What size mag starter for compressor.

[Crank1]

I'm not 100% certain on these electrical things. But I recently purchased a used Champion compressor and want to purchase a new mag starter for it. It has a 5 hp Dayton motor on it, which draws 23.5 amps, single phase.

It looks to me that a NEMA class 1 mag starter is required. Is this correct? Anything wrong with getting one bigger than my application? As in a NEMA 2 or will it have adverse affects? Which brands are good? I am scoping a few Square D units.

Also, I keep reading about these heaters installed on the starters, these are rated to the amperage on the motor? So I need to make sure I get a mag starter that still has parts available or are pretty much all these heaters interchangeable?

All help is appreciated. Thanks

 

[metaldad]

dont have my chart with me at this time.
going up in size is not an issue, as long as the CORRECT size overloads will fit.
overloads are rated on heat/amperage draw. the size that is correct for a size 1 for your application may not be correct for a size 2. usually within a brand, the heaters are interchangeable.
square d is a popular brand.

 

[Underdog]

Ck's this company, Presume 5hp 1phase. Have to buy a "heater" for it. Sure they can size it for you.
http://williamsonneelectric.com/siemensmagneticstarterws5-2301pforbaldormotors.aspx

 

[Crank1]

Metaldad- So what you are saying is that even if I got a size 0 or 00 instead of a 1, but put the correct overloads in it, it wouldn't matter? Are the overloads or heaters, the same thing?

Here is the chart I was using to try to figure out what size NEMA I needed: http://www.southlandelectric.com/Square D Magnetic Starters and Contactors.htm

It looks like I can pick up a size 0 for considerably less than I can a size 1, then just change the overloads?

 

[W-Cummins]

Metaldad- So what you are saying is that even if I got a size 0 or 00 instead of a 1, but put the correct overloads in it, it wouldn't matter? Are the overloads or heaters, the same thing?

Here is the chart I was using to try to figure out what size NEMA I needed: http://www.southlandelectric.com/Square%20D%20Magnetic%20Starters%20and%20Contactors.htm

It looks like I can pick up a size 0 for considerably less than I can a size 1, then just change the overloads?

No you can not use a smaller sized starter and have it meet code. You will find that your need a NEMA size 2 starter or if you can find a rated for single phase operation a NEMA size 1 1/2

Here is a link to another discussion about this

http://www.garagejournal.com/forum/showthread.php?p=2144186#post2144186

and here is an excerpt from the above link about starters

Quote:
<table cellpadding="6" cellspacing="0" width="100%" border="0"><tbody><tr><td class="alt2" style="border:1px inset"> Originally Posted by BMS
See, there is the problem. And by the problem, I mean MY problem. Not really understanding motor starters anyway, I thought they were phase specific. I'll have to look up how it would be wired for a 1-phase motor.

I also have no clue what "heaters" are. Again, back to the not understanding motor starters.
</td></tr></tbody></table>
Well....... ok I will try

A Motor starter is a switch, that is actuated ( in the non-manual style like yours) by an electromagnet (this part is called a contactor) with motor over current protection device connected to its output. There are several types of over current protectors that can be used to make a starter, but in your case, the starter uses a mechanical overload. This device uses "heaters" these are the bimetallic "strips" ( in your case they are bent like a "V") that you can see screwed to the bottom block of your starter. They are sold in different amperages ( for the different current requirements of your specific motor) and when they get hot from a too large current flowing through them, they bend tripping the overload, this will cause the contactor to disconnect the motor from the incoming power.

3 phase VS single phase
A 3 phase starter, has 3 poles to switch all three legs of the incoming power, where as a single phase starter at 230V switches 2 poles at a time. So it's not a problem (physically) to run a 3 phase starter on a single phase system, as it has enough poles. Of course the manufacture of the 3 phase starter may not test or rate it for use on single phase. I didn't find any single phase "Rating" for your 1 3/4 size starter, when I looked, and of course that doesn't mean that there is not one. If that single phase rating is important to you, you should delve further into it and see if some one rates a NEMA 1 3/4 size for single phase use.

