MULTIPLE FAN MOTORS ON ONE CONTACTOR

[ronmarx]

I HAVE A WAREHOUSE PROJECT WITH 20-5HP, 480V VENT FANS. SHORT OF BUYING 20 STARTERS, CAN I USE ONE STARTER FOR 5 FANS AND ROUTE A COMMON FEEDER TO A POWER DISTRIBUTION BOX WITH FUSE BLOCKS/TIME DELAY FUSES FOR EACH MOTOR ? COST IS A FACTOR FOR THIS INSTALLATION. LOOKING FOR IDEAS.

 

[dpc]

As long as each motor has individual overload protection meeting the NEC, you can do what you're talking about. But do you really want all 5 fans starting and stopping at the same time? By the time you put in the overload protection, I'm not sure you'll be saving all that much.

I certainly wouldn't recommend it.

 

[waross]

Running multiple fans from one contactor is commonly done in lumber drying kilns. I have also seen it used in other multi-fan installations. It is well to check the starting KVA of the motors and size the contactor accordingly.
Five 5 HP. fans started together will usually have a greater starting current then one 25 HP. motor.
You may want to size the feeders at 125% of the total load rather than the sum of the currents plus 25% of the largest motor.
Does anyone know the NEC requirement for feeders for simultaneously starting motors?
respectfully

 

[dpc]

I don't think the NEC makes any distinction regarding number of motors started at once.

 

[BJC]

Check out a nearby switchyard or ohter place with a power transformer with cooling fans. Most of the time all the fans on one radiator will be connected to one contactor.

 

[jraef]

It's done all the time. No special NEC rules as long as you are going to fuse each circuit and provide individual OL relays. You may actually be able to fuse only the entire group circuit if you read all the exceptions and special conditions in the NEC.

A better method is to use devices that are very common in IEC countries called Motor Protective Switches (or any one of a dozen similar names). The are often sold in the US as Manual Motor Starters but they provide more functionality than a typical NEMA MMS. All of the big IEC suppliers offer them, and most are now UL listed for what is called "Group Fusing" applications. Each device would be on one motor circuit and provide the Short Circuit Protective Device (SCPD, replacing the fuses), Overload (OL) and Disconnect for each individual motor. They are much easier to mount and wire than all those fuse blocks and OL relays and provide you with a simple way to isolate motors that are down for maintenance while still running the others on that group.

http:/

http://www.jraef.com

Eng-Tips: Help for your job, not for your homework Read faq731-376