Resideo Troubleshooting Polling Loop Zones - Tech Notes - Dated 02/20/19

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1

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Updated:
2/20/19



Tech Note



Honeywell Vista Panel Polling Loop Troubleshooting Guide


Table of Contents


G
ENERAL
N
OTES
.......................................................................................................................................................
2

R
ANDOM
C
HECK ON ZONES
......................................................................................................................................
3

G
ENERAL
N
OTES

S
MOKE
M
AINTENANCE
F
EATURE

P
OLLING
L
OOP AND
O
THER
V
OLTAGE
T
HRESHOLDS

W
IRING

T
ROUBLESHOOTING


C
ONTINUOUS
C
HECK ON ZONES
...............................................................................................................................
4

S
LOW
Z
ONE
R
ESPONSE
.............................................................................................................................................
5

V-
PLEX
S
MOKE
D
ETECTORS
....................................................................................................................................
6

V-
PLEX

M
OTION
S
ENSORS
........................................................................................................................................
6

Z
ONES WILL NOT FAULT
...........................................................................................................................................
6

C
HECK
97/997

(
POLLING LOOP SHORT
) ...................................................................................................................
7

L
IMITATIONS OF
V-
PLEX
C
ABLE RUNS
....................................................................................................................
7

P
ROCEDURE FOR
D
ETERMINING THE
M
AXIMUM
W
IRE
L
ENGTH PER
P
OLLING
L
OOP

W
IRING
N
OTES AND
R
ECOMENDATI
ONS


U
SING THE
4297

P
OLLING
L
OOP
E
XTENDER
M
ODULE
(
APPLIES TO PANELS WI
TH
128
MA ON POLLING LOOP
) ... 9

S
INGLE
4297
TO
E
XTEND
P
OLLING
L
OOP
..............................................................................................................
11

U
SING THE
VPLEX
-VSI

S
HORT
I
SOLATOR
..........................................................................................................
11

G
ROUND
F
AULT
T
ROUBLESHOOTING
(A
PPLIES TO
C
OMMERCIAL
F
IRE
P
ANELS
O
NLY
) ....................................
12

T
ROUBLESHOOTING

P
REMISE
/T
HEORY

N
ORMAL OPERATION

G
ROUND
F
AULT
FAQ’
S


Table of Figures

F
IGURE
1:

4297

S
UPPLEMENTARY
P
OWER
S
UPPLY
...................................................................................................................
9

F
IGURE
2:

U
SING
M
ULTIPLE
4297'
S
....................................................................................................................................
10

F
IGURE
3:

S
INGLE
4297
TO
E
XTEND
P
OLLING
L
OOP
................................................................................................................
11


List of Tables

T
ABLE
1:

P
OLLING
L
OOP
W
IRING
U
SING
U
NSHIELDED
T
WISTED
(
OR NON
-
MET
AL CONDUIT
) ..............................................................
7

T
ABLE
2:

P
OLLING
L
OOP
W
IRING
U
SING
S
HIELDED
(
OR METAL CONDUIT
)
ONE SIDE OF THE SHI
ELD TO GROUND
. ...................................
8

T
ABLE
3:

G
ROUND
F
AULT
V
OLTAGES
....................................................................................................................................
13






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Tech Note



General N
otes

1.

Do not connect/disconnect devices when the panel is live, may cause alarms and trouble condition, use
caution when doing so during troubleshooting process.


2.

Adding a
module in Dip Switch mode to a polling loop of all
Serial devices should be avoided,
because it
can cause problems, especially on the 100+ zone panels.


a.

It can cause very slow zone response, and possibly slow the polling loop to where a ran
dom zone
troubl
e occurs.

b.

4101sn relay response may be inconsistent.

Note: Adding a Serial device to a polling loop that is all Dip Switch devices should have no ill effects, as
long as any existing 5192SD’s and 998MX’s are set for serial mode.


3.

