ECN Forum Forums Code Related Discussion NEC & other Code issues Grounded metal cabinet?

My understanding is that metal cabinet needs to be grounded to the common or neutral 3 wire.

Questions:

When is 3 wire required and when 2?

Why are some plastic cabinets polarized 2 wire or 3 wire?

Why is this metal cabinet space heater that im try to fix, why its 2 wire and neither is common grounded to its metal cabinet?

Short answer is,

Metal enclosures are required to be 'bonded'.

NOT to the neutral conductor, except in MOCP equipment.

The other questions can be answered by you reading a book on basic electricity.

You may want to consult a Qualified Electrical Contractor regarding the space heater as you may be endangering yourself or your property by attempting to DIY.

I am closing this thread as the forum rules do not allow DIY.