ENGLISH
The programme-controlled blowdown system is exclu-
sively suited for GESTRA intermittent blowdown valves
types MPA . . . . All maintenance or repair work of the
equipment must only be carried out by GESTRA Tech-
nical Services.
Important Safety Note
Danger
During maintenance work at the valve or blowdown line
a blowdown pulse can unintentionally be released. This
presents the danger of severe personal injury. Be fore
carrying out any maintenance work, it is essential to cut
off power supply and isolate control- fluid line.
Cycling Timer PRS 8
Dimensions
See
Fig. 1
Interval time t
off
(blowdown interval)
Adjustable within a range of 0.5 to 10 h
Pulse duration t
on
(blowdown duration)
Adjustable within a range of 0.5 to 10 s
Indicators
One LED mains supply
One LED pulse duration
Voltage supply
115 V – 230 V, 50 – 60 Hz
or 24 V DC
Protection
IP 65
Permissible ambient temperature
0 °C to 60°C
Cable entry
PG cable gland for 0.6 to 7 mm cable
Approx. weight
60 g
Three-Way Solenoid Valve 340 C
Connection
¼" BSP (G ¼, ISO 228-1)
Max. service pressure
16 barg (230 psig)
Technical Data
Electronic unit for the generation of periodic pulses to
initiate a blowdown cycle via the GESTRA rapid-action
intermittent blowdown valves type MPA 26, MPA 27
or MPA 110.
The equipment meets the German regulations for use in
steam-boiler plants operating without constant supervi-
sion or with limited supervision (TRD 604 or TRD 602).
Purpose
The programme-controlled blowdown system
(Fig. 2)
consists of an electronic cycling timer
A
, a three-way
solenoid valve
B
, a strainer
C
, and a screwed redu-
cer
D
.
The cycling timer type PRS 8 generates a control pulse
which operates the three-way solenoid valve. This in turn
actuates the rapid-action blowdown valve by means of
compressed air or pressurized water and closes it again
at the end of the pulse duration.
Function
Lay control-fluid pipe (made from stainless steel), pipe
diameter
3
/
8
" for water, 10 x 1 mm pipe (with compres-
sion fitting) for com pressed air. Install TA 7 only where
the temperatures do not exceed 55 °C.
Installation
Min. differential pressure
0.5 bar (7.2 psi)
Duty cycle
100 %
Position of installation
as required
Code letters for connections
P = Pressure connection
A/B = Valve outlet
R = Exhaust or drain outlet
Voltage supply
115 V, 50 Hz, 15 VA, inrush 30 VA
or
230 V, 50 Hz, 15 VA, inrush 30 VA
or optional
24 V DC 8 W
Protection
IP 65
Maximum permissible ambient temperature
55 °C
Approx. weight
0.9 kg
Strainer
Connection
½" BSP (G ½, ISO 228-1)
Material
Body: gun metal RG 5
Filter cartridge: austenitic stainless steel 1.4571
Mesh size
0.5 mm
Approx. weight
0.3 kg
Control fluid
Compressed air or pressurized water, 4 to 8 barg
(58 to 116 psig) depending on the blowdown valve used
and the boiler pressure (see chart in data sheet MPA 26,
MPA 27, MPA 110).
Effect connections to solenoid valve in accordance with
diagram
(Fig. 3)
.
Control-Fluid Connections
Loosen screw
1
on top of cycling timer and unplug
terminal box from solenoid valve (see
Fig. 4
). Unscrew
cable gland
2
and open the transparent lid.
Effect wiring to the terminal strip
4
in the cycling timer
using three-conductor cable. e.g. 3 x 1.5 mm
2
. Connect
supply voltage. The supply voltage is indicated on the
name plate of the solenoid valve.
The position of the cable entry can be modified by max.
270°. Proceed as follows: Insert a screwdriver with a 3
mm blade into the opening
9
and lever out plug plate
0
. Select the required direction, and reinsert plate.
Plug cycling timer onto solenoid valve and fasten with
screw
1
.
Wiring
1. Switch on mains voltage, the red LED “Mains supply”
3
must light up
(Fig. 4)
.
2. Set dip switch
5
to the required position
(Fig.
4/5)
.
3. Turn potentiometers
6
/
7
with a screwdriver
(1.5 mm blade) to the left against stop
(Fig. 5)
.
4. Set pulse duration t
on
with the aid of potentiometer
6
(Fig. 5)
.
5. Set interval time t
off
with the aid of potentiometer
7
(Fig. 5)
.
Initial Adjustments
Normal operation
1. Switch on supply voltage, the red LED “Operation”
3
lights up
(Fig. 4)
.
2. Admit pressure to control-fluid line.
3. In case of a blowdown pulse t
on
the red LED “Pulse
duration”
8
lights up
(Fig. 4)
.
Manual operation
The three-way solenoid valve can be actuated manually
for test purposes of in the event of a voltage failure. The
push button provided on the three-way solenoid valve
allows a test of the blowdown valve as required by
certain regulations in force (e. g. TRD 604).
1. Push button on solenoid valve and release.
2. Push button on solenoid valve and turn through 180°
(continuous pulse).
Operation
An uncontrolled continuous pulse can cause a con-
siderable level decrease in the boiler, and the water level
limiter may switch off the heating.
Notice
