Magnetic Starter Options

[thecj3man]

I am getting everything together to install a 7.5 HP compressor in my shop. I have never owned a piece of equipment that is big enough to require a magnetic starter so this will be first time installing one. The compressor is currently equipped with a 3 phase motor and starter. My question is around the style of starter that is preferred for this application. I see some starters that utilize heater strips that must be sized for the load while others use an adjustable relay.

Is one type better, or more preferred, than the other? Which ever I choose I will have to purchase new.

Thank you for any opinions,

WP

 

[Rookie2]

You say it's equipped with a starter ! Do you have 3 phase in your shop ?

 

[thecj3man]

I am sorry, I should have clarified that. I will switch the motor to a single phase unit. The power company came by and said they would gladly run 3 phase 115' for $10K. I decided that the new motor would be a better option.

 

[Rookie2]

You may be able to use the same starter, upload some pictures and model numbers and someone will chime in and get you going. It's all about load amps and voltage.

 

[dave89iroc]

probably just use the 3 phase starter

 

[EdT]

There is some weirdness in the NEC regarding motor circuits. In particular, wire and breaker sizes that are going to seem screwy compared to "conventional" circuits for outlets and such.
I dont have a good enough memory to quote the numbers, but it's worth looking into before you have to undo it all to get inspected. that 7.5 HP motor will pull some serious amperage so you will probably have to make some adjustments to the heaters in your starter if you can use it at all, which you probably can.

 

[rockwithjason]

I prefer the adjustable type. If you change out the motor for a 1 ph unit you will need bigger overloads than a 3ph unit would.

 

[alfredeneuman]

The single phase motor (about 40 Amps) will draw more current than the 3Ø motor.(about 22A)
You'll have to upsize the entire mag starter from a size from a size 1 to a size 2.

I, too prefer the adjustable type (they sense current electrically, whereas the fixed amperage ones have a bimetal strip that heats up and breaks the contact.)

 

[motofool33]

i used this brand, i picked a plastic case, one with start stop. but as i found out i should have bought the reset only version as it would not turn on and off with the pressure switch unless i modified the circuitry.

http://www.temcoindustrialpower.com/products/Motor_Starters/MS0249.html#

i used it to convert my 10hp 3P quincy to a 7.5hp single phase.

 

[thecj3man]

Thank you for the replies and the link. I do not have the old starter in front of me yet, but I figured that I would need to upsize due to the increased amperage load.

I will start reading today on the various brands of adjustable type magnetic starters.

WP

 

[matt_i]

It might be obvious but I feel its important to point out that a 3-pole overload heater section (discrete elements or adjustable) won't work well on single phase as there's an automatic phase loss there....only 2 poles would be used. And thus it would be tripping the overload constantly.

Along the same lines, there's no reason that a 3 pole contactor can't be hooked up to a 2 pole overload element. The contactor/starter doesn't care a whit about whether 1, 2, or 3 poles are in-use.

So, if you can source an overload section for single phase (2 poles) you can find a 3 pole NEMA-2 starter and graft the two together. They don't have to be physically attached to each other. Mounted to the same backplane, yes, but only the wiring between counts.

 

[md21722]

Or you can buy a new Square D which is the old heater element type for $150 shipped. The compressor shop I talked to said the Square D's have been more reliable even though they sell both and the Eatons cost more.

 

[Norcal]

Or you can buy a new Square D which is the old heater element type for $150 shipped. The compressor shop I talked to said the Square D's have been more reliable even though they sell both and the Eatons cost more.

Those starters use definite purpose contactors which are about the bottom of the line, only the Asian sourced starters are worse. A SQ D starter with a type S contactor or Siemens (formerly Furnas) ESP 100 starter, Allen-Bradley are good choices. SQ D adjustable overload relays are branded "Motorlogic", & Siemens / Furnas "ESP 100".

 

[CompressorPros.com]

We carry Eaton starters that we buy from Atlas Copco if you are interested...

7.5 HP Single Phase Starter

 

[wyliesdiesels]

There is some weirdness in the NEC regarding motor circuits. In particular, wire and breaker sizes that are going to seem screwy compared to "conventional" circuits for outlets and such.
I dont have a good enough memory to quote the numbers, but it's worth looking into before you have to undo it all to get inspected. that 7.5 HP motor will pull some serious amperage so you will probably have to make some adjustments to the heaters in your starter if you can use it at all, which you probably can.

Really not weird at all. And pretty straight forward

Wire is sized at 125% of NEC FLC table amps which is based on motor nameplate horsepower NOT nameplate FLA.

Breakers can be sized maximum 250% of NEC table FLC...

It might be obvious but I feel its important to point out that a 3-pole overload heater section (discrete elements or adjustable) won't work well on single phase as there's an automatic phase loss there....only 2 poles would be used. And thus it would be tripping the overload constantly.