William......

 

[Crank1]

Man, I am so electronics dumb! haha

So if I understand correctly, you are saying I need a NEMA size 2 starter for a 5 horse motor? Unless I could find a 1 1/2.

Also I could use a 3 phase motor on an application for a single phase motor? Just wiring it differently is all that is required. With this being said, would something that a NEMA size 2 be the same rating of power carrying capacity between a single phase and 3 phase or would I have to step to a bigger or smaller NEMA size if I used a 3 phase?

It does appear that there are plenty more options for purchasing a cheaper mag starter if I purchased a 3 phase versus a single.

I think I'm overwhelmed with this! Sorry if I am being confusing.

 

[W-Cummins]

So if I understand correctly, you are saying I need a NEMA size 2 starter for a 5 horse motor? Unless I could find a 1 1/2.

Yes

Also I could use a 3 phase motor on an application for a single phase motor? Just wiring it differently is all that is required.

No, to use a three phase motor you need 3 phase power, or you need to make it from single phase power (VFD, Phase convertor etc.).

With this being said, would something that a NEMA size 2 be the same rating of power carrying capacity between a single phase and 3 phase or would I have to step to a bigger or smaller NEMA size if I used a 3 phase?

It does appear that there are plenty more options for purchasing a cheaper mag starter if I purchased a 3 phase versus a single.

Yes the size 2 starter is rated for up to 7.5hp on single phase for most of them I have seen, so it will work fine for your 5hp motor. I would for sure buy a 3 phase starter as they are much cheaper and you can find a used one for a few$$. Then just get the correct heaters and your all set. When looking for a used starter make sure that the coil voltage is what you want as some are non "standard" ie. 24vdc, 480V etc...

William....

 

[RangerDaleXp]

I am a bit confused here on this as well. Since when do you need a mag starter on a 5 HP single phase compressor? I see the need for it on 7.5 hp and up but every one I have seen in the 5 hp range runs the power switching through the pressure switch. Even the one I have is done that way and motor is rated a 21 amps?

 

[Crank1]

No, to use a three phase motor you need 3 phase power, or you need to make it from single phase power (VFD, Phase convertor etc.)

I didn't mean to put that I meant to say I can use a three phase starter for a single phase motor. HAHA.

Sounds like I got it. NEMA size 2 three phase mag starter on the cheap, then size the heaters accordingly. Does it have a wiring diagram if you use it like that or are you all wiring guru's smart enough to just know how to do it?

 

[Alchymist]

Everything you need to know is here:

http://wiki.vintagemachinery.org/Motor Starter Wiring Diagrams.ashx

 

[Steevo]

I am a bit confused here on this as well. Since when do you need a mag starter on a 5 HP single phase compressor? I see the need for it on 7.5 hp and up but every one I have seen in the 5 hp range runs the power switching through the pressure switch. Even the one I have is done that way and motor is rated a 21 amps?

I always thought a mag starter was used when the amperage of the motor exceeds to rated amperage of the pressure switch.
For this reason, I used a Hubbel 26 amp pressure switch for my Baldor 5HP 230V single phase motor.

How does one decide when they should add a mag starter if things appear to work fine? Do you run a current draw load test at startup and see if it exceeds the pressure switch rating?

 

[OccupantRJ]

I always thought a mag starter was used when the amperage of the motor exceeds to rated amperage of the pressure switch.
For this reason, I used a Hubbel 26 amp pressure switch for my Baldor 5HP 230V single phase motor.

How does one decide when they should add a mag starter if things appear to work fine? Do you run a current draw load test at startup and see if it exceeds the pressure switch rating?

All correct. A magnetic starter also gives you the ability to control a unit remotely, using low amperage switches, since all the switch controls is the coil in the mag starter, a very low amp draw.

