I am working on a project which requires a 480 / 277 volt sub panel. Due to voltage drop we are using 600 mcm thwn wire. The 400 amp breaker (feeding the sub panel is a Sq d I line series) has a maximum wire lug size for 500 mcm. Is it code compliant to splice the 600 to 500 for termination to the breaker, or is there another solution?
Wire too big for breaker (roy g)
- Thread starter roy g
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- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
The splice is code compliant. Just locate it where you do not have any fill factor problems.
- Occupation
- Licensed Electrician
It is okay to splice on a smaller piece of wire.
Why does a 400A breaker only allow up to 500 MCM?
Why does a 400A breaker only allow up to 500 MCM?
- Location
- Massachusetts
My guess is it accepts up to two 500s per phase
I would look at the breaker to see of other lug kits are available.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
You could use a crimp on adapter like this in the correct size:
https://www.platt.com/platt-electri...luminum/Ilsco/ACM-350/product.aspx?zpid=29088
https://www.platt.com/platt-electri...luminum/Ilsco/ACM-350/product.aspx?zpid=29088
mjc763
Member
- Location
- Minneapolis Minnesota
I think they have been around for awhile, I web then used in a sweet of gear that was at least 20 years old. I have never used them though, I always wondered if they make a good connection to the beaker since its a solid piece is aluminum vs the wire stands that smash into shape when torqued.
qcroanoke
Sometimes I don't know if I'm the boxer or the bag
- Location
- Roanoke, VA.
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- Sorta retired........
I agree.
kwired
Electron manager
- Location
- NE Nebraska
If it is similar alloy as the lug they will expand and contract at same rate won't they?
Nom Deplume
Senior Member
- Location
- USA
I would try the Greaves reducing adapters.
www.greaves-usa.com%2Fpdf%2FReduceR%2520Color%2520Sheet.pdf
www.greaves-usa.com%2Fpdf%2FReduceR%2520Color%2520Sheet.pdf
- Occupation
- Licensed Electrician
That makes sense and leads to a better solution than splicing on smaller wires.
- Location
- Massachusetts
As an electrician in the US I could not do that without the parts being a listed accessory for that breaker ....... or the AHJ approving it which would be doubtful.
This was part of a contract between us as manufacturers and the end user of the equipment.
To that extent, it is a private transaction and an agreed contract between supplier and end user in their works only with no third party involved or any member of the public being affected.
Who would be the authority having jurisdiction on such a matter? Would there actually be one?
Listed accessories?
Are you saying that copper bus bars connected to the inputs and outputs of a breaker would have to be listed?
Would you really consider them as accessories?
I just don't know.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
If the listing information for the contactor showed only a range of wire sizes for the terminals or if some of the original hardware had to be removed to attach the bus bar, then I can see at least a technical violation.
If the finished assembly containing the modified parts was required to be in some way NRTL validated, I could see that setup passing a field inspection handily.
If the finished assembly containing the modified parts was required to be in some way NRTL validated, I could see that setup passing a field inspection handily.
- Location
- Massachusetts
Which an AHJ could cite me on.
When I have had jobs that required switchgear modifications we have either used the manufacturers parts or used a custom panel board or switch gear company to provide the parts and more importantly the engineering.
Maybe, but an inspector is not likely going to take my word for it.
What is the SCCR of that set up?
Are the bus bars sufficiently braced?
An electrician cannot typically answer those questions about their own modifications.
I have no issue at all with Besoeker's picture, I am just pointing out that things are different for electricians compared to manufacturers.
kwired
Electron manager
- Location
- NE Nebraska
I think most of what Besoeker builds would be listed if he were doing similar work in the US. He would probably be a UL 508? panel shop or something along that line.
electricalist
Senior Member
- Location
- dallas tx
We have crimp tool for that. I think it was pricey. More than a few hundred.
I had to crimp 3/0 to fit 100 amp breaker. The tool crimped a cone shape 3/4 of the way into the wire. Be carefull that theres enough spacing for the crimps to be side by side going into the breaker
I had to crimp 3/0 to fit 100 amp breaker. The tool crimped a cone shape 3/4 of the way into the wire. Be carefull that theres enough spacing for the crimps to be side by side going into the breaker
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
The OP said his breaker was I-Line construction, therefore the limiting factor will be the wire bending space. The offered 'reducers' will most assuredly also have space issues.
The breaker normally has field changeable lugs that accept 600kcmil, and can also be connected to bussing, but none of these options fit into I-Line panels. Surprisingly(?) a larger frame size (e.g. 1200A with 400A trip) would have 600kcmil as an available option in I-line construction.
The breaker normally has field changeable lugs that accept 600kcmil, and can also be connected to bussing, but none of these options fit into I-Line panels. Surprisingly(?) a larger frame size (e.g. 1200A with 400A trip) would have 600kcmil as an available option in I-line construction.
kwired
Electron manager
- Location
- NE Nebraska
Bending space would be a limiting factor to what NEC would let you install, will not change what size lugs are in the breaker used.
The lugs will depend on what breaker is used, there is more then one 400 amp breaker. Just some fairly common examples from the catalog would include the LA/LH series with lugs accepting 1 -600 or 2 - 250's or the LC/LI (which is a 600 amp frame) accepts 2 -500's
At the bottom of the chart is a note telling you to go to a different page for optional lugs, which unfortunately I think sent me to wrong page, but I believe it is sending you to same options as there is for the general use L series breakers you just have the plug on bus end for I line that is not changeable the other end is same as other L series - or for within any other series for that matter.
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