ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

ECN Shout Chat
Top Posters(30 Days)
Admin 16
Recent Posts
fuse rejectors
by gfretwell. 03/23/17 01:12 PM
Another Forum Update
by Admin. 03/22/17 03:04 PM
Dining room plugs
by watersparkfalls. 03/21/17 10:31 PM
TRUE POWER
by jraef. 03/21/17 09:13 PM
WEG CFW-11 Frequency Inverter
by jraef. 03/21/17 08:50 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
231,301 Are you busy
166,025 Re: Forum
160,511 Need opinion
Who's Online Now
0 registered members (), 53 guests, and 10 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#100324 - 11/10/06 10:36 AM Space Heater calculations  
WhiteRook  Offline
Member
Joined: Feb 2004
Posts: 48
Republic of Texas
I am looking at a job installing 4 electrical space heaters with fan forced air(hung in the red iron) in a 16000 sq ft unfinished strip mall. The units are 7.5 Kw. The house panel is 208/120 3-phase with 150A main. The spec sheet lists the units as drawing 27A for 208 3-phase. When I was figuring the load, 7500 divided by 360, I get 20.83A...am I correct in figuring the difference in amperage is for the fan portion? I believe the code states that fixed electric space heaters (Art. 424.3(B)are to be considered continuous loads. So would I need 35A breakers for this? And if I put the branch circuit wiring for 2 of these heaters in one conduit the derating for the 7 wires at 70% would mean that I would have to run #6??? If I put all four in one conduit from the panel to a pull box inside then @13 wires I would have to run #4??? This doesn't even take in to account voltage drop. So what do ya'll think, am I right or am I confused.


2017 / 2014 NEC & Related Books and Study Guides

#100325 - 11/10/06 04:12 PM Re: Space Heater calculations  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,057
Estero,Fl,usa
I get 6 wires (80%) and 12 (still 50%), you don't count the neutral where it only carries unbalanced current and you never count grounds for derating, only fill.


Greg Fretwell

#100326 - 11/10/06 07:14 PM Re: Space Heater calculations  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
I don't think there is a neutral Greg. Maybe he's running an EGC. In either case I agree with your numbers.


George Little


Member Spotlight
Samurai
Samurai
Fl.
Posts: 46
Joined: May 2007
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.013s Queries: 14 (0.003s) Memory: 0.7498 MB (Peak: 0.8726 MB) Zlib enabled. Server Time: 2017-03-24 10:16:15 UTC