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How Does a BASO Switch Work? - PartsFPS

how does a baso switch work

Do you want to know how does a BASO pilot safety switch work? You have reached the right place to get the details on BASO switch. Here, we have provided the information regarding the BASO pilot switch working process, installation, importance, etc. So, have a look at this blog post to get the details on Baso pilot safety switch.

How Does a BASO Pilot Safety Switch Work?

BASO pilot switches are used on all gas-fired and standing pilot equipment that requires the main burner to shut off when the pilot is extinguished. Typical applications include domestic central heating and commercial space heating appliances as well as industrial processing equipment.

These pilot switches monitor the pilot flame through the use of a thermocouple. In 100% shutoff model applications, if the pilot flame is extinguished, then the switch will be interrupted gas flow to the pilot burner as well as the main burner and caused for shutting down the appliance.

In non- 100% shutoff model applications, the switch will interrupt gas flow to the main burner only when the pilot flame is extinguished. Pilot gas will continue to flow until the pilot gas is manually shut off.

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Now, in this blog, we will see about BASO L61 and L62 Pilot Switches.

L61 BASO Pilot Switch

The L61 is an automatic resetting device that opens the main gas valve electrical circuit if the pilot flame is extinguished. Lighting or relighting the pilot burner causes the device to close the electrical circuit of the main gas valve and allowing the appliance's main burner to operate.

This switch receives its energy from a heated thermocouple. Because BASO L61 has features like automatic resetting and minor pilot flame fluctuations which may cause the device to drop out and will not shut down the unit permanently. Moreover, it will automatically close and restore service upon resumption of a normal pilot flame. L61 models are available with Single Pole Double Throw switching actions when an additional switching function like a need of signal light.

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BASO L62 Pilot Safety Switch

The BASO L62 switch has a manual reset feature and it is available with or without 100% shutoff models. It has a thermoelectric power unit assembly that receives its energy from a heated thermocouple. If the pilot flame is extinguished, the main valve circuit is interrupted and gas flow to the main burner is stopped.

Both models of L62 contain an electric interruption feature that only allows pilot gas flow during the lighting or resetting cycle. When lighting the pilot, the main valve electrical circuit is interrupted until the pilot flame is established and the reset button is released.

BASO Safety Shutoff Device Installation

  1. Before starting the installation process, you should turn off the power to the appliance.
  2. Shut off the gas at the main manual shutoff valve adjacent to the appliance.
  3. Remove the device cover by loosening the screws at the side.
  4. Now, mount the switch in any convenient position using the mounting holes provided.
  5. Push the circuit wires through the conduit opening on the bottom of the device. Strip the ends of the wires just enough to put the bare wire under the terminated screws and attach them to the two-wire terminals.
  6. Replace the cover. Do not loosen the grass hex nut.
  7. Attach the thermocouple securely to the pilot burner. And, screw the terminal end to the BASO power unit terminal on the pilot switch. Ensure that this connection is secure. Tighten the thermocouple lead nut finger tight that is finger tight plus a maximum of 1/8 turn. You should not overtighten it.

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Check the Adjustments after Completion of BASO Switch Installation

Make sure all components are functioning properly by performing the following tests.

  • Test all joints and connections for leaks with a soap solution.
  • Set the thermostat to the lowest setting.
  • Close the main manual shutoff valve and pilot valve and wait at least 5 minutes for unburned gas to escape from the appliance.
  • Reopen the pilot valve and ignite pilot gas and wait for 30 to 45 seconds.
  • Push down the red indicator and aluminum reset button to its full limit of travel and release. If the red indicator remains depressed, the unit is operative. If the red button doesn't stay depressed, wait for another 30 seconds and try again. If the second attempt also not successful, check that the thermocouple output meets the desired value.
  • Open the manual main shutoff valve after the red indicator button remains in the depressed position. The main burner will ignite from the pilot burner when the thermostat calls for heat.
  • Disconnect the thermocouple from the device. The main shutoff valve should close immediately. If it is not closing, you have to check for wiring errors. Once, you have decided there are no wiring errors, reconnect the thermocouple to the pilot switch.
  • Re-light the pilot and observe at least 3 complete operating cycles to make sure that all components are functioning correctly.
  • Reset the thermostat to a normal temperature setting before leaving the installation.


Hope the information updated above on the BASO pilot switch useful for you. If you know the basic working process, installation, and testing, then you can easily fix the problems yourself when it has trouble.

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