Soilid conductor - Electrician Talk - Professional Electrical Contractors Forum

brian john · 02-28-2009, 06:22 PM

We just completed a project in the Maryland State House utilizing 1/0 MI solid, shortly after completing I saw a install at the World Bank utilizing 4/0 MI solid.

I did a little checking and MI cable is made in sizes up to 500 kcmil solid.

I cannot imagine installing this.

http://www.tycothermal.com/assets/No...s1850-0102.pdf

jdsmith · 02-28-2009, 06:44 PM

What is the reason for solid MI like that rather than THHN or XHHW?

brian john · 02-28-2009, 06:45 PM

I do not know.

eddy current · 02-28-2009, 06:48 PM

Did a big generator job a while back. Two Mega watt gennerators. Each one fed the transfer switch with three sets of 3-350kcmil MI and one 3/0 MI banded together. 750 feet from main electrical room to the generators through three levels of parking garage.

It took us a long time and many dead blow hammers to get that stuff to bend and look good.

I was one of many on that job, still an apprentice at the time actually but I still work for the same shop so I''l see if I can get some pictures. It looked really impressive when we were done.

brian john · 02-28-2009, 07:00 PM

Quote:

Originally Posted by eddy current

Did a big generator job a while back. Two Mega watt gennerators. Each one fed the transfer switch with three sets of 3-350kcmil MI and one 3/0 MI banded together. 750 feet from main electrical room to the generators through three levels of parking garage.

It took us a long time and many dead blow hammers to get that stuff to bend and look good.

I was one of many on that job, still an apprentice at the time actually but I still work for the same shop so I''l see if I can get some pictures. It looked really impressive when we were done.

350 kcmil....Man that is work.

brian john · 02-28-2009, 07:01 PM

Megger the MI the minute you receive it, after initial installation, after forming it and just prior to energizing. Keep the ends sealed to prevent moisture intrusion

eddy current · 02-28-2009, 07:13 PM

I got to terminate one end of the MI and came home with a few small scraps. (The forman got most of it.) I still have a one foot piece of 3/0 that I stripped in the garage. It's so odd to see a condutor of that size solid.

MDShunk · 02-28-2009, 07:23 PM

I've run a good bit of solid bus bar overhead on wooden racks, but ne'er solid MI cable. I guess they figure it will last a minute or two longer in a fire?

eddy current · 02-28-2009, 07:35 PM

I remember a 3hr fire rating on the stuff we installed but I'm going to check on that.

2 Hour Fire Rated

Passed UL 2196. Tested to ASTM E-
119 time temperature curve reaching
1850°F at the end of two hours,
followed by hose stream, and
remaining operational at the
conclusion of the test.

william1978 · 02-28-2009, 07:39 PM

500 MCM MI cabel would be tough to install. I wouldn't want to have to install it for sure.

MDShunk · 02-28-2009, 07:40 PM

Yeah, MI in general has a pretty long fire rating. I just guessed that the solid might last a tad longer in a fire at full ampacity over stranded. I just pictured the strands burning away one by one.

nick · 02-28-2009, 07:59 PM

Well i maybe out of line but i think MI cable is a bad axx cable to fire its a self sealing inside kind of made of magnesium oxide which when high voltage is applied changes the material in a resistance kind of way like material atoms change and also temp or heat MQ expands in size the reason its conductor is solid is air internal tracking or air lock inside conductor stranding is bad!! solid is fail safe it does not leak air in a fire its jacket will burn but the cable will still pass current until its almost gone we used it in the navy lots of cable like MI its also a high pressure tested cable to impact extreme . MD you are most correct it does last long in a fire if theres one thing we learnd any cable in the navy was extreme fire rated . best to ya