Along the same lines, there's no reason that a 3 pole contactor can't be hooked up to a 2 pole overload element. The contactor/starter doesn't care a whit about whether 1, 2, or 3 poles are in-use.

So, if you can source an overload section for single phase (2 poles) you can find a 3 pole NEMA-2 starter and graft the two together. They don't have to be physically attached to each other. Mounted to the same backplane, yes, but only the wiring between counts.

U can actually use a 3-pole motor overload that has phase loss protection with a single phase motor by running a jumper from T2 through the overload coil and back up to L3. Motor L2 connects to T3 on overload relay block.

I have seen many compressors wired like this from the factory. Manufacturers do this so they dont have to stock so many different motor starters...

 

[thecj3man]

Bringing this back for another question.

The starter that is on currently on the compressor is a Furnas unit, with a 30 amp maximum rating. I was tempted to try to use it since the Baldor motor specs as 31 FLA, but I hate to risk damage to a new motor over cheaping out now.

Looking around at newer equipment there are several nice units like the Eaton referenced above for between $150 and $200. Square D, Siemens, and WEG are also in this price range. There are also a multitude of cheap units on eBay for between $50 and $100. Are the cheap units imported and a waste of my money, or are they a quality unit. I would like to hear any opinions on one brand vs. the others as far as quality or reliability.

Thanks,
WP

 

[Norcal]

Furnas is Siemens now, a SQ D w/o a definite purpose contactor, or a Allen-Bradley starter are good choices, I would avoid cheap Asian starters.

 

[md21722]

There are some comments above. After talking to some shops I went with the Square D definite purpose type. You can get them from Pacific Air Compressors out of Portland on eBay for about $150 shipped. Norcal brings up that they are lower end, not type S, etc. but those cost 3-4X as much and are likely overkill for non-industrial settings. Compressors you can buy for $2000-$3000 are using definite purpose contactors as standard equipment. If you can get the top end versions at a steal go for it.

 

[wyliesdiesels]

Bringing this back for another question.

The starter that is on currently on the compressor is a Furnas unit, with a 30 amp maximum rating. I was tempted to try to use it since the Baldor motor specs as 31 FLA, but I hate to risk damage to a new motor over cheaping out now.

Looking around at newer equipment there are several nice units like the Eaton referenced above for between $150 and $200. Square D, Siemens, and WEG are also in this price range. There are also a multitude of cheap units on eBay for between $50 and $100. Are the cheap units imported and a waste of my money, or are they a quality unit. I would like to hear any opinions on one brand vs. the others as far as quality or reliability.

Thanks,
WP

Starters for motors are sized based on HP. U need to check the max HP rating on the contactor NOT the max amp rating.

 

[thecj3man]

Starters for motors are sized based on HP. U need to check the max HP rating on the contactor NOT the max amp rating.

My current Furnas starter is rated 5hp at 240 volts, so it is definaty undersized.

I appreciate all of opinions and help.

 

[matt_i]

I would take a look at Automation Direct, seems they have WEG and Fuji contactors, if a NEMA-sized one, good-used isn't your cup of tea.

 

[930cabman]

Those starters use definite purpose contactors which are about the bottom of the line, only the Asian sourced starters are worse. A SQ D starter with a type S contactor or Siemens (formerly Furnas) ESP 100 starter, Allen-Bradley are good choices. SQ D adjustable overload relays are branded "Motorlogic", & Siemens / Furnas "ESP 100".

Question: why are "definite purpose starters" near the bottom of the pile? I just purchased a Square D planning to use it with our Hitachi resaw with 3 ph 5hp motor.

 

[Bert_]

Definite purpose starters are definitely lower grade compared to nema stuff, I'm not sure exactly how they compare to IEC stuff probably not much worse. The IEC style are cheaper from both a cost and quality standard compared to nema gear. Lots of compressors come either of these style starters from the factory. The best would be a NEMA starter but they command a premium.

If I were looking at Ebay a NEMA starter would be a good choice, they rarely fail unless abused.

What ever you get make sure it is rated for 7.5hp on single phase, that doesn't mean amps they are actually rated in HP. And make sure you get the correct coil voltage. I'm guessing you will want a 240v coil.

 

[Norcal]

Question: why are "definite purpose starters" near the bottom of the pile? I just purchased a Square D planning to use it with our Hitachi resaw with 3 ph 5hp motor.

DP contactors are used in HVAC & food service equipment, they are rated for a certain number of cycles & are a throwaway item, no repair parts, no replacement coils if you get the wrong voltage, if they last past the warranty period, all is good.

 

[930cabman]

DP contactors are used in HVAC & food service equipment, they are rated for a certain number of cycles & are a throwaway item, no repair parts, no replacement coils if you get the wrong voltage, if they last past the warranty period, all is good.

