ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
UL 508A SPACING
by ale348 - 03/29/24 01:09 AM
Increasing demand factors in residential
by tortuga - 03/28/24 05:57 PM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
1 members (Scott35), 369 guests, and 17 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#92238 03/10/05 09:20 AM
Joined: Oct 2003
Posts: 259
J
Joey D Offline OP
Member
I have a walk in cooler I wired, needed a 3phase 20 amp line to the compressor, draws 12 amps, and it needed a 20 240v line to the fan coil unit. The fan coil unit draws 3.3 when the fans are on and 12.5 when the defrost coil is on.
The refridge guy was questioning my bill as he thinks 1 circuit would have done it all. Now I know the compressor draw and the fan draw would not overload the breaker but taping of the 3 phase line for single phase sounded odd to me and something I would never think to do. He says they do it all the time and most electricians don't know how to wire the refridgeration stuff. Anyone have input on this? Thanks.

Stay up to Code with the Latest NEC:


>> 2023 NEC & Related Reference & Exam Prep
2023 NEC & Related Reference & Study Guides

Pass Your Exam the FIRST TIME with the Latest NEC & Exam Prep

>> 2020 NEC & Related Reference & Study Guides
 

#92239 03/10/05 12:07 PM
Joined: Dec 2002
Posts: 337
S
Member
Maybe I do things wrong also, for I am with you. I tend to look at the 50% rule (NEC 2005 210.23), but that only applies to not fastened in place equipment. Based on 440.34 I feel their method is allowed though I do not do it that way. Sometimes I note that I do not do things the cheapest or the best.

I would be interested to know if someone else could show that the single circuit method were not allowed, but right now I don't see it.

P.S. Buffalo him by telling him that refrigeration equipment confuses the electrons in single circuits. The cold ones from the fan unit run into the hot ones from the compressor and they just end up bouncing back and forth with a period of 16.7 milliseconds (60 Hz), creating a changing magnetic field.

#92240 03/10/05 01:24 PM
Joined: Apr 2004
Posts: 156
R
Member
Most electric defrost fan coil units are designed so that the heaters will not operate when the compressor is on. The defrost time clock will open, de-energizing the liquid line solenoid. The compressor will pump down and when it's contactor opens an auxiliary contact will close allowing the heaters to work. After defrost is over the compressor starts up again but there is usually a fan delay to keep the fans from coming on until the coil is frosted.

If the system is designed like this the defrost load and the comp/fan load will not be energized at the same time.

The main disconnect would be sized for the combined comp/fan load and would handle the resistive load without a problem.

If I knew how to do it I would post a generic version of the way my company does it.

#92241 03/10/05 04:31 PM
Joined: Oct 2003
Posts: 259
J
Joey D Offline OP
Member
rad74ss is correct. The total operating load is OK. My only concern was taping the 3 phase for a single phase power use.

#92242 03/10/05 04:38 PM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
Joey, lots of equipment has a single phase load on the 3p inputs. It was very common in the computer biz


Greg Fretwell
#92243 03/12/05 06:02 PM
Joined: Apr 2001
Posts: 507
G
Member
Joey,
I have wired many coolers/freezers and I do them the same way you did.

I think that you should stick with the bill you submitted. You may not get any more work from them but that happens, not much you can do about it.


Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5