Calling all electricians/general contractors - job cost question

[JEDI]

24 - 20 amp circuits in 1 - 3" conduit. Will need to use at least # 8 maybe # 6 awg in the 3". # 6 cost ~5 times as much as #12. The 12 inch box will not be near big enough for the reduction splices down to # 12 for the 1" pipe.

Another box will be installed near the panel to reduce the wire size down to # 12 to fit in a 20 amp breaker. The cost just tripled at least!

The only time I have ever done reduction splices like that is for voltage drop. Doing it for derating is to costly.

.

wha? 24 #8's in the 3" WHY?!
at most 24 #10s. but since it's dedicated circuits, why not #12s?

 

[Kneedragger]

* derating of conductors. After 3 current carrying conductors in a raceway you need to up the size of the wire.

 

[JEDI]

* derating of conductors. After 3 current carrying conductors in a raceway you need to up the size of the wire.

de-rating? I think i'll stick to romex

and why de-rate? heat?

 

[Kwatt]

de-rating? I think i'll stick to romex

and why de-rate? heat?

Yes

Putting 24 # 12's @ ~20 amps in a single conduit is called a heater. The insulation will melt off. After a few hours you will not be able to hold your hand on the pipe.

.

 

[natto fire]

de-rating? I think i'll stick to romex

and why de-rate? heat?

Most commercial spaces are framed in metal, and don't allow for romex. There is MC, which is almost as simple as romex, but doesn't look as "professional" as EMT/Rigid conduit in many applications.

eddy currents.

 

[Scarpozzi]

Your best bet is to spec out what you need to get done...then bid it out to the local electrical companies. It shouldn't take them but a few days to do the work, depending on who they have doing the job.

If you don't know what you need, call a company in for an estimate and have them look at what you're working with....then spec out what you need in writing. That way you can use their quote to more easily get additional quotes.

 

[Eli]

Thanks for all the advice guys, I really appreciate it! Good stuff in here.

It's starting to become obvious that I'm being a little too bold with my needs. I'm not going to spend 6k+ on this, at least not all at once.

I was going to give each workstation two circuits; one for the heat gun and one for the computers and other equipment. There are four stations. The fast charging/testing station as it is currently setup needs at least 5 individual circuits, hence the idea to put in 6. Each slow charging station(three) would get two circuits, and shipping needs a circuit. That's totally future proof.

But I could probably get away with two circuits at each of only two of the assembly stations, and one each at the others. If I move the test rig from 120V to 220V, I could come down to a single or couple of beefy 240V outlets instead of all of the individual 120's... probably the best way to go, but I'll have to purchase new power supplies which might wash out any cost savings anyway... hrm.

Lots to think about.

To be up and operational, we need a minimum of say... 6 or 8 circuits installed. There is service broken out in conduit already about 1/3rd of the way around the interior of the shop, but it's all 240V and 208V 3 phase. Maybe I will just have that done first while we work out the rest of it. I was just thinking it would be better to have it all done at once...

 

[Howard]

Thanks for all the advice guys, I really appreciate it! Good stuff in here.

It's starting to become obvious that I'm being a little too bold with my needs. I'm not going to spend 6k+ on this, at least not all at once.

I was going to give each workstation two circuits; one for the heat gun and one for the computers and other equipment. There are four stations. The fast charging/testing station as it is currently setup needs at least 5 individual circuits, hence the idea to put in 6. Each slow charging station(three) would get two circuits, and shipping needs a circuit. That's totally future proof.

But I could probably get away with two circuits at each of only two of the assembly stations, and one each at the others. If I move the test rig from 120V to 220V, I could come down to a single or couple of beefy 240V outlets instead of all of the individual 120's... probably the best way to go, but I'll have to purchase new power supplies which might wash out any cost savings anyway... hrm.

Lots to think about.

To be up and operational, we need a minimum of say... 6 or 8 circuits installed. There is service broken out in conduit already about 1/3rd of the way around the interior of the shop, but it's all 240V and 208V 3 phase. Maybe I will just have that done first while we work out the rest of it. I was just thinking it would be better to have it all done at once...

A plan view drawing really helps.