Adjustable trip units on breakers 1

[NickParker]

What is adjustable trip unit? Using the knob on the front fascia of the breaker, the thermal / instantaneous settings could be changed. Is this called "Adjustable trip unit"?

or

If the trip unit could be replaced by another called as "Adjustable trip unit"?

Is Adjustable and Interchangeable trip unit are one and the same?

 

[wbd]

An adjustable trip unit means that trip settings can be adjusted. Typically this is on larger breakers and depending on the trip unit, the Long Time Pickup, Long Time Delay, Short Time Pickup, Short Time Delay, I2t, Instantaneous, Ground Fault Pickup, Ground Fault Delay, and I2t, can all be adjusted. This aids in coordination with downstream breakers.

The simplest molded case breakers will typically have an adjustable instantaneous settings on larger (200A and greater typically) breakers.

 

[thermionic1]

Some molded case and insulated case beakers have rating plus that can be changed in rating.

 

[dpc]

"Adjustable Trip Unit" generally implies more than just adjustable instantaneous. Generally refers to digital trip units commonly found on low voltage power circuit breakers and larger (new) molded case breakers.

 

[JG2828]

Here is an example of a Solid State trip unit on a breaker. The settings are changed by moving the pins on the front. Not sure if you are referring to something different.

 

[JASGripen]

It is an adjustable settings unit on usually larger or MDP (Main Distribution Panel) molded circuit breakers that can be adjusted for the following situations:

1) Enables coordination settings (based on engineered studies) with the downstream breakers so if there is a fault downstream the whole building does not go black.

2) Enables adjusting the Amp trip rating on your generator or emergency spider box for the appropriate load so you do not have to change out the main breaker.

3) ... There might be other uses, but someone else will have to explain.

 

[jraef]

Adjustable trip means the individual trip settings can be changed in the field and generally refers to the Thermal or Long Time trip settings. Magnetic (Instantaneous) Trips are quite often adjustable.

Interchangeable Trip Units means the trip unit part of the circuit breaker can be removed and replaced with another entire trip unit.

The two concepts are not mutually exclusive, meaning you can have an interchangeable trip unit that has adjustable trips on it.

In North America, adjustable thermal trips are not permitted for Molded Case Circuit Breakers (MCCBs) used as Feeders or as Branch circuit protection on non-motor loads. The only legal use for them is for what are now called Motor Protection Circuit Breakers (MPCBs) where they are the Branch protective device on an AC motor control circuit where the adjustable thermal trip is used AS the Overload device (in lieu of an Overload Relay). The only type of adjustable trip MCCBs that are allowed for Feeders and Branch non-motor applications are those with Electronic Trip Units (ETUs).

Outside of North America, Adjustable Trips are quite common for all MCCBs.


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