TuffSeal Heavy Capacity Junction Box

1.0 Introduction

The TuffSeal eight-channel signal trim junction box is used in truck scale installations and can accommodate up to eight load cells. Additional load cells can be connected to the junction box by wiring additional junction boxes to the expansion terminal located on the main board. Both the JB8SP and JB8SPT models can withstand 900 PSI water pressure when correctly installed. Both models feature a Prevent® breather vent that inhibits pressure buildup caused by sudden temperature or environmental changes. The breather vent should be changed every six months to one year. Both models function properly without modification, but load cell output can be individually trimmed with potentiometers. Transient protection is standard with the JB8SPT model. Manuals and warranty information are available at www.ricelake.com/manuals and www.ricelake.com/warranties respectively.

Figure 1-1: A rectangular, grey metal junction box with multiple cable glands on the right side. It has the Rice Lake Weighing Systems logo.

1.1 Model Designations

The TuffSeal eight-channel junction box comes in two main models:

1.2 Safety

Safety Definitions:

• DANGER: Imminently hazardous situation; death or serious injury if not avoided.
• WARNING: Potentially hazardous situation; serious injury or death if not avoided.
• CAUTION: Potentially hazardous situation; minor or moderate injury if not avoided.
• IMPORTANT: Information about procedures; damage to equipment or loss of data if not observed.

General Safety Precautions:

• Read and understand the manual before operating or working on the equipment. Failure to follow instructions may result in injury or death.
• Do not install where water may accumulate, as this can cause electric shock and unit damage.
• Do not use if wiring is frayed or worn.
• Do not use if the cover is off or the unit is not sealed properly.
• Keep fingers away from slots or pinch points.
• Do not use if any components are cracked.
• Do not make alterations or modifications to the unit.
• Do not remove or obscure warning labels.
• Ensure load cells are correctly wired; incorrect wiring can damage the unit.

1.3 Disposal

Product Disposal: The product must be brought to appropriate separate waste collection centers at the end of its life cycle. Proper collection helps prevent negative environmental and health effects and promotes material recycling. Illegal disposal may result in administrative sanctions.

2.0 Installation

Mount the junction box in a location convenient for servicing and away from standing water. Ensure the location allows the load cell cable to be installed without cutting or adding length, as output is temperature compensated for the supplied cable length. The enclosure is attached using four pan-head screws, bolts, or other suitable fasteners (not included).

Figure 2-1: A diagram showing the dimensions of the JB8SP/JB8SPT enclosure. It indicates a length of 11.50 inches, a width of 10.75 inches, and a height of 5.25 inches. Mounting holes are shown, with a recommended screw size of 1/4 - 20NC. It also lists the types and sizes of cord grips: eight 3/8" NPT cord grips for cables 0.157" - 0.314" and two 1/2" NPT cord grips for cables 0.272" - 0.472". A note specifies that with reducing glands, cable diameter changes to 0.295 in - 0.353 in.

3.0 Wiring the Junction Box

TuffSeal junction box models connect and trim up to eight load cells per board. Multiple junction boxes can be connected in series using the expansion port on the main board to accommodate applications with ten or more load cells.

Wiring Procedure:

1. Determine the wiring pattern, route load cell cables through cord grip assemblies, and leave grips loose until final closure.
2. Strip wire insulation back 1/4 inch to expose the wire. The pluggable connector accommodates 12 to 28 gauge wire.
3. Open each pole with a small screwdriver and insert the appropriate wire into the exposed wire opening to connect to the appropriate connectors.
4. Tighten the end screw with the screwdriver to secure each wire.
5. Plug the terminal into the appropriate header socket.
6. The indicator terminal connects the main cable to the weight indicator. Refer to the operation manual for indicator load cell input connections.
7. Run a cable from the indicator terminal into the junction box through the larger cord grip.
8. Make connections on the indicator terminal using the same procedure as for load cell cables.

