1. Free cooling on RTAF Chiller
Integrated option

2. Water based free cooling principle.
Use full aluminum (car radiator based) flat channel dry cooler exchangers.
Modulate 3 way valve to reach required free cooling capacity.
Need low air pressure drop coil to avoid upgrade of fans.
Oil
Sep.
Evaporator

3. Technical proposition
Alternative 1 : no change on condenser fan = lower EER, but no fan impact on cost, almost no impact on sound level
Total Free cooling
Direct free cooling version (With glycol on customer loop)
Total Free cooling
Glycol Free version (With water on customer loop) 1 2
Partial Free cooling
Direct free cooling version (With glycol on customer loop)
Partial Free cooling
Glycol Free version (With water on customer loop) 3 4
Trane FreeCool
External drycooler 5
External Dry cooler – Standard RTAF
With or without glycol on customer loop

4. Optionnal Pump package
Flow chart - Free cooling Direct free cooling version (With glycol on customer loop) 1 3
Service valve
(Vent)
Dry cooler coils
Dry cooler coils
Service valve
(Vent)
Tchill OUT
Tevap IN
Evaporator
Free cooler
Modulating 2way valve
Free cooler Bypass 2way valve
Tchill IN
Optionnal Pump package
Service valve
(Drain)

5. Optionnal Pump package
Flow chart - Free cooling Glycol Free version (With water on customer loop) 2 4
Service valve
(Vent)
Dry cooler coils
Dry cooler coils
Service valve
(Vent)
Tchill OUT
Tevap IN
Water/glycol
BPHE
Tfc OUT
Evaporator
Free cooler
Modulating 2way valve
Exp.tank
Free cooler Bypass 2way valve
Tchill IN
Optionnal Pump package
Tfc IN
Service valve
(Drain)
Service valve
(Drain)
Circulating pump

6. Free cooling enabling condition
Condition to get free cooling active :
Unit is in active cooling mode.
Outdoor temperature shall be low enough. Cf. diagram here below
Free cooling enabled
Proposed default value
FC Offset = 3K (Min 0.5°K, max 15°K)
FC Hysteresis = 1K (Min 0.5°K, max 3°K)
FC Offset
Free cooling disabled
Water Cooling setpoint
Outdoor air
temperature
FC setpoint = Active chilled water cooling setpoint – FC_offset
FC Hysteresis
The free cooling function is enabled when outdoor air temperature is below (Active chilled water cooling set point minus FC_offset).
An hysteresis shall be applied to avoid short cycling of FC enable logic.
FC offset is the parameter adjusted by user to make free cooling active.
Free cooling becomes the 1st stage of cooling, whatever the compressor sequence selected:
If free cooling is enabled while compressor is running, then unload command of the algorithm shall apply to running compressor . In case of load command, then free cooling capacity shall be increase

7. Free cooling capacity modulation3 3
Dry cooler coils
Dry cooler coils
Dry cooler coils
Dry cooler coils 2 2
Free cooler
Modulating 2way valve
Free cooler
Modulating 2way valve
Free cooler Bypass 2way valve (ON-OFF)
Free cooler Bypass 2way valve (ON-OFF) 1 1
FC pump 4
FC disabled
FC 1st step
FC 2nd step
Bypass Valve
100%
100%►0% for TFC
100%►30% for PFC
0% for TFC
30% for PFC
FC valve
CLOSE
0%►100% (modulating)
Condenser fan
airflow
Follow compressor fan sequence 0%
or follow compressor fan sequence if compressor are still running
0%►100%
FC pump
OFF ON 1 2 3 4

8. Freeze protection (only for Glycol free version)
If Free cooling is active, the pump is ON. At start up or when heat transfer over the drycooler increases, the glycol stored in the system could be very cold, resulting in freezing risk on the BPHE. To avoid this, the strategy is to run the pump with recirculation of the glycol in a short loop (dotted line arrow). The freeze protection mode is targeted to restore positive temperature at BPHE glycol inlet. The heat from return chilled water and from the pump heat loss will try to maintain the BPHE glycol temperature above 0°C.
Difficulty here is to have quick enough system response to avoid partial freezing into the BPHE
Condition to have freeze protection active:
Outdoor air temperature <3°C
Free cooling is active : Chiller water flow is present & there is a call for cooling.
If Tfc OUT is < chilled water freeze protection setpoint and FC pump is ON then we are in FC freeze protection mode
FC Freeze protection limiting mode :
Reduce Free cooling capacity to keep TfcOUT > chilled water freeze protection setpoint from 100% to 0% (following accelarated unload sequence).
If Tfc IN < chilled water freeze protection then
Lockout free cooling operation and report alarm. Auto reset when Outdoor temperature is >3°C.
To dry cooler coils
Tchill OUT
Tevap IN
Water/glycol
BPHE
Tfc OUT
Evaporator
FC Modulating 2way valve
FC Bypass 2way valve
Tchill IN
Optionnal Pump package
Tfc IN
Service valve
(Drain)
Service valve
(Drain)
Circulating pump

9. Schedule 2015 2016 Q1 Q2 Q3 Q4 Q1 9 IRPDP gates reviews
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
Jan.
Feb.
Mar. G1 G2 G3 G4 G2 G4
IRPDP gates reviews
Jul-09
Program key steps
Mockup
build & Test
Validation unit Ph1
build & Test
Validation unit Ph2
build & Test
Industrialization Ph1
Industrialization Ph2
Literature update Ph1
Literature update
Ph2
Phase 1 = All RTAF sizes – Direct free cooling version - Partial and Total Free cooling
Phase 1 : All RTAF sizes – Glycol FREE version - Partial and Total Free cooling
The Schedule & Next steps slide provides a snapshot of the schedule to the next Gate review.
Many tools can be used to create this… simple table, Microsoft Project or other schedule tool. For a Gate 1, there should be detail to get to the Gate 2 review and milestones for the balance of the project. A full integrated schedule is not required until Gate 2.
Pre-annoucement
Topps Release
Topps Release
1ST SHIP
1ST SHIP 9