Honeywell P520 User Manual

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P520 Signal Processor

SPECIFICATIONS

Electrical Ratings

Input Power: 22 - 26VDC, 130mA (plus 100mA for each

Viewing Head.)

Battery Backup: 24VDC, 130mA (plus 100mA for each

Viewing Head.) Main Voltage > Battery Voltage

Ambient Temperature:

0°C to 52°C (32°F to 125°F) CSA Rating
0°C to 60°C (32°F to 140°F) FM Rating

Outputs:

Flame Relay: 2 Form C Contacts (DPDT)
Self-Checking Relay: 1 Form C Contact (SPDT)
Contact Ratings: 5A at 30 VDC, 125 VAC and 277 VAC

Max switching voltage 220Vdc, 250Vac

Analog Flame Signal: 0 to 19.8mA current output for

remote meters and 4 to 19.8mA output. (360 ohm max.
resistance.)

Power to Viewing Head:

+26VDC maximum, fused 0.25A (self-resetting)
+14.3VDC pulsing 0.2 seconds ON, 0.8 seconds OFF

USER MANUAL

APPLICATION

The Honeywell P520 is a rack mounting signal processor that
is compatible with viewing heads in the S5XX and S55XB/BE
series. These include models S506, S509, S511 and S512,
and the advanced viewing head series models S550B/BE,
S552B/BE and S556B/BE. There is only one model of the
P520 available, which is DC powered. A rear backplane PC
Board is required for termination (order part number
REARPCB separately for initial installation).

FEATURES

• Rack mounted system, designed to conform to the DIN
41494 19 inch card frame system

• 3U high and 21HP wide, or 5.06 x 4.18 inches with a
length of 8.66 inches (220mm)

• Once rack mounted, together with a power supply and
appropriate viewing head makes up a complete flame
monitoring system

Inputs:

Channel Select (Isolated Input):

7.5-30VDC range
Input resistance 3900 ohms
26VDC maximum, 6.4mA
10VDC, 2.3mA
Flame Signal from Viewing Head (Isolated Input):

7.5-30VDC range
Input resistance 3900 ohms

13.6VDC, 3.2mA

Serial Communications:

RS-422 (Differential)
4800 or 9600 baud (user selected)
4 wire / 2 twisted pair

Cable (between viewing head and signal processor):

4 conductor, #16 AWG or #18 AWG, one wire shielded with

braided shield for flame signal. Honeywell C328 cable is
recommended.

66-2066-01

P520 SIGNAL PROCESSOR

M33219

4-3/16 (106)

5-1/16

(129)

M33226

9-3/32 (231)

5-1/16

(129)

35/64

(14)

Fig. 1. P520 front faceplate dimensions.

Fig. 2. P520 side view dimensions.

INSTALLATION

When Installing this Product…

1. Read these instructions carefully. Failure to follow them

could damage the product or cause a hazardous
condition.

2. Check the ratings given in the instructions and on the
product to make sure the product is suitable for your
application.

3. Installer must be a trained, experienced, flame safe­guard control technician.

4. After installation is complete, check out product opera­tion as provided in these instructions.

66-2066—01 2

Grounding and Shielding

NOTE: Installer must be a trained, experienced flame

safeguard service technician and should be
familiar with the equipment operation and limita­tions and be aware of any applicable local codes
and regulations.

1. Connect a safety ground to the viewing head housing (if

applicable).

2. The viewing head and all associated cable/conduit must
be at least 12 inches (31 cm) from any source of high
energy or voltage (for example, igniter equipment).

P520 SIGNAL PROCESSOR

3. Install a ground wire from the ignition transformer case
to the igniter assembly.

4. Ensure all igniter wires and cables show no signs of
wear. Replace any igniter cables or wires that are frayed
or cracked.

5. The viewing head must be electrically isolated from the
burner front.
a. Electrical isolation can be accomplished by install-

ing an Ultem nipple or an Ultem locking coupler
adapter in conjunction with a locking coupler
between the viewing head flange and the burner
mount.

b. The purge air line should also be isolated from the

viewing head. This can be accomplished by install­ing any insulating material, for example a rubber
hose, in between the purge air line and the viewing
head.

