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Hi everyone,

I am fairly new to the field and trying to figure out a simple fact. Quite often, I am working in multi-residential buildings. These buildings typically have a switchgear with a nominal line voltage value of 208v or 600v (Ontario, Canada). As many of you know, within the switchgear are three phase bus bars to distribute the power.

My Question: As an example, let's say we are working at a wye-connected building with 347/600v. How is the individual 347v L-N bus bar converted to 120v at the residents plug level? Is there a step-down transformer for each phase or something? Also, is it only one phase feeding the whole buildings plug levels? or is the plug load distributed evenly between all three phases (Ex: Phase A feeds floors 1-10, Phase B feeds floors 11-19, Phase C feeds floors 20-25)

All answers would be greatly appreciated.

Thank you,
24V
 

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Master Electrician - Ontario
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There are many ways to accomplish this depending on the situation.

There could be one large transformer to stepdown the voltage for distribution or there could be several of them (remotely located in each floor / area).

Typically there would not be the parsing off of phases; each transformer would be fed with all three phases for equal distribution.

Cheers
John
 

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Around here;

Small residential property one large transformer

Large residential properties they run 480 delta out tomultiple electrical closets and transform there. Cheaper and easier to do due to lenghts of feeders.
 
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Usually you'll have a 600v to 208v transformer on every floor or on every other floor. You bring 600v 3phase 4 wire to the electrical room on some floor. There you can have a 600v/347v Panel or disconnects. You can have a 600v to 208v transformer in this area and now put a 208v/120v Panel. From this panel you could feed all the 120v outlets in the area.

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