Need Help w/ Compressor Setup - Motor & Starter

[BMS]

Posted this in tools section, but thought it might be more appropriate here....

Bought 3-phase compressor off a guy locally. It's an 80-gallon Speedaire with a 3-phase, 10-hp Dayton motor. I know this compressor was available in 10hp and 7hp configurations, so my thought was I could replace the 10hp 3-phase motor with a 7.5hp, 1700rpm, 1-phase motor. I can't seem to wrap my head around phase converters so I figured I'd just replace it with single phase. I only paid $200 for the compressor, so I have room to put a little $$ into it. Problem is, I am not 100% sure what I have / what I can reuse.

Pretty sure the pic of the two boxes is the motor starter and the disconnect switch. Are motor starters phase specific or should I be able to reuse it with the 7.5hp motor? I can take additional pics if needed for help.

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[uhohjim]

I've got a quincy compressor with asingle phase 5 horse motor that was originally 3 phase..........I installed the single phase motor and power it up using the pressure switch that was already there...........I have a breaker box on the wall at the compressor but thats it......My pressure switch looks like the one in your picture as long as the motor you use has the capacitors already on it I wouldn't think you need a starter setup..........Jim

 

[uhohjim]

I've got a quincy compressor with asingle phase 5 horse motor that was originally 3 phase..........I installed the single phase motor and power it up using the pressure switch that was already there...........I have a breaker box on the wall at the compressor but thats it......My pressure switch looks like the one in your picture as long as the motor you use has the capacitors already on it I wouldn't think you need a starter setup..........Jim

Correction it looks like you would need a higher capacity pressure switch to handle the motor......as it would pull more amps thgat a 3 phase motor.........

 

[Jim Johnstone]

Correction it looks like you would need a higher capacity pressure switch to handle the motor......as it would pull more amps thgat a 3 phase motor.........

The pressure switch would be fine, but he would need to add a magnetic motor starter to handle the amperage of a 7.5 or 10hp single phase motor.

 

[Charles (in GA)]

That appears to be a single stage compressor. The pressure switch, and 80/100 switch means that the MOST pressure you will ever see is 100 psi and it will get as low as 80 psi before the compressor comes on. Probably a unit used for a fire supression system or an HVAC system in a large building that uses air to move dampers.

Charles

 

[BMS]

hmmmmm, thanks for pointing that out. Looks like the pump is rated to 125psi, so I imagine I could use a different pressure switch with slightly higher settings. I haven't moved my regulator off 90 psi on my craftsman noise generator for anything I've ever needed. Guess I could look at using this pump too

http://www.eatoncompressor.com/catalog/item/518643/1017632.htm

Even with that pump and a new 7.5hp motor, new starter, etc, I'd still have well under $1500 into it.

 

[W-Cummins]

That appears to be a single stage compressor. The pressure switch, and 80/100 switch means that the MOST pressure you will ever see is 100 psi and it will get as low as 80 psi before the compressor comes on. Probably a unit used for a fire supression system or an HVAC system in a large building that uses air to move dampers.

Charles

I'm not sure that's a single stage compressor it appears to have an intercooler and both large and smaller pistons on each side. Could be that some one just put on a lower pressure, pressure switch on it. It's hard to tell from sure from the pictures though, as they don't really show the pump well.

William......

 

[Mmfh]

If its originally a 10hp 3 phase compressor, you can almost guarantee its going to be a two stage, I would think. I wouldn't buy a new pump and motor, another used compressor would be much cheaper.

If you wanted to try 3 phase, its not all that hard to do and being thrifty it can be fairly cheap as well.

 

[930dreamer]

I'd build a rotary phase converter.

 

[Norcal]

The magnetic starter will not be able to be reused for a similar size single phase motor, it looks to be a NEMA size 1 which will handle a 3 HP 1Ø motor, Dayton brand (Grainger) starters were made by ITE* & they are now obsolete, I will have to look up what size is required for a 7½ HP 1Ø motor.

*ITE's industrial control div. was bought by Telemechanique who is now part of the company who owns SQ D, searching for"Telemechanique heaters" should yield some results if one wishes to repurpose the starter, but as I wrote earlier they are obsolete.....

