Motor Starters vs Motor contactors 2

[HarlanT]

Hello All,

I am trying to come up with a cost estimate for a client. In trying to save money, I am looking at using motor contactors instead of starters for all of the motors less than 5 hp. Will I be saving any money doing this? Is there any limitations/code violations with contactors that I should be aware of?

Harlan

 

[rbulsara]

Contactor alone is not a substitute for a starter as it does not have overload protection.

You need overload protection somewhere in the motor branch circuit. It could be in the starter or in the motor or built in the branch overcurrent protection device.

 

[dpc]

A starter is simply a contactor plus an overload device. So, yes, you would save money and yes, you would likely be violating the NEC.

 

[jraef]

Jeez, the hazards of having electrical engineering work performed by non-EEs....

Kudos HarlanT for not going ahead without asking someone! You would have likely started fires and or damaged equipment, not exactly a "cost saving" measure.

There are methods of doing small motor control systems like that in more cost effective ways than the traditional methods of large NEMA motor starters if that's what you were thinking, such as "group fusing" installations using IEC contactors and Motor Protection Switches, but it's not to be done without proper engineering by someone who truly understands the concept.

 

[waross]

You could probably use dual element fuses for motor protection and go with contactors. By the time you buy the dual element fuses, and fuse holders and pay the labour to mount and wire everything it won't cost too much more than overload relays.
respectfully

 

[HarlanT]

The responses have been awesome thak you.

If I use a LCP with 20 amp fuses for each motor(less than or equal to 1hp), and the motors have motor overload protection and the contactors are rated for FLC, will that not be sufficient?

 

[rbulsara]

Harlon:
With all due respect, I think any further answers will make you even more dangerous. I would say hire or get help from a professional electrical engineer. Stick to what you do best.

 

[dpc]

Where is the motor overload protection being provided? All a contactor can do is start and stop the motor. It provides no protection.

With properly sized **individual** fuses for each motor, it's possible for the fuse to protect against overloads (at least according to the NEC).

But when you start trying to cut corners on motor protection, the NEC gets tricky to apply.

 

[itsmoked]

Besides fuses for small motors is an lousy way to save money. Unless replacing motors, and down time are not an issue.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Everybody is concerned with saving money. If you go out for bids, the contractor will plan on doing the job right the first time. Lost time and money on redoing inspection deficiencies will not make up for the money that short cuts may appear to save.
Well, you may just go ahead and do the job with no permits or inspections. Consider your possible liability when the insurance company voids the policy on the grounds of substandard and uninspected installations.
OHSHA may also jump on the wagon.

If I use a LCP with 20 amp fuses for each motor(less than or equal to 1hp), and the motors have motor overload protection and the contactors are rated for FLC, will that not be sufficient?

Are these three phase motors at 480 volts or single phase motors at 120 volts. Believe it or not, it does make a difference to the proper fuse size.
You have the benefit here of perhaps several hundreds of years of combined experience. If saving money by forgetting overload relays was a good idea, many of us would have been doing it for years. Many of us have repaired and corrected other peoples substandard installations after the smoke cleared.
Just bite the bullet and do it properly.
yours

 

[HarlanT]

Thanks all for your contributions.

I have decided that for all 120/220 VAC motors thate are rated less than or equal to 1 hp I will go with the lightning panel/contactor/integral motor protection(with nameplate). This meets all necessary CEC codes standards

All other motors 480VAC will be fed from the MCC starters.

 

[waross]

Be sure to get competitive bids for the MCC even if you know which one you prefer.
If you already have an MCC installed and ask for additional sections, predatory pricing sets in.
I have seen the price for an MCC section drop from $20,000 to about $5000 when it was priced as a competitive unit rather than as an addition to existing switchgear.
My boss came to me with the original price and said we would have to cancel the project at that price.
I suggested getting competitive bids and letting the vendors know it was a competitive situation.
Boy, did I look good when the price dropped about $15,000.
respectfully

 

[jraef]

MCCs are like Desk Jet printers, they practically give them away just to get the future business. The rule-of-thumb is that if you need more than 2 starter "buckets", buy an entire MCC section full of buckets and call it a new project, you will pay less overall and have more spares for the future.