Air Compressor Wiring Question

[iusamson]

I'm trying to wire in a new-to-me compressor, and wanted some advice on the correct way to do this. It's a Champion R15 80 gallon hooked up to a 5PH Single Phase Magnetek Starter (Pic Attached) and uses an older Furnas Pressure Switch (pic attached). The way the wiring looks, it appears the previous owner used a magnetic starter - but i could be wrong. In the garage I have a 50A 220 breaker wired to a fusible disconnect switch with a 30A fuse in it from home depot (https://www.homedepot.com/p/Siemens...sible-Indoor-Safety-Switch-GF221NAU/309777794). The breaker is 50A because the same circuit is also powering the EV Chargers in the garage. I was intending to only turn the fusible disconnect on if I was using the compressor and not the chargers. I do not see a red button on the motor, so I assume there is no overload protection in it. I have two specific questions (right now):

1. Even though the pressure switch is not rated for 5HP - coudl this work? I read somewhere (not furnas/hubbel website) that it's rated for 24amps. I have a feeling people are going to say the 5HP rating is important and to get a magentic starter, but wanted to ask just in case

2. Assuming the answer to #1 is "no". Will this inexpensive WEG magnetic starter work for me, wired after the fusible disconnect? https://www.ebay.com/itm/191584768569. My main concerns are around the fusable disconnect and lack of overload protection on the motor. Not an expert - just looking for the right information so I can implement.

Thanks in advance!
Josh

 

[Bert_]

Weg starters are actually decent, especially for the money. I would not use a 30A fuse, it's on the small side for a 5 hp motor. You said you already have a 50 amp breaker, that's perfect for a 5 hp motor.

That starter should have an overload

 

[MKSJ]

I have a Champion HR5-8 compressor, it came with a magnetic starter. The starter carries the motor carrying current, the pressure switch just connects the power to the pressure switch which operates only the contactor. A magnetic starter with a thermal overload like in the eBay link takes care of the motor overload so you do not need additional fusing. I have my 5 Hp compressor wired to a 50A beaker from my panel with #8 wire. I used a 50A extension cord hard wired to the magnetic starter and the other end connects to a 50A plug. My motor is 27A and a SF of 1.25 so can draw high initial current. I use a disconnect switch in the magnetic contactor box which disconnects power to the contactor coil when the compressor is not in use, in case an air line breaks.

 

[Terry D]

I have a Champion HR5-8 compressor, it came with a magnetic starter. The starter carries the motor carrying current, the pressure switch just connects the power to the pressure switch which operates only the contactor. A magnetic starter with a thermal overload like in the eBay link takes care of the motor overload so you do not need additional fusing. I have my 5 Hp compressor wired to a 50A beaker from my panel with #8 wire. I used a 50A extension cord hard wired to the magnetic starter and the other end connects to a 50A plug. My motor is 27A and a SF of 1.25 so can draw high initial current. I use a disconnect switch in the magnetic contactor box which disconnects power to the contactor coil when the compressor is not in use, in case an air line breaks.

Someone is going to ask, so i will be the first. Is that plug rated for 5 hp

 

[MKSJ]

Rated extension cords have plugs to match their wire ratings, I use a 50A welding extension cord with a molded plug. The wall receptacle is rated at 50A and it is wired with #6 Romex to a 50A breaker. A 5 Hp single phase motor FLA is between 22-27A, a SF is 1.25 and is only a short term load so nowhere close to the maximum continuous current rating of the power line. I do not recommend it, but I have seen people run 5 Hp motors on 30 and 40A circuits. It can be done but the NEC requirement for the motor power wire is a minimum of 125% of the motor FLA and the breaker size varies depending on the type used. The welding cable extension cord I used #8, which would be good for up to 7.5Hp.

 

[Terry D]

Its not just the amp rating, its the hp rating also. Plugs rated for 5 hp are very expensive. Just because it it is a 50 amp device does not mean it is rated for 5 hp. It probably only has a 3 hp rating. Unless you want to spend big bucks for the correct devices, it should be hard wired

 

[iusamson]

Weg starters are actually decent, especially for the money. I would not use a 30A fuse, it's on the small side for a 5 hp motor. You said you already have a 50 amp breaker, that's perfect for a 5 hp motor.

That starter should have an overload

But do I even need the mag starter? Regardign the fuse - it's what my electrician friend recommended to me - He actually said 50A would is way too high and won't offer protection.

 

[wyliesdiesels]

I'm trying to wire in a new-to-me compressor, and wanted some advice on the correct way to do this. It's a Champion R15 80 gallon hooked up to a 5PH Single Phase Magnetek Starter (Pic Attached) and uses an older Furnas Pressure Switch (pic attached). The way the wiring looks, it appears the previous owner used a magnetic starter - but i could be wrong. In the garage I have a 50A 220 breaker wired to a fusible disconnect switch with a 30A fuse in it from home depot (https://www.homedepot.com/p/Siemens...sible-Indoor-Safety-Switch-GF221NAU/309777794). The breaker is 50A because the same circuit is also powering the EV Chargers in the garage. I was intending to only turn the fusible disconnect on if I was using the compressor and not the chargers. I do not see a red button on the motor, so I assume there is no overload protection in it. I have two specific questions (right now):

I would not use the 30a fused disconnect. it may blow with that size motor. IS the breaker panel in sight of and no more than 50' from the compressor? If so then you dont need the disconnect at all.

