compressor motor starter questions

[396foxRN]

I have the 7.5hp single phase baldor/quincy compressor setup now, and ready to wire it up. I am uncertain as to what all I need. I have a Schneider GV3P50 37-50A motor starter/circuit breaker (first two pics), a pressure switch, and an on/off switch. I figure that I need the LC1D50A contactor (pics 3 & 4) to go with it, but am not really sure what else from the catalog pics below (last 2 pics) that I need or don't need. Also, am unsure on which of the available coils to get with the contactor, as they seem to be offered in 12,24,115,230v setups.

So far, I have a 60A breaker, with 6ga wire into a 60A a/c disconnect and hardwired into the motor starter box.

Any help is greatly appreciated. Thanks!

 

[396foxRN]

pic retry....

 

[Bert_]

Compressor doesn't come with a starter?

Yes you need a contactor, 230v coil would be the easiest since that is the same voltage as the motor.

 

[wyliesdiesels]

Make sure whatever you buy, it has an overload relay.

and as said above 230v coil would be easiest

 

[Bert_]

Make sure whatever you buy, it has an overload relay.

and as said above 230v coil would be easiest

The manual motor protector pictured is a fine alternative for a overload relay.

 

[wyliesdiesels]

The manual motor protector pictured is a fine alternative for a overload relay.

Whoops

I wasnt paying attention

Thouht he had just a contactor.

yeah that will work

he just needs a contactor.

 

[wyliesdiesels]

OP according to this website, the coil you need is an U7 which is for 240v.

If you went with a low voltage coil, then you will need a control transformer.

https://www.imc-direct.com/product_p/lc1d50a.htm

 

[396foxRN]

OMG, the more I try to learn on this, the more confused I get. Elsewhere in the Schneider catalog, it has m7, p7, u7 as coil options for, respectively, 220v, 230v, 240v. Does it really matter? I thought 208v to 240v was generally considered the same. If not, how do I know which to get?

Thanks!

 

[Norcal]

OMG, the more I try to learn on this, the more confused I get. Elsewhere in the Schneider catalog, it has m7, p7, u7 as coil options for, respectively, 220v, 230v, 240v. Does it really matter? I thought 208v to 240v was generally considered the same. If not, how do I know which to get?

Thanks!

Use 240V, 208 & 240V are not the same.

 

[wyliesdiesels]

OMG, the more I try to learn on this, the more confused I get. Elsewhere in the Schneider catalog, it has m7, p7, u7 as coil options for, respectively, 220v, 230v, 240v. Does it really matter? I thought 208v to 240v was generally considered the same. If not, how do I know which to get?

Thanks!

not the same. not sure how that even makes sense

if you use a 240v coil on 208v, the contactor could chatter, and if reverse, could smoke it.

You need a U7 as i previously said

 

[396foxRN]

or, I assume I can just use the older/cheaper-to-buy Schneider model such as this, that shows 230v coil, and rated for single phase 7.5hp.

 

[396foxRN]

You need a U7 as i previously said

Not doubting you, I just want to understand this for myself.

 

[396foxRN]

Can someone lay out for me why there is a need to make separate 220/230/240v coils for a given contractor, and why you recommend the 240v? Again, wylie, I don't doubt you, I just want to understand WHAT I am doing rather than just doing it. And, thanks!

 

[yatg]

Match the coil to your line voltage for best results.
240 is used in mostly is the us/canada.
230 is used in most of the rest of the world.
220 is used in some countries that didn't get the message.
Schnieder is an international company and makes equipment for the world market.

 

[Norcal]

230V is the rated voltage for motors, and 240V is the supply voltage in the US and Canada, it is very common for a coil to be dual rated as 240 volts 60 hertz, and 220 volts 50 hertz.

 

[wyliesdiesels]

Can someone lay out for me why there is a need to make separate 220/230/240v coils for a given contractor, and why you recommend the 240v? Again, wylie, I don't doubt you, I just want to understand WHAT I am doing rather than just doing it. And, thanks!

yatg answered your question

The coil needs to be rated for your utilization voltage.