Figure 3-1: A diagram illustrating the expansion port wiring location on the junction box main board. It shows connection points labeled EXPANSION/J9 and INDICATOR/J10, with terminals for SHD, +SI, -SI, +SEN, +EX, -SEN, -EX. It also details internal connections with jumpers and traces, including instructions to cut traces to isolate sense lines and connect/disconnect shunts.

Figure 3-2: A diagram showing a "Drip Loop Cable". It depicts a cable entering a cord grip and then forming a downward loop before continuing, designed to allow fluids to drip off before reaching the junction box.

4.0 Transient Board Installation Procedure

The JB8SPT model includes transient protection (PN 89894). Figure 4-1 shows where the transient protection board plugs into the main CPU board.

Figure 4-1: A diagram of the TuffSeal Junction Box main CPU board, highlighting the location where the transient protection board plugs in. It shows various components like section potentiometers, individual potentiometers, section isolation jumpers, and the grounding lug.

4.1 Grounding Transient Protection

To ensure proper operation and protect the junction box from stray voltage, the JB8SP and JB8SPT must be grounded. A ground wire is pre-attached to the grounding lug on the main board and extends out of the cord grip. Securely attach a 10 gauge ground wire to this existing ground wire. The final ground wire connection must be made at the AC power supply ground terminal, separate from the truck scale ground.

Figure 4-2: A schematic illustrating "Single Point Grounding" for the junction box and truck scale. It shows the JB8SPT junction box connected via a ground wire to the AC power supply ground terminal, which is separate from the truck scale ground. It includes components like a fuse panel, indicator, printer, AC outlet, power company ground rod, and the connections for serial communication and load cell cable.

5.0 Trimming Procedure

Trimming is the process of equalizing the output from multiple individual load cells. Load cell output can be trimmed with potentiometers if needed. If substantial trim (over 7% of normal output) is required, check for other potential issues. The best trim uses the least amount. The JB8SP and JB8SPT feature individual and section trimming potentiometers.

Trimming Steps:

• NOTE: If using two junction boxes with an expansion cable, cut the sense trace on the board with the homerun cable to ensure proper sensing to the furthest box. A six-conductor cable must be used between boxes.
• Determine the number of load cells needed. Combinations of load cells other than eight are acceptable for section trimming, but the total must be an even number.
• Turn all individual cell and section potentiometers clockwise for maximum signal output. Remove shunt jumpers from unused cells and ensure section potentiometers are fully turned.
  • NOTE: Potentiometers can be adjusted 3-5 turns counter-clockwise for positive and negative trim capabilities.
• Trim by turning potentiometers counter-clockwise to lower output to match the lowest value.
• Remove all weight from the scale and zero the indicator. Place calibrated test weights over each load cell or section. Refer to Handbook 44 (NIST) for specific weight recommendations based on scale configuration.
• Record the indicator value after placing test weight over each cell/section. Select the cell/section with the lowest value as the reference point (this one will not be trimmed).
• Place the same test load over each cell/section. Using the corresponding potentiometer, trim each cell/section down to match the reference point. Check zero after each adjustment to avoid zero shift, as corrections are interactive.
• Recheck cells/sections and repeat steps six, seven, and eight as needed.

Figure 5-1: A detailed diagram of the junction box board showing various shunt locations and potentiometers, labeled with cell numbers and section numbers.

Final Steps for Trimming:

1. Pull excess cable out of the enclosure.
2. Using a wrench, tighten the cord grip nut until the rubber touches the cable.
3. Tighten the nut an additional 1/2 turn (180 degrees) to ensure a watertight seal, allowing the rubber sleeve to protrude slightly.
4. Plug any unused hubs to prevent moisture entry. Extra hole plugs are provided.
5. Remove the desiccant from its bag and place it inside the junction box before closing. Inspect and change desiccant as needed during service.
6. Replace the cover and torque cover screws in an alternating pattern to 15 in-lb to ensure the gasket is compressed equally.