Model-TR-7

Supported Applications

The Dwyer Series TR-7 Safe-T-Ground is a ground and continuity control system designed for truck grounding applications. It ensures safe grounding during loading operations by monitoring the connection between a tank truck and an earth ground, preventing static discharge hazards. The unit instantly stops loading operations if the tank truck loses its ground when wired into pump controls or connected to audible alarms.

Key operational constraints documented in the source include:

• The TR-7 does not ground the loading structure or equipment; it monitors continuity only.
• Rigid mounting is required near the truck grounding location, typically under a protective canopy.
• The unit must be kept dry as the cover is not watertight.

Operating Conditions & Performance

The Series TR-7 operates within an ambient temperature range of -13 to 104°F (-25 to 40°C). The housing is constructed from 356-T6 cast aluminum alloy (copper-free) and carries an explosion-proof rating for Class I, Group D environments. Power requirements are 105-125 VAC, 60 Hz standard, with optional support for 220-240 VAC, 50/60 Hz.

Electrical performance specifications include:

• Relay Rating: DPDT, 10 A, 125 VAC, 60 Hz contact rating.
• Power Consumption: 7.75 watts with lights; 1.75 watts without lights (for standard power supply).
• Housing Dimensions: 6-5/8" W x 10-3/8" H x 5-5/8" D.
• Conduit Connection: 3/4" NPT.

The system includes a relay with two sets of contacts (N.O., Common, N.C.) for integration into external control circuits. Compliance is listed as UL.

Configuration Options

The Series TR-7 offers configurable options regarding power supply voltage, cable length, contactor type, and status indicators. The model number construction follows the format: TR-7 - [Power Supply Option] - [Cable Length] - [Cable Connection] - [Options].

Cable and Contactor Configurations:

• Cable Lengths: Standard 36" coiled cable (extends to 16'); optional 72" coiled cable (extends to 32').
• Contactors: Stud type contactor with beryllium copper clips is standard; battery clamp (alligator) style is available for temporary use only.

Status Indication Options:

• Audible alarm and LED status indicators are available options.
• Red and green indicating lights are offered but are not available with the 220/240 VAC power supply option.

Accessories:

• #4H Brass grounding studs (two required per truck).
• #4H-T Temporary grounding stud assembly.
• I.C.C.-7 Internal chassis circuit replacement parts.

Key Product Differences

The series distinguishes between models based on the presence of integral pilot lights and specific contactor configurations. The base model TR-7 provides Safe-T-Ground functionality, while the TR-7-L variant includes integral red and green indicating lights.

Variants differ by:

• Power Supply: Standard 120 VAC versus optional 220/240 VAC (which excludes light options).
• Cable Length: Shorter coiled cable versus extended length.
• Contact Type: Permanent stud connection versus temporary battery clamp.