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Author Topic: Low Voltage Concern  (Read 484 times)

Mark Hannah

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Re: Low Voltage Concern
« Reply #10 on: June 05, 2018, 08:00:12 am »

My guess is that this is an older venue.  460 used to be common-used to even see motors rated at 440 VAC (not in my day-but in motors made back when stuff was made to last decades not years-so I've seen a few-a lot of old prints show nominal 440 or 460 supplies).  The POCO has no incentive to swap out the transformer-just an added expense for something that is already working. That's why I think the voltage issue is a mismatch with a 480-208/120 transformer being fed with 460 nominal.

There is not enough info to tell where the voltage drop is coming from.  A loaded/unloaded measurement on both the incoming service and the 120 v supply would be needed to diagnose that.

It is not an older venue.  The stage is part of a residential/commercial development near a large convention center (opened 2008).  I would share the location but I do not know if the site would be sensitive to such information.  Particularly if I ultimately find it easier to share the whole thread with them rather than compile the advice all of you have shared.

I believe the "local" panel has a higher load on it than it should.  The panel is not labeled.  I am 98.6% certain that the large, outdoor video wall, directly above and behind the stage, is off the panel.

I have no site plan so I cannot provide any details on how far the transformer is from the panel.

Between the 2015 & 2016 summer seasons, I worked with the property management to get mini-cams installed which has made our life much easier.  This allowed us to not climb down into a hot, damp service hole where the breaker panel is.  The site is next to a river, the "hole" is below grade and thus has a sump pump. 

Unfortunately, the email chain is archived in Outlook PST files.  It is on my to-do list to dust of the files and see if there might be additional & helpful information.

Other that getting a queasy feeling as voltage drops are you experiencing any failures or other issues?  I get shit from some touring personnel at one of our venues, particuarly in the summer when the grid is powering a whole bunch of air conditioning and the voltage drops.  They seem to think there is something we can do to make the PoCo flog the little rodents that turn the generators and raise the voltage but the reality is that on site, day of show, we can't do anything.


No failures or damage experienced so far.  There could be accumulative/long term damage that I would never be able to connect to working at this venue.
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Mike Sokol

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Re: Low Voltage Concern
« Reply #11 on: June 05, 2018, 08:05:25 am »

This is illuminating (no pun intended) as I'd never heard of nominal 460v service from a utility company. 
I'm with Swaffer - either there is undersized service wiring, the transformer isn't tapped in the right spot to deliver nominal 120/208v or 120/240v to the secondary, or both.

...a boost transformer, as suggested by TJ, is probably your best option.

I tend to agree with this explanation. I've installed Buck and Boost transformers many times in both my industrial jobs as well as my worship venue jobs. We used them in warehouses to drop 277 volts down to 240 volts for lighting (in buck mode), or increase 208 volts up to 240 volts (in boost mode). Exact same transformer, but to change from buck to boost you just reverse the output winding to be either in or out of phase with the primary feed. Since they're not carrying the full load, just the full current times the small voltage difference they're adding or subtracting from the main feed, they're much smaller and cheaper than what you need for a full isolation transformer carrying the full KVA of the entire load.

Don't expect residential electricians to know what they are. But any good industrial electrician should have experience with Buck and Boost Transformers and know how to install them.
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Mike Sokol
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