Justin MTP Series Specifications

INSTALLATION AND OPERATORS GUIDE
JUSTIN, INC.
ELECTRONIC PRODUCTS DIVISION
2663 No. Lee Avenue
South El Monte, CA 91733
626 444-4516
• Fax [phone]
www.justinin . om
If you have a on ern or problem with any Justin produ t, first onta t your lo al distributor. For ontinuing or unresolved problems, onta t fa tory te hni al
department at [phone] between 8:00am and 4:00 pm PST, Monday through Friday
For Professional Series Landscape Lighting Transformers
Covers GL, MTP and GLP Series Transformers from 100 to 1200 watts
Made in the USA

Take-apart stai less steel hi ges
The door can be removed for greater access to
wiring compartment during installation. To
remove, open door and lift straight up and off
of hinges. To replace, line up door hinges over
pins of housing hinges and carefully push
down.
Operati g I structio s i side door.
Refer to these instructions for additional infor-
mation on wiring to the transformer.
Mag etic overload circuit breakers
For reliable automatic secondary circuit protec-
tion. Circuit breakers may also be used as
on/off rocker switches.
1/2” - 3/4” k ockouts
For conduit and accessory mounting.
1-1/4” - 2” k ockouts
For conduit and accessory mounting.
Accessory termi al strip
For easy installation of optional photocell,
motion sensor, or other external switching
devices.
Collapsible, swi g-dow bottom tray
Bottom tray can swing-down for greater access
to wiring compartment during installation. The
tray is held in place with a hinge screw and a
retaining screw on each side of the transformer
enclosure. Loosen the two retaining screws
(nearer to the front of the enclosure on each
side) and pull down on tray to open.
Power cord
-foot, heavy-gauge, grounded, water-resist-
ant power cord with integrally molded plug.
Lockable, stai less steel latch
Can be secured to prevent tampering.
120-volt accessory receptacle
For use with optional, removable multi-setting
mechanical 24-hour timer or remote photocell
module PCM12.
Termi al strip
For multiple low voltage cable connections. Cover
flap opens to individually marked voltage taps.
Security screw hole
OFF
OFF
FEATURES AND CONTROLS
1
10
11
12
2
3
4
5
6
7
8
9
1
2
3
4
Warning: Transformers must be installed in accor-
dance with the National Electrical Code (NEC) and
local codes. Failure to do so will void the warranty and
may result in serious injury and/or damage to the
transformer.
1. Find a suitable, flat-surfaced location to mount
transformer, taking into consideration proximity to 120
volt AC power source.
2. Attach provided template to wall at desired height.
(Should be mounted at least 1.5’ from the ground for
safe and convenient operation.)
3. Center punch and drill (with an appropriate bit size
for the screws to be used) at crosshair marks on the
template.
4. Using appropriate screws for the selected mounting
surface, insert screws into predrilled holes deep
enough to slip transformer keyhole slots over. (Make
sure screws are of a load bearing quality.)
5. ang transformer case securely over screws.
6. Install security screw if desired. #10 minimum.
MOUNTING INSTRUCTIONS
Low voltage lighting systems require the use of a
transformer to reduce the standard 120 volt power
from ordinary household electricity to the 12 volts
needed to power low voltage lamps. Transformers vary
in size or capacity. The total lamp wattage (load) of all
fixtures connected to one transformer must not exceed
the wattage capacity of the transformer. Therefore, to
determine the transformer size needed, simply add up
the wattage of all lamps you plan to use +10% for
cable & connections that add hidden watts to your sys-
tem.)
Transformer si e = total fixture watts x 1.1
Tip: All low voltage connections must be tight and
waterproof.
Select a transformer that matches as closely as possi-
ble to your total lamp wattage. For example: if you
have 13 fixtures all rated at 20 watts, you will need a
300-watt transformer (13 x 20 = 260) watts plus 10%
= 286). If your total wattage is too great, either divide
the total load between two transformers or use a more
powerful model. Selecting a transformer with about
20% higher capacity than your total lamp wattage will
allow for adding a fixture or two later.
