Who should I look at for a 15 CFM plus compressor?

[md21722]

I was doing some googling from what I can find and assuming this is the same one, it says it requires 3 phase power ( not for residential homes). I am ignorant on that front too but I do know in our garage we have a 230 volt power. Am I looking at the right unit?
http://www.homedepot.com/p/Ingersol...t-3-Phase-Air-Compressor-2475N7-5-V/203751642

How would I tell? It looks like this one is single phase.
http://www.aircompressorsdirect.com/Ingersoll-Rand-2475N7.5-Air-Compressor/p707.html

Both seem the same to me.

Generally anything 7.5 HP and below (and sometimes 10 HP and below) is available either as single or three phase. The Home Depot link shows the 3 phase version and the Air Compressors Direct link shows the single phase version. The only difference is the motor & magnetic starter.

Verify its a single phase before you buy it otherwise you'll need to change the motor and adapt the magnetic starter.

As the other poster alluded, the nameplate should show whether or not its single or 3 phase. If its three phase it will generally say something about 460 V somewhere on the motor nameplate. They do have motors that will run at 575 V and more in industry but at the size of air compressor we are looking at to run in our home shops you generally won't see anything more than 460 V on the nameplate. If it says anything about 460 V its not single phase, and won't run in your home.

 

[md21722]

Is there any way to determine from the photo in the ad that it is indeed single phase?

Ask the seller. They should know. If they are hemming and hawing ask them to take a picture of the motor data plate or go down and look. From the pictures they've put with the ad you cannot tell.

 

[xbeatles4x]

He verified it is a single stage and sent me this.



But to add an other element to this factor I just ran to the garage and checked with the fuse box and the 230 volt outlet we have here for the clothes dryer and it looks like a double switch of 30 amps each. #6 and #8.



I need to do more research on electrical systems but would the 230/240 volt run a 120 volt from each switch for the combined 23/240 giving it 60 amp protection?

Edit: never mind. Found the answer, nope still would be a single 30 amp breaker even when combined.

 

[DSLTRK]

Is there any way to determine from the photo in the ad that it is indeed single phase?

Yes, single phase motors often have capacitors mounted in a large box on the motor case. These capacitors are needed to get the motor running a certain direction from a standstill.

Unlike single phase, 3 phase motors develop good starting torque from a standstill without capacitors. Hence, they will be absent.


The picture in the ad does appear to be a single phase unit since there is a large box on top of the motor.

 

[md21722]

I'm somewhat confused by what you're asking on the circuit breaker. The electric code has specific rules for motor circuits. 7.5 HP motor FLC = 40A per the NEC tables. Multiple 40A FLC X 125% = 50A. That's #6 NM-b (Romex) or #8 THHN (in conduit). Breaker can be maximum 40A X 250% = 100A as long thermal protection is present (the magnetic starter should provide this). Most of the compressor suppliers will say 80A for this compressor, but a 40, 50, or 60A will probably work. After 60A they get expensive. It must be hardwired, no plugs allowed. And a disconnect next to the compressor must be installed if the panel is more than 50 feet away/out of line of sight.

I am guessing the 50A breaker is for your stove, the 30A is for your clothes dryer, and the 60A is your heat pump.

Plan on buying a new breaker.

 

[DSLTRK]

He verified it is a single stage and sent me this.


But to add an other element to this factor I just ran to the garage and checked with the fuse box and the 230 volt outlet we have here for the clothes dryer and it looks like a double switch of 30 amps each. #6 and #8.


I need to do more research on electrical systems but would the 230/240 volt run a 120 volt from each switch for the combined 23/240 giving it 60 amp protection?

Edit: never mind. Found the answer, nope still would be a single 30 amp breaker even when combined.

If you do end up getting the compressor on CL, consult a qualified electrician.

The 30 amp breaker shown is too small, per NEC 430.32, overload protection should be 125% of the motor's FLA rating. A 7.5 HP motor draws about 40 amps, so 40*1.25= 50 amps, get a 50A two pole breaker with no 6 wire.

Also, motors over 3 hp should be hardwired. IE, don't use a plug.