 

[Steevo]

All correct. A magnetic starter also gives you the ability to control a unit remotely, using low amperage switches, since all the switch controls is the coil in the mag starter, a very low amp draw.

That would be an advantage.

 

[RangerDaleXp]

I always thought a mag starter was used when the amperage of the motor exceeds to rated amperage of the pressure switch.
For this reason, I used a Hubbel 26 amp pressure switch for my Baldor 5HP 230V single phase motor.

How does one decide when they should add a mag starter if things appear to work fine? Do you run a current draw load test at startup and see if it exceeds the pressure switch rating?

Thanks for clearing that up. What you said is what I thought as well. If the pressure switch is not currently rated for the current draw, you either change the pressure switch to one that can or install a mag switch to handle the load instead. Between reading this thread and the other attached thread, It kind of sounded like it was required code for a 5 HP motors. So when I read both threads, I go "WAIT" a minute. What is with all these 5HP compressors now days using the pressure switch to run the compressor without the Mag switch.....

 

[OccupantRJ]

Thanks for clearing that up. What you said is what I thought as well. If the pressure switch is not currently rated for the current draw, you either change the pressure switch to one that can or install a mag switch to handle the load instead. Between reading this thread and the other attached thread, It kind of sounded like it was required code for a 5 HP motors. So when I read both threads, I go "WAIT" a minute. What is with all these 5HP compressors now days using the pressure switch to run the compressor without the Mag switch.....

Ideally, the pressure switch should be a control device, instead of a load switch, but by using a pressure switch that will technically handle the amp draw, big money is saved in manufacture. A pressure switch operating as a control only, has less arcing on the contacts, allowing it to last much longer in use, and less likely to stick closed, which will in turn excite you when the pressure relief valve let's the magic air out.

 

[RangerDaleXp]

Ideally, the pressure switch should be a control device, instead of a load switch, but by using a pressure switch that will technically handle the amp draw, big money is saved in manufacture. A pressure switch operating as a control only, has less arcing on the contacts, allowing it to last much longer in use, and less likely to stick closed, which will in turn excite you when the pressure relief valve let's the magic air out.

Thank you for the information. I do understand relay Logic because we use it all the time in our business. I was just concerned it was a NEC code I was not familiar with on 5 hp motors. I can see a Mag start on a 7.5 HP or more motor being a code requirement but not on a 5hp motor. I'm not saying it would be a bad idea though as an option if someone wanted to set it up that way.....

 

[John Timmins]

This is among the BEST discussions I've read on the Garage Journal. thanks and beer for everyone !

 

[Jim Johnstone]

Awesome timing, I was just planning to pick up a motor starter for my 5hp compressor, to save wear on the pressure switch. Thanks for all the info.

 

[OccupantRJ]

I'll throw this into the mix, as it may help someone down the road. This is a post I made previously relative to a motor starter on a compressor.

Consider the pressure switch as a triggering device for the magnetic starter. When the need is for more air, the pressure switch will close it's electrical contacts and turn on the magnetic coil of the motor starter. The mag starter will then slam closed, passing power to the motor, through the starters electrical contacts. When pressure is achieved, the pressure switch will tell the mag starter to open up or (drop out). The starter has heavy electrical contacts to handle the required amperage draw of the motor. At the base of the mag starter, there should be a heater (current overload protective device), which should be rated for the expected motor load. These heaters are coded and marked for their amp rating. Some newer starters have a built-in electronic adjustment for this, so no removeable heater is needed. I just whipped up a hand drawn sketch of a simplified hookup for 240 volt air compressor motor for you. Note that this is for a motor starter with a 120 volt control coil. A 240 volt coil is wired differently. A simple house light switch can be used for your on-off switch, since it is only controlling the starter's coil. Hope this helps you. I did not include the green ground wire for simplicity. I did not use schematic symbols, but instead used a more pictorial diagram, so as hopefully not to make things confusing to someone new at it.

