Honeywell A4021, A4021A1010, A4021A1002 Product Handbook
VALVE PROVING SYSTEM
PRODUCTHANDBOOK
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 closure 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 status, 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,whereaccording
to the European norm EN676 a valve proving system can be
used as an alternative for pre--purging the combustion chamber. 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 diag rams 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--con figu ratio n 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
[kW
]
≤ 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--offvalve 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.
4
EN2R--9023 9705R0--NE
DESCRIPTION
The A4021 valve proving system checks the effectiveclosure
of the valves
before
burner start--up (pre--configuration) or
at
the end of
a heat demand (post--configuration). The
configuration can be set by means of wiring the A4021 in two
differentways, see Fig. 2. and 3.
The flow chart (Fig. 5. ) and sequence diagram (Fig. 6. )
explain the procedure during the valve proving.
An external pressure switch monitors the pressure between
both valves. The pressure switch must be set to half the inlet
pressure in order to test both valves with the same sensitivity.
After a short interruption of the mains supply during valve
proving or during RUN, the A4021 restarts automatically.
The A4021 valve proving system can be used with several
pilot--valve configurations,like intermittentand interrupted
pilot systems and 3--valve configurations as well.
14
9
L
12
A4021
ignition
controller
H.D
LGPS
Fig. 2. Valve proving
pre--configuration
.
14
9
L
12
A4021
ignition
controller
LGPS
H.D
Fig. 3. Valve proving
post--configuration
.
V1
V2
heat
demand
burner
Pinlet
Pinlet
2
L.G.P .S.
G.P.S.
gas
air
Servo Motor MT4000 Series
Combi--valveVQ400 Series
ValveProving System
A4021 Series
burner--controller
7800 SERIES
Gas pressure switches
C6058A Series
Fig. 4. System set--up .
Working principle
The A4021 valve proving system is based on the pressure
status--principle. This means that the valves are checked by
means of measuring (on/off) the pressure in the gas--pipe
between the two safety--valves. This system will only work
when there is sufficient gas--pressure (line--pressure).
Therefore a Low Gas Pressure Switch (LGPS) is part of the
installation. When the line--pressure (Pinlet) is too low the
LGPS will disable the valve proving system.
The section between the two valves is filled with gas
(high--pressure status) by opening valve--1(upstream valve)
and the pipe is emptied (low--pressure status) by closing
valve--1 and opening valve--2 (down--stream). When one of
the valves is l eaking this will mean that either the pressure
will not maintain the high--pressure status or the low--pressure
status at the end of the test period.
For this method of testing, the test time is a function of three
parameters.
− inlet pressure
− volume between the valves.
− maximum burner capacity.
The test time can be calculated as given on page11. Different
test times are available by different O.S. numbers.
5
EN2R--9023 9705R0--NE
stabilization
time (3 sec.)
pressure
=low?
open valve 2
(5 sec.)
wait
(22 sec.)
open valve 1
(5 sec.)
pressure
=low?
stabilization
time (3 sec.)
pressure
=high?
wait
(22 sec.)
pressure
=high?
enable
ignition
controller
error + lock--out
no
no
no
no
yes
yes
yes
yes
test valve 1
test valve 2
self test
=OK?
yes
no
manual reset
1
2
3
4
5
6
7
8
10
11
12
13
pin 12
connected
enable
ignition
controller
yes
?
self test
=OK?
each 4 hours
no
no
yes
14
15
15
STANDBY
RUN
0
9
start
Fig. 5. General flow chart valve proving (given timings
for A4021A1002/1010
Table 2. Sequence timings for normal operation
State
Description Time1)(s)
0 STANBY infinite
2)
1 self--test + memory test <2
2 V2 powered 5
3 waiting for pressure to get low 3
4 wait 22
5 valve 1 powered 5
6 waiting for pressure to get high 3
7 wait 22
8 waiting for ignition controller to start indefinite
3)
9 RUN period, every 4 hours self--test
10 alarm, “error during test valve 1” indefinite
11 alarm, “valve 1 failing/leaking”
5)
indefinite
12 alarm, “error during test valve 2” indefinite
13 alarm, “valve 2 failing/leaking”
5)
indefinite
14 alarm, “error heat demand” indefinite
15 alarm, “self--test error”
4)
indefinite
1)
Timingsdepending on O.S. numbers, shown
A4021A1002/1010
2)
STANDBY can be infinite time period
3)
Depending on pre--purge and start--up time of the used
ignition controller
4)
When during the test sequence a fault is discovered by the
A4021, the system will go into a non- -volatile lock--out and
generate an alarm “self test error” (see also
Troubleshooting section).The “self test error” also occurs
when the anti--recycle--counter reaches the value 10, see
also page 10 of the Product handbook.
5)
Leakage ≥ 0.1 % of maximum flow rate.
WARNING
No standard valve proving after lock--outof the
ignition controller.
Valve proving after lockout maybe required, this can
be achieved by special wiring diagrams. E.g. when a
DTSP switch is used to reset the ignition controller
and interrupting the heat--demand for the A4021A.
Heat demand
Line voltage
Lock--out
(Ignition controller)
Reset ign. control.
power--up start
heat--demand
end
heat--demand
lock-- outstart
heat--demand
reset
burner controller
Leak test
GPS
Valve V1
Vent valve
(normally open)
Valve V2
Leak test
GPS
Valve V1
Vent valve
(normally open)
Valve V2
PRE
POST
CONFIG
CONFIG
start whithoutvalve proving !
Fig. 6. Systemsequence of A4021A inpost and pre--configuration.
6 EN2R--9023 9705R0--N
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