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.