GESTRA PRS 50 User manual
Original Installation &
Operating Manual
EN
English
Blowdown Timer
PRS 50
850652-00
2PRS 50 - Installation & Operating Manual - 850652-00
Contents
Content of this Manual................................................................................................................................... 3
Scope of delivery / Product package............................................................................................................. 3
How to use this Manual.................................................................................................................................. 4
Illustrations and symbols used...................................................................................................................... 4
Hazard symbols in this Manual...................................................................................................................... 4
Types of warning ............................................................................................................................................ 5
Specialist terms / Abbreviations.................................................................................................................... 6
Usage for the intended purpose..................................................................................................................... 7
Applicable directives and standards........................................................................................................... 7
Improper use .................................................................................................................................................. 7
Basic safety notes .......................................................................................................................................... 8
Required personnel qualifications................................................................................................................. 8
Notes on product liability............................................................................................................................... 8
Function .......................................................................................................................................................... 9
Technical data .............................................................................................................................................. 11
Name plate / Identification PRS 50.............................................................................................................. 13
Factory settings............................................................................................................................................ 14
Functional elements and dimensions.......................................................................................................... 15
Installing the PRS 50 blowdown timer ........................................................................................................ 16
Safety notes for maintenance work on the intermittent blowdown valve or blowdown pipes.................16
Electrical connection safety notes............................................................................................................... 16
Wiring diagram for the PRS 50 blowdown timer......................................................................................... 17
Electrical connection.................................................................................................................................... 18
Connecting the 24 V DC power supply ..................................................................................................... 18
Connecting the intermittent blowdown valve/alarm output contacts ......................................................... 18
Notes on connecting inductive loads........................................................................................................ 18
Connecting the standby/burner input (24 V DC) ........................................................................................ 18
Connecting the “Manual intermittent blowdown” input............................................................................. 18
Connecting the “Limit switch” input......................................................................................................... 18
Changing the equipment settings................................................................................................................ 19
Configuring the standby/burner function .................................................................................................. 20
Bringing into service – starting, operation and testing ............................................................................. 21
Changing the equipment settings when required ..................................................................................... 23
Valve relay/alarm relay test...................................................................................................................... 25
Monitoring the limit switch....................................................................................................................... 25
Indication of malfunctions using error codes ............................................................................................. 26
What to do in the event of system malfunctions......................................................................................... 27
Taking out of service .................................................................................................................................... 27
Disposal ........................................................................................................................................................ 27
Returning decontaminated equipment........................................................................................................ 27
EU Declaration of Conformity....................................................................................................................... 28
3PRS 50 - Installation & Operating Manual - 850652-00
Content of this Manual
Product:
Blowdown timer PRS 50
First edition:
BAN 850652-00/04-2021cm
Applicable documents:
None
You can find the latest Installation & Operating Manuals on our website:
http://www.gestra.com/documents/brochures.html
© Copyright
All rights reserved. Any misuse, particularly reproduction and dissemination to third parties, is not permit-
ted. The General Terms & Conditions of GESTRA AG apply.
Scope of delivery / Product package
■ 1 x Blowdown timer PRS 50
■ 1 x Installation & Operating Manual
4PRS 50 - Installation & Operating Manual - 850652-00
How to use this Manual
This Installation & Operating Manual describes the correct use of the PRS 50 blowdown timer.
It applies to persons who integrate this equipment in control systems, install, bring into service, operate,
maintain and dispose of this equipment. Anyone carrying out the above-mentioned activities must have
read this Installation & Operating Manual and understood its contents.
■ Read this Manual in full and follow all instructions.
■ Please also read the instructions for use of any accessories.
■ The Installation & Operating Manual is part of the product package. Keep it in an easily accessible
location.
Availability of this Installation & Operating Manual
■ Make sure this Installation & Operating Manual is always available to the operator.
■ If you pass on or sell the equipment to a third party, please also hand over the Installation & Operating
Manual.
Hazard symbols in this Manual
Danger zone / Dangerous situation
Danger of death from electric shock
Illustrations and symbols used
1. Action to be taken
2.
■ Lists
◆ Bullet points in lists
A Keys to illustrations
Additional
information
Read the relevant
Installation & Operating Manual
5PRS 50 - Installation & Operating Manual - 850652-00
Types of warning
DANGERDANGER
Warning of a dangerous situation that results in death or serious injury.
