Best way to run four 3 phase fans?

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milemaker13

Senior Member
Location
Suburbs of Chicago
Hi,
I have been asked to design a control circuit for a ventalation system at my plant. The system will have 2 identical intake fans(4.8a @ 480, 3hp), 4 identical circulation fans(1.5a @ 480, 1/2hp) and one exhaust fan(7.6a @ 480, 5hp). I have seperate starters for the intake fans, and a VFD for the exhaust fan, but my question is about the 4 circulation fans.

These are just simple wall mounted fans moving ambiant air across a room. They do not have any thermal motor protection built in. All 4 of these fans will come on together.

Is there anyway to get away from buying 4 seperate motor starters in order to reduce cost? I have thought of using a single contactor and 4 seperate overload blocks, but it really isn't much cheaper than just using 4 starters. Can I use a contactor and 4 seperate fuse blocks? Would a single VFD be able to handle 4 fans in some way? Any thoughts or ideas would be great. Otherwise, we will just go ahead with 4 seperate starters. Thanks-
 
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milemaker13

Senior Member
Location
Suburbs of Chicago
Right. There may be several ways to actually start the 4 motors, but they still all need indivual run protection. So no matter what we do, we still must incorperate 4 seperate sets of motor overloads. Thank you.
 
bob

bob

Senior Member
Location
Alabama
Those are small motors. I think you should be able to start all 4 at the same time. Do you think
this is a problem? I do not see the need for a VSD just to start them. If you need control then
that is another problem.
 
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T.M.Haja Sahib

Guest
milemaker13 said:
Right. There may be several ways to actually start the 4 motors, but they still all need indivual run protection. So no matter what we do, we still must incorperate 4 seperate sets of motor overloads. Thank you.
Click to expand...

If they overload protection is inbuilt in each motor under consideration,you need not provide them separately..........
 
Joethemechanic

Joethemechanic

Senior Member
Location
Hazleton Pa
Occupation
Electro-Mechanical Technician. Industrial machinery
I think he should tell whoever bought the fans to take them back and get thermally protected ones.

Why is it somebody always buys the equipment before they talk to the electrician/EE
 
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topgone

Senior Member
Joethemechanic said:
I think he should tell whoever bought the fans to take them back and get thermally protected ones.

Why is it somebody always buys the equipment before they talk to the electrician/EE
Click to expand...

Maybe because we charge them so high? Or they think they can do it DIY?
 
T

T.M.Haja Sahib

Guest
Joethemechanic said:
I think he should tell whoever bought the fans to take them back and get thermally protected ones.

Why is it somebody always buys the equipment before they talk to the electrician/EE
Click to expand...
One problem is single phase motors do have inbuilt thermal protection,while three phase motors do not usually have them.Know any such makes?
 
Joethemechanic

Joethemechanic

Senior Member
Location
Hazleton Pa
Occupation
Electro-Mechanical Technician. Industrial machinery
T.M.Haja Sahib said:
One problem is single phase motors do have inbuilt thermal protection,while three phase motors do not usually have them.Know any such makes?
Click to expand...

I've only seen 2 or 3 thermally protected 3 phase motors in my life. All were fractional HP and 3600 RPM machines
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
You can buy an IEC contactor and 4 overloads for around $100. just spend the money and get it over with. you probably spent $100 just writing this post and reading the responses.
 
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milemaker13

Senior Member
Location
Suburbs of Chicago
OK, well we have in stock 4 indivual magnetic starters. So I plan to use 1 disconnect to feed all 4 starters. All I need to buy is new overload heaters.

Any opinions on using 1 disconnect? I know that I should not put 4 wires into one lug (although it is done all around this factory already). Should I mount a J-box under the disconnect in order to splice these 4 starters in? Any cleaner way?
 
C

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
We use AB IEC contactors for most of what we do, so we buy feeder buss that links all the contactors together with only one set of wires to feed it.

But for older stuff that doesn't use feeder buss, we'll use a distribution block and split the circuits out that way. Don't forget you need OCPD before hitting each starter. Din rail mount breaker, fingersafe fuseholder, manual motor protector, etc
 
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milemaker13

Senior Member
Location
Suburbs of Chicago
Do I really need to add OCPD before each starter?
The single disconnect will be fused at 10 amps.
All of the wire will be #12.
And all of this will be mounted next to each other on the wall, within 10 feet.

I don't see any danger to the wire from overcurrent....
 
kwired

kwired

Electron manager
Location
NE Nebraska
milemaker13 said:
OK, well we have in stock 4 indivual magnetic starters. So I plan to use 1 disconnect to feed all 4 starters. All I need to buy is new overload heaters.

Any opinions on using 1 disconnect? I know that I should not put 4 wires into one lug (although it is done all around this factory already). Should I mount a J-box under the disconnect in order to splice these 4 starters in? Any cleaner way?
Click to expand...

What brand is the starter. Most smaller sizes do accept two conductors on the line and load terminals.
 
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milemaker13

Senior Member
Location
Suburbs of Chicago
These 4 starters are cutler hammer. And these are all mounted in their seperate enclosures, not open starters in a common panel. I have a plan to feed two sets of wires from the disconnect, feeding 2 starters, then jump from those two starters to the next two. Only two wires under any one lug.
 
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