100- or 200- Amps CT for 200 A service panel

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alexk
Posts: 2
Joined: Thu Apr 12, 2012 12:37 am

100- or 200- Amps CT for 200 A service panel

Post by alexk » Sun Apr 15, 2012 12:22 pm

I am trying to understand if installing 100 Amps CT on 200 A service panel in my house would be me appropriate. I assume it is more accurate on lower loads than 200 Amps CT (I am not sure if this is true though yet).

Here are my rough estimates based on some more assumptions.

Fact: The highest monthly average power is 4 kW.
Assumptions (I do not have any real data - need a PM for that :-) )
load unbalance = 50%
load factor = 50%

This yields the maximum expected current as:

4000 W / 240 V / 50 % / 50 % = 70 A

Diameter of wires on the main is 15 mm, which fits the SPLIT-100 CT spec (15.7 mm).

I guess there will be some spikes in the load. Thus here is the question: what happens to a SPLIT-100 CT if current exceed the nominal value?
Are my assumptions valid?

Thanks,
- alexk
ben
Site Admin
Posts: 4271
Joined: Fri Jun 04, 2010 9:39 am

Re: 100- or 200- Amps CT for 200 A service panel

Post by ben » Mon Apr 16, 2012 11:02 am

alexk wrote:I am trying to understand if installing 100 Amps CT on 200 A service panel in my house would be me appropriate. I assume it is more accurate on lower loads than 200 Amps CT (I am not sure if this is true though yet).

Here are my rough estimates based on some more assumptions.

Fact: The highest monthly average power is 4 kW.
Assumptions (I do not have any real data - need a PM for that :-) )
load unbalance = 50%
load factor = 50%

This yields the maximum expected current as:

4000 W / 240 V / 50 % / 50 % = 70 A

Diameter of wires on the main is 15 mm, which fits the SPLIT-100 CT spec (15.7 mm).

I guess there will be some spikes in the load. Thus here is the question: what happens to a SPLIT-100 CT if current exceed the nominal value?
Are my assumptions valid?

Thanks,
- alexk
All of our split CTs are around the same accuracy (within 1%). Most likely, your accuracy will be way off when it exceeds the nominal value.

I'll have to get someone to look at your math as I'm not too sure.
Ben
Brultech Research Inc.
E: ben(at)brultech.com
alexk
Posts: 2
Joined: Thu Apr 12, 2012 12:37 am

Re: 100- or 200- Amps CT for 200 A service panel

Post by alexk » Fri Apr 20, 2012 2:21 pm

1% for 100 Apms CT is 1 A, which becoms 2 A for 200-Amps CT.

I also suspect that going out of rated current range most likely result in much greater errors. I just wanted to confirm that as the spec diagrams do not show this data.

Thus I am staying with the SPLIT-200 CT option for now as it "is commonly used for monitoring 200A main panels" for a good reason I guess :-)

Alex
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