WARNING
Warning of a dangerous situation that may possibly result in death or serious injury.
CAUTIONCAUTION
Warning of a situation that may result in minor or moderate injury.
ATTENTIONATTENTION
Warning of a situation that results in damage to property or the environment.
6PRS 50 - Installation & Operating Manual - 850652-00
Specialist terms / Abbreviations
Here, we explain some abbreviations, specialist terms, etc., which are used in this Manual.
Intermittent boiler blowdown
During the evaporation process, fine sludge is deposited on heating surfaces and on the floor of the steam
generating unit. This sludge is caused by adding oxygen-scavenging agents, for example. The accumulated
sludge sediments form a thermally insulating layer and can damage the boiler walls due to excessive heat.
Intermittent blowdown is achieved by the abrupt opening of the intermittent blowdown valve. The
resulting suction effect occurs only at the moment the valve is first opened. The opening time should last
approximately 3 seconds, as longer opening times result in water losses.
Time-based pulse/interval actuation of the intermittent blowdown valve optimises the removal of sludge
from the boiler. The interval between the intermittent blowdown pulses can be set between 1 and 96
hours (intermittent blowdown interval). For efficient operation, the intermittent blowdown interval can be
configured in line with the sum total of burner firing times.
The duration of intermittent blowdown can be set between 1 and 10 seconds. For large boilers, repeated
intermittent blowdown pulses may be required. Repetition can be set between 1 and 10 with an interval
from 1 – 10 seconds (pulse interval).
Standby/burner mode
To prevent loss of water, automatic intermittent blowdown can be disabled in standby mode or when the
burner is switched off. To do this, a control signal is applied to the standby input.
When the system has switched to normal operation, a blowdown pulse is triggered with the set parameters
(blowdown time and number of pulses).
For demand-based intermittent blowdown, the standby input can be configured as a burner input. In
this mode, the remaining runtime until the next blowdown only begins counting down if the burner is active
(control signal applied to the burner input).
In this mode, the blowdown interval equals the sum total of burner firing times.
PRS ... / MPA ...
GESTRA equipment and type designations.
SELV
Safety Extra Low Voltage
7PRS 50 - Installation & Operating Manual - 850652-00
Usage for the intended purpose
The PRS 50 blowdown timer is used to trigger periodic blowdowns by means of the MPA 26, MPA 27,
MPA 46, MPA 47, MPA 48 or MPA 110 rapid-closing intermittent blowdown valve.
It is used in pressurised steam plants for keeping the boiler water in good condition, particularly during
operation where supervision is limited or not constant.
Configuration, operation and visual display
Configuration, operation and visual display are achieved using the rotary knob and the integrated 4-digit,
7-segment display.
To ensure proper use in all applications, please also read the Installation & Operating Manuals
for the system components used.
■ You will find the latest Installation & Operating Manuals for the system components named
here on our website:
http://www.gestra.com/documents/brochures.html
Applicable directives and standards
The PRS 50 blowdown timer has been tested and approved for use in the scope governed by the following
directives and standards:
Directives:
■ Directive 2014/35/EU Low Voltage Directive
■ Directive 2014/30/EU EMC Directive
■ Directive 2011/65/EU RoHS Directive
Standards:
■ DIN EN 60730-1 Automatic electrical controls – Part 1:
General requirements
■ EN 61326-1 Electrical equipment for measurement, control and laboratory use -
EMC requirements
Declaration of Conformity see page 28.
Improper use
There is a danger of death due to explosion if the equipment is used in potentially explo-
sive atmospheres.
Do not use the equipment in potentially explosive atmospheres.
8PRS 50 - Installation & Operating Manual - 850652-00
Basic safety notes
There is a risk of electric shock during work on electrical systems.
■ Always switch off the voltage to the equipment before performing work on the terminal
strips.
■ Check that the system is not carrying live voltage before commencing work.
Faulty equipment is a danger to system safety.
■ If the PRS 50 blowdown timer does not behave as described on pages 21 to 26, it may
be faulty.
■ Perform failure analysis.
■ Only replace faulty equipment with identical equipment from GESTRA AG.