 

[cnc-me]

You are going to need a larger motor starter, with two larger contacts, instead of three
smaller ones.
Certain Square D three phase starters had an auxiliary contact for the control circuit,
that was the same size and shape, as the main contacts, I have paired these together
and used them on single phase before. I doubt yours is setup the same, so you are
going to need a single phase starter or a larger three phase starter.
Don't even try to run a 7.5 HP single phase off the pressure switch you will cook
the contacts in short order. Make sure to change the overloads(heaters) to suit the current drawn by the new motor.

 

[Charles (in GA)]

Cylinders on motor side have parallel outputs with cooling fins, they go down to what appears to be a manifold on the side of the crankcase. From there, one line comes around the near end of the crankcase, does a 360 loop, goes into an elbow and a T and enters the tank. Cylinders on the left side (end of tank side) also have separate outputs that have cooling fins on the tubes, run straight down and disappear around the pulley side of the pump. The light glare makes it difficult to tell, but I don't see them coming up and entering the heads on the motor side bank. I think they also join that manifold on the bottom and thus all four cylinders output to the same place, making me think its single stage. I cannot see any size difference in the cylinders. Again, difficult to tell with the pics, need better close ups, I could be wrong, and it would not be the first time.

Charles

 

[phiftyseven]

That compressor pump is definitely a single stage pump. Look on grainger.com and search that stock# 3Z241 and you'll get all the specs for that pump. As stated above by Norcal, that Dayton motor starter is obsolete and would have to be replaced. Motor starters are sized to match whatever motor you decide to use, so don't buy a new starter until you have all the specs for the motor you choose. As long as that pressure switch works ok, I see no reason to change it. You might be able to adjust it a little bit, but if 90 psi has been working for you, then I see no reason to change. The pump is only rated for 120 psi maximum anyway. The CFM rating is more important I think. I don't know what your Crafstman puts out, but I'll bet this pump will give you much more air volume. It's rated for about 27 CFM with a 7-1/2 hp motor, but that could be a little lower, depending on how much internal wear the pump may have. As long as it's in good shape you should be very happy with that pump,

 

[W-Cummins]

The magnetic starter will not be able to be reused for a similar size single phase motor, it looks to be a NEMA size 1 which will handle a 3 HP 1Ø motor, Dayton brand (Grainger) starters were made by ITE* & they are now obsolete, I will have to look up what size is required for a 7½ HP 1Ø motor.

*ITE's industrial control div. was bought by Telemechanique who is now part of the company who owns SQ D, searching for"Telemechanique heaters" should yield some results if one wishes to repurpose the starter, but as I wrote earlier they are obsolete.....

Unless it was setup to run at 480V ( 10hp 3phase @480v use a nema #1) it will have a #2 starter, and a #2 will run a 7.5hp motor at 240v single phase.

Cylinders on motor side have parallel outputs with cooling fins, they go down to what appears to be a manifold on the side of the crankcase. From there, one line comes around the near end of the crankcase, does a 360 loop, goes into an elbow and a T and enters the tank. Cylinders on the left side (end of tank side) also have separate outputs that have cooling fins on the tubes, run straight down and disappear around the pulley side of the pump. The light glare makes it difficult to tell, but I don't see them coming up and entering the heads on the motor side bank. I think they also join that manifold on the bottom and thus all four cylinders output to the same place, making me think its single stage. I cannot see any size difference in the cylinders. Again, difficult to tell with the pics, need better close ups, I could be wrong, and it would not be the first time.

Charles

Yep looks like your correct, I guess I should have looked up the model # on granger. It looks like ( now that I have seen a good picture on their site) this is an old model of that pump. It looks like there is some type of manifold cast into the base of the pump.
That is an expensive pump at over 3k for a new one!

William....

 

[Norcal]

That starter is not a NEMA size 2, too small, BTW, "nema #1" denotes the enclosure type (Indoor dry locations), not the size group.

 

[BMS]

Appreciate all the discussion, I'm trying to learn as I read along here. Would pics of the insides of that motor starter help?

I do realize that the pump is single stage, which I was fine with as I wasn't looking for high PSI anyway. More volume and capacity for glass beading and painting in the future.