The following is a link to a crude drawing I made relative to this. It is for a 120 volt coil setup.

http://www.garagejournal.com/forum/attachment.php?attachmentid=97547&d=1296393730

 

[OccupantRJ]

The only difference in the drawing I linked to for the use of a 240 volt coil versus a 120 volt coil, is that instead of a neutral being involved, the wire on the upper terminal of the coil would go to the L1 terminal of the starter, to pick up the other leg of the 240. For 240 to be present, the power must come from different legs of the supply power. Each leg would read 120 volts to ground, but would read 240 volts relative to each other. The switch in the drawing is a simple household light switch, not a stop/start pushbutton type. Hopefully this is a clear explanation.

 

[RangerDaleXp]

What, no Autocad Drawing or even a ruller used? Just kidding. Very well explaned and thanks OccupantRJ. It will help a lot of people

 

[Alchymist]

Did anyone bother to read the link In posted? (Post #10).

 

[RangerDaleXp]

Did anyone bother to read the link In posted? (Post #10).

Yes I did, I even printed it into a PDF so I will have it for latter. Very good information.....

 

[OccupantRJ]

Did anyone bother to read the link In posted? (Post #10).

Yes, but I have the day off, and felt like honing my art skills.

 

[Alchymist]

Yes, but I have the day off, and felt like honing my art skills.

.......

 

[Crank1]

Hey fella's I appreciate all the help. I've found a few 3 phase mag starters on ebay, in a size 2 and before I pop for one, can someone verify these are what I'm looking for?
http://www.ebay.com/itm/NEMA-Size-2...949?pt=LH_DefaultDomain_0&hash=item2a1bd30635

 

[OccupantRJ]

Hey fella's I appreciate all the help. I've found a few 3 phase mag starters on ebay, in a size 2 and before I pop for one, can someone verify these are what I'm looking for?
http://www.ebay.com/itm/NEMA-Size-2...949?pt=LH_DefaultDomain_0&hash=item2a1bd30635

The one you linked looks like it may work for you, as it is a Square D, parts should be available, but be aware that it has a 240 volt coil. That is actually good in a sense, as a neutral would not be required at the compressor for it to operate. That is a bare starter, so no electrical enclosure seems to be included. I feel that the start/stop buttons originally mounted in the face of that enclosure. You would have to come up with a code approved can to mount it in for it to be proper. You may want to end up with one that includes the enclosure, to reduce your installation efforts. The proper separate enclosure may not be easy to locate.

 

[Crank1]

I figure if I can get the starter I'll be good as i can locate a starter in the wrong size with an enclosure I can rob for cheaper than any of the size 2 starters I've found except for this one. And I'd probably eliminate those switches anyway. The big thing is being able to wire using my single phase using the three phase starter.

 

[W-Cummins]

The starter in the auction link will work fine for you as long as it works when you get it Snap it up and get the 2 correct heaters for it and then pick up a cheap NEMA 1 enclosure with a screw lid. It's a slight pain to reset the starter, but if your setup is correctly matched ( heaters to motor amps) you will probably never need to reset it. I guess you could also install one of the plunger reset buttons into the screw cover if your worried about it. Make sure that you use the charts for an enclosed starter when you size the heaters for operation at your ambient temperature.

William....

 

[Crank1]

Well I picked up a 3 phase starter that looks like it's in decent shape. Hope when it arrives all is well. Just will need help setting up the heaters hopefully and putting it in an enclosure. Found a cheap NEMA 1 enclosure with a reset button on ebay I can stuff it into. This one look like it'll work? www.ebay.com/itm/Square-D-9991SDG8-...478?pt=LH_DefaultDomain_0&hash=item3f1366dede

 

[OccupantRJ]

Well I picked up a 3 phase starter that looks like it's in decent shape. Hope when it arrives all is well. Just will need help setting up the heaters hopefully and putting it in an enclosure. Found a cheap NEMA 1 enclosure with a reset button on ebay I can stuff it into. This one look like it'll work? www.ebay.com/itm/Square-D-9991SDG8-...478?pt=LH_DefaultDomain_0&hash=item3f1366dede

Look up the enclosure on the Square D website to see if it tells what starters work in it. I personally would feel pretty safe giving it a try, but then again, it's YOUR money.

