Step Down Circuit Breaker

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Old 05-12-20, 05:00 PM
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Step Down Circuit Breaker

In California.
A county inspector visited and chatted with us about how to install our solar panel monitoring system, among other topics. Each panel has a micro-inverter and the monitor unit chats with them via the power lines. That means that the monitor unit is connected to 240 power. But,…, the monitor unit draws a lot less than one amp. It has a screw down terminal strip for the power connection. That strip is sized for something like 18 gauge wire. Keeping this short: I will be mounting the monitor in a box with a DIN rail. The wire from the panel will be 15 amp wire, 14 gauge. It will go to a pair of DIN mount circuits breakers maybe one amp. The protected side of the breaker will be the 18 gauge wire to the monitor box.

I just checked, there are a whole bunch of DIN rail circuit breakers. More types than I imagined. The first one I looked at states Hydraulic Delay. Nah, don’t need that. But I do think I need a two pole breaker so the monitor will be completely cut off from power when the breaker is thrown.

When I go to Digikey, for example, what should I look for in a circuit breaker?

Then again, maybe DIN not required. Just bolt it to the enclosure. Might that be acceptable?

Thank you for your time and patience.
 
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Old 05-12-20, 11:18 PM
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I didn't have a chance to dig too deep but I didn't see any two pole breakers at Digikey.
Probably going to have to use DIN mount.
I did see them at Mouser. First link. Reasonably priced.
Eaton breakers are good but may be too expensive.

Look for the pdf product descriptions in both links.

Mouser - Phoenix Contact breakers
Eaton DIN mount breakers.
 
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Old 05-13-20, 07:28 AM
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Mouser and Eaton. And nothing special for the breakers.
Thank you for your time.
 
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Old 05-14-20, 08:04 AM
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1 amp double pole, B curve, 35 mm DIN

amp double pole, C or D curve, 35 mm DIN

The monitor is about 8 x 5 inches in size. It is barely warm to the touch. amp at 240 is about 100 watts. It is nowhere near hot enough for 100 watts. This is a small box of electronics. It appears to have a switching power supply as is not large enough for a power input transformer.

But, the smallest B curve for two pole is 1 amp. As I understand my reading about the curves, did not know about these curves until now, C and D will not break until much higher currents. Because of that I suspect the 1 amp B curve will be better than the amp C curve.

What is your opinion?
 
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Old 05-14-20, 07:41 PM
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I see in the product spec for the Eaton circuit breakers there is a section that states the mounting position is vertical. That can be taken several ways. The throw switch (right term?) must be facing up, against gravity. Or maybe the longest side id vertical and the throw switch moves up and down. Would that require up = on and down = off? I would prefer the long side be horizontal and the throw switch move left and right.
Do I need to be concerned with this?
 
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Old 05-14-20, 08:23 PM
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I think either would be fine. Your not really concerned with any type of protection for the device. You just want to protect the wiring going to them and to limit that max available current. Those units will be internally protected. Anywhere from 1A to 5A would be plenty of protection.

I see it says vertical mounting. That would mean the handle goes up and down. That's the typical way I see them used. I've never seen them mounted horizontally. Would have to contact tech services to see what the issue is with that.
 
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Old 05-14-20, 09:26 PM
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I went with Mouser, better selection on circuit breakers. Selected an enclosure that is a bit larger than really needed, but a standard size, 12 x 12, x 4. With that I can mount the circuit breakers properly.
Thank you for your time and patience.
 
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Old 05-14-20, 09:28 PM
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Your welcome. Stop back if you need further help.
 
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Old 05-28-20, 06:16 PM
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I have completed the project of installing the solar panel monitor in my garage. It connects to an ethernet switch, then to a remote wireless box. It continuously chats up the manufacturer who sends monthly reports. I do have a question about the circuit breaker. I was very careful to select a 1 amp breaker. When I look at the breaker, there is no clear indicator as to its current rating. I see the text FAX-B1/2 and presume that means 1 amp two pole. But that is not what I call definitive. I am adding a picture of the top and side. What do you think?

Well. When I try to add a picture, the dialog demands a URL. The path to the file is not accepted. Dropping a an image on the picture dialog does not work. I will try the attachment tool. That appears to work, but only one image allowed. Lets see where this goes.
Edit: when I view this the path to the file on my hard drive is shown. When I try to edit, it is not shown.
 
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Old 05-28-20, 06:19 PM
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From what I detect, I am only allowed one image. Ok, maybe two. See what happens when I save

 
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Old 05-28-20, 06:50 PM
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You have to click on the "Go Advanced" editor" at the bottom of the reply box and then click on the paper clip. You can post up to your attachment limit of 10mb's.
How-to-insert-pictures.

Good job. The only other thing you could have done would be to have taped the white wire a different color.... like red to show that the wire is not neutral. Breaker is 1A.

Here's the link to your breaker
 
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Old 05-29-20, 07:51 AM
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Thanks for the check on the breaker. I feel like the current should be clearly shown on the breaker when installed.
In my rather limited experience, for a 240 volt circuit, the white has always been a hot wire. When it goes through a breaker that is a not subtle indicator that it is hot. Am I incorrect on that point.
 
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Old 05-29-20, 09:39 AM
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for a 240 volt circuit, the white has always been a hot wire. When it goes through a breaker that is a not subtle indicator that it is hot.
Definitely not. You must at least mark the ends black or red, or a few other, NON-WHITE, color.

And, please use green or yellow/green bonding wires inside that box; to the DIN or the metal subplate, as one example. Many places want that door bonded too.
 
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Old 05-29-20, 10:26 AM
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When you are dealing with a house electrical panel ...... it is understood that all the breaker are hot.... Seeing a white wire in that location being used for 240v is normal. (excluding GFI/AFCI breakers)

In your application..... a quick look could give the impression that the neutral and hot are breaker protected.

The box is grounded. The device is connected to that ground point. The DIN rail looks to be screwed into the box so that is ok. The door needs to be bonded if it's removable.
 
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Old 05-29-20, 03:09 PM
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PJmax,
Thank you for your comments.
Now that you mentioned the GFI/AFCI breakers, I am adding some instant how water heaters, 240 volt, 40 amp. Since they are "water" heaters, I decided to go with GFI. The cable I installed is 8 gauge two conductor with ground. The wires inside are black, white, un-insulated ground. Does the white need to be marked with a red label or something to indicate it is a hot wire?

Wow, GFI breaker at 40 amp is quite expensive.
 
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Old 05-29-20, 06:40 PM
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Yes..... remarking the white is an excellent idea.
Many people don't have colored tape so black is ok too.

240v instant hot water heaters are not required to be GFI protected.


 
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Old 05-30-20, 06:19 PM
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Ok, I will mark with some black electrical tape.
I see your comment that these heaters don't need GFI. The county inspector said that also. However, when mixing water with that level of power, I do feel better about having a GFI installed.
Thank you for your time.
 
 

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