Required personnel qualifications
Activity Personnel
Integration in control system Specialist staff Plant designer
Installation/electrical connection/
bringing into service Specialist staff Electrician/installer
Operation Boiler service technician Staff trained by the plant operator
Maintenance work Specialist staff Electrician
Setup work Specialist staff Plant construction
Fig. 1
Notes on product liability
The manufacturer cannot accept any liability for damages resulting from improper use of the equipment.
9PRS 50 - Installation & Operating Manual - 850652-00
Function
The PRS 50 blowdown timer generates configurable control pulses for opening an intermittent blowdown valve.
When the power supply to the PRS 50 blowdown timer is switched on, a two-minute remaining run-
time until the first blowdown begins counting down. Once this time has elapsed, blowdown takes
place with the parameters set in the timer. The time until the first intermittent blowdown is fixed at
2 minutes and cannot be changed by the user.
After this, the set interval begins. The remaining runtime until the next blowdown pulse is shown on the
7-segment display.
Standby/burner mode
To prevent loss of water, automatic intermittent blowdown can be disabled in standby mode or when the
burner is switched off.
■ Configuration as standby function
An external 24 V DC command (see Fig. 4 wiring diagram) switches the PRS 50 blowdown timer to
standby.
◆ The intermittent blowdown valve also closes when intermittent blowdown is active.
◆ The S/B LED lights up yellow.
◆ When the system has switched to normal operation (0 V DC at the terminals), an intermittent
blowdown pulse is triggered.
◆ In normal operation, the remaining runtime until the next intermittent blowdown pulse is counted
down and displayed.
■ Configuration as burner function
An external 24 V DC command (see Fig. 4 wiring diagram) signals burner firing.
◆ The remaining runtime until the next intermittent blowdown pulse is counted down and displayed.
◆ The S/B LED lights up yellow.
◆ After the remaining runtime has elapsed, an intermittent blowdown pulse is triggered.
◆ An external 0 V DC command freezes the remaining runtime. The S/B LED does not light up.
Manual intermittent blowdown
To trigger a manual blowdown pulse manually, a button (N/O contact) can be connected to the “Manual
intermittent blowdown” input. After this, a new blowdown interval begins and the remaining runtime until
the next intermittent blowdown is displayed.
Monitoring by limit switches
Volt-free limit switches can be used to monitor problem-free operation of the intermittent blowdown
valve. For this, you need to enable limit switch monitoring (factory setting = Off). The contact is closed
in standby mode and open during intermittent blowdown. The opening and closing of the limit switch is
monitored during intermittent blowdown. In the event of a malfunction, an alarm is triggered.
10 PRS 50 - Installation & Operating Manual - 850652-00
Function
Function test and failure diagnosis
Function testing and failure diagnosis can be performed using the rotary knob and the 7-segment display.
Display and actions in the event of errors
■ Errors in the PRS 50blowdown timer, the electrical connection or in settings are shown with an error
code.
■ An alarm is triggered in the event of an error. The alarm relay opens.
By turning the rotary knob, you can change the parameters, simulate the alarm or initiate an intermittent
blowdown pulse.
11PRS 50 - Installation & Operating Manual - 850652-00
Technical data
Supply voltage
■ 24 V DC +/-20 %
Power consumption
■ Max. 4 W
Current input
■ Max. 0.3 A
Required external fuse
■ M0.5A
Inputs
■ 1 x input for manual intermittent blowdown (external button)
■ 1 x input for limit switch (volt-free) on intermittent blowdown valve
■ 1 x volt-free 24 V DC input (standby/burner) for inputting an external switching command
(intermittent blowdown OFF/burner active)
Outputs
Intermittent blowdown valve
■ 1 x volt-free relay contact (changeover relay)
Alarm output
■ 1 x volt-free N/O contact (as an alarm contact, open in the event of an error)
■ Maximum switching current - 8 A at 250 V AC / 30 V DC - cos ϕ = 1
■ Contact material AgNi0.15, AgSnO2
■ Inductive loads must have interference suppression (RC combination) as per the manufacturer's
specification
