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Clicking the ECO EXV button invokes the scree below with
following controls.
1. Setpoint – SSH value usually 9 R
2. PI parameters
3. Valve Max and Min output values
4. Requires external pressure and temperature sensors to
calculate SSH actual value.
5. Loop Delay – solenoid opens first.
Flash-Tank Level Control
An alternative method of obtaining flash gas is to
implement a flash tank. This vessel sits on the liquid line
with EXVs both upstream to the condenser and
downstream to the evaporator. The upstream EXV is
controlled by the standard EXV in Sub Cool mode. The
downstream EXV is controlled by the level in the flash tank.
Flash tank level is a permissive for the economizer
solenoids in so far as if the level is above a threshold
(Settable) the valves are closed. This is to prevent liquid
refrigerant into the interstage port of the compressor. Flash
tank control option also displays ECO EXV button which
invokes the following pop-up.
ARTC-SVX014A-EN
1. Flash Tank Level.
2. PI loop parameters.
3. Level Setpoint (default – 25 percent).
4. Valve max and min output values.
5. Loop delay.
6. Flash Tank Max Level (default – 60 percent) – this
closes the solenoid valve to prevent liquid refrigerant
from entering the interstage port.
Hot Gas Bypass Valves Control
HMI HGV Control option should be changed to Enabled in
order to expose Hot Gas Valve control screen under
Devices Menu.
Controls accessed on main Hot Gas Bypass valve screen
and Setup pop-up screen are common for all Hot Gas
Bypass Valves. Controls available on HGVs / Solenoids
pop-ups, however are individual for each Hot Gas Bypass
Valve.
Figure 30. HMI HGV control enabled screen
Operating Procedures
57
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