Also, if the motor doesnt have integral overload protection, then you will need a mag starter. The pressure not only wont provide overload protection but its probably not rated for 5HP either...

1. Even though the pressure switch is not rated for 5HP - could this work? I read somewhere (not furnas/hubbel website) that it's rated for 24amps. I have a feeling people are going to say the 5HP rating is important and to get a magnetic starter, but wanted to ask just in case

yes the HP rating is important. for a motor load components need to be rated for the same or higher HP as the motor. Doubt that PS is rated for 5HP. Regardless, you dont have integral overload protection, so you need a mag starter

2. Assuming the answer to #1 is "no". Will this inexpensive WEG magnetic starter work for me, wired after the fusible disconnect https://www.ebay.com/itm/191584768569. My main concerns are around the fusible disconnect and lack of overload protection on the motor. Not an expert - just looking for the right information so I can implement.

Thanks in advance!
Josh

yes the WEG magstarter will work

I would ditch the fusible disconnect and if you must have a disconnect get an A/C non-fused pull out disconnect.

I have a Champion HR5-8 compressor, it came with a magnetic starter. The starter carries the motor current, the pressure switch just connects the power to the pressure switch which operates only the contactor. A magnetic starter with a thermal overload like in the eBay link takes care of the motor overload so you do not need additional fusing. I have my 5 Hp compressor wired to a 50A beaker from my panel with #8 wire. I used a 50A extension cord hard wired to the magnetic starter and the other end connects to a 50A plug. My motor is 27A and a SF of 1.25 so can draw high initial current. I use a disconnect switch in the magnetic contactor box which disconnects power to the contactor coil when the compressor is not in use, in case an air line breaks.

I doubt that 50a plug and receptacle is rated for 5HP....

Rated extension cords have plugs to match their wire ratings, I use a 50A welding extension cord with a molded plug. The wall receptacle is rated at 50A and it is wired with #6 Romex to a 50A breaker. A 5 Hp single phase motor FLA is between 22-27A, a SF is 1.25 and is only a short term load so nowhere close to the maximum continuous current rating of the power line. I do not recommend it, but I have seen people run 5Hp motors on 30 and 40A circuits. It can be done but the NEC requirement for the motor power wire is a minimum of 125% of the motor FLA and the breaker size varies depending on the type used. The welding cable extension cord I used #8, which would be good for up to 7.5Hp.

The problem here is that the plug is most likely not rated for 5HP. for a motor overload, you need to compare HP ratings not amp ratings, especially for a plug that can used as a disconnect under load.

In terms of wire ratings, you dont use the motor FLA. Code requires you to use the FLC rating in the tables. so for a 5HP motor you need 35a rated wire- 28a x 1.25- 35a. This means #10 THHN in pipe or #8 NM-b. A #8 cord would be good for 35a and thus 5HP NOT 7.5HP.....

 

[wyliesdiesels]

But do I even need the mag starter? Regarding the fuse - it's what my electrician friend recommended to me - He actually said 50A would is way too high and won't offer protection.

yes, you need the mag starter. the PS is most likely not rated for 5HP and the 30a fuse is probably rated too high to protect the motor since the FLA is 24a.

Do it right and get a magstarter

 

[iusamson]

yes, you need the mag starter. the PS is most likely not rated for 5HP and the 30a fuse is probably rated too high to protect the motor since the FLA is 24a.

Do it right and get a magstarter

Purchased the magstarter - thank you for the advice (everyone)

Regarding the disconnect - I'll talk to my electrician to confirm his thoughts. It's already purchased and mounted, so the money is spent. The main purpose of it was provide me the ability to turn the compressor off when i'm not in the garage. I don't want it coming on in the middle of the night. If the fuse isn't helping or it's hurting, I suppose we can always increase that fuse to a 50A and call it a day.

 

[Terry D]

Purchased the magstarter - thank you for the advice (everyone)

Regarding the disconnect - I'll talk to my electrician to confirm his thoughts. It's already purchased and mounted, so the money is spent. The main purpose of it was provide me the ability to turn the compressor off when i'm not in the garage. I don't want it coming on in the middle of the night. If the fuse isn't helping or it's hurting, I suppose we can always increase that fuse to a 50A and call it a day.

The disconnect that you posted is a 30 amp. Since a disconnect has to be sized 115% over the FLC of 28 amps, A 30 amp would be to small anyway. You would need to go to a 60 amp, I would do a non-fusible.

