CT can inside home

Well, not being an old timer nor an electrician, I’ve not seen this before. I consulted with my local “sparky” and his opinion was to have the local utility relocate to the exterior. My report stated that the utility is responsible for the transformer and the utility rep said the owner/seller is responsible for the can. I recommended that box be moved outside utility said they probably would not unless paid to do so. I asked them about their liability, considering that it is at floor level and easily accessible to kids, etc. The response was a sticker stating that the components were the property of the Public Utility District, NO locks on box. I feel like this is ultimately between the seller and the utility, however, my basic concern is safety. Any advise or opinions would be highly appreciated.




I see no problems, save for the fact that a CT can is supposed to have a seal tag, lead seal, or a padlock provided by the utility.

The only problem I have with it is how EASY it was to get into it…I would consider it a liability if I had small kids in the house…they need to figure out a way to seal it up…

But alas…it is POCO’s and well…we could not do alot about it anyway so all is good…just note that it should be sealed to prevent children and young adults wanting to end life quickly from getting into it.

I would call this a 230.70(A)(1) violation but I run on the stricter side of this ambiguous language.

It looks like there is an unnecessary amount of unprotected service equipment inside the building before you get to the service disconnect.
This is a judgement call so other inspectors will have other opinions.

I have never seen CT Cabinets inside a home before and believe they should be at the exterior near the meter and usually are sealed by the Public Utilities for that area.

I have found this to reiforce that statement, which is in Colorado Springs,

And yet another that agrees in the same way.

It might be prudent to check with the requirements of the local jurisdiction of that particular area you are in at the time.

I can not imagine they would allow this in most places. But that is just my opinion.

Marcel :slight_smile: :slight_smile:

Thank you, again you’ve shown your professional attitude in offering help to those of us with less experience. You guys rock.

You need to get out more. :mrgreen:

There is no general prohibition against indoor CT cans, save for POCO rules. For every POCO that required them outdoors, there’s one that will permit them indoors. Matter of fact, most larger indoor switchgear has the CT can (called CT section) built into the switchgear at the factory.

There is no hazard in the photo, other than the lack of sealing.

Pop quiz…

Homes that have a 200 amp CT can indoors, where they could have had traditional across the line metering equipment, normally also have the phone NID (demarc), and CATV splitters mounted indoors also. Why do you suppose that is? I know the answer, but I’m just encouraging a little expanded thinking…

I do go out once in awhile Mark. :slight_smile:

And you are right, they do allow them indoors as you said, like this photo;

But this is not the standard for Residential and far from it.

They even have monitoring systems integegral also like this.

All I am saying is that different Utilities will prohibit interior CT cabinet installations, so it would be wise to check with that first before one inserts foot in month. :mrgreen:

Marcel :slight_smile: :smiley:

I agree, but when you consider that the utility both provides and wires the actual CT, it would be safe to assume that this was a permitted installation during its time.

Agree ,it was approved by someone on the original timeline.

But this is being inspected for a client and the client needs to be made aware of this installation, for any extensive repair that might occurr in the future, there might be a possibility of an upgrade to the electrical system an this portion there/of might have to be re-installed to more current standards and compliance to the local Authorities.


Marcel :slight_smile:

I didn’t realize you guys did that. I thought the present requirements were generally poo-poo’d. Seems like different inspectors have reminded me here many times that you’re only concerned if it’s safe or not. Perhaps you’re talking about the value-added service that many inspectors provide, that being the “head’s up” on what might have to happen if the equipment requires replacement?

Could someone explain without acronyms what this CT (spelled out) is. In the south I have not seen one at least not what the picture shows in the first post. What does it do what are the concerns?


A CT stands for “current transformer”, also known as “doughnuts” for slang. The CT in the picture is the round black thing that says “200” on it (that’s the amp rating). It’s just another way of measuring the electricity usage. The CT has little wires that connect to the meter outdoors that tell it how much electricity has flowed through the actual CT, to put it in simple terms. These are used on services above 400 amps in size normally, since a regular “across the line meter” (such as you would normally find for a dwelling) would be prohibitively large. Matter of fact, across the line meters for greater than 400 amps just don’t really exist, so large services are CT metered. The service conductors run through the center of the CT.

You’ll find indoor CT cans for 200 amp services in some homes where security was a prime concern. These are typically homes originally constructed for people like congressmen, company CEO’s, CIA agents, and so fourth. The service conductors arrive from underground, directly from the padmount transformer. The service conductors run through the CT, and right to the panel’s main. The metering conductors are just little wee conductors run to the meter outdoors. This prevents future ne’er do wells from pulling the meter to put the place in the dark, since the service conductors don’t even appear at the meter.

Wow…that hurts! :smiley:

Indoor CT cans are the norm here. I have one in my house. I have never found one that was not sealed, and I would call it out if I did.

Let me add one more item related to the CT’s

there is one golden rules with CT’s is never open the CT’s lead while it is under the load.

if you open the CT’s leads what will happend it they will build up insane amout of voltage and can blow the CT’s myself i did see few blow up by either careless or corroded connections ]

Merci , Marc


It is probably a good idea to make an even broader statement…if you can help it refrain from opening ANY connection like that with a load being drawn on it if you help it. Opening contacts with a large amp draw for example can cause one heck of an arc…bussman fuses has a nice video on that…I will see if I can find it.

Paul :

I do agree with your statement.

but let you know that i allready see some pretty good arc flashover while disconnecting well loaded system espcally true with Meduim voltage system i work on 4160- 7200 volt system from time to time ]
the last arc flash when i was disconnecting a 150 amp Med voltage fuse that arc can jump much as 2 -4 feet after breaking it open.

Yes i did remember seeing the veido from Bussman fuse co.

Prettty nasty one i did see

Merci , Marc

P.S. Paul i am well verised with both USA and France electrical codes just let you know head up with this

I don’t doubt it at all Marc…but I can promise you I am ONLY well versed in the NEC…lol