Twisted
or
Shielded Wire
with one end of the shield to ground
is a
must
for polling loop r
uns.
See the
Wire Limitations on Page
7
.

4.

Serial number mode is
A MUST
if the panel and RPM are both able to do this mode
(except 4208U and
4209U).


a.

See
direct wire
numbers 134
and 135 “Mixing Serial and Dipswitch V/Plex Devices”


5.

The key to any troubleshooting process is isolation. Isolate individual devices until you have a basic sub
-
system that works properly. Then add more of the total system piece
-by piece, until everything is working.


6.

A zone that has a trouble condition will display as “CHECK xx” where xx is the zone number.


a.

After pressing “*” to scroll through these, they may
display “FAULT xx.” This can make it
difficult to isolate which zones have a trouble condition versus a simple fault.
b.

It may help to strap the zones with a resistor to eliminate a “fault” condition, or disarm to show
checks, and do not press the * after that.
In addition
, some panels have the option to display
“TRBL” instead of “CHECK”. This is only a display difference. “TRBL” and “CHECK” mean
the same thing.


7.

V-plex smokes and motions can cause other devices to appear to have problems. The symptoms may
not
directly point to the real cause of the problems. Always look at the whole system configuration. For
specific notes on V
-plex smoke detectors and motion sensors, see notes under the appropriate sections.


8.

To assist trouble shooting, be sure that P
ollin
g Loop
Short detection (zone 97 or 997) and
Earth
Ground
fault detection (zone 72 or 972) are enabled
, Earth Ground fault detection is only a feature of a commercial
fire panel
. This will help find the
real
problem.


a.

If a ground fault exists, reference the
ground
fault
-troubleshooting
document for troubleshooting
steps.


9.

As a last resort, bring the devices back to the control panel to see i
f they work alone at the panel. Other
steps are:


a.

Default the panel and start
hand programming in each zone and check operation
.
b.

Replace the RPM and/or control panel


10.

Abbreviations: RPM = remote point module,
SIM = Serial Interface Module,
V-plex/multiplex/mux
/mpx
=
polling loop




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Tech Note



Random Check on zones

General Notes

Global polling devices (such as
5192 or 998mx
)
MUST
be set in serial number
mode on any panel that supports
serial number polling loop devices.

a.

These devices have the ability to operate in either dip
-switch or serial mode, but
MUST
be set for
serial mode on all panels that support serial (all current panels).

b.

Failure to do this will cause problems on these zones as well as other polling loop zones.

c.

The 998MX must have dip switches 1
-7 OFF and the jumper JP1 cut all the way off at the base.

Smoke Maintenance Feature

When using the
5192

Smoke Detector
on a panel that does not support the M
aintenance feature, it must
remain

disabled on the detector by leaving dip
switch 8
ON
.

a.

Smoke detectors with the
maintenance feature
enabled must
be enabled as “
Smart
Contact” in
programming.

b.

Maintenance signals may only be used on devices operating in serial mode. (All panels that
support maintenance also use serial mode).

c.

Failure to follow these rules
will cause problems on these zones as well a
s other polling loop
zones.

d.

The
5193

series smoke detectors Maintenance feature is always on and cannot be disabled. This
will not affect panels that do not support the feature, but if the panel does support this feature then
it must be enabled per that z
one.

e.

When using the Maintenance Feature 1*77 must be on to log the first maintenance signal.

i.

The panel must accumulate a total of 6 ‘out’ of calibration samples in order for the panel
to log it.
ii.

With
1*77
enabled,
it will bypass this logic and lo
g it on the first signal.

Polling Loop and Other Voltage Thresholds

The polling loop voltage should be fluctuating
anywhere
between
7-12VDC.


a.

This should be tested at the panel and at the end of the line. If it is not fluctuating, you probably do
not have polling loop zones enabled, or your meter may not be sensitive enough to see it
.
b.

If you have voltage
below 7 volts
, confirm load (current draw and wire limits) on polling loop is
within specs.

c.

