Recently I had an air handler shut down due to a wire rubbed where it goes into the motor. The wire rubbed and arced to ground where it went into the motor and the overload opened the circuit (this destroyed the overload, at 600 Volt!!!) The surprise to me was the fact that the wires are three hots and a bond tie wrapped to the frame of the air handler from the starter/overloads to the motor. Not teck or BX but just three hots and a bond. There are six other air handlers that are wired the same way. The motors have an anti short put into the motor where a connector would thread in. The air handlers are electically certified for Canada but this does not seem proper. Shouldn't these wire be ran in armour or sheathing with proper connectors or???? This particular motor that arced had no anti short installed.
Wacked. How the unit is wired is a function of the product approval standard for air handling equipment. This is Part 2 OF the Canadian Electrical code. This is why an inspector looks for an approval label to verify the thing was made to the OTHER electrical code. Ther is a part 3 , 4 and 5 too.
Your work as an electrician is the installation of electrical products which is PART 1 of the CEC and the portion of the code electricians break and inspectors reject or approve.
How the product is wired intenally is not governed by your part 1 installation code. It is regulated by Part 2 which is a lot of code books that govern how the product is made and how it performs as well as the market it is approved for like household and commercial.
Just like the wiring for your range is open inside the stove so may be some of the wiring inside your AH unit.
This unit does have an approval label... that still doesn't make it proper due to the fact that there was a failure. I have looked at other air handlers and teck is used more often than not. Maybe the "other code" for packaged units need to be reviewed.
You are saying a manufacturer like engineered air is using teck internally to wire the motors? I don't see that. I built this stuff briefly in an earlier life and we did not use tech or acwu internal wiring. Sometimes we used seal tight. it is very common to see what you describe inside of these air units. The fault is a manufacturers error and I would report that to the Certification Body that approved it. I.E. CSA or cUL. We regulary report product defects to them as they can make the manufacturer fiz the wiring methods used internally. You cannot judge how a piece of approved equipment is internally wired by comparing it to the code book methods. The code book is about how we wire the parts together the other part of the coed is how the factory makes the products we wire. Your description of how various factories wire the motors is more related to their designs and what is more important to them withing the part 2 standards.