6. On the terminals going to the viewing heads on the back
of the P520, the terminals marked GND go to pin 5 of
the S5XX and S55XB viewing head plug and to the des­ignated ground pin for the S55XBE viewing head plug.
Pin 5 of the S5XX and S55XB and the ground pin for the
S55XBE viewing head male receptacles have an inter­nal tab that grounds this connection to the viewing head
housing. The terminal marked GND connects to the
chassis ground of the P520. This ground is made
through the internal PCB to the metal base of the P520.

It is important that good grounding practices be followed when
connecting power supplies. Interference problems can occur if
the power supply chassis and the P520 chassis are at a
different ground potential than the viewing head housing,
which will be at a ground potential associated with the burner
front. In these situations, the Honeywell viewing head
effectively supplies a plant ground between the burner front
and the panel enclosure. If there is a large potential difference
between these points, considerable current can flow through
the viewing head cable, which can, in turn, damage the P520
signal processor or the associated power supply.

Card Frames

Four card guides are required for each P520 module;
therefore, a total of sixteen card guides would be required to
mount four P520 modules. Card guides are available as off
the shelf parts and are not available from Honeywell.

The resulting rack will require spacers for the top and bottom
of the rear backplane PCB. Card guides are required as well
for installation. Spacers and card guides are available from
electronic vendors and are not available from Honeywell.

A half-card frame, or “half rack” (9.5 inches wide) may be used
as an alternative to the 19-inch card frame. A half rack will
mount two P520 modules.

Wiring the Rear PC Board

A diagram of the rear backplane circuit board is shown in Fig.

1. The relay outputs are located on the nine-contact terminal
block located on the upper right of the board

RC C refers to the common terminal of the self-checking relay.
There is only one pair of contacts used for the self-checking
function. Here, the designation ON refers to the self-checking
taking place in a normal manner. OFF indicates a failure in the
viewing head or processor resulting from

- the internal or external hardware

- electronic critical component failure

- the power to the unit is OFF – the most likely condition

The horizontal set of six terminals (top left) is used for the
main power into this plug-in module (PWR IN). Each
designated terminal is a double terminal, or pair, so that the
wiring from the power supply can be “daisy chained” from one
P520 to the next without having to twist wires together into
one termination.

The pair designated BAT is for battery backup, if used. The
backup battery, if used, should be 24 volts, to ensure that the
24VDC power feeding the P520 will not feed back into the
battery. In other words, no current will flow from the battery as
long as voltage of the main power supply is above that of the
battery. The negative side of the battery goes to the GND
terminal on the right.

Fig. 1 shows how these terminals are connected inside the
P520. Note the two fuses marked F1 and F2. F1 is the main
power fuse for the signal processor as well as the viewing
head(s), and is rated at .75 Amp. Fuse F2 feeds only to the
viewing head(s), and is rated at .25 Amp. Each viewing head
draws about 100mA, so this output can supply up to two
viewing heads. On all currently manufactured units, these
fuses are self-resetting types, and will recover from an
overload automatically after power is removed from the P520
for 10 seconds.

Just below the six-pin PWR IN terminals are two, five-pin
vertically-mounted viewing head terminals identified as V.H. A.
and V.H. B. If only one viewing head is used, you must wire to
the V.H. A. terminals. Below the V.H. A. terminals are two
terminals marked V.H. SEL (viewing head selector relay).
Energizing this connection with 24VDC will cause the relay on
this PCB to switch to viewing head B.

Only the viewing head signal wire (SIG) and the signal ground
wire (SIG GND) are switched with this changeover relay; the
24VDC and power ground circuit is not disturbed. Make sure
that the viewing head signal wire and signal ground (braided
shield in the four-conductor cable) are both connected,
because this ground connection is the only return path for the
signal and self-checking circuit. The 24VDC used to switch
this relay can be connected without regard to polarity. The two
terminals marked V.H. SEL go directly to the relay coil.

The two-pin terminal to the right of V.H. SEL designated
CHAN SEL is used for selecting channel A or channel B on
the P520. Energizing this pair of terminals causes the B
channel to be selected.