TRANSFORMER SIZING
In planning a low voltage system, it is necessary to consider the impact of voltage drop. Because of cable’s inherent resistance, voltage drops along its length; the end-of-run lamps will be
dimmer than those at the beginning. Since voltage drop is a function of cable length and cable size and total fixture wattage, voltage drop can be minimized in serveral different ways:
• Use multiple cable runs
• Use heavy gauge cable (8 or 10 gauge)
• Shorten cable lengths or runs
• Reduce wattage of individual fixtures
• Reduce the total number of fixtures on a run
• Use multiple transformers in different locations
Cable is measured by gauge. The lower the number, the thicker the cable and the more current it carries. Cable for low voltage lighting is available in three gauges: #12-2, #10-2, and #8-
2. As noted, #8-2 gauge is the largest and is capable of carrying the most current. Refer to the Cable Length Guide to estimate the maximum allowable cable length that will keep the far-
thest fixture from the transformer from becoming dim (below 10.5 volts). In addition to, your transformer’s output options, the design of your lighting system and corresponding cable lay-
out can help minimize voltage drop (see 12-Volt Cable Layout Options, Output Adjustment Switch, and Multi-Tap Installation sections.)
LOW VOLTAGE CABLE LENGTH
5
12 678
10
9
11
Model: MTP600 Shown

Tip: Connect all lamps in parallel. EXAMPLE: Connect one side of each lamp to
‘COM’ terminal, the other side to ‘12V’ terminal.
1. Straight run installation: Fixtures run in sequence directly from the transformer.
2. Loop Installation: Fixtures are arranged in a looped circuit, reducing the effects of
voltage drop. See “Dual Circuit”, next column.
3. Split load installation or multiple cable run: Fixtures run in two or more directions
from the transformer. Locating the transformer in the center of the run reduces the
effects of voltage drop.
4. “T” Installation (RECOMMENDED): Allows more equal distribution of power to
the center of the run, or to a run some distance away. Cable running from the
transformer must be of a heavier gauge (#8 or #10).
Tip: For proper connection, strip off 3/4” of cable installation, twist wire strands
tightly and use a high quality straight blade screwdriver with minimum 3/16” wide
tip to tighten all screw terminals firmly.
TIP: 1 -3 Watt units are single circuit, 6 Watt units are two
circuits, 9 Watt units are three circuits and 12 Watt units are
four circuits. See installation instructions in transformer cover for single and mul-
tiple circuit output terminal details. All transformers have one manual reset circuit
protector per circuit.
SINGLE CIRCUIT - 100-200 WATT - GL
SINGLE CIRCUIT - 300 WATT - GLP
DUAL CIRCUIT - 600 WATT - GLP
Vd=Voltage drop in the section of cable, in volts
L=Length of the section of cable (one way distance), in feet.
W=Total Watts carried by the section of cable for the lamps it supplies
Kc=‘Cable Constant’, as follows:
Cable Size (AWG) Kc
12 7500
10 11920
8 18960
V
d
=
L x W x 2
K
c
T
T
T
T
T
12 VOLT CABLE LAYOUT OPTIONS:
OUTPUT ADJUSTMENT SWITCH
MULTI-TAP INSTALLATION
CABLE CONNECTION DETAIL
T
Tip: When using single circuit transformers, full rated load
may be connected to one pair of ‘COM 12V’ or ‘COM 15V’
terminals.
FOUR CIRCUIT - 1200 WATT - GLP
SAMPLE MULTI-TAP CONNECTION
600 WATT MTP TRANSFORMER W/2 CIRCUITS
Tip: In a loop installation, low voltage polarity must be main-
tained by connecting the start and return of the first conduc-
tor to the ‘COM’ terminals, the other conductor to the ‘12V’
terminals.
COM COM 12V 15V
COM 12V COM12V
CIRCUIT 1
OF LOAD
CIRCUIT 2
OF LOAD
COM 12V COM12VCOM12V
CIRCUIT 1
300W
CIRCUIT 2
300W
CIRCUIT 3
300W
COM12V
CIRCUIT 4
300W
50'
(connect at center)
75'
(connect at center)
4 Each 20 Watt MR-16 Fixture = 80 Watts
4 Each 35 Watt MR-16 Fixture = 140 Watts
Common Terminals
300w Max. 300w Max.
Cir 1 Cir 1 Cir 2 Cir 2 11V 12V 12V 13V 13V 14V 14V 15V
Output Taps
Cir Cable Run =
100' of #12 Wire
Cir Cable Run =
300' of #8 Wire
Justin GLP transformers come equipped with a 2-position output voltage switch. Set the switch using the following as a guide.
HIGH - The correct setting in most cases. Provides expected lamp life while maintaining good brilliance..
LOW - Increases lamp life when fixtures are located very near the transformer and/or when fixtures total less than 1/2 the transformer’s rated wattage.
Tip: Multi-Tap transformers supply output voltage which exceeds 12 volts. Extreme care must be taken dur-
ing installation to avoid premature lamp burnout due to high voltage. Use of a voltmeter during installation
is the only way to ensure a proper voltage at the fixture. As a guide when designing your job, expect a 2 volt
drop for every 100 feet of 12-2 cable to which 200 Watts of evenly spaced fixtures are connected.