I'd love the idea of doing a rotary phase converter, but I haven't found any explanation that seems to really help me clearly understand what I need. From what I gathered, to do a phase converter for a 10hp motor, I'd need a 15-20hp electric motor to make the phase converter to run this 10hp motor. It really looked like it was cheaper to buy a new 7.5hp 1-ph baldor at about $700.

 

[Norcal]

Appreciate all the discussion, I'm trying to learn as I read along here. Would pics of the insides of that motor starter help?

I do realize that the pump is single stage, which I was fine with as I wasn't looking for high PSI anyway. More volume and capacity for glass beading and painting in the future.

I'd love the idea of doing a rotary phase converter, but I haven't found any explanation that seems to really help me clearly understand what I need. From what I gathered, to do a phase converter for a 10hp motor, I'd need a 15-20hp electric motor to make the phase converter to run this 10hp motor. It really looked like it was cheaper to buy a new 7.5hp 1-ph baldor at about $700.

2 places to go for RPC info are, 1) Practical Machinist, 2) OWWM,Old Wood Working Machines, you will have to register at OWWM in order to view the electrical forum.

http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/

www.owwm.org

 

[W-Cummins]

That starter is not a NEMA size 2, too small, BTW, "nema #1" denotes the enclosure type (Indoor dry locations), not the size group.

I have no idea the actual dimensional size of the starter enclosure in the picture, so I can't say if it's too small. I do know however, if it was not setup to run at 480v, either it is not the correct starter, or it's not a size 1 starter. The correct size for a 10hp 3 phase 240v motor is a 2.
If BMS posts a picture of the inside of the starter enclosure we will know for sure what it is.

William....

 

[BMS]

2 pics of the starter and one of the switch

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[W-Cummins]

Ahh there ya go we were both wrong! It's a size 1 3/4, not some thing I have seen before. It appears to be called a MM sized starter for "motor matched" and is rated at 10hp 230V 3 phase, and 40 amps continuous.
As a size 2 is good for 15hp at 230V, 10hp at 200V 3 phase and 7.5 hp single phase 230V ( all @ 45 amps continuous), I would probably run the 1 3/4 starter on the 7.5hp single phase (even though it's not listed specifically for single phase operation as far as I can see) _IF_ it was mine, and used in my home shop.
My thoughts here are, there is some head room in the ratings, NEMA rated starters are built for severe duty operation, your 7.5 hp motor should not pull more than the 40 amps continuous, and additionally your going to be running it at 240V not the rated 230V.
So if it was mine and I could get the proper heaters for it I would use it. Now if it's in commercial or industrial installation my logic will probably not fly with the inspector as it's not "listed" for single phase use.

William...

 

[BMS]

.................
As a size 2 is good for 15hp at 230V, 10hp at 200V 3 phase and 7.5 hp single phase 230V ( all @ 45 amps continuous), I would probably run the 1 3/4 starter on the 7.5hp single phase (even though it's not listed specifically for single phase operation as far as I can see) _IF_ it was mine, and used in my home shop.
.......................
So if it was mine and I could get the proper heaters for it I would use it. Now if it's in commercial or industrial installation my logic will probably not fly with the inspector as it's not "listed" for single phase use.

William...

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.

I do have an electrician that is going to run my circuits from my subpanel for the compressor and my welder, but he didn't seem to have any experience with phase converters or hooking up air compressors with motor starters and I wanted a setup where he could just land the wires onto the disconnect for me.

 

[W-Cummins]

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.

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......

 

[79mudbugg]

i must say bravo!! SPOT ON W-CUMMINS


so heres something to throw a loop in, wonder if he could use a phase converting vfd??? that way he could just buy that and use the existing motor, and just set the limits of what he plans to do with it?

 

[BMS]

W-Cummins, you rock. Let me digest and get back in here.

 

[wyliesdiesels]

Yes, this is an old thread!!

i must say bravo!! SPOT ON W-CUMMINS


so heres something to throw a loop in, wonder if he could use a phase converting vfd??? that way he could just buy that and use the existing motor, and just set the limits of what he plans to do with it?

A VFD to power that size motor will be really expensive!

W-Cummins, you rock. Let me digest and get back in here.

OP: did u ever get this going?

 

[MTW]

If you want to use this starter, here is the heater element table for size 2 elements.