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Old 15-07-2013, 20:35   #1
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Shunt Placement

Hello,

Correct me if I am wrong !!!

The placement of a shunt on a negative cable in different areas will provide different amp readings.

1 - If I have a shunt at the "House Bank" before the bus bar. That will allow monitoring for the entire house bank.

2 - If I place a shunt after the distribution bus bar, on a cable to a device. I will be able to monitor the amps of the single device.

3 - Thus I am able to monitor the amps for individual devices, as well as the entire house bank total accurately.

Basic Diagram is attached to show my meaning.

Thanks !

Alan
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Old 15-07-2013, 22:03   #2
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Re: Shunt Placement

There will be difficulties in accurately monitoring the current to the DC panel with this setup. The DC panel return is not the same as ship's ground in this drawing. Thus any device that draws DC power from the DC panel and connects the minus side directly to ship's ground will bypass the DC panel shunt and that device's current will not be monitored. It is really hard to keep any and all DC devices isolated from ship's ground.

Similarly the inverter DC minus terminal is not connected to ship's ground in your schematic. You may want to verify whether or not there are ABYC compliance issues with that aspect.
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Old 15-07-2013, 23:53   #3
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Re: Shunt Placement

generally all the loads coming from a house panel would also return to a neg bus at the house panel. so should be fine. shunts will also work on the pos line if this is a problem.

his inverter neg is fine. no idea what you are talking about. the inverter chassis ground would also be run to the 500amp neg bus.

I would remove the pos switch and 500a anl though and put them after the pos buss. both the inverter and house panel should have it's own switch and fuses. if the run from the battery to the pos bus is more then a few feet. then you can put a main fuse back in as well.
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Old 16-07-2013, 02:18   #4
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Re: Shunt Placement

Hello,

Thanks for the feedback !

1 - The DC panel and Inverter positive lines from the Bus Bar do have an ANL fuse for each. The large 500A and disconnect at the house bank are for safety.

2 - All circuits that are fed from the DC panel are connected to the negative at the DC Panel ONLY. There is only ONE path from the DC panel back to the main Bus Bar that is connected to the Ships Ground.

Alan
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Old 16-07-2013, 03:15   #5
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Re: Shunt Placement

Hello,

I have updated the diagram to provide a little more detail.

Thanks,

Alan
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Old 16-07-2013, 05:12   #6
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I think you will find there are numerous ways for current to sneak around the inverter and DC panel shunts. High side shunts for these will work better I would think. The battery shunt is fine as there is no way for current to bypass that shunt.
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Old 16-07-2013, 05:17   #7
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Quote:
Originally Posted by transmitterdan View Post
I think you will find there are numerous ways for current to sneak around the inverter and DC panel shunts. High side shunts for these will work better I would think. The battery shunt is fine as there is no way for current to bypass that shunt.
What is a "high side" shunt ?

Alan
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Old 16-07-2013, 05:28   #8
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Quote:
Originally Posted by Hkalan View Post

What is a "high side" shunt ?

Alan
It is a shunt placed in series with the fuse of the positive bus. But make sure the current meter is compatible with that arrangement. Some current meters will not work with the shunt in that location because it is less expensive to design the electronics by limiting the shunt to the negative path. Digital meters are available that will work with the shunt in either positive or negative side. For the DC panel metering that would be my choice. When installing be sure to follow the meter installation instructions about fusing the 2 meter wires connecting the shunt.

In my opinion I would not use the inverter shunt and meter. It is easy to compute the inverter draw by subtracting the DC panel current from the battery current.
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Old 16-07-2013, 08:33   #9
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Re: Shunt Placement

Hello,

I do have some matching DC shunts and digital meters that use AC to power the display.

The shunts and LCD digital panel meter (gauges) I have can be used on the (+) positive as well as the (-) negative of the DC side (the manufacturer has confirmed).

The shunts are 500 Amp 75mV, and the meters are 75mV to match.

Attached are a few images of the digital meters as well as the shunt.

Alan
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Old 16-07-2013, 12:22   #10
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As long as you can live with the AC power requirement these should work fine.
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