How to determine CTs for your panel
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How to determine CTs for your panel
We've been getting a lot of requests for suggestions on CT setups. Below is a short guide to selecting CTs.
We have the following CTs:
Solid (Wire has to be removed, and CT needs to be slid over, relatively inexpensive)
- Micro 40 (Up to 40 Amps)
- Micro 80
- Micro 100
Split (CT can split apart and be clamped around the wire, but expensive)
- Split 60 (Up to 60 Amps)
- Split 100
- Split 200
- Split 400
Special Application:
- Split 170 (Bus bar)
All you have to do is look at each breaker and find its rating (usually labelled on the breaker switch), then choose a CT that is rated greater than or equal to the breakers rating.
If it's a 240V load, you need 2 CTs instead of 1.
Special consideration:
- for 240V loads with no neutral – you can get away with monitoring 1 side of the breaker and doubling the rating, if there’s a neutral, you must monitor both sides.
There are some circumstances where if you know a breaker isn't going to exceed a certain amperage, you can use a lower CT than it's rating.
The most common setup is a pair of Split 200s, or 100s, a small amount of Micro-80s, and a large amount of Micro-40s.
We have the following CTs:
Solid (Wire has to be removed, and CT needs to be slid over, relatively inexpensive)
- Micro 40 (Up to 40 Amps)
- Micro 80
- Micro 100
Split (CT can split apart and be clamped around the wire, but expensive)
- Split 60 (Up to 60 Amps)
- Split 100
- Split 200
- Split 400
Special Application:
- Split 170 (Bus bar)
All you have to do is look at each breaker and find its rating (usually labelled on the breaker switch), then choose a CT that is rated greater than or equal to the breakers rating.
If it's a 240V load, you need 2 CTs instead of 1.
Special consideration:
- for 240V loads with no neutral – you can get away with monitoring 1 side of the breaker and doubling the rating, if there’s a neutral, you must monitor both sides.
There are some circumstances where if you know a breaker isn't going to exceed a certain amperage, you can use a lower CT than it's rating.
The most common setup is a pair of Split 200s, or 100s, a small amount of Micro-80s, and a large amount of Micro-40s.
Ben
Brultech Research Inc.
E: ben(at)brultech.com
Brultech Research Inc.
E: ben(at)brultech.com
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Re: How to determine CTs for your panel
Excellent timing I'm talking with my electrician about moving my panel...
I'm in northern europe, (sweden) where we have 3 phase 240. My house has 3x25 amps incoming, in this case, I can go only for the Micro 40, right?
I'm waiting for the GEM, but will probably have to wire the panel before it arrives.
Micael
I'm in northern europe, (sweden) where we have 3 phase 240. My house has 3x25 amps incoming, in this case, I can go only for the Micro 40, right?
I'm waiting for the GEM, but will probably have to wire the panel before it arrives.
Micael
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Re: How to determine CTs for your panel
If it's anything like it is here (can't remove the mains once they're installed without intervention from the Power Company), you'll want to go with Split 60s on your mains.vespaman wrote:Excellent timing I'm talking with my electrician about moving my panel...
I'm in northern europe, (sweden) where we have 3 phase 240. My house has 3x25 amps incoming, in this case, I can go only for the Micro 40, right?
I'm waiting for the GEM, but will probably have to wire the panel before it arrives.
Micael
99% of the time, you'll be using splits on your mains.
Ben
Brultech Research Inc.
E: ben(at)brultech.com
Brultech Research Inc.
E: ben(at)brultech.com
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Re: How to determine CTs for your panel
I can access the incoming after the meter, so I figured that I'd put them there. Before the meter, we (well, atleast in my old house) it is very little space to reach the wires anyway, so no place for a CT there.
But maybe it is wise to put split 60 there anyway, just to be sure.
Thanks!
Micael
Edit: One thing came to mind, being 'micro', are the micro 40 classified for 400V isolation?
But maybe it is wise to put split 60 there anyway, just to be sure.
Thanks!
Micael
Edit: One thing came to mind, being 'micro', are the micro 40 classified for 400V isolation?
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Re: How to determine CTs for your panel
The Micro-40 leads are only rated at 300V, the Split 60 leads are up to 600V.vespaman wrote:I can access the incoming after the meter, so I figured that I'd put them there. Before the meter, we (well, atleast in my old house) it is very little space to reach the wires anyway, so no place for a CT there.
But maybe it is wise to put split 60 there anyway, just to be sure.
Thanks!
Micael
Edit: One thing came to mind, being 'micro', are the micro 40 classified for 400V isolation?
Ben
Ben
Brultech Research Inc.
E: ben(at)brultech.com
Brultech Research Inc.
E: ben(at)brultech.com
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Re: How to determine CTs for your panel
Aha!
Are all the 'Micro-xx' sharing the same leads? I'll have to check, but I think all CT needs 400 rating when installed in a 3-phase panel over here..
Thanks
Micael
Are all the 'Micro-xx' sharing the same leads? I'll have to check, but I think all CT needs 400 rating when installed in a 3-phase panel over here..
Thanks
Micael
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Re: How to determine CTs for your panel
Yeah, none of our Micros will work, you could put tubing over top of the leads.vespaman wrote:Aha!
Are all the 'Micro-xx' sharing the same leads? I'll have to check, but I think all CT needs 400 rating when installed in a 3-phase panel over here..
Thanks
Micael
Ben
Ben
Brultech Research Inc.
E: ben(at)brultech.com
Brultech Research Inc.
E: ben(at)brultech.com
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Re: How to determine CTs for your panel
How long can the CT leads be for the various devices? I have an application where I can place the GEM very near a large sub-panel where 95% of the circuits are located, but I want to also monitor three circuits that are 35 feet away. All power originates from one master panel.
thanks, -john-
thanks, -john-
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Re: How to determine CTs for your panel
We've had people successfully extend CT leads up to 100FT with CAT5.jloram wrote:How long can the CT leads be for the various devices? I have an application where I can place the GEM very near a large sub-panel where 95% of the circuits are located, but I want to also monitor three circuits that are 35 feet away. All power originates from one master panel.
thanks, -john-
Ben
Brultech Research Inc.
E: ben(at)brultech.com
Brultech Research Inc.
E: ben(at)brultech.com
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Re: How to determine CTs for your panel
Hello Ben,
About this:
===============
Special consideration:
- for 240V loads with no neutral – you can get away with monitoring 1 side of the breaker and doubling the rating,
===============
Do we have to double "manually" the rating, i.e. to remember that the Watts for this channel will need to be doubled, or is there a means in the software to apply automatically this x2 factor for the concerned channels before it is graphed ?
All electric baseboard heaters for example are 240V with no neutral, I intended to install a single CT on each.
I have received my GEM+Dashbox but did not install yet.
Brgds/Jerome
About this:
===============
Special consideration:
- for 240V loads with no neutral – you can get away with monitoring 1 side of the breaker and doubling the rating,
===============
Do we have to double "manually" the rating, i.e. to remember that the Watts for this channel will need to be doubled, or is there a means in the software to apply automatically this x2 factor for the concerned channels before it is graphed ?
All electric baseboard heaters for example are 240V with no neutral, I intended to install a single CT on each.
I have received my GEM+Dashbox but did not install yet.
Brgds/Jerome