Re
move polling loop from panel
and verify the
voltage returns.

d.

Add ru
ns one at a time to find the one that is pulling down the voltage, and then break down that
run to find the cause of the voltage drain.

e.

Also,
confirm
panel voltages
as noted i
n above
.

Basic Panel voltages: With a meter check: AC, auxiliary power, and battery (with and without AC).

Wiring

Verify that all wire runs are within specifications
,
twisted wire or shielded wire
(Stranded or Solid does not
matter)
with one end of the shield to ground
,
and not run near sources of induced noises. Realize that capacitance
on the wire, not resistance, is our real enemy. Consult
Page 7
for limitations.






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Tech Note



Troubleshooting
1.

If the device has the option to go serial, it must be in serial mode
(except 4208U and 4209U)
.

2.

If using
Dip
-Switch
devices, verify that you do not have any 2 zones set for the same address.


Note: if a 4208u
is operating in dip
-switch mode, and has only some of its zones in use, you may not use
other dip
-switch RPMs to overlap the unused zones. You may ove
rlap these with wireless zones.


3.

While in programming, the voltage on the polling loop should be 10.5VDC steady. When a device is
tripped,
you will see the voltage quickly fluctuate
. If voltage is fluctuating while in programming
and
nothing is being tripp
ed, there is likely a device on the polling loop broadcasting constant
garbage.


Isolate different branches of the polling loop to isolate the problematic device. A device that is
broadcasting garbage on the loop will eliminate global polling causing slow
zone response and random
troubles.


4.

Verify that no RPMs are connected to the polling loops, which
are not programmed into the panel
.

This may be difficult to verify, but if a device is talking on the polling loop and the panel is not
programmed to list
en to it troubles and slow response will result.


5.

When using
smoke detectors with maintenance features
, the smoke detector may be sending continuous
high sense/high sense restore messages to the control. This continuous broadcasting can cause problems on
these zones as well as other polling loop zones.
See the section on Maintenance
for more information
.


6.

In zone programming, the
“V
-plex relay”
option
must only
be enabled for
4101SN module
s and not
other
devices.


7.

In zone programming, the
“Access point number” option
must
only
be enabled for Vista
-key DSM Backup
zones.

Continuous Check on zones

1.

Disable tamper either by dip switch on the RPM or by setting *24 = 1 (or both). This may be re
-enabled
later after the trouble has been isolated.

Note: Tamper is usually disabled by turning a switch ON, not off.


2.

If using dip
-switch RPMs, check
all

the dip
-switches. Make sure that they are not backwards, that the
correct chart was used, and that all dips are
set correctly, including dip switch 1 and 2.


3.

Zones set for zone type 05, 09, 16, 17, 18 may be in “Check” because of a zone fault (open). For any other
zone types, proceed to the next step.

a.

Verify the zones are correctly wired
and on the correct termin
als.

b.

Check voltage on the zone terminals. This should be approximately 5
-6 volts DC on any panel
zone, or expansion zone (except zones that can use 2
-wire smokes) when the sensor loop and end
-
of-line
-resistor are normal.
c.

Note: a “right loop” zone will be
0VDC when normal because it does n
ot use an end
-of-line
resistor.
If you
do not
see correct voltage on the zone terminals, the zone loop is not correct. Also,
try setting as a burg zone type to isolate this.

d.

Temporarily programming as a non-
24 hour
zone type will help you isolate it even further.




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Tech Note



4.

Verify polling loop voltage on the control panel and at the R
PM
.

a.

This should be
fluctuating
between
7-12
VDC.

b.

Verify that the wires are the correct polarity and on the correct terminals.


5.

Verify that all devices are correctly wired.


a.

It is often easy to misinterpret our instructions and connect devices incorrectly.

b.

This includes panel connections, RPM connections, and field wiring.


6.

Verify that the zone programming is correct
:
a.

Correct inpu
t type

b.

Serial number and loop number if applicable.

c.