Refer to sample diagram. Connect one side of fixtures (common) up to 300 watts per circuit, using 12 gauge
or larger direct burial cable. Strip 3/4” of cable insulation and twist wire strands tightly before insertion into
transformer’s output terminals. Each terminal will accept two #8, four #10, or 6 #12 wires. Tighten connec-
tor screws firmly. Connect remaining side of fixtures to output tap according to your voltage needs. Retighten
all connections after one week of operation. It is always best to connect your fixtures to the 12-volt tap first,
then use a voltmeter to measure the AC voltage of the fixture nearest to the transformer. Subtract the meas-
ured voltage from 12 and add the result to determine your higher tap. Example: With fixtures connected to
12-volt tap, measured voltage at first equals 10. 12 volts required at fixture minus 10 volts measured equals
a 2-volt difference. Add the difference to 12 in order to determin the appropriate tap to be used. (2 + 12 =
14)
Tip: Expect a voltage drop of greater than 1.5 volts when cable length is longer than recommended. Use the formula below to calculate maximum cable length.
Calculate Approximate Voltage Drop
Tip: When using single circuit transformers, full rated load
may be connected to one pair of ‘COM 12V’ terminals.
COM 12V COM12V
NOT
USED
NOT
USED

REMOTE PHOTOCELL CONTROL FUNCTION FOR PCM12 MODULES
MECHANICAL TIMER SETTING PROCEDURE
LOW VOLTAGE DIMMER
TIMER SETTING PROCEDURE WITH
FIELD INSTALLED PHOTOCELL
TIMER REMOVAL & REPLACEMENT
INSTALLATIONN OF FIELD
INSTALLED PHOTOCELL
Photocell Mounting
1. Mount photocell eye where exposed to sunlight.
2. Run photocell cable with plug end back to transformer enclosure.
3. Locate square shaped hole in enclosure bottom and feed plug through to socket on PCM12 marked “P OTOCELL INPUT’. Plug photocell in.
4. To test, apply input power to transformer and turn photocell control knob to position 6. “DUSK TO DAWN’.
5. Cover photocell eye completely. Transformer should turn on within 5 minutes.
6. Uncover photocell eye for normal operation.
Timer Setting:
Timer does not require time-of-day setting or battery backup
maintenance. It depends on the photocell “darkness signal”
to begin the ‘on duration’ cycle. It has six modes of operation.
• By moving the dial to one of the four ‘on time’ switches (2,
4, 6, 8 hours), you tell the unit to turn on at darkness, begin
timing, and turn off when the selected time period ends.
• With dial turned to ‘DUSK TO DAWN’, the timer never
activates, allowing the unit to operate from dusk until dawn.
• To test your system during daylight hours, use “ALL ON
/TEST” to override the photocell and turn the system on.
Whenever input power is applied to the transformer, the lights
will remain on.
1. Turn the outer rim of the timer face (the section
with numbers) Clockwise until the arrow on the inner
rim points to the approximate time of day.
Note: The numbers on the timer face correspond to
the hours in a day. Each hour is divided into four fif-
teen-minute sections.
2. To set time ‘ON’: Locate push pegs on the outer rim
of the timer face and firmly push pegs outward from
the timer face until you hear and audible ‘click’
Note: Each peg keeps light or appliance ‘ON’ for fif-
teen-minute sections. Use as few or as many pegs as
necessary throughout the day. All pegs must be
pushed out between the desired hours of on time.
3. Time ‘OFF’ is automatically set by leaving the pegs
flush against the timer face.
Note: You can set multiple on or off programs.
4. Locate override switch on top of timer Make sure it
is set to ‘AUTO’.
TIP: When equipped with timer, transformer may be
operated manually by sliding override switch to ‘ON’.
When so equipped, the timer supplied with your new
transformer is a removable (plug-in) style. Located
inside the cover of the transformer enclosure. It can be
pulled out and replaced with a new timer, remote
photocell module, or remote control module. To
replace a timer, simply grasp both sides of its plastic
case and pull firmly. Next, remove the timer plug from
the timer.
To install a new timer, insert timer plug into timer
before plugging into transformer’s timer receptacle.
1. Turn input power off.
2. Select a location or mount the photo control so
that artificial light doesn’t cause the unit to turn off.
Do not install the photo control so that it directly
faces the midday sun. Take care to keep the photocell
EYE free of obstructions.
3. The photo control can be mounted in any approved
outdoor junction box or fixture.
4. Wire the photo control according to the illustration.
5. Switch power on. The controlled load should turn
on regardless of whether you are installing the unit
during the day or at night.
6. If it is daylight the control should switch off within
a few minutes.
