If you can do that, why do you say:
Are the demand readings from the customer only on an aggregate basis, not per line? If only on an aggregate basis, for an open delta, how do you use demand readings to tell the required relative size of the single phase (lighting) and 3 phase (power) pots?
I meant when you said you dont look at reports much until peak months. is that peak ambient temperature or because almost everyone's usage is highest?
Well they are for calculating the maximum load that can go on the power phase (A-B) and the lighting phase ( A-C ) when a known load is on the open phase B-C.
Good point I'd need to set up a data logger.
Okay but how do you know if you can add the 6kw load in the example other than tossing a coin?
Given the numbers in your example, you can only add the 6 kVA load without nominally overloading one of the transformers if you figure out which phase is open. Then you can put the 6 kVA on the power pot. Or move the 9.6 kVA load on the open phase to the power pot to free up capacity on the lighting pot to enable you to put the 6 kVA on either pot.
Isn't your suggestion of moving loads from one transformer to another the same as what the utility company wants you to do - balance your loading?
Not in the context of my previous post and for the usual meaning of balancing.
This way you are using two separate single-phase transformers that are divided across a 3-phase feeder. You are not using an open-delta configuration to feed 3-phase loading.
Okay, sure, for a new installation, you wouldn't generally choose an open delta if you only have single phase loads.
I thought the point of this thread was for a PI to require identification of a specific phase conductor.
I thought that was the premise of the entire thread?
Oh wait, that was another open delta thread where the question was asked about fully loading the two transformers with single phase loads.
I think… these open delta threads are hard to distinguish one from the other at this point..
Not one conductor, but two conductors. The conductors forming the "open phase" of the open delta. Although for the usual case of high-leg open deltas, one of them is already identified as the orange high-leg.
Agreed, not 3-phase loads, but single phase loads. The goal is to allow future installers to easily identify the open phase of an open delta supply so they can avoid adding L-L single phase loads across that phase.
I don't see any discussion that is a side track to the OP.
Yes, but this thread is an outgrowth of that thread, it's basically the same topic. In order to be able to fully and efficiently load the two transformers with single phase loads (or to load whatever capacity remains after accounting for the true 3 phase loads), you need to be able to identify which pair of line conductors form the "open phase."