If using serial devices, attempt to manually enroll the serial number. This verifies that the panel is
able to talk to the device as well as the proper serial number.


7.

*86: On all control panels from 4140-
4140XMPT2, Vista
-40, and Vista
-50, *86 allows a single 4208 to
operate as zones 10
-17.

a.

With this field enabled, no other polling loop devices will operate.

b.

There is a special dip
-switch confi
guration that allows this mode.

c.

The Vista
-50
P
and higher contro
ls do not have the *86 option. The First Alert FA1000-
FA1340c
have *86. The FA1500c and FA
1600c
and up
do not.


8.

Isolate the zone by removing all other polling loop devices; connect a single module directly to the panel.


9.

Set the RPM for serial mode (if it can) and try to manually enroll the device.


a.

If using dip
-switch devices, try setting the RPM for another address; or switch this address with
that of a known good RPM.


10.

Consult items under
“Random Checks”
on
Page 3
.
Slow Zone Response

If there is an extreme amount of activity on the polling loop (
i.e.
50+ motions tripping at once, etc) the panel may
start to delay the display of restore of zon
es.
This abundance of activity,
to the Global Poll
logic,
will cause the
pri
oriti
zation
of the
events and start
processing
faults/alarms before restores.


In addition to the Global poll prioritization,
the
panel’s
processor will start to prioritize the status updates sent
to the
ECP
(keypad)
data
. This
will result
in a delay of t
he
restore display
, all of this can
add up to one or two minutes

before the keypad displays the restore of a zone.


This
is more noticeable
when partitionin
g. A partition
with only a few zones
will
notice
latency in restores
due to
large amounts of activi
ty on another partition. A solution would be to use SMART motions on a panel that supports
the SMART motion feature on large installs like this.


This
will not cause a slow display of faults/Alarms on the polling loop. Faults/Alarms should display within 5
seconds even on a fully loaded busy panel. If Faults/Alarms are slow
, check
the following
:

1.

Verify that there are no ECP devices enabled in programmi
ng, that do not exist
. The easiest way to do this
is by requesting an ECP LIST from the COMMANDS menu on the compass communication screen.


2.

Check
troubleshooting section under

“Random Checks
”
and note 1
under
“General Notes
”
.



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Tech Note



V-plex Smoke Detectors

1.

Check troubleshooting section under
“
Random Checks
”
regarding dip/serial modes and maintenance
signals.


2.

There
are no base tampers
on our V
-plex smoke detectors.


3.

V-Plex Smoke Detectors on the Fire Panels (FB, FBP, FBPT, etc)
MUST
be on Partition 1. If assigned to
any other Partition
once tripped
they will
latch and not reset.


4.

When first connected, the LED
may
latch in the ON state. This is normal. Once the panel has polled the
device it will reset. This will happen only after the zone is
programmed
properly
and dips set correctly
.

5.

When a polling loop smoke detector goes into alarm on any 4140/4142 platform pa
nel, the LED will not
latch
, this is normal.
It is also true of the 5140XM. All other 5140 platform panels
(V100/128/250
/32/FA1600/
1670c/
1700c) will latch the LED when the smoke detector is in alarm.


6.

4192SDM, 4192SDTM, 4192CPM smoke detectors use maintena
nce signals. This cannot be disabled by a
dip
-switch like the 5192sd.
a.

These can be used on
ly on
panels that support maintenance signals. Any 4192 model without an
“M” in the part number is a dip
-switch device and may be used on any panel.

b.

4192 switches ar
e often set backwards because “on” looks like “off”.


7.

If using a 5192SD smoke detector, Switch 8 for maintenance must match the “smart contact” question (yes
or no) in order for it to enroll. If this is not set correctly, it will not enroll.


8.

5193 smoke detectors have Maintenance always enabled, so Maintenance must be turned on for those
zones on panels that support Maintenance for them to enroll properly.

V-plex Motion Sensors

1.

Consult
note 1 under
“Random Checks”
on Page 3
.

