Transformers are heavy and bulky. The less you move them around before installing them, the safer you are. If, for example, you transport, place, and mount a transformer only to find it’s got a big dent in one side or it really doesn’t fit in the intended space, you’ll have to repeat all those steps in reverse and then do them again with a replacement transformer. So before you install the transformer:
- Read the nameplate. Verify the transformer is the correct one for this application. For example, it is it the 120/208 Delta specified in the drawings?
- Give it a visual inspection. Look for dents, creases, and other signs of damage.
- If it’s a dry-type, remove the cover and look a the frame (ensure it’s not bent) and windings (ensure there’s no visible insulation damage).
Plan out the placement
Check the weight of the transformer and verify that any lifts, hoists or other rigging devices you might use can safely support the transformer for the purpose of transporting it and setting it in place.
Double check the installation location. Use a tape to measure the dimensions of the transformer and write these down. Then ensure the transformer can go in the intended location while meeting the NEC clearances and not having an issue such as the vent is blocked or facing other equipment.
Also verify that if the transformer sits as intended, there is a path for the raceway for the supply conductors and load side conductors. Liquid-filled transformers obviously must be oriented so a person can take an oil sample and do related maintenance work.
Check the transformer pad or other mounting system. Is it suitable for the weight and dimensions of this transformer? Can it provide proper support In the correct installation orientation?
Plan out the path from where the transformer is now to where it will go. Is there sufficient room for the lift truck or other device to transport it on that intended path, or must another path be taken or equipment temporarily moved?
If the transformer is going overhead, you will need to build a mock-up skeleton that you can easily raise into that space and take measurements again. You could use the metal strut you’re already working with, or you could cut 2×4s. Cut these to the correct lengths and fasten them at right angles (bolts for the strut and maybe deck screws for the boards). Mark the vent side of this and put your dummy transformer base into the space. Now measure one more time. This may seem like a waste of time, but it is a lot safer than trying to rotate the transformer once it’s overhead.
For a pad mounted transformer, you don’t need a mock up. Once it’s set in place, get out the tape to check it fits and there’s no issue with vent blockage or routing the supply or load conductors.
Using this approach, you will measure more than twice, but you will transport, lift, and mount the transformer only once. This will leave you with more time to perform insulation resistance testing on the supply conductors before terminating them, terminate the supply conductors properly, perform any required baseline testing, and make the connections to ground and the equipment grounding (bonding) conductor. Before energizing, double-check your connections, clean debris from the area, and secure all covers.
