................................................................................................... 16
Tank temperature. ......................................................................................................................... 17
Compensation T. ........................................................................................................................... 18
Reg. recovery. ................................................................................................................................ 19
Control par., export ....................................................................................................................... 20
Boost. ............................................................................................................................................. 21
Circuit 2, schedule 2....................................................................................................................... 22
Circuit 3, tank temperature. .......................................................................................................... 23
Circuit 3, schedule 3....................................................................................................................... 24
Connection of ECL 310 to ECL portal. ........................................................................................... 25
Integration with the cooling plant. ............................................................................................... 27
Configuration of heat requirement signals from HRU unit ............................................................. 27
Safety function. .............................................................................................................................. 27
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HRU Unit with ECL Comfort 310 – P501.12
Versions A1- A4
Versions A6- A7
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Primary function
Utilisation of excess heat from CO2 refrigeration plants.
The unit prioritises heating of own plant before any sales to e.g. district heating suppliers.
In order to balance different usage patterns (temperatures and heating requirements) on the
heating side and the production of excess heat on the cooling side, the unit has been designed
as a buffer charging circuit.
This results in very stable and uniform charging, also ensuring a long service life for the CO2 heat
exchanger.
The flow temperature from the HRU unit is controlled by the building requirements (heating, hot
water or ventilation), either via signals from other ECLs or via Modbus from an existing SCADA
system.
In the event of possible sale of excess heat to the district heating supplier or other buyers, this
can be managed in such a way that a constant temperature is supplied to these buyers.
The HRU unit can send a reference signal to the cooling plant indicating how much heat can be
accumulated.
A safety function has been embedded to protect against boiling over on the water side.
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Function description P501.12
Operation
The system is configured and monitored via the ECL Comfort 310 regulator or a PC/Mac/mobile
via the ECL portal.
Link to the ECL portal: ecl.portal.danfoss.com (Internet connection required)
Control
ECL operating mode
The mode of operation of the unit can be selected:
: AUTO The unit switches between comfort/saving mode via a time program.
Or this can be done via a heating request from a slave regulator (ECL Comfort 310)
The mode of operation for this application must be AUTO.
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Regulation
Flow temperature
The flow temperature can be controlled using the following principles:
1. Fixed flow temperature or flow temperature based on the outdoor temperature from
the HRU unit
2. Determined by external reference (via Modbus)
3. Determined by references from other ECL 310 regulators for domestic hot water,
heating or ventilation units via ECL 485 bus communication
The control intelligence ensure that predominantly heat from buffer tanks is used. If, during
certain periods, this is not adequate, auxiliary heat can be added from external heating sources
such as district heating or boiler systems, etc.
The charging temperature is controlled in accordance with the desired buffer temperature and
the cooling plant load, so that maximum energy is transferred from the cooling plant at all times.
This ensures that minimal energy is discharged from the gas cooler on the roof.
Cooling circuit
A signal is transmitted to the cooling plant about how much energy can be accumulated so that,
during periods without the possibility for accumulation, energy is not transferred from the CO2
exchangers to the buffer charging system.
Sale of excess heat
In the event of sale or export of excess heat, energy is pumped out via the same supply
connection used to buy heat using a frequency-controlled booster pump controlled by the
differential pressure and the desired sales flow temperature.
Energy monitoring
If desired, consumption data can be collected via the ECL 310 from heat, water and electricity
meters via M-bus connections. The data is transferred to Danfoss' ECL portal.
The energy data is logged on an hourly basis and can also be retrieved for use with third-party
energy management systems, in which it may be possible to create an overview of the total
energy consumption, corrected for heating degree days, allowing for comparison of the energy
consumption of buildings in connection with energy management.
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S1
Outdoor temperature
S2
Return temperature, CO2 to gas cooler
S3
Flow temperature from HRU to the heating
circuit
S4
Charging temperature to accumulation tank
S5
Return temperature to district heating
S6
Top temperature in the accumulation tank
S7
Return temperature from the heating circuit
S8
Bottom temperature in the accumulation tank
S9
Flow temperature, sale of excess heat
S10
Return temperature from the accumulation
tank
S11
CO2 temperature from the cooling
compressor
Alarms
Flow failure in charging circuit
An alarm can be configured so that, in the event of a flow failure in the charging circuit (flow
meter F3), can stop the circulation pump P3, and at the same time 0V will be transmitted to the
cooling plant so that the three-way valve on the CO2 side leads the gas directly to the gas cooler
on the roof.
The alarm is given in accordance with the configured time delay.
Sensor overview
Sensor ID Sensor description
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Configuration guide:
Heating circuit:
The mixing circuit (M1) operates in three phases:
1: 100% use of recovered heat
2: mixture of recovered heat and auxiliary heat
3: 100% use of auxiliary heat
Note: in the event of 100% use of recovered heat, mixing takes place via the purchase exchanger with
a closed M2 valve.
REMEMBER
The return temperature from the heating plant (S7) must always be as low as possible, as only
five degrees lower could have a major impact on the utilisation of CO2 heat recovery. For radiator
heating, the return temperature at S7 should ideally be around 30-35 degrees, and for
underfloor heating it should be 20-25 degrees.
It is therefore crucial to the utilisation of excess heat that the heating circuit is optimised and
correctly configured.
The mixing circuit (M1) is configured as an ordinary mixing circuit. The desired flow temperature
from the HRU unit (R3 reference) can be configured as a fixed temperature or a flow
temperature based on the outdoor temperature. It can also originate from another ECL 310 or
via Modbus from an existing SCADA system.
Remember to configure night setback in the heating system. This means that less energy is used
from the accumulation tanks at night. Several refrigerators are now also covered at night and, in
such situations, less energy is generated for heat recovery.
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Flow meter F1, F2 and F3 configuration
Menu -> Settings -> Flow temperature
• The M-bus from flow meters is connected to the terminals 37 and 38 in the ECL 310.
• All flow meters must be configured in settings. Flow meter F1 must be configured as
Energy meter 1, flow meter F2 must be configured as Energy meter 2 and flow meter F3
must be configured as Energy meter 3.
• Energy meter F3 - shows how much energy is being recovered.
• It is important to ensure that the Baud rate has been set to 2400 for all connected meters.
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