> On Aug 26, 2015, at 3:16 PM, Jay Jaeger <cu...@charter.net> wrote:
>
> On 8/26/2015 8:19 AM, Paul Koning wrote:
>>
>> I heard of this sort of thing happening to the DEC building at Marlboro.
>> Supposedly it had two mains entrances, served from different power lines
>> (and different companies? Seems odd). One of the machine rooms had feeds
>> from both ends, and one particular system was fed from both. What happened
>> is that the "grounds" were offset enough, and with enough of a current
>> supply, that the ground strap that's supposed to connect the row of RP06
>> drives melted.
>>
>> This sort of thing is a major electric code violation: you can certainly
>> have multiple services, but all the grounds are required to be connected by
>> substantial wire; you're not allowed to stick ground rods in at multiple
>> places and leave it at that. (The same goes for lightning rods.)
>>
>> paul
>>
>
> Quite possibly two different phases, and if so, the would be 90 degrees
> out of phase with each other.
90? Three phase power is 120 degrees apart, center-tapped "two phase" home
power is 180 degrees, but I don't know of any power company service that
produces 90 degree shifts.
In any case, RP06s use three phase power. The issue wasn't the power in this
particular story, but rather the ground wire (the green "protective ground"
that isn't supposed to carry current at all under normal operation).
paul
