Common Transformer Grounding Mistakes

[edf]

I am much too frequently amazed how little electricians in the field understand about grounding a transformer.
I often find grounds from Building steel , the water main and other perfectly good grounding sources on lugs
bolted to the case of the transformer without a single connection to XO. I found a building that had a live ceiling grid.
(the steel studs had to be live also)
The transformer has no grounding connection to XO so when a sheet rocker or ceiling grid person drilled a screw through the MC cable and hit a phase wire everything connected to the steel was live. This was not a new building. It was likely this way for many years. (Cheshire Connecticut)

I recently found another where a transformer installed at a college to boost 208V to 280/277V for the long runs to light poles down a long driveway and parking lot.
No ground to the common! What could possibly go wrong ????? We repaired the 15 year old problem...

EdF

Inspectors should consider asking to see transformer connections.
It takes time but would be worthwhile

Frustrated!!!

 

[kwired]

Many those same guys are the ones that are or would be scared to ground a phase to make a corner ground system.

They don't fully understand there is no grounded conductor until you actually ground a system conductor.

 

[infinity]

There are good and bad electricians just like there are good and bad inspectors. When you get two bad ones one the same installation you will see the stuff that you've mentioned. Some electricians think that transformers have factory bonded neutrals (37 years I've never seen one) so that don't bother with the SBJ. It's a basic lack of understanding as to how the system works. For some reason where I work sparkies love bonding bushings but can't seem to get the rest of it right.

 

[hillbilly1]

The most common un-bonded transformers I’ve seen, is the panel for computers. They see “isolated ground” on the prints, and think it’s not supposed to be bonded!

 

[ActionDave]

.... For some reason where I work sparkies love bonding bushings but can't seem to get the rest of it right.

That's not unique to your area. I find them on both ends of the secondary conduit and then no bonding jumper. It's not all the time, but frequent enough that I'm not surprised by it.

 

[infinity]

That's not unique to your area. I find them on both ends of the secondary conduit and then no bonding jumper. It's not all the time, but frequent enough that I'm not surprised by it.

I've asked many electricans why they install them and they say "inspectors want to see them". I then ask based on what and they shrug their shoulders just saying that they're "required", which we all know they are not.

 

[Steve16]

I am much too frequently amazed how little electricians in the field understand about grounding a transformer.
I often find grounds from Building steel , the water main and other perfectly good grounding sources on lugs
bolted to the case of the transformer without a single connection to XO. I found a building that had a live ceiling grid.
(the steel studs had to be live also)
The transformer has no grounding connection to XO so when a sheet rocker or ceiling grid person drilled a screw through the MC cable and hit a phase wire everything connected to the steel was live. This was not a new building. It was likely this way for many years. (Cheshire Connecticut)

I recently found another where a transformer installed at a college to boost 208V to 280/277V for the long runs to light poles down a long driveway and parking lot.
No ground to the common! What could possibly go wrong ????? We repaired the 15 year old problem...

EdF

Inspectors should consider asking to see transformer connections.
It takes time but would be worthwhile

Frustrated!!!

Unfortunately in Connecticut a licensed building official is required to have 0 electrical experience. They just have to be able to answer 15-20 pretty easy questions in the NEC. There are some that put the time and work into learning it, but many just don't care enough. I also beleive that the majority of transformers installed are done so without a permit.

As to the bonding bushings... many guys I've spoken with trying to explain where they are required or not required just do not get it. But theres also nothing wrong with exceeding the code