stevephillips
Member
- Location
- knoxville tn
Was brought in on a job today, we were bidding to to the electric on a building (theater) that had an HVAC system that was horribly undersized. Each theater had its own system that simply could not keep up in the heat. Each system was wired 208 3ph?? (odd because the building feeder was 480) Additional systems were being installed to literally double the heating/cooling capacity. (yeah, it was that undersized) The way the building was built, there is an electrical room at the top of the steps on the roof that housed the distribution panels. The transformer that fed this was in the basement was a huge 300kva.
Engineers solution: Add another transformer, and feeder breaker to the main panel in the basement. (the main panel has ample capacity) Get a concrete cutting/drilling company in to make holes as needed for the conduit, build an addition to the building on the roof to put in another distribution panel. Basically double the existing installation.
My solution: Rewire all the HVAC units to 480 (these units were capable of this, not many Ive seen are) , wire all the new units to 480, change the 208 distribution equipment to 480 equipment, and remove the 300kva transformer. No concrete cutting, no new cable pulls, no new transformer and no new distribution panel. The old panel in the roof was big enough to house the 480 equipment with capacity for all the new AC units.
At first the engineer thought I was nuts. Said that THHN in rigid was only good for 225 volts...I asked several times, he was sure it was only good for 225 volts. Also said something to the effect that once cable is installed and used at one voltage, it cannot be used on another. I handed him my extra copy of 2011 and said, show me where it says this. (this was on Friday) Monday rolls around and he wants to do it my way. He re-planned everything over the weekend and work started Wednesday. I left for vacation Tuesday night so im not there to work the job.
So, anyone else ever run across a plan from an engineer that is plain stupid and more expensive that it needs to be?
Engineers solution: Add another transformer, and feeder breaker to the main panel in the basement. (the main panel has ample capacity) Get a concrete cutting/drilling company in to make holes as needed for the conduit, build an addition to the building on the roof to put in another distribution panel. Basically double the existing installation.
My solution: Rewire all the HVAC units to 480 (these units were capable of this, not many Ive seen are) , wire all the new units to 480, change the 208 distribution equipment to 480 equipment, and remove the 300kva transformer. No concrete cutting, no new cable pulls, no new transformer and no new distribution panel. The old panel in the roof was big enough to house the 480 equipment with capacity for all the new AC units.
At first the engineer thought I was nuts. Said that THHN in rigid was only good for 225 volts...I asked several times, he was sure it was only good for 225 volts. Also said something to the effect that once cable is installed and used at one voltage, it cannot be used on another. I handed him my extra copy of 2011 and said, show me where it says this. (this was on Friday) Monday rolls around and he wants to do it my way. He re-planned everything over the weekend and work started Wednesday. I left for vacation Tuesday night so im not there to work the job.
So, anyone else ever run across a plan from an engineer that is plain stupid and more expensive that it needs to be?
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