Coolerado C60A, Installation Manual

Page: 32 / 53

Coolerado Installation
Page
32
of 53
Appendix 8: Freeze Protection
The Coolerado freeze protection option provides the electronic controls needed to disable the cool call from the space-mounted
thermostat, if there is a cool call, and drain the water supply lines in the event that the outdoor air temperature falls below 40
o
F.
The Freeze Protection Daughter Board (optional accessory, see Figure 3) provides the additional terminals and board-mounted relay
needed. All other freeze protection wiring, water solenoid valves, relays, transformers and electrical box are supplied by others, see
Figure 2.
Logic

When the outdoor air temperature, (temperature as sensed by the Coolerado Water Control Board temperature sensor
based on the inlet air to the Coolerado unit), drops below 40
o
F, the Coolerado Water Control Board will no longer allow a
cool call to turn the supply fan on. This prevents drying out of the unit’s heat and mass exchangers (HMXs) when the water
is turned off for freeze protection.

In addition, when the temperature drops below 40
o
F (4.4
o
C) for a period of 5 minutes or longer, the daughter board will
break the 24 VAC signal being sent from terminals "2" and "C". This actuates a relay which closes the Main Water Supply
Solenoid Valve, (supplied by others), and opens the water line Drain Water Solenoid Valve, (supplied by others). During
normal operation, when the outdoor temperature is above 40
o
F (4.4
o
C), terminals “2” and “C” on the Coolerado Freeze
Protection Daughter Board output 24 VAC. When the outdoor temperature falls below 40
o
F (4.4
o
C), or during a power
failure, there will be no power on terminals "2" and "C".

When the temperature drops below 36
o
F (2.2
o
C) for a period of 5 minutes or longer, the Coolerado water distribution
solenoid valve will open for 2 minutes. This allows air to be drawn into the Coolerado water distribution solenoid valve and
water line. It is important to have the Coolerado solenoid valve closed until the Main Water Supply Solenoid Valve has
been closed or the water will run unfettered.

If there are multiple Coolerado Air Conditioners on the same water line and located on the same area (i.e. building roof)
only one unit needs the Daughter Board mounted to the Water Control Board. All of the Coolerado units will need to have
their respective Water Control Boards programmed for freeze protection by turning dipswitch 8 on in order to turn off their
respective supply fans at 40
o
F (4.4
o
C) and open the Coolerado water distribution solenoid valve at 36
o
F (2.2
o
C) .
Note: If unit is off more than 48 hours the HMX’s may start to dry out and need to be rewetted when the temperature warms up
and a cool call is needed. This can be done by powering down the unit and repowering. On the next cool call the unit will go
through a wet out procedure.
Main Water Supply Solenoid Valve and Drain Solenoid Valve:
The water supply solenoid valve is normally closed and the drain solenoid valve is normally open. In the event of a power failure the
supply valve will not open. If there were a leak in the supply valve the drain valve would be open to keep the line from filling. The
main water supply solenoid valve must be at least as large as the supply line in order to reduce the pressure loss through the supply
valve. Refer to the water pressure chart in Appendix 1 for sizing of the water lines and solenoid valves.
The HMXs are not damaged by freezing as the water distribution system in them drains every time the water is turned off at the
unit. Water freezing in the HMXs will not damage the plate material. Additionally, the HMXs have an air gap internally that prevents
back flow of water. However the water line, pressure switch, pressure regulator and solenoid valve must be drained to prevent
damage.
Failure to properly slope the water supply lines towards the drain solenoid valve so they will drain to a heated space that is not
subject to freezing temperatures could void the warranty on the Coolerado unit, see figure 2.