Even if you could use that 30 amp disconnect, it will not hold fuses larger than 30 amp.

Now that I re read your first post. This compressor is sharing the same circuit with an EV charger. Do you have a space problem in your panel. They should each be on their own circuit so you don't have to worry about shutting one off to run the other. When I looked up the number on GE's website, it shows this disconnect as a 3 pole. You could still use it. You just would not have anything hooked up to the 3rd pole

ABB 60 Amp 240-Volt Non-Fuse Indoor Safety Switch (TGN3322) TGN3322 - The Home Depot

Visit the Home Depot to buy GE 60 amp 240-Volt Non-Fuse Indoor Safety Switch TGN3322

www.homedepot.com

 

[PoorUB]

If nothing else you can use the existing pressure switch to run the contactor coil in the mage starter. I would assume that is how it is wired, but maybe not.

 

[Bert_]

But do I even need the mag starter? Regardign the fuse - it's what my electrician friend recommended to me - He actually said 50A would is way too high and won't offer protection.

Get the starter. You already showed us the picture with the 3hp rating.

A 30A disconnect is to small anyway, they are usually rated for 3hp. A lot of guys that do residential only just don't have a grasp on motor stuff, not sure if that's the case or not no disrespect to the guy. Nec actually allows up to 70A circuit breaker for a 5 hp motor. The breaker never offers protection for the motor, that is the job of the overload. The breaker is just to protect from short circuit.

 

[wyliesdiesels]

Get the starter. You already showed us the picture with the 5hp rating.

A 30A disconnect is to small anyway, they are usually rated for 3hp. A lot of guys that do residential only just don't have a grasp on motor stuff, not sure if that's the case or not no disrespect to the guy. Nec actually allows up to 70A circuit breaker for a 5 hp motor. The breaker never offers protection for the motor, that is the job of the overload. The breaker is just to protect from short circuit and ground fault.

fixed it for you

 

[wyliesdiesels]

Purchased the magstarter - thank you for the advice (everyone)

Regarding the disconnect - I'll talk to my electrician to confirm his thoughts. It's already purchased and mounted, so the money is spent. The main purpose of it was provide me the ability to turn the compressor off when i'm not in the garage. I don't want it coming on in the middle of the night. If the fuse isn't helping or it's hurting, I suppose we can always increase that fuse to a 50A and call it a day.

the fuse is too small so he sized it wrong. should return it if he purchased it and buy a non-fused pull out disconnect.

If you don't want it coming on in the middle of the night you could wire a light switch in-line with the contactor coil, place it by the door and shut it off when you leave. make sure to use a 240v rated light switch.

 

[iusamson]

the fuse is too small so he sized it wrong. should return it if he purchased it and buy a non-fused pull out disconnect.

If you don't want it coming on in the middle of the night you could wire a light switch in-line with the contactor coil, place it by the door and shut it off when you leave. make sure to use a 240v rated light switch.

Please forgive my confusion - just seeking some understanding (not pretending to know) so this is put in correctly. If the tag on the motor says 22A and the recommendation is 115% over that (25.3), why wouldn't 30A be enough? Assuming that's right, wouldn't I want a fuse to stop current in case of an overload - does the mag starter perform this function - This fusible disconnect was purchased when the intent was to run it just off the PS (no mag starter). Can't be returned at this point, but can just resell on craigslist without issue - I want this to be right.

 

[Terry D]

You do not go by the data on the name plate on the motor you must get the data out of the table of the code book for a 5 horse motor it is 28 amps then you take 115% of that so that is over 30 amps that's why you have to go to a 60 amp disconnect plus a 60 amp disconnect is rated for 10 horsepower and the 30 amp is only ratwd for 3 horsepower. The circuit breaker is oversized so you don't get a nuisance trip on startup of that motor it still will protect the wiring for a shortcircuit or ground faults. the overloads in the starter will protect the motor for overloads

 

[Bert_]

If you open the cover on your fuse disconnect and look at the label it should say 3hp max for 240v single phase. Generally you need to go to a 60 amp disconnect when running a 5 hp single phase motor. Personally I would just get a non-fused 60A disconnect, let the breaker and the overload relay do their jobs. If you want an on-off switch for convenience all you need is a little toggle switch controlling the magnetic starter coil.

The magnetic starter and overload relay will protect against overloads. A breaker cannot protect against overloads without causing nuisance tripping. A time delay fuse sometimes can be used to protect against overloads but it takes careful sizing and the wrong equipment will still cause nuisance trips.

When used with a separate overload the NEC allows breakers to be sized 250% of the motor full load current. Time delay fuses are allowed to be $175%

 

[haveissues]

But do I even need the mag starter? Regardign the fuse - it's what my electrician friend recommended to me - He actually said 50A would is way too high and won't offer protection.

Use a mag starter. My 5hp compressor came with just a pressure switch and one day I found the compressor running in my garage blowing air out of the pop off valve. The pressure switch contacts welded together and it was running like that for at least a day.