Indicators and controls
■ 1 x green 4-digit, 7-segment display for showing status information
■ 3 x LEDs (2 x yellow, 1 x red)
◆ S/B yellow (standby/burner input active, depending on configuration)
◆ yellow (intermittent blowdown valve open)
◆ red (alarm)
■ 1 x 4-pole code switch for configuration (standby/burner function)
■ 1 x rotary knob with integrated push-button for setting parameters and executing the test function
12 PRS 50 - Installation & Operating Manual - 850652-00
Technical data
Protection class
■ II double insulated
IP rating to EN 60529
■ Housing: IP 40
■ Terminal strips: IP 20
Electrical safety
■ Degree of contamination 2 for installation in control cabinet with protection rating IP54, fully insulated
Admissible ambient conditions
■ Service temperature: - 10 °C – 55 °C (0 °C – 55 °C at power-on)
■ Storage temperature: - 20 °C – 70 °C *
■ Transport temperature: - 20 °C – 80 °C (< 100 hours) *
■ Air humidity: max. 95 %, non-condensing
* Only switch on after a 24-hour defrosting period
Housing
■ Housing material: Lower section of black polycarbonate (glass-fibre reinforced), front of grey polycar-
bonate
■ 2 x 8-pole terminal strips, removable separately
■ Max. cross-section per screw terminal:
◆ 1 x 4.0 mm2solid, or
◆ 1 x 2.5 mm2stranded with sleeve, or
◆ 2 x 1.5 mm2stranded with sleeve
■ Housing attachment: Mounting clip on support rail TH 35 (to EN 60715)
Weight
■ Approx. 0.2 kg
13PRS 50 - Installation & Operating Manual - 850652-00
Name plate / Identification PRS 50
External fuse for
output contacts
Manufacturer
Safety
note
Equipment
designation
M0,5A
4W
24V
±20%
1
2
3
4
5
6
7
8
+
_
+
_
Manuelles Abschlammen
Manual intermittent
blowdown
Manuelle de purge de
désembouage
Endlagenschalter
End-position switch
Interrupteur de fin de
course
_
+
IP (IP20)
Abschlamm-Timer
Boiler blowdown timer
Temporisateur de purge
de désembouage
PRS 50
Betriebsanleitung
beachten
See installation
instructions
Voir instructionsde
montage
250V ~ T2,5A
+
_Standby/
Burner
GESTRA AG
Münchener Str. 77
28215 Bremen
Made in Germany
Tamb = 55°C (131°F)T
Alarm
24V DC
16
17
18
19
20
21
22
23
40
IP rating / Protection class
Admissible ambient temperature
Outputs
wiring diagram
Standby/
burner-
input
Supply voltage /
Power con-
sumption /
Required external
fuse
Inputs wiring
diagram
Current approval / CE marking /
Disposal information
Serial number
Fig. 2
The date of production is printed on the back of the equipment.
The current name plates may change during the course of production.
14 PRS 50 - Installation & Operating Manual - 850652-00
Factory settings
The PRS 50 blowdown timer is delivered with the following factory default settings:
■ Code switch setting: Sliding switch, white (1 to 4 = OFF)
Configuring the standby/burner function,
see page 20, Fig. 6.
■ Interval (Ti): 24 hours
■ Pulse duration (tP): 3 seconds
■ Number of pulses (nP): 1
■ Pause between pulses (tb): 2 seconds
■ Limit switch monitoring (SW): no
■ Password (PW): oFF
15PRS 50 - Installation & Operating Manual - 850652-00
1
ON 234
567
234
19 20 21 2217 18
46
74
120
!
A Upper terminal strip
B Operating panel with 7-segment display,
status LEDs and rotary knob, see page 21
C Lower terminal strip
D 4-pole code switch for configuring the equip-
ment function
E Housing
F Support rail TH 35
Functional elements and dimensions
The code switch can be accessed by
removing the lower terminal strip.
Equipment settings, see page 20.
Fig. 3
A
B
C
F
D
E
1
ON 234
15
16 PRS 50 - Installation & Operating Manual - 850652-00
Installing the PRS 50 blowdown timer
The PRS 50 blowdown timer snaps onto a TH 35 support rail in a control cabinet.
DANGERDANGER
There is a risk of electric shock during work on electrical systems.
■ Switch off the voltage to the system before you install the equipment.
■ Check that the system is not carrying live voltage before commencing work.
1. Switch off the voltage to the system, or secure the surrounding equipment in the control cabinet, if
live, so it cannot be touched.
2. Carefully press the unit onto the support rail until the holder clips into place.
Safety notes for maintenance work on the intermittent blowdown valve or
blowdown pipes
DANGERDANGER
Severe scalding of the entire body is possible
During maintenance work on the intermittent blowdown valve or pipe, a blowdown pulse can
be triggered inadvertently.