2.

998mx: on all current panels, the 998mx
must
be set for serial number mode.
a.

To set this, set switches 1
-7 OFF, and cut the white jumper
off at the base completely
.
b.

Do not
forget the tamper on the motion sensors that cannot be disabled by a dipswitch
.
Zones will not fault

1.

Disconnect polling loop module from the polling loop. The zone should go into check. If not, the
n the
zone
programming is not correct
. Check
the following
:

a.

Zone type

b.

Input type

c.

Wrong loop
(loop 1 must be used before loop 2, left loops must be used before right loops)

d.

Wrong partition


2.

Verify the partition the zone’s partition assignment,
as well as the keypad you are working on.


3.

Make sure tamper is enabled on the device and in *24 (*24=0). See if the RPM tamper causes a “check”.


4.

If the zones go into check in step 1, verify field wiring/connections. Then troubleshoot the RPM itself.




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Tech Note



Check 97/997 (polling loop short)

Indicates that there is a physical short or Low Voltage on the polling loop, or too much current being drawn
.

1.

The panel recognizes a short when the voltage on the polling loop drops to 4.5 Vdc or below.
2.

Isolate this by checking voltage on the polling loop with wires connected and with all wires removed.
Check troubleshooting section under
“
Random Checks
”
.
Limitations of V
-plex Cable runs

The ADEMCO Polling Loop (V
-plex) has the following limitation
s, which apply to panels with 128ma:

Procedure for Determining the Maximum Wire Length per Polling Loop
1.

Use table 1A for
U
nshielded

Twisted cable and table 1B for
Shielded
cable.


2.

Determine the maximum device loading on the polling loop branch by adding the load currents
per device

determined from Table 2
.
a.

Example: One 4190SN requires 2.0 mA. One 4208U requires 27.3 mA. The total load for
one

4208U plus
five
4190SNs
on the same loop

would be (27.3+ 10.0) = 37.3 ma.


3.

Locate the row in the table selected in step 1 corresponding to the total device load curren
t determined in
step 2. Example: A total load current of 37.3 mA, corresponds to the row of (33-
40) mA.


4.

The maximum cable length can now be determined from the size, or gauge, of the wire used in the cable.

5.

Example: The maximum cable length of No. 20 gauge wire for a total device load of 37.3 mA is 4,680 ft if
either unshielded (table 1A) cable or shielded (table 1B) cable is used. If No. 18 gauge wire were used
instead, the maximum allowable cable length would be 7,410 ft for unshielded cable and 6,0
00 ft for
shielded cable.

Total Load (ma @ 11.5) Vdc

22 ga

20 ga

18 ga

16 ga






1
-
16

12,000

12,000

12,000

12,000

17
-
24

4,850

7,810

12,000

12,000

25
-
32

3,640

5,850

9,260

12,000

33
-
40

2,910

4,680

7,410

11,760

41
-
48

2,420

3,900

6,170

9,800

49
-
56

2,080

3,350

5,290

8,400

57
-
64

1,820

2,930

4,630

7,350

65
-
72

1,620

2,600

4,110

6,540

73
-
80

1,450

2,340

3,700

5,880

81
-
88

1,320

2,130

3,370

5,350

89
-
96

1,210

1,950

3,090

4,900

97
-
104

1,120

1,800

2,850

4,520

105
-
112

1,040

1,670

2,650

4,200

113
-
120

970

1,560

2,470

3,920

121
-
128

910

1,460

2,310

3,680


Table
1: Polling Loop Wiring Using
Unshielded
Twisted (or non-
metal conduit)




