Application Note: Current Switch Comparison

May 15, 2013

There are a variety of current switches and current transducers currently available for use in HVAC applications. Each product provides different features and benefits for that particular job. This post reviews two common types of current switches and a new technology that eliminates the risk of arc flash hazard during installation.

Here's a scenario:
You're a controls contractor who installs current switches. A job calls for the installation of 15 current switches. In the past, you have had had two options for current switches: a fixed set-point or and adjustable set-point switch. However, a recent innovation will change the way current switches are installed.

Fixed Set-Point Switches

  • Benefit
    Setra Model CSC split core current switchThe install is completed without ever working on a live circuit, increasing safety and eliminating the chance of encountering with an arc flash.
  • Problem
    There are 15 switches to install and the horsepower of each of the motor is unknown. As the controls contractor, you're forced to carry a variety of fixed set-point switches in order to ensure that you have enough switches with the proper set-points to complete the job.Not only is it expensive to carry this type of inventory, but unless you carry 15 of each switch, you can’t guarantee that you have the necessary switches for the job. If it happens that you run out of one type of switch, you may have to come back again to finish the project, costing you time that you could have spent on another job site.

Adjustable Set-Point Switches

Arc flash explosion

  • Benefit
    Adjustable set-point switches are flexible enough to be used on a variety of different powered motors, thus it eliminates the cost of carrying excess inventory.
  • Problem
    The safety of the controls contractor is compromised due to the increased risk of experiencing an arc flash hazard. During the installation of an adjustable current switch, the installer is working on an energized circuit and must wear a cumbersome PPE (Personal Protective Equipment) suit required by NFPA. The switch is placed on the cold circuit, the power is then returned and the installer must adjust the potentiometer with an insulated screwdriver until the LED indicates that the switch is at the appropriate set point. Arc flash hazard is unpredictable and can be caused by a number of different circumstances, which makes installing a current switch within a live enclosure, a dangerous job.

Is the money saved from carrying less inventory worth the price of your safety?

Pre-Configured Adjustable Set-Point Switches


    Setra Sure-Set Current Switch Sure-Set Current Switch

    The new Sure-Set Split Core Current Switch (Model SSC) offers all of the same cost savings associated with the adjustable current switch without compromising the safety of the installer. Each Sure-Set (4 models) has 9 pre-configured set-points, allowing the installer to safely match the settings of the switch to the rating of the motor and complete the installation on a cold circuit.

    This eliminates the need to make any adjustments in the vicinity of a live enclosure. If the installer knows the rating of each motor, each switch can be pre-configured prior to arriving on the job site, saving significant time on the installation.

Most motors where these switches are installed are rated in horsepower (hp) rather than amps. Calculations can be time consuming if the installer needs to match the amp settings on the switch with the hp settings on the motor. The Sure-Set is the first current switch in the industry to be calibrated in horsepower, with a scale that covers the most common motors. There is no need to make time intensive calculations, saving time on installation. The scale selector also has mechanical detents to assure the installer that the correct range has been selected.

The Sure-Set is the solution for every controls contractor. Not only does it solve inventory and safety issues, but also save time on installation because there is no need to wear a PPE suit. The Sure-Set is a contractor’s best opportunity to save money on installation, inventory and safety.

Ditch the suit, cut your install time and put the savings back in your wallet.

Watch the Sure-Set video to learn more about this new current switch.

>> Click to watch the video

Topics: Energy Management, Building Automation