emt hours
- Thread starter normbac
- Start date
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yep #12 two wires 277v going to hang 99 high bay fluorescent fixtures on 10ft of jack chain figured 7 circuits
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
I'd like to add a day (now 4) to my initial estimate. I'm assuming 3 men per day. 3*8*4= 96
(I hope I'm not too optimistic).
thats for conduit only? Thanks for reply
Thanks
first time with this amount of fixtures running 277v from elec rm up 30ft and down across truss cieling 200 ft to light a 180 x 250 area figured 99 T5 ho fixtures hang from ceiling 10 ft with jack chain whip mc from j box off the 9 rows of emt
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hardworkingstiff
Senior Member
- Location
- Wilmington, NC
Yes, conduit only. It's all about the planning.
All circuits will have there own neutral? That would be 14 ccc. Or are we talking 2 MWBC and 1 individual branch circuit? That would be 10 current carrying conductors. Neutrals count 310.15 B 4 c
With only 1 home run pipe you will need to increase wire size up from #12.
310.15 B 2 a 10 ccc. Or 2 home runs. Assuming 16 amps on each circuit.
10 ccc #12 = 15 amps.
I believe if you just install #10 wires in the one 1 inch home run pipe you would be fine. I would think you would need to up size wires for voltage drop anyway.
How far away will the furthest 230 ft row be from the OCPD in the panel?
If 200 ft away with a 16 amp load 2 x 12.9 x 16 x 200 / CM #12 6530 = 12.64 VD. 277 x 3% = 8.3 Volts allowed. # 12 is too small.
Or find needed wire size CM = 2 x 12.9 x 200 x 16 / 8.3 = 9946 CM #10
2 = single phase (three phase system but single phase load.)
12.9 = K value for copper
200 = distance
16 = current on circuit (Assumed load on each circuit.)
8.3 = voltage drop allowed 277 x 3%
This math is only for the home runs. Does not include the length for the rows of lights. Just to show why I don't believe the #12 wire would be large enough. More info would be needed to do the complete circuit VD calculation.
21019 A 1 FPN 4. I know FPN's are not enforceable but this is a good rule. You wouldn't want premature failure or lamps and ballasts due to under voltage.
Please correct me if I missed something.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Presuming 3-ph power, I'd suggest nine circuits with 11 fixtures per.
14 x 7 = 98, but 11 x 9 = 99.
MWBC's will help reduce voltage drop, too.
home run will be #10 furthest row 11x280ballast watts*277=11.1a was going to increase fixture count per circuit as they got closer to cb but I
will use #10 wire as you suggested no headaches later fixtures are 120-277v
Thanks again I would not have put that many hours on it and of course got burnt that is why I asked dipping into commercial slowly a lot more codes to study after work what fun resi is slow so gotta survive
Keep in mind once you go over 9 ccc in a raceway with #12 THHN you can no longer terminate those wires on a 20 amp OCPD.
after research not comfortable with 12 will use 10cu
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
Thanks again I would not have put that many hours on it and of course got burnt that is why I asked dipping into commercial slowly a lot more codes to study after work what fun resi is slow so gotta survive
Let me share something with you that I learned the hard way. Running a conduit straight can be difficult if you just pull a constant dimension off of a piece of steel, the steel can/will have a wave in it and your conduit will look bad. Pull a string from point to point and use the string as your straight line, it will be worth the few minutes putting up the string.
Have you decided how you are going to locate the box for the light fixture?
Don't cheap out on the lift. 2 lifts with a man in each plus a ground man and you might just fly through this thing. You'll probably need the 2 lifts to pull the wire. Do you get to install the fixtures immediately or do you have to wait?
Good luck and let us know how it works out.
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