fire on a job site

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tenite

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was called out for a trouble call for a project at Nasa they had a fire in a AC unit first thing I found was a auto transformer 480 input hooked up to H1 and H4, H2 and H3 were not connected the transformer was on fire at some point duct detectors did work and shut down the unit, my question is what voltage would you get out the secondary of this transformer with the primary wired like this
 
tenite said:
was called out for a trouble call for a project at Nasa they had a fire in a AC unit first thing I found was a auto transformer 480 input hooked up to H1 and H4, H2 and H3 were not connected the transformer was on fire at some point duct detectors did work and shut down the unit, my question is what voltage would you get out the secondary of this transformer with the primary wired like this
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Were H2 and H3 connected to each other?

What is the primary voltage rating?

What is the secondary voltage rating?
 
tenite said:
H2 and H3 were not connected 480 volt primary 120 sec.
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Then as far as I know there would be two windings open on the primary, no current would flow, and there would be 0 volts on the secondary.

As you mentioned it was an auto-transformer, what secondary lead was connected to which primary lead?
 
On those type of transformers it will work, usually it has multiple tap points on the primary, a common, then a 208 volt tap, 240 volt tap, and then a 480 volt tap. The transformers that you are thinking of have two seperate windings which are connected differently. Was the unit actually run on 208 volt? If so, that is probably what burnt the transformer up. You did not say whether this was a new or exsisting installation.
 
tenite said:
H2 and H3 were not connected 480 volt primary 120 sec.
Click to expand...

Is this the transformer for the optional convience outlet? If so then I'm with the others about it not working at all, because it is usually a larger standard step down type of transformer. Most package A/C units (but not all) use 24 volt ac controls which commonly have the multi tap step down transformer around 40-100 va.
 
It doesn't sound like an autotranformer and it shouldn't work at all without H2 and H3 not connected. H2 and H3 should have been connected together for a 480 volt input.

If H2 and H3 were not connected, the transformer couldn't be the cause of the fire.
 
I've never hooked one up that way, so I wouldn't swear on a stack of bibles that there would be zero voltage - but I wouldn't expect there to be.
 
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