3 66-2066—01

P520 SIGNAL PROCESSOR

P520

F1/.75A

M33217

F2/.25A

P520
RELAYS

FLAME RELAY

RF

RF

RC

SELF
CHECKING
RELAY

PWR IN

BAT

+26VDC

GND

RF C

OFF

ON
ON

OFF

RF C

ON

OFF

RC C

GND

+V
SC

SIG

SIG

GND

+

GND

REMOTE METER V.H. SEL

CHAN SEL

TX+ TX- TX+ TX-

RX- RX+ RX- RX+

Fig. 3. Rear PCB terminal wiring.

Polarity must be observed when wiring this connection (the
positive terminal is on the top). This is an isolated input, so
two wires are required. Any DC voltage from 7.5 to 30 may be
used. The current required will depend upon the voltage,
because this is a photocoupler interface circuit with a 3900
ohm resistor feeding the LED light source.

For example: a 26VDC voltage will result in a current flow of
25/3900 =.0064 Amp.

If flame is being detected and the channels are switched, the
flame relay will remain energized for one cycle regardless of
the new set points, allowing channel changes “on the fly,” so to
speak. If the new flame OFF set point is equal to or greater
than the current signal count, then the flame relay will de­energize on the subsequent cycle.

The remaining two-pin terminal designated REMOTE METER
(to the left of the V.H. SEL terminals) is for the remote meter
connection. This output is a current-driven signal that ranges
from 0 to 20mA for remote meters, and can be switched to a
range of 4 to 20mA (refer to section 4-20mA REMOTE
OUTPUT). Connect the terminal marked “positive” to the
positive meter terminal. This current signal can be used with a
volt meter by feeding the signal to a resistor connected to the
ground. The voltage developed across the resistor will follow
Ohm’s law V=IR.

For example: a 3-volt meter can be used with a resistor of 3/
.02 = 150 ohms, which will result in a full-scale reading of 3
volts for a 20mA output.

The terminals called TX+, TX-, RX+, and RX- (at the bottom of
the PCB) are used for the serial communication link. They are
also in pairs to accommodate “daisy chaining,” but the pairs
are arranged for twisted pairs instead of adjacent redundancy.
The serial communication is achieved by using ASCII
character code transmission at 4800 through the USB port on
the host computer. The P520 uses RS-422 data transmission
which is over two, twisted pairs that are differentially
transmitted and received, allowing long wire runs to be used
through noisy environments. A USB to RS422 converter must
be used to communicate with the P520, and the connections
are made to the terminals marked TX+, TX-, RX+ and RX-.
The transmitting, twisted pair goes to the TX terminals, and
the receiving, twisted pair goes to the RX terminals.

NOTE: The terms “transmit” and “receive” used here

with respect to the P520 will be reversed with
respect to the converter connection on the host
computer. Refer to later sections in this manual
for a detailed description of the software and
how it is to be used with the P520.

66-2066—01 4

P520 SIGNAL PROCESSOR

M33509

CABLE CLAMP

CONNECTOR WITH
REAR COVER REMOVED

CONNECTOR
JACKSCREW

FINAL ASSEMBLY

OPTIONAL LTA5XX ADAPTER

CONNECT SHIELD
TO TERM 3
USE SHRINK TUBING

WIRING SIDE VIEW – COVER REMOVED

P520

RED

GREEN

BLACK

WHITE

SHIELD

C20

C28

A24

A26

A28

+24 VDC

GND

SHUTTER
DRIVE

GND

SIGNAL

R

4

3

2

1

5

G

W

B

Wiring the Viewing Head

Wiring of the viewing head is made to the terminals on the rear backplane PCB. These terminals are described as follows:

Table 1. Terminal Descriptions.

Terminal Description

+V 24VDC power to viewing head

GND Power Ground

SC Self-check/shutter drive signal to viewing head

SIG Flame signal from viewing head

SIG GND Signal ground

Fig. 4 and 5 show four-conductor cable to the viewing head. Note that the flame signal wire going to terminal SIG is shielded, and
the shield is terminated at both ends of the cable to SIG GND.

IMPORTANT

Source impedance resistor required at the signal processor between SC and SIG GND terminals for proper signal trans­mission. For resistor value, refer to Wiring of Viewing Head section.

Fig. 4. Viewing head wiring.

5 66-2066—01