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Tech Note




Total Load (ma @ 11.5) Vdc

22 ga

20 ga

18 ga

16 ga






1
-
16

6,000

6,000

6,000

6,000

17
-
24

4,850

6,000

6,000

6,000

25
-
32

3,640

5,850

6,000

6,000

33
-
40

2,910

4,680

6,000

6,000

41
-
48

2,420

3,900

6,000

6,000

49
-
56

2,080

3,350

5,290

6,000

57
-
64

1,820

2,930

4,630

6,000

65
-
72

1,620

2,600

4,110

6,000

73
-
80

1,450

2,340

3,700

5,880

81
-
88

1,320

2,130

3,370

5,350

89
-
96

1,210

1,950

3,090

4,900

97
-
104

1,120

1,800

2,850

4,520

105
-
112

1,040

1,670

2,650

4,200

113
-
120

970

1,560

2,470

3,920

121
-
128

910

1,460

2,310

3,680


Table
2: Polling Loop Wiring Using
Shielded
(or metal
conduit) one side of the shield to ground.

Wiring Notes and Recommendations

•

Twisted, non-
shielded cable is recommended. Avoid sharp bends in the wire.


•

Shielded cable, running Aux power in the same jacket, and/or running wire in metallic conduit increase the
capacitance of the wire run, which limits distances.


•

Observe device and control requirements on serial number vs. dip-
switch mode.

•

Avoid running the cable near keypad wiri
ng, intercom, or AC power lines, anything emitting RF noise.


•

If the V/Plex de
vice will go serial the device should
be programmed as serial.


•

Shielded wire should have one end of the shield to good Earth Ground.






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Tech Note



Using the 4297
Polling Loop Extender
Module
(applies to panels with
128ma on polling loop)

The 4297 V
-plex extender
module may be used to:


1.

Increase the number of V
-plex polling loop loading in a given system;

2.

Extend the total cable length of a specific application
(See limitations of V
-plex Cable Runs)

3.

Provide
short circuit isolation from one loop branch to another.


The maximum number of V
-plex device loading that can be placed on one or more polling loops with a single
supporting control panel is 128 mA.


1.

If a given control panel can support a total number of devices requiring more than 128 mA, a 4297 module
may be used in the manner demonstrated in Figure 1
, below.
2.

Each 4297 module can individually support up to 128

mA
.

The maximum number of 4297 modules which can be configured as shown in Figure 1
is limited to no more than 8,
and
by the need for a DC power supply to furnish 50ma @ 12 Vdc plus the polling loop output current per module.

For
example,
if each 4297 module is to supply the maximum of 128 mA, it will require a supply current of
50+128=178 mA. f
rom a local power supply
, even though it only requires 0.1ma from the polling loop. If the
4297 output is shorted, the power supply current increases to 400ma.


The total wire length allowed at the output of a 4297 module, as well as for the control panel’s V
-plex output, is
lim
ited using Tables 1 and 2 and the procedures described above. In addition, the
sum
of the wire lengths of both the
input
and
output
of a single 4297 is also limited to 12,000 ft. of unshielded wire and 6,000 ft. of shielded wire, as
indicated in Figure 1




Figure
1: 4297 Supplementary Power Supply













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Tech Note



Using Multiple 4297 Polling Loop Extenders


































L
E

= Total wire length on output side of each 4297.

L
P

=

Total wire length on input side of each 4297.

L
E1

+

(L
P1
+ L
P2 +
...

L
PN +
L
PE
) ≤

12,000 ft., unshielded; ≤

6,000 ft., shielded

L
E2
+
(L
P1
+ L
P2
+...

L
PN + LPE
) ≤

12,000 ft., unshielded;

≤

6,000 ft., shielded

L
En

+ (L
P1
+ L
P2 +
...

L
PN + LPE
) ≤

12,000 ft., unshielded; ≤

6,000 ft., shielded

Note:


The maximum number of 4297 modules which can be connected in parallel to a single system control is limited to
no more than 8, and by the maximum wire lengths specified above and the need for the Aux or Local power source
to supply 50 ma per 4297. For exa
mple, if five 4297 modules are used, the Aux or Local power source must supply
(5) (50) = 250 ma and the total system load current would be (5)(128)+128 = 768 ma, max. Also, from the above
relations;

If (L
P1
+ L
P2 +
...

