ECN Forum Forums Code Related Discussion Canadian Electrical Code Topics Grounding Transformer

Can you ground a transformer to a steel column of a steel building or do you have to run the ground wire to a system ground?

Ontario code allows it, provided the steel building is bonded at two separate points to ground using the same size ground wire as the main service.

This is a very handy practice, say, in a machine shop that use a separate transformer for each piece of equipment.

My quick answer is no. there are circumstances where i would allow it but only if it can be easily proven that the building steel is continuous and solidly connected to the grounding system and electrodes. 10-700 mentions in-situ electrodes and defines what that might be. In buildings where the engineering required the steel to be bonded in 2 widely seperated places (very old code for High voltage substation grounding) and was made continuous via bonding jumpers, welding, or mechanical joints proven to be electrically continuous then we might allow the column to be part of the system ground. A lot of homework to do in an old building but might be simple to establish when the power distributution is planned and the bonding and grounding is included in the inspections of the building. The long answer is maybe.