ECN Forum Forums General Topics of the Trade General Discussion Area wires in conduit and derate

I agree the code teaches derating, but in real world practice I have seen many ignore it. I mean you would have to run multiple conduits for simple things like wall outlets ect. Matter of fact in code class many working electricains were just as shocked as I was by how much you must derate. Looking backwards at that point I saw several projects not derated admittley out of my own ignorance, the wire fill for conduit is useless when you cross it with the derating table, your wires are rated down so much long before the fill is reached (when dealing with smaller conductors #14-10#).
That said on any future designs I will derate for safetys sake!, but I to tryed explaining this to my boss and it was just easyer to run 2" emt and stuff it full. Sorry guys but thats what happened and does happen. Like I say I now know better.

Also running seperate conduit for control wiring is like pulling teeth.

Not for industrial use, matter o fact it's common. If your replying to my comments, we were running from a control room not a box. Also, I never saw an inspector in industrial except OSHA.

I agree with Redsy and Resistor. I too work in an industrial setting and we tape wires in bundles to avoid rat's nests but cut the tape before it enters the conduit(right at the mouth of the conduit). I also have never seen an inspector on an industrial maintennance job only the boss who knows less aboout electrical work than my 18 year old daughter!! We have to run the low voltage (120 volts or less) in a seperate conduit from the high voltage (480 volt 3 phase)wiring.

Thanks SCOTT,
guys tell me if I'M wrong here but what i think is the conduit fill tells you that yes you may stick 36 # 10 wires in an 1 1/2 " emt it does not say that you can use them at full amp load so that is why you derate them
if those # 10 wires were running 500 foot and only pulling 2 or 3 amps then it says you can stick all 36 in there now if u are not sure about the amperage then the derate table tells you how many amps you can safely put to each wire takes out the guessing of you over heating the wiring am using these numbers as examples only dont have book at hand.
Have worked in 3 locations where an inspector showed up now in 2 of the 3 locations 2 of the inspectors mostly turned their head on most items but one was tougher than a boot and he would tell you " I may be wrong by code but until a judge tells me I'M wrong you either do it my way or you stop work "
AS for running mixed voltages in the same conduit I know it is legal but it is just something I do not do and have taught guys that have worked for me to not do it and if the case arises where they have to at least run BOY for the 277-480 and red black and blue for 120 240 also white for the 120/240 and gray for 277/480

When I talk about control wiring I mean, from thermostat to relays and so on, I know its good to put them in a seperate conduit yet..., I work commercail, radio, tv, broadcast stations, better yet run the suckers in the open much quicker if below 60 volts throw them across that false ceiling. Strap them to the outside on the emt along with the cat 5 ! Ha Ha Ha.
Ive seen 2" emt stuffed with 30 wires no derating.
Like I say the fill tables are a joke, if you derate why would you fill that conduit up? You would not. Run 10 3/4" pipes instead that way you can have 3-6 wires in a stick. Ha Ha would'nt that look nice. And remember you can not use conduit to support conduit! Those 10 pipes be hanging all over the place!

Little off the wall tonight but you get the idea, about what a shock these derating tables are.

[This message has been edited by Jim W (edited 07-20-2001).]

I don't know all the details of your project, but with the over whelming number of branch circuits in one conduit, it might be time to consider running a feeder to a distribution panel located central to your loads. Bring the overcurrent devices closer to the loads being served.

STU,
now did u read all of the post on here these guys dont even know what derating is and now u want to suggesrt they run a feeder and add a panel YOU do want me to be hung from a light pole dont you HA HA ,
I made all kinds of suggestions to these two fine outstanding gentlemen and got no where with them,but can you imigine if they put a feeder and panel over there then we would be running a 100 wires out of there before they were done ,they really think that the closer to the panel and the bigger the conduit the more wires they can stick in