L
PN +
L
PE
) = 1000 ft., then L
E1
= L
E2
=... L
En

≤ 11,000 ft., unshielded



≤
5,000
ft., shielded.



Panel Polling
Loop Output

Control

4297

Aux or Local

Power Source

(50 ma per
Extender)

L
P1

4297

L
P2

L
PN

L
E1

L
E2

L
EN

4297

Refer to Table
1 or
2 for maximum
L
E1
wire length per wire size , wire type, and total unit
loads.


Refer to Table
1 or
2 for maximum
L
E2
wire length per wire size ,
wire type, and total unit
loads.


Refer to Table
1 or

2 for maximum
L
EN
wire length per wire size , wire type, and total unit
loads.


Refer to Table
1 or
2 for maximum
L
PE
wire length per wire size , wire type, and total unit
loads.


L
PE

Figure
2
: Using Multiple
4297's




-

11

-

Updated:
2/20/19



Tech Note



Single 4297 to Extend Polling Loop







Figure
3: Single 4297 to Extend Polling Loop

D1
-i + ... Dn
-i = 128 max, or per Tables 1 & 2, above.

D1
-o

+ ... Dn -
o

= 128 max, or per Tables 1 & 2, above.

L
in
+ L
out

≤

12,000 ft., unshielded
,
or per Tables 1 & 2, above, whichever is smaller.


≤

6,000 ft., shielded, or per Tables 1 & 2,
above, whichever is smaller.

Using the V
PLEX
-VSI Short Isolator
The
VPLEX
-VSI Short Isolator provides short circuit isolation for devices on
V-plex
control panels. When a short
occurs on a polling loop branch, it illuminates a trouble LED and isolates
the
defective branch from the system
—
reducing troubleshooting time.


1.

Detects and isolates polling loop branches with complete or resistive shorts, and overload
or defective polling loop devices on initial power up

2.

Can be used to isolate burglary devices from fire devices,

3.

LED indicator reduces troubleshooting time. Low power consumption, powered directly
from the V
-Plex two
-
wire polling loop • Can be placed on any major or minor branch in
any configuration on the polling loop.


The VPLEX
-VSI automatically returns to normal operation
and the Trouble LED is extinguished
, when the trouble

condition on the output side of the VPLEX
-VSI is rectified.


A control panel normally reports a short on a polling loop
as a trouble on zone 97 or 997. When using the VPLEX
-
VSI
in a properly configured polling loop, this trouble condition
will not occur. Instead, the zones isolated by the
VPLEX
-VSI
will report in trouble.
A few panels do not have any delay on reporting a polling
loop short as a
trouble. With these panels, a 9
7 or 997
trouble will be reported for a polling loop short. Otherwise,
operation is as
described above.




Polling Loop

Control

Panel

4297


L
out

L
in
Dn
-
i

D1
-
i

Dn
-
o

D1
-
o




-

12

-

Updated:
2/20/19



Tech Note



Ground Fault Troubleshooting
(Applies to Commercial Fire Panels
Only)

Troubleshooting
1.

Measure Volts DC between terminals
12

(Panel Negative) and term
inal
30

(Ground)


(Note: KP (
-), zone (
-) and polling loop (
-) are all common. Any of these may be used. The exception to
this is any zone that supports 2
-wire smoke detectors, and the bell circuits.)


2.

To determine where the ground fault is coming from, re
move system wires until the voltage between
terminal 12 and 30 returns to 1VDC. Note: as you remove each wire, leave it off until the problem is
corrected. There may be more than one wire with a problem. Note: Leave the earth ground wire connected
during t
his process.


3.

As this progresses, you may eventually reach a point where all wires are removed except the battery and
the earth ground. The next step is to remove the panel from the cabinet. Lay the PCB on a non
-conductive

material (wood or cardboard). With the earth ground wire now disconnected the panel should give you
1VDC from terminal 12 to 30. If not, the panel is defective.



