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VALVE PROVING SYSTEM
PRODUCT HANDBOOK
A4021 Series
UNIVERSAL GAS VALVES
EN2R--9023 9705R0--NE
APPLICATION
The A4021 is a self--checking microprocessor based Valve
Proving System (VPS). The A4021 checks the effective clo-
sure of automatic shut--off valves by measuring the pressure
differential between two valves during the test sequence.
Subbase and pressure switch are required to complete the
system.
When during the test sequence of the A4021 a failing valve is
detected, the A4021 will go into a non--volatile lock--out sta-
tus, generates an alarm and prevents a burner start--up.
The intended application is for gas fired power burners and
other large capacity gas firing installations, where according
to the European norm EN676 a valve proving system can be
used as an alternative for pre--purging the combustion cham-
ber. And for installations with or without pre--purge with a
capacity of more than 1200 kW.
Subject to change without notice. Printed in the Netherlands.
L
CONTENTS
Application 1................................................................
General 2....................................................................
Application (continued) 2.....................................................................
Features 3...................................................................
Description 4................................................................
Working principle 4..........................................................................
Specifications 7.............................................................
Mechanical 7...............................................................................
Electrical 7.................................................................................
Functional 7................................................................................
Dimensional drawings 9......................................................
Safety Provisions 10..........................................................
Energizing valve 1 and 2 10...................................................................
Use of terminal 12 10.........................................................................
Fail--safe relay drivers 10......................................................................
Anti--recycle--counter 10.......................................................................
Calculations 11...............................................................
General 11..................................................................................
Calculation examples 11.......................................................................
Installation and wiring 12......................................................
Installation 12................................................................................
Mounting Wiring Subbase 12...................................................................
Wiring 12....................................................................................
General considerations 12.....................................................................
Wiring 12....................................................................................
Pressure switch 12...........................................................................
General wiring diagrams 13....................................................
Applications with EC7850 14..................................................
Checkout 17..................................................................
Final checkout of the installation 17.............................................................
Troubleshooting 18...........................................................
Standards and Approvals 19...................................................
Ordering information 20.......................................................
2
EN2R--9023 9705R0--NE
GENERAL
Application (continued)
The A4021A can be used for both single and combination
valves with or without pilot valve.
For valves with large nominal sizes, valve proving is possible
by use of auxiliary valves (pre--configuration only, see page 4).
For mounting the A4021 on a typical combination valve as the
VQ400 Series or on a large valve like the VE5000 Series
there is a mounting bracket available (order separately)
According the European standard EN676 a valve proving
system can be used under certain conditions, as an
alternative for pre--purging the combustion chamber. EN676
prescribes a valve proving system for capacity rating over
1,200 kW, see Table 1.
Table 1. Application valve proving systems according EN676
Heat--Input
With Pre--Purge Without Pre--Purge
p
[
kW
]
Main Gas Start Gas Main Gas Start Gas
[
k
W
]
≤ 10% ≥ 10% ≤ 10% ≥ 10%
≤ 70 2xB B*) 2xB 2xAor
2 x B +VPS
A**) 2xA
>70,≤ 1200 2xA 2xA 2xA 2xA+VPS 2xA 2xA
>1200 2 x A + VPS 2xA 2xA 2xA+VPS 2xA 2xA
NOTE: A: Automatic shut--off valve approved on EN161, class A
B: Automatic shut--off valve approved on EN161, class B
Valve Proving System required
Valve Proving System as alternative for pre--purge of the combustion chamber
*) For third family gases: two class B valves are required
**) For third family gases: two class A valves are required
Fig. 1. VQ400 combination valve with A4021 valve proving System.
3
EN2R--9023 9705R0--NE
FEATURES
• Microprocessor technology
• Based on 7800 SERIES Burner Programmer safety
technology
.
− Dynamic relay test
− Safe start test
− Self--diagnostic test
• Testing independent of type of gas at any inlet
pressure.
• Valve proving done by using the line pressure of the
gas.
• Non--volatile lockout.
• Automatic valve proving before heat demand, after
heat--demand or during pre--purge possible.
• Different test--times (per valve) available by different
O.S. numbers.
• Clear visual indication of the test sequence and
faults--causes through 5 LEDs.
• Storage of fault code when line interruption occurs
• Can be applied in all common valve configurations
• 2--wire gas pressure switch.
• Output for external alarm signal.
• Optional external remote reset.
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