I have a problem that comes up alot due to the fact that we use these interlocks about twice a year. The shelf life for memory here is about two months.

On industrial control enclosures with an external disconnect we use a door solenoid to lock the doors closed anytime main power is applied to the unit. If the disconnect is put in the off position the solenoid de-energizes and the doors can be opened.

When we have a panel mount disconnect with through the door operation we do not use the solenoid. This is due to the fact that the operator has to be turned to the off position to get the door open and the solenoid would be redundant.

Or so I thought.

Now I am being told to put the solenoid in even though the panel mount disconnect serves the purpose of not allowing the door to be opened without being power being disconnected.

The item of a technician bypassing the disco came up to explain the solenoid.

I explained that the solenoid can be bypassed as well and either way the door is open at that point. In addition the safeties will need to by bypassed to take volt and amp readings anyway, and that the purpose of the interlock is to ensure that when the door is first opened the power is off. The working on live voltage is a totally different item in itself.

California code only states that the power be off when the door is opened. There are seperate codes for re-energizing and testing live equipment.

We also have a door switch that de-energizes the control circuit. In our case the tech would have to bypass the disconnect and the door switch (or the solenoid and the switch) in order to get the unit to operate with the door open.

The line side of the disconnect on this particular unit will be hot regardless of whether or not the solenoid is installed.

Any comments on this situation? Any California electrical workers with first hand knowledge.

I would appreciate your views on this.