Notes


Under normal conditions (no ground faults) you should read 1.0VDC (+ or -
.5VDC)


A ground fault is sensed when some external input causes the voltage between terminal 12 (Panel Negative) and
terminal 30 (ground) to either drop below .5 VDC or increase above 1.5 VDC






-

13

-

Updated:
2/20/19



Tech Note



Premise/Theory

The control panel internally causes its power negative t
o float 1 volt below earth ground as shown in the first
diagram below. If any wire attached to the panel shorts to earth ground or a voltage source, it will become the same
reference level as earth ground, causing the panel to see a ground fault.




1VDC

Normal
operation

1VDC measured
from KP(
-) to earth


Panel is happy


Negative wire
shorted to
ground.


0VDC measured
from KP(
-) to earth


Panel not happy


0VDC

13VDC

Positive wire
shorted to
ground.


13VDC measured
from KP(
-) to earth


Panel not happy


Zone Positive
shorted to ground
.


6 VDC measured
from KP(
-) to earth


Panel not happy


6VDC

Zone (+)


Aux Power (+)


System (
-
)

Earth Ground


Zone (+)

Earth Ground

Aux Power (+)

System (
-
)

System (
-
)

System (
-
)

If panel does not have a
proper earth ground, it
is unable to sense a short
to earth ground.


1 VDC measured

from KP(
-) to earth


Panel is happy


(Despite the real ground fault!)

System (
-
)

Earth Ground

1VDC

Terminal 30 not
connected to a
proper ground

0VDC

Earth Ground


Earth Ground


Zone (+)


Aux Power (+)



Aux Power (+)


Aux Power (+)

Tabl
e
3
: Ground Fault Voltages




-

1
4

-

Updated:
2/20/19



Tech Note



Ground Fault FAQ’s

1.

I have a Ground fault on my display. Does this mean that I have a bad
earth ground?


No. This means that something in your system has a path to earth ground. In fact you must have a good
earth ground to sense a system ground fault.


2.

Can I assume that with the earth ground disconnected from terminal 30 that I cannot sense an
earth ground?


In general, you must have a good earth ground to properly sense a ground fault. However, if you remove
the earth ground wire, your panel may still have a connection to earth ground through the cabinet and
conduit connected. You may notice t
hat the mounting screws for the panel are on a trace that is connected
to the earth ground terminal. This is by design and allows the cabinet to be grounded through the panel.


3.

What terminals can affect a ground fault?


Any wire connected to the control can cause ground fault except the auxiliary relay terminals (these are dry
contacts) Sources of problems include: keypad wires, polling loop, bell circuits, zone circuits, peripheral
devices, powered devices J
-connectors, phone lines, PS
-24, battery connecti
ons, transformer, auxiliary
power supplies, radio backup devices....


4.

Can other boards or peripherals (Power supplies, LRR radios, etc) cause a ground fault?


Yes. Any device wired to the control panel can cause a ground fault.


5.

Can induced voltage cause an
earth ground fault?


Yes. Anything that affects the voltage potential between earth ground and the rest of the system would
cause the system to report an earth ground fault, even though there is not, in fact, a real earth ground fault.
In this case, the “f
alse” earth ground message still alerts you to a system problem.


6.

Can conduit (that is usually grounded) affect ground fault?


Conduit can provide another path to earth ground. As mentioned in note#2 above, the panel mounting
screws provide an electrical p
ath between the earth ground terminal (30) and the panel cabinet. This would
allow an earth ground to be sensed through the conduit even with nothing connected to terminal 30. This is
not a bad thing.

Some peripheral devices (7835C for example) Use a commo
n negative to their chassis. In this case, if the
cabinet is grounded or has conduit that is grounded, an earth ground fault would be sensed through the
other connections to the device.


7.

Does grounding the metal can affect ground fault?


As noted above, the panel mounting screws provide an electrical path between the earth ground terminal
(30) and the panel cabinet. Grounding the cabinet should not cause any problems.