Sounds as though NEMA is the only way to go.

thanks

 

[Bert_]

Almost any compressor will come with either a definite purpose starter or an IEC starter from the factory. Maybe industrial sized stuff comes with NEMA gear, but most do not.

The DP or IEC contractor will last a long time if sized right, NEMA is way higher quality though. NEMA stuff will outlast the machine.

 

[manwithtools]

Almost any compressor will come with either a definite purpose starter or an IEC starter from the factory. Maybe industrial sized stuff comes with NEMA gear, but most do not.

The DP or IEC contractor will last a long time if sized right, NEMA is way higher quality though. NEMA stuff will outlast the machine.

The NEMA starters will outlast and out-cost the machine. An IEC starter properly sized will last more than the life of an air compressor used in a personal or med commercial shop. NEMA starters are way over priced for what they do on a compressor. IEC is fine if sized correctly. 100,000 cycles is well within their expected lifetime. Do the math on that with a home setup - we are into decades.

DP is probably fine as well as long as not an industrial setting. I just had a customer specify DP contactors for 40hp and 60hp HVAC compressors for a chillers on a data center - think Google or Amazon servers running 24/7. Seems foolish to me, but it's their money. I'll bet we end up redesigning that control package in a year or so when things start to fail.

 

[wyliesdiesels]

The NEMA starters will outlast and out-cost the machine. An IEC starter properly sized will last more than the life of an air compressor used in a personal or med commercial shop. NEMA starters are way over priced for what they do on a compressor. IEC is fine if sized correctly. 100,000 cycles is well within their expected lifetime. Do the math on that with a home setup - we are into decades.

DP is probably fine as well as long as not an industrial setting. I just had a customer specify DP contactors for 40hp and 60hp HVAC compressors for a chillers on a data center - think Google or Amazon servers running 24/7. Seems foolish to me, but it's their money. I'll bet we end up redesigning that control package in a year or so when things start to fail.

yeah thats not gonna last long...especially with the heat...

 

[nsula_country]

The NEMA starters will outlast and out-cost the machine. An IEC starter properly sized will last more than the life of an air compressor used in a personal or med commercial shop. NEMA starters are way over priced for what they do on a compressor. IEC is fine if sized correctly. 100,000 cycles is well within their expected lifetime. Do the math on that with a home setup - we are into decades.

DP is probably fine as well as long as not an industrial setting. I just had a customer specify DP contactors for 40hp and 60hp HVAC compressors for a chillers on a data center - think Google or Amazon servers running 24/7. Seems foolish to me, but it's their money. I'll bet we end up redesigning that control package in a year or so when things start to fail.

Saving pennies now... Going to need dollars later! That should have NEMA controls written all over it.

CT

 

[manwithtools]

Saving pennies now... Going to need dollars later! That should have NEMA controls written all over it.

CT

No Need for NEMA on anything anymore IMHO. Properly sized IEC will work just fine. Understand the application and it might require a larger sized contactor than just the HP indicates.

 

[nsula_country]

No Need for NEMA on anything anymore IMHO. Properly sized IEC will work just fine. Understand the application and it might require a larger sized contactor than just the HP indicates.

IMHO, I'm not impressed with IEC. Even A-B IEC, in high volume manufacturing with thousands of cycles per day. Some hold up, some fail early. No rhyme or reason...

Professionally I am an Electrical Controls Engineer for a high volume manufacturing facility and we have thousands of contactors. Have see a handful of A-B NEMA need contacts, no coils. C-H is good too, Citation and Freedom. Have seen hundreds of IEC fail within a couple of years. They are disposable.

With this said, for the OP's air compressor a DP or IEC contactor will be sufficient.

For the chiller application for servers... I'd not risk IEC hardware, even if upsized. A-B 509 or equivalent NEMA.

CT

 

[manwithtools]

IMHO, I'm not impressed with IEC. Even A-B IEC, in high volume manufacturing with thousands of cycles per day. Some hold up, some fail early. No rhyme or reason...

Professionally I am an Electrical Controls Engineer for a high volume manufacturing facility and we have thousands of contactors. Have see a handful of A-B NEMA need contacts, no coils. C-H is good too, Citation and Freedom. Have seen hundreds of IEC fail within a couple of years. They are disposable.

With this said, for the OP's air compressor a DP or IEC contactor will be sufficient.

For the chiller application for servers... I'd not risk IEC hardware, even if upsized. A-B 509 or equivalent NEMA.

CT

I'm a controls engineer as well. I manufacture several hundred control panels a year. I've probably installed a few tens of thousands contactors over the years, most for high volume manufacturing. Lots of different opinions, most don't have space for 40 nema contactors in a cabinet. Hell, you can buy a VFD for less than a nema starter in most cases and probably should for the energy savings alone.

Sent from my Pixel using Tapatalk