For you that's 240v

For people in another country, it may be 230v or 220v.

these contactors are used all over the world.

 

[wanderer]

yatg answered your question



The coil needs to be rated for your utilization voltage.



For you that's 240v



For people in another country, it may be 230v or 220v.



these contactors are used all over the world.

Umm...coil voltage is usually line to ground. That’s 120v, not 240.


Sent from my iPad using The Garage Journal mobile app

 

[Norcal]

Umm...coil voltage is usually line to ground. That’s 120v, not 240.


Sent from my iPad using The Garage Journal mobile app

Incorrect.

 

[Terry D]

Umm...coil voltage is usually line to ground. That’s 120v, not 240.


Sent from my iPad using The Garage Journal mobile app

Coils can be a variety of voltages

Sent from my SM-G960U using The Garage Journal mobile app

 

[wyliesdiesels]

Umm...coil voltage is usually line to ground. That’s 120v, not 240.


Sent from my iPad using The Garage Journal mobile app

Aww no

 

[wanderer]

It’s not incorrect because every magnetic starter I have happens to be this way. 120 V is also a very common control voltage used in all types of industrial machinery.

Regardless, he needs to use something available in the panel or use a transformer. Control voltage does not have to be the same as the voltage going through the contacts.

To your question about using 240 V… Of course it can be done but you would need to switch both L1 and L2 to provide power to the coil. Most momentary contactors are single pole single throw. That’s why I said 120 V. That’s when you get between L1 or L2 and neutral. The only alternative to a DPDT momentary switch is leaving control voltage powered to one side of the coil, which is bad practice.


Sent from my iPhone using The Garage Journal mobile app

 

[Norcal]

It’s not incorrect because every magnetic starter I have happens to be this way. 120 V is also a very common control voltage used in all types of industrial machinery.

Regardless, he needs to use something available in the panel or use a transformer. Control voltage does not have to be the same as the voltage going through the contacts.

To your question about using 240 V… Of course it can be done but you would need to switch both L1 and L2 to provide power to the coil. Most momentary contactors are single pole single throw. That’s why I said 120 V. That’s when you get between L1 or L2 and neutral. The only alternative to a DPDT momentary switch is leaving control voltage powered to one side of the coil, which is bad practice.


Sent from my iPhone using The Garage Journal mobile app

Normal and code compliant to only switch one leg of the coil.

 

[alfredeneuman]

Normal and code compliant to only switch one leg of the coil.

The ONLY places where all poles need to be switched are at the disconnect and circuit breaker

 

[Norcal]

The ONLY places where all poles need to be switched are at the disconnect and circuit breaker

Should have added that to my post but was too lazy.

 

[wyliesdiesels]

It’s not incorrect because every magnetic starter I have happens to be this way. 120 V is also a very common control voltage used in all types of industrial machinery.

Regardless, he needs to use something available in the panel or use a transformer. Control voltage does not have to be the same as the voltage going through the contacts.

To your question about using 240 V… Of course it can be done but you would need to switch both L1 and L2 to provide power to the coil. Most momentary contactors are single pole single throw. That’s why I said 120 V. That’s when you get between L1 or L2 and neutral. The only alternative to a DPDT momentary switch is leaving control voltage powered to one side of the coil, which is bad practice.


Sent from my iPhone using The Garage Journal mobile app

you said usually and thats incorrect. Ive worked on lots and lots of motor starters that had either a 240v or 480v coil.

Usually is not correct.

Also you do not need to switch both legs of the coil. not sure where you came up with that but its not required.

 

[wanderer]

you said usually and thats incorrect. Ive worked on lots and lots of motor starters that had either a 240v or 480v coil.

Usually is not correct.

Also you do not need to switch both legs of the coil. not sure where you came up with that but its not required.

I don’t want to get into what the term usually means, but it has been the standard in industrial control systems for years. Sure, there are other things out there. I just don’t usually see them.

 

[alfredeneuman]

Also you do not need to switch both legs of the coil. not sure where you came up with that but its not required.

None of the control contacts in the motor starter itself switch both legs of the coil.