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Old 04-08-2012, 10:12   #1
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Digital volt-amp meter with amp sense question

Lately doing a lot of electrical items on the old boat, shows volts and amps.
A few questions.

IF I put 2 hot wires inside the sense ring it show the sum of the amps flowing in both wires?

IF the 2 hots are on different phases does it show the sum of the amps flowing in both wires?

IF the hot and neutral are inside the ring, does it read zero amps unless there is a current leak?

Idea is if it can monitor amps on a twin 30 system.

Digital AC 300V 100A Blue Lcd Dual Panel Volt Amp Combo Meter +CT 110v 220v 240v | eBay

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Old 04-08-2012, 10:17   #2
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Re: Digital volt-amp meter with amp sense question

Have you considered trying Google to find the actual instruction manual. Otherwise, we're all just guessing.
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Old 04-08-2012, 10:42   #3
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Re: Digital volt-amp meter with amp sense question

I think you'll want to add a double pole switch and a second sense ring to monitor the two 30 amp services. In theory putting the two hot wires from each service will give you to sum of both, if they are both the same phase. But it will not tell you your pulling 29 amps on one and 2 amps on the other.
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Old 04-08-2012, 11:15   #4
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Re: Digital volt-amp meter with amp sense question

A Twin 30A Installation (240V or 120/240V 3W) will require 2 CT’s.

Current Transformer Installation:

120 volt: 1 hot and 1 neutral - Requires 1 CT, installed around the L1 hot wire (or wires if parallel conductors used).

120/240 volt: 2 hots and 1 neutral - Requires 2 Cts installed around the L1 & L2 hot wires

3-phase 3-wire: 3 hots - Requires 2 CTs, around any 2 of the hots.

3-phase 4-wire: 3 hots and 1 neutral, Requires 3 Cts, around each of 3 hots (L1, L2, & L3).

CTs are usually marked with a symbol (arrow) or label, which indicates the correct mechanical orientation of the CT on the conductor being measured. Find the arrow or label “THIS SIDE TOWARD SOURCE” on the CT and install the CT with the label facing toward the current source, or arrow pointing to load.
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Old 04-08-2012, 18:18   #5
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Re: Digital volt-amp meter with amp sense question

I know two would be better. The idea is to get a general sense of how many amps are flowing. I can turn things on and write down what they use.

The twin hots if they are ever hooked up, my slip has only one small plug, will be different phases, how does that affect it?

I watched a video where if you take a clamp ammeter and put it around the entire cable, it will zero out the reading unless some of the current leaks out and takes another path back to its source. Which is one way of telling if your leaking current into the water.

I thought about a switch to select another shore line.
But where would you get another sense ring coil, wind your own? Find one out of a solenoid? The gauge also has some possibilities like leakage current detection, so more sense rings and switches needed, gets rather complex.

Anyway what your saying is perhaps each wire could have its own sense ring and then connect all of them to the gauge to read all or a switch to read separately. I see no point in having multiple gauges cluttering up the space.

If they were all connected at once to the display gauge, would they be wired parallel or in series?
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Old 04-08-2012, 19:15   #6
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Re: Digital volt-amp meter with amp sense question

Really does not work well with all connected to one meter. Sort of works if same phase on the hots, but really no idea if the reading is meaningful. Why you need separate sense rings or CT's. Trying that with different phases just will not work at all.

A electric supply house might have a CT that's compatible. Could experiment with wire and number of turns and see if you get the same reading with the homebrew one as the one that came with it. Then you would have two....
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