 

[xbeatles4x]

Thank you guys. This is what I was afraid of. I think getting a smaller air compressor like that husky I was looking at earlier is probably what I will end up going with. This is just a hobby and I am already frightened and put off by the entire experience. I guess I will deal with waiting for the pump to cycle up and compress. I am not planning to blast the whole car at the moment (VW Bus). Just a few sections here and there, then weld as necessary, primer over it, then some light body work. I don't plan to run a shop and my uses aren't that numerous. Maybe even use a die grinder if necessary.

I guess this boils down to what can be the best compressor I can run on my existing setup without going crazy and hard wiring the compressor or swapping panels?

 

[md21722]

IYou can't install a breaker bigger than 50 amps

This is wrong. See my post above.

 

[md21722]

Thank you guys. This is what I was afraid of. I think getting a smaller air compressor like that husky I was looking at earlier is probably what I will end up going with. This is just a hobby and I am already frightened and put off by the entire experience. I guess I will deal with waiting for the pump to cycle up and compress. I am not planning to blast the whole car at the moment (VW Bus). Just a few sections here and there, then weld as necessary, primer over it, then some light body work. I don't plan to run a shop and my uses aren't that numerous. Maybe even use a die grinder if necessary.

I guess this boils down to what can be the best compressor I can run on my existing setup without going crazy and hard wiring the compressor or swapping panels?

I am not sure it is a deal breaker? Do you not have any room in your panel? Can you convert some of the breakers to duplex breakers? Just about any compressor you want will cause you to deal with this issue. A true 2 HP is the largest you can run on an existing 120 V circuit and even a true 2 HP requires #12 wire and a 20A breaker and they will prefer 230V. 2 HP is about the largest you can run with a plug. The maximum CFM out of a 2 HP compressor I have ever seen is 8 @ 100 PSI.

 

[xbeatles4x]

I was planning to unplug the dryer in the garage when I was going to use the compressor. That already has 230v and from my breaker box appears to be 30 amp breakers. Edit: Unless you see something that I don't have the knowledge of in fitting an air compressor directly into the breaker box. The box would be about 4 to 5 feet away from where the compressor would go.

It doesn't look like we have any more room in our breaker box but I am not sure about converting to duplex breakers. I would have to consult an electrician at this point.

You know what. I am going to snag a photo of the whole breaker box now.

 

[DSLTRK]

This is wrong. See my post above.

You're correct, inverse time trip breakers can be sized at 250% FLC. Got confused with overload requirements.

 

[xbeatles4x]

I am not sure how accurate this is anymore but if my understanding is correct, a double breaker can be used on 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30. This looks like the time that an electrician needs to be brought in but before doing so I wanted to know what my options are if a dedicated line needed to be run if things can be moved around to accommodate such a thing.

 

[md21722]

Looks like anywhere in the panel will give you 230V using a double pole breaker. Siemens seems to suggest you use duplex breakers in the bottom half (like the lower left breaker), but as you can see from the Jacuzzi 50A breaker on the lower right in 28-30 you are getting 230V. So you need to buy 2 duplex breakers to replace 4 non-duplex to free up two adjacent slots for your compressor breaker. If you aren't comfortable with electricity its a good idea to get an electrician. It's not for everybody. If you have more questions, I suggest you post this specific question in the lighting & electrical forum. Then some of the electricians there can answer your questions.

 

[xbeatles4x]

Thank you so much md21722. You really were a great help. I will take a better look in the morning at all of this and re assess the situation. I'm thinking about that ingersoll rand again.

 

[md21722]

You're welcome. If you get bad vibes or cold feet when you go look at that compressor walk away. It is the best price for a working 7.5 you're likely to see. I'd say if you don't buy it someone else probably will pretty quick.

 

[bugdust]

I'm looking for a new compressor too. My Quincy QT-54 died after 26 months. I hated it anyway...it was very loud. I guess the Baldor motor died...replaced the start capacitor and it's still dead, flashes in the breaker panel.

 

[CompressorPros.com]

I'd be happy to give you a deal if you find something you like on our site. We will be adding Industrial Gold in the next week or so also.

 

[Xicaque]

OP,

what did you end up doing? Did you get it?

Bugdust, sorry to hear about your Quincy. I wonder what happened to your unit. What are your plans?