Table des Matières
Publicité
Les langues disponibles
Les langues disponibles
c. For analog control actuators either:
(1) Change setting of reverse/direct-acting
switch, or
(2) To change spring return direction: remove,
flip over, and replace actuator on bracket.
3. If the control scheme requires fail-safe operation,
ensure that, upon removal of power, the fail position
coincides with the control sequence.
4. Spring return actuators are factory-configured for
normally-closed, fail-safe operation on power loss.
To change this action to normally-open, remove and
reinstall the actuator in the opposite orientation as
follows:
a. Loosen the shaft coupling bolt using a 10 mm
wrench.
b. Loosen all other mounting bolts connecting the
actuator to the mounting bracket, and set aside.
c. Remove the actuator from the valve shaft.
d. Move the Self-Centering Shaft Adaptor to the
opposite side of the actuator, as displayed in
Fig. 30.
Fig. 30. Change actuator to normally open.
(1) Remove the retainer clip from the Self-Cen-
tering Shaft Adapter and set it aside for later
use.
(2) Remove SCSA from actuator.
(3) Reinstall SCSA on the opposite side of the
actuator, aligning it based on the stroke label-
ing.
(4) Replace the retainer clip on the shaft cou-
pling using the groove of the coupling.
e. Reconnect the actuator to the valve mounting
bracket by replacing the screws previously
removed (step b).
f.
Tighten the shaft coupling bolt using a 10 mm
wrench or socket using maximum 120 lb-in
torque.
Operation
P
changes constantly in a multi-zone system as other
IN
valves open and close, changing system flow and head
pressure according to the characteristics of the supply
pump curve. Reaction of the mechanical pressure
regulator is instantaneous, eliminating changes in room
temperature due to changes in fluid flow, and reducing the
need for the control system to constantly operate the
control portion of the valve to correct for the non-load
related temperature changes that occur in a system with
standard control valves.
VRN DYNAMIC PRESSURE-REGULATING CONTROL VALVES AND ACTUATORS
Fig. 31. VRN2 cross section showing fitting, control ball,
At full flow in a 2-position control application, a VRN2
behaves as a flow limiter.
The pressure regulator takes a minimum pressure to
operate, and has a maximum differential regulation
capability. See Fig. 32. The high pressure drop across a
VRN2 Valve is comparable to the pressure drop across a
control valve and balancing valve in a conventional
system design.
M27714
12
10
8
FLOW
RATE
6
(GPM)
4
0
5.8
Fig. 32. Pressure regulation, large body models.
SETTINGS AND
ADJUSTMENTS
At the full open position, VRN2 valves will maintain flow in
the loop. Flow rates are listed in the Specification Data
form 62-3115EFS. Under steady state operation, the
control system will only require the valve to open enough
to satisfy load conditions. During morning recovery from
night setback, the controller will usually command the
valve to 100%. For optimum performance, choose only the
next larger valve size needed to satisfy design load. Do not
oversize valves—reduced rangeability and may result in
less accurate temperature control.
9
and pressure regulator.
8
12
16
22
28
34
DIFFERENTIAL PRESSURE (PSID)
M29908A
100% OPEN
80% OPEN
60% OPEN
40% OPEN
20% OPEN
40
50
60
M29707A
38-00005EFS—04
Publicité
Table des Matières
