Author Topic: 240 VAC versus 120 VAC  (Read 2343 times)

ottsm

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240 VAC versus 120 VAC
« on: October 13, 2012, 06:09:34 AM »
I know that the 120 VAC hookup gives a stronger signal, but, is there an advantage to hooking up to 240 VAC.  Is it possible this would increase the accuracy of the wattage reading by knowing both voltages for each phase?
My MTU and TED gateway are within a few feet of each other because my ethernet router is mounted next to my power panel.  Noise doesn't seem to be a problem and I don't have any MTU skips except the two that always happen on startup. 
Probably not worth messing with now that I've already got it installed on the 120 VAC but it's one of those things that is in the back of my mind, after all, why did they bother adding the extra wire?

RussellH

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Re: 240 VAC versus 120 VAC
« Reply #1 on: October 13, 2012, 10:50:36 PM »
I know that the 120 VAC hookup gives a stronger signal, but, is there an advantage to hooking up to 240 VAC.  Is it possible this would increase the accuracy of the wattage reading by knowing both voltages for each phase?

The TED doesn't know which voltage goes with which clamp.  I think all you'd gain by going to 240 is that instead of taking a single 120V reading and assuming it's the same for the other, you'd be taking the 240V reading and assuming that each phase is half.  IOW, the 240V setup does a average of the two phases.  Either way, you're assuming the two phases are the same, so the upshot is - no real difference.

ottsm

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Re: 240 VAC versus 120 VAC
« Reply #2 on: October 14, 2012, 08:19:41 AM »
That does make sense, most of the large loads are going to be on both phases so the single phase should see an equal or average drop.  The large loads, such as a bathroom heater that's just on one phase and that MTU isn't on that phase is the one I was thinking about.  But you are correct, they don't keep track of which CT goes with a particular phase.
Thanks, at least now I'm not dwelling on the thought of getting back into the panel to hook up the other wire.