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Important Safety Note
The programme-controlled blowdown system is
exclusively suited for GESTRA intermittent blowdown
valves types MPA . . . . All maintenance or repair work
of the equipment must only be carried out by GESTRA
Technical Services.
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.
Purpose
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
supervision or with limited supervision (TRD 604 or
TRD 602).
Function
The programme-controlled blowdown system (Fig. 2)
consists of an electronic cycling timer
B
C
solenoid valve
, a strainer
, and a screwed reducer
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.
Technical Data
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
Mains supply
115 V/230 V ± 10 %, 50-60 Hz
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)
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
Mains supply
115 V ± 10 %, 50 Hz, 15 VA, inrush 30 VA
230 V ± 10 %, 50 Hz, 15 VA, inrush 30 VA
60 Hz optional
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
A
, a three-way
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).
Installation
Lay control-fluid line; pipe diameter
10 x 1 mm pipe (with compression fitting) for com-
pressed air. Install TA 7 only where the temperatures
do not exceed 55 °C.
Control-Fluid Connections
Effect connections to solenoid valve in accordance with
diagram (Fig. 3).
Wiring
Loosen screw
terminal box from solenoid valve (see Fig. 4). Unscrew
2
cable gland
Effect wiring to the terminal strip
using three-conductor cable. e.g. 3 x 1.5 mm
voltage 115 V or 230 V. The mains 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
0
plate
. Select the required direction, and reinsert
plate.
Plug cycling timer onto solenoid valve and fasten with
1
screw
.
3
/
" for water,
8
1
on top of cycling timer and unplug
and open the transparent lid.
4
in the cycling timer
2
. Supply
9
and lever out plug
Initial Adjustments
1. Switch on mains voltage, the red LED "Mains
3
supply"
must light up (Fig. 4).
5
2. Set dip switch
to the required position (Fig.
4/5).
6
7
3. Turn potentiometers
/
with a screwdriver
(1.5 mm blade) to the left against stop (Fig. 5).
4. Set pulse duration t
with the aid of potentiometer
on
6
(Fig. 5).
5. Set interval time t
with the aid of potentiometer
off
7
(Fig. 5).
Operation
Normal operation
1. Switch on mains voltage, the red LED "Mains
3
supply"
lights up (Fig. 4).
2. Admit pressure to control-fluid line.
3. In case of a blowdown pulse t
on
8
duration"
lights up (Fig. 4).
Manual operation
The three-way solenoid valve can be actuated manually
for test purposes of in the event of a mains 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).
Notice
An uncontrolled continuous pulse can cause a con-
siderable level decrease in the boiler, and release the
low-water level alarm signal.
the red LED "Pulse
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