■ Switch off the supply voltage to the PRS 50 blowdown timer and seal off the control fluid
pipe before performing maintenance work.
■ Check that the system is not carrying live voltage before commencing work.
Electrical connection safety notes
DANGERDANGER
Incorrectly connecting the blowdown timer or any associated components
is a danger to plant safety.
■ Connect the blowdown timer and all associated components as shown in the wiring diagram
in Fig. 4 of this Manual.
■ Do not use unused terminals as jumpers or support terminals.
17PRS 50 - Installation & Operating Manual - 850652-00
Wiring diagram for the PRS 50 blowdown timer
Fig. 4
Supply voltage
Fuse provided by customer
M0.5A
Button (N/O contact) for manual blowdown
Limit switch
Standby/burner input for an external command:
intermittent blowdown OFF/burner active
Alarm
17
17
18
18
19
19
20
20
21
21
22
22
234567
!
–
+
–
+
ZEP
24 V DC M 0,5 A
–
+
+
–
24 V DC
Intermittent
blowdown
valve
18 PRS 50 - Installation & Operating Manual - 850652-00
Electrical connection
Connecting the 24 V DC power supply
■ The PRS 50 blowdown timer is supplied with 24 V DC.
■ A safety power supply unit that delivers a Safety Extra Low Voltage (SELV) must be used to supply the
equipment with 24 V DC.
■ Use an M0.5A fuse as an external fuse.
Connecting the intermittent blowdown valve/alarm output contacts
■ Connect the outputs as shown in the wiring diagram in Fig. 4. The alarm relay is closed in the event of
an error. In the wiring diagram, there is no electrical supply.
■ Only use the terminals specified in the wiring diagrams.
■ Use a T2.5A fuse to protect the switching contacts.
Notes on connecting inductive loads
All connected inductive loads, such as contactors and actuators, must have interference suppression
using RC combinations as per the manufacturer's specifications.
Connecting the standby/burner input (24 V DC)
■ 24 V DC input, for external command intermittent blowdown OFF/burner active
(standby/burner configuration).
■ Maximum cable length = 30 m.
Connecting the “Manual intermittent blowdown” input
■ Connect a button (N/O contact) here if you require this function.
■ Use a shielded, multi-core, twisted-pair control cable with a minimum conductor size
of 0.5 mm2, e.g. LIYCY 2 x 0.5 mm2.
■ Apply the shield at both ends.
■ Maximum cable length = 100 m.
Connecting the “Limit switch” input
■ Connect the volt-free limit switch of the intermittent blowdown valve here.
■ Use a shielded, multi-core control cable with a minimum conductor size of
0.5 mm2, e.g. LIYCY 2 x 0.5 mm2.
■ Apply the shield at both ends.
■ Maximum cable length = 100 m.
19PRS 50 - Installation & Operating Manual - 850652-00
Changing the equipment settings
DANGERDANGER
Danger of death from electric shock if live connections on terminal strips are touched.
■ Always switch off the voltage to the equipment before performing work on the terminal
strips.
■ Check that the system is not carrying live voltage before commencing work.
You can change the standby/burner function of the PRS 50 blowdown timer using code switch D
(see Fig. 3) at any time if necessary.
Make changes before installing the blowdown timer, when access is easier.
You will need the following tools:
■ Slotted screwdriver, size 2.5, fully insulated
Proceed as follows:
1. Switch off the supply voltage to the equipment or plant.
2. Carefully unscrew the lower terminal strip with a screwdriver, then remove, see Fig. 5.
3. Set the code switch as desired, see page 20, Fig. 6.
4. When your changes are complete, re-install the terminal strip.
1
ON 234
567234
!
1
ON 234
567234
Fig. 5
Code switch
1
ON 234
20 PRS 50 - Installation & Operating Manual - 850652-00
Changing the equipment settings
Code switch D- sliding switch, white, see Fig. 3
Configuring the standby/burner function
PRS 50 blowdown timer
Code switch D
Function S1 S2 S3 S4
Reserve (default) OFF
Reserve ON
Standby function (contacts 22-23) (default) OFF
Burner function (contacts 22-23) ON
Reserve (default) OFF
Reserve ON
Reserve (default) OFF
Reserve ON
Fig. 6
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