Chilled Water Valve Control; Chilled Water Face And Bypass Damper And End Of Cycle Valve Control - Daikin MicroTech Operation And Maintenance

Chilled Water Valve Control

If the UVC is configured for a modulating chilled water valve,
it is operated by a proportional actuator. The modulating valve
actuator contains a spring that ensures that the chilled water
valve is closed upon loss of power. Each proportional actuator is
driven by the UVC using 0-10VDC outputs (scaled to 2-10VDC).
Figure 15: Cool State Operation - Valve Control
Staging
Up
SatHi
SatLo
Staging
Down
Discharge Air
The 2-way modulating chilled water valve is furnished to
fail closed to the coil. 24VAC is required to power the valve
actuator. When the actuator is powered, a controller will
provide a 2-10VDC signal to the actuator. A signal of 2VDC or
less will drive the valve closed; the valve will drive open as the
signal increases to a maximum of 10VDC.
If 24VAC is lost to the actuator, valve will spring-return to its fail
position (closed to the coil for chilled water valves).
The 3-way modulating chilled water valve is furnished to
fail closed to the coil. 24VAC is required to power the valve
actuator. When the actuator is powered, a controller will
provide a 2-10VDC signal to the actuator. A signal of 2VDC or
less will drive the valve closed (bypassing coil); the valve will
drive open as the signal increases to a maximum of 10VDC
(flow through the coil).
If 24VAC is lost to the actuator, valve will spring-return to its fail
position (closed to the coil for chilled water valves, full bypass
around the coil).
OM 1280-2 • MICROTECH UNIT CONTROLLER
Chilled Water Face and Bypass Damper
and End of Cycle Valve Control
Both a wet-heat end-of-cycle (EOC) valve and a chilled water end-of-cycle
(EOC) valve are strongly recommended by Daikin. If an EOC valve is not
installed, it is likely that over-heating or over-cooling of the space will occur.
The UVC can be configured for a two-position, normally-open
wet heat end-of-cycle (EOC) valve and/or a two-position,
normally closed chilled water end-of-cycle valve. The two-
position valve actuators contain springs that ensures that the
wet heat valve is open and the chilled water valve is closed
upon loss of power. The two-position actuators are driven by the
UVC using one binary output per actuator.
Face and Bypass (F&BP) dampers are used in conjunction with
2 or 3 way End of Cycle (EOC) valves. The UVC is configured
for a face and bypass damper operated by a proportional
actuator. The proportional actuator is driven by the UVC using a
0-10VDC output (scaled to 2-6VDC).
Cooling
When the F&BP damper is used with an EOC valve, the F&BP
Capacity
damper maintains the DATS. When there is no call for hydronic
cooling, the EOC valve will isolate water flow unless there is
a Valve Freeze Protect condition, in which case the valve will
Warmer
go full open and the F&BP damper will be used to maintain the
control temperature.
Figure 16: Cool State Operation – Face and Bypass
Damper Control
Staging
Up
Staging
Down
EOC Valve Open –
EOC Valve Closed –
Satisfied
22
Description of Operation
CAUTION
SatHi
SatLo
Discharge Air
www.DaikinApplied.com
Primary
Cooling
Capacity
Warmer