 

[71flh]

This thread reminds me of the wiring on my CL compressor formerly owned by an artist (I have difficulty w/ artists). Even though it had a mag starter, contactor, or (specialized) relay to control it, the 3A rated pressure switch was wired to control one leg of the 240V. That set of contacts was pretty crispy so I used the other set to wire it more correctly. 120V coil in the contactor if anyone wondered.

Apparently its their bread and butter/cash cow compressor since its the one on the right: http://www.saylor-beall.com/home.php

The control has a date stamp of 1979 and its essentially identical to the one in the pic. Right down to the made in USA sticker and the red tag. VT-735-80

 

[metaldad]

Metaldad- So what you are saying is that even if I got a size 0 or 00 instead of a 1, but put the correct overloads in it, it wouldn't matter? Are the overloads or heaters, the same thing?

Here is the chart I was using to try to figure out what size NEMA I needed: http://www.southlandelectric.com/Square D Magnetic Starters and Contactors.htm

It looks like I can pick up a size 0 for considerably less than I can a size 1, then just change the overloads?

forgot about this thread.
depends on horse power, phase, volts. you can go bigger on starters, but not smaller. your op stated 5hp, 23.5 A.
(someone swiped my slide chart).
going by Square D/ Schneider's chart,the minimum size starter you could use is a 1P. A size 1 is too small. you can definitely use a size 2, or higher, just costs more.
Size 0,00, 1 will have smaller contacts and will not be able to safely carry the load, also, heaters in the range you specify will not apply to the smaller starters.
Hope this will help.
http://static.schneider-electric.us/docs/Motor Control/Contactors and Starters-NEMA Style/M-386A.pdf

 

[metaldad]

I figure if I can get the starter I'll be good as i can locate a starter in the wrong size with an enclosure I can rob for cheaper than any of the size 2 starters I've found except for this one. And I'd probably eliminate those switches anyway. The big thing is being able to wire using my single phase using the three phase starter.

I don't see a problem, other than having to size the starter and o/l's to your load, and using 3.

 

[PRH44]

If a motor has built in thermal protection and a lot of single phase lower HP do. External thermal protection in the form of are starter is not required.
Thus a HP rated contactor or pressures switch is all that is needed to control your machine.
However some prefer to have redundant protection and choose to spend the money and purchase a starter. But it would not be required.

 

[metaldad]

If a motor has built in thermal protection and a lot of single phase lower HP do. External thermal protection in the form of are starter is not required.
Thus a HP rated contactor or pressures switch is all that is needed to control your machine.
However some prefer to have redundant protection and choose to spend the money and purchase a starter. But it would not be required.

that is correct.

 

[123Go]

Sorry if this was covered, I didn't see this even with so much discussed here.
I have a Puma PK-6560V 5hp air compressor, single phase 220. I was looking into Mag starters and read conflicting info over having the on/off "Toggle/Rocker" switch vs not having a Toggle on your Mag for Compressors.
I keep my units powered up 24/7 so its always ready & they occasionally run a minute or so on their own as needed.
So Toggle or no Toggle Mag?

Fwiw I read Mag starters with the toggle switched to "on" allows a compressor to cycle correctly on its own? But without the toggle on a Mag or when the toggle/rocker is left in the "off" position they dont cycle?
Saw some reviews from guys who had to add a toggle on their mag that didnt have one?
The Mags with momentarily "on/off" push buttons dont cycle compressors continuously, they're for saws, lathes & so forth where an operator manually powers the machine on/off. I get that.

Sorry I got long, but Ive read do get & not to get the toggle mag so often now I feel as foncused as they do or dont? U Know, Idk, yeah that.....
Thanks all!