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 (ale348), 302 guests, and 14 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#129825 09/16/05 09:50 AM
Joined: Sep 2005
Posts: 2
T
Junior Member
Hi,
New to this forum.
I need help in showing a circuit diagram.
There is an exhaust fan in a hood over a convection oven. The exhaust fan motor needs to be circuited in such a way that the fan must run all the time as long as the oven is ON. In other words the oven and the fan motor are tied together thru a common switch.
The fan motor specs are: 208V, 60 HZ, 3phase, 1725 RPM, 1/2 Horsepower, Vol(CFM):1300.
Also what would the load of this fan motor in terms of KVA??
Thanks in advance.

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
 

#129826 09/16/05 10:01 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Welcome to ECN

This is tricker then it sounds as you should not be modifying the wiring in the convection oven. And the oven should probably not be controlled on a regular basis from an external switch. It may have electronics or built in cool down modes that will not like having the power killed like that.

My first thought is to use a current sensing switch installed in the branch circuit to the oven. When the oven is turned on the current sensing switch closes and starts the fan.

If this is commercial you may also want to provide an off delay for the fan of 15 - 30 minutes after the oven shuts down for a cool down period.

Sometimes we also have to provide proof of air flow before the oven can start that can be a problem also.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#129827 09/16/05 10:15 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Here is a current sensor that I mentioned.

[Linked Image from grainger.com]

You run one leg of the load you want to monitor through the hole in the unit, the trip point on this one is adjustable from 2 to 20 amps.

This is handy as it can ignore a few amps of control power but activate when the running load is on.

[This message has been edited by iwire (edited 09-16-2005).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#129828 09/16/05 11:24 AM
Joined: Sep 2005
Posts: 2
T
Junior Member
Thanks for the response.
But here is the situation. The electronics involved in oven is not at all a concern. The project is in the construction phase and the electrician is on the job. I need to provide him a circuit diagram just to show that the switch for the oven is directly hooked on to the fan motor. Can u draw a simple circuit showing 3 phase 208v coming to the oven and also going to the fan siting right above it. The main branch circuit is 20 Amps for a panel. Appreciate. And yes what would be the load of the fan motor, 1/2 HP?

#129829 09/18/05 03:00 PM
Joined: Jun 2004
Posts: 1,273
T
Member
Traineee you are in over your head.

Get a real electrician involved as soon as possible.

Your situation is not simple at all and would typically be drafted by a licensed electrical engineer and provided as a detail in the prints.


Tesla

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