Convert corner ground delta service to 3 phase ungrounded delta servic

[electric73]

The existing old 600 amp, 240V 3 phase service is corner grounded delta. The main fusible service panelboard is rated for 1 phase (with two bus-verified after opening the switchboard). All the HVAC loads fed from this panel are 3 phase loads fed from 1 phase rated switchboard. This installation is not code compliant and now there is some proposed HVAC renovation work.

So, when I specify a new 3 phase service entrance rated switchboard, I am not sure whether to leave the service as corner ground delta or change it to 3 phase ungrounded delta.

Converting this to 3 phase 4 wire would be ideal but the owner doesn't have budget for that.

This is a bank building so there is no maintenance on-site.
Any suggestions; corner ground delta or ungrounded delta?

 

[waross]

Forget both. Use a four wire, center grounded delta. That will give you 240V Volt three phase, 120/240 Volt single phase and a good safe grounding system.
Use a three phase panel and one extra wire from the center tap of one of the 120/240 volt transformers.

Bill
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"Why not the best?"
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