|>| What makes you think that its up to you to chose? The utility
|>| company is going to tell you what is available. The elevator company is
|>| going to tell you what they need, as well. As usual, you're playing
|>| another of your long winded, and useless games of 'What if'...
| I think that logically, the process goes something like this.
| 1. The architect or building contractor responsible for the
| electrical system needs to research the utility tariffs and policies
| and determine what services are available.
| 2. Further research may be necessary to see what services are
| available at the specific location of the building under construction.
| This may be different then #1.
| 3. Given the available choices, it is up to the person designing the
| electrical system within the building the most economical and useful
| service, given the specific needs of the building (elevators, HVAC,
| pumps, machine shop tools, etc.) That is, should it be 120/208,
| 120/240, volt single phase or three phase, open wye, or closed-delta,
| #3 is the most interesting and the most difficult, apparently, from
| the comments offered on this thread. It doesn't seem that there are
| any carved-in-stone rules for what is best, only tradeoffs and
| different opinions.
| Have I got this right?
Basically, yes. One point is that to choose 120/240 when the building size
(in terms of load) is above the point where three phase is required means a
greater cost. Unlike single homes, such developments, even if residential
in nature, are treated like commercial, at least up to the point where the
tenant metering takes place. So the developer has to pay most or all of the
electrical service installation costs. Since traditional 208Y/120 is lower
in cost (one stock transformer, one entrance disconnect), it may well be
the one chosen. It can cost more to then get special appliances for each
unit to operate at 208 volts. Or, as appears to be the case quite often,
the developer just passes the cost on to the owner(s) or tenants in the
form of poorly chosen appliances, or leaving it up to condo buyers to find
the 208 volt appliances, or suffer with 240 volt appliances. The fact that
so many cases are decided in bad ways does not mean better choices are not
available; they just cost a little more.
I do know some apartment buildings are large enough to have transformers
on each floor. I was in one building many years ago that had 8 units on
each of 12 floors. There was a transformer on each floor, and metering
for each tenant was in a small room on the same floor. The meter room did
not have the transformer. That would certainly be essential of the feed
was at distribution voltage (I don't know what it was in that building as
I did not actually inspect the rooms). I do know it had 208 volts to each
unit, and specially bought 208 volt appliances. But they could have just
done this with a single phase transformer on each floor and saved on the
cost of appliances but getting normal 240 volt ones. In this case, it
would not have been any more expensive, and it would have been at least
as well balanced across the distribution phases as the existing setup.
Any needs for three phase power could have been satisfied with a separate
three phase transformer at the top or bottom of the building. It would
have to be separately metered, anyway.
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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