7. If a timer is also installed, it must be set to turn on
during daylight hours, then off at desired time. (see
below)
The combination timer and photocell is designed for
photocell-on, timer-off operation.
1. Set ON TIME during daylight hours - 2 PM or so.
2. Set OFF TIME at desired off time.
3. Set timer dial to the current time of day.
EXAMPLE: For on at dusk, off at 12 PM, PUS OUT
all 40 pins between 2 and 12 PM.
Tip: It is normal for the transformer to temporarily
turn on during daylight at the timer on setting.
Approximately 5 minutes is required for the photocell
to stabilize and turn the unit off.
Tip: When equipped with plug-in timer and photocell,
normal operation requires uninterrupted 120 volt
power.
Justin transformers are ready for use with a low volt-
age system (inductive load) dimmer. When wired in the
120 volt line, the dimmer will allow you to adjust dif-
ferent levels of lamp brilliance. Your transformer will
not work with any dimmer not specifically designed for
low voltage systems. A dimmer can be installed at the
120v Accessory Terminal. (Item LVD 1000K)
Although low voltage lighting systems operate with a
minimum of maintenance, occasionally some prob-
lems will occur. ere are solutions to some of the
most common problems.
Entire system will not operate
1. Check 120-volt outlet to ensure you have power to
outlet.
2. Check or reset circuit breakers on transformer
3. Check low voltage cable connection at transformer.
4. Check transformer alone by disconnecting low volt-
age cable from output terminals, by passing timer
and/or photocell.
System operates for 15 minutes, and t en
turns off.
1. Timer incorrectly set. See setting procedure.
Circuit breaker on transformer trips
1. Check end of cable to ensure copper strands are
not touching.
2. Check connection of cable at transformer to ensure
copper strands are not touching.
3. Recalculate total wattage to ensure that you have
not exceeded rated wattage of transformer or circuits.
4. Check for other shorts at fixture connection points.
TROUBLESHOOTING CHECKLIST
PRODUCT WARRANTY
ALL JUSTIN, INC. TRANSFORMERS AND CONTROLS
(EXCLUDING PLUG-IN TIMERS AND PHOTOCELLS)
ARE GUARANTEED TO BE FREE OF DEFECTS IN
WORKMANSHIP AND MATERIALS WITH NORMAL
USE FOR A PERIOD OF 10 EARS FROM THE DATE
OF MANUFACTURE STAMPED ON EACH UNIT. LIMITED
LIFETIME WARRANT ON STAINLESS STEEL UNITS.
FOR WARRANT SERVICE, THE PRODUCT MUST BE
SHIPPED PREPAID TO THE FACTOR IN IT’S ORIGINAL
PACKING CARTON. JUSTIN, INC. RESERVES THE RIGHT
TO MAKE THE FINAL DETERMINATION REGARDING
WARRANT VALIDATION. AN TRANSFORMER
JUDGED IN WARRANT WILL BE REPAIRED OR
REPLACED AND RETURNED TO IT’S OWNER AT NO
ADDITIONAL COST. AN UNIT JUDGED OUT OF
WARRANT WILL, AT THE OWNER’S OPTION, BE
EXCHANGED WITH A NEW UNIT AND CHARGED AT
OUR CURRENT PRICING, RETURNED FREIGHT COLLECT.
TRANSFORMER
RECEPTACLE
PHOTOCELL
INPUT
ALL ON/TEST
DUSK TO
DAWN
2 HRS.
4HRS.8 HRS.
6 HRS.
OFF/RESET
AT TENTION: See Installation & Operation
Instructions on bottom of this plug-in module

C CB
MOUNTING TEMPLATE
INSTRUCTIONS
1) ATTACH TEMPLATE TO WALL AT
DESIRED HEIGHT.
2) CENTER PUNCH OR DRILL AT KEYHOLE
CROSS-HAIR MARKS.
3) USE AT LEAST TWO #10 SCREWS FOR
MOUNTING
USE
B FOR GL SERIES 100-200 WATT TRANSFORMERS
USE
B FOR GLP AND MTP 300 WATT TRANSFORMERS
USE
C FOR GLP AND MTP 600/900/1200 WATT TRANSFORMERS
THIS POINT DOUBLES AS SECURITY
MOUNTING HOLE
MADE AND PRINTED IN USA JAN/22
B
C
BTOP
9.75"
12.25"
6.50"
4.00"
LANDSCAPE LIGHTING TRANSFORMERS
SOUTH EL MONTE, CA USA
Note: This template will only print to scale when printed on
8 1/2" x 14" Paper in Actual / Original size. Please note actual
dimensions highlighted.