Compressor Motor Issues

[El_Diablo]

I have a brand new 220v 5hp motor with twin capacitors and over heat protection which is rated at 23 amps. I can get the motor to run on 110v either leg but if I flip on both legs the 30amp breaker immediately trips. Being a capacitive start I don't believe I need a mag starter but I'm starting to think that I may need a soft starter or perhaps some other way to combat the issue? Any and all help is greatly appreciated!

 

[WhoWhatNow]

A 30 amp breaker is most likely too small for that motor without a mag starter. Starting amps can be significantly more that the motor plate amps.

 

[El_Diablo]

Even though it's a capacitive start?

I've now even tried a 50 amp breaker. It still wants to trip. Thats over double what the motor is rated for (23amps).

 

[454ragtop]

I've never heard of running a 230 volt motor off of 110, is this a recommended procedure? I have a similar or larger Baldor 5 HP on a compressor and it runs just fine on a 30 amp breaker. Can you post a pic of the wiring schematic on the motor? I think you will need a mag starter, but don't think it will help with the tripping breaker.
Jim

 

[larry_g]

I have a brand new 220v 5hp motor with twin capacitors and over heat protection which is rated at 23 amps. I can get the motor to run on 110v either leg but if I flip on both legs the 30amp breaker immediately trips. Being a capacitive start I don't believe I need a mag starter but I'm starting to think that I may need a soft starter or perhaps some other way to combat the issue? Any and all help is greatly appreciated!

A proper 30a 240 v breaker would not allow you to flip only one leg at a time. I suspect something is wrong in the primary wiring as you should not have that motor start on a single hot leg. Give us some detailed information on the breaker box, pictures of the wiring, make & model of the compressor and motor. Right now your only going to get guesses on what little information is provided.

on edit, a mag starter does nothing to prevent inrush current.

lg
no neat sig line

 

[JHAUK]

110 plus 110 does not always equal 220. Make sure you are not pulling from 2 110 legs instead of the 220 bar. If you are on 220 you will have 1 breaker not 2. Safety hazzard to only break one side.

 

[El_Diablo]

I popped the 30a breakers cross bar off so that I could test either leg of the feed briefly to try and see if the problem was one one leg or the other.

The compressor pump is a 5hp harbor freight unit. The motor is a northern tool "iron ton" 5hp capacitive start motor. Basically I have a 50a service out to the garage (soon to be 100a) which leads to a main lug box. From there it goes from a 30a breaker to 10-3 wiring directly to the motor for testing purposes currently.

The motor:
http://www.northerntool.com/shop/tools/product_200596343_200596343

 

[El_Diablo]

110 plus 110 does not always equal 220. Make sure you are not pulling from 2 110 legs instead of the 220 bar. If you are on 220 you will have 1 breaker not 2. Safety hazzard to only break one side.

I'm running a single breaker with two hots (red and black) of 50 amps to the garage and the same with a 30 amp breaker to the motor.

 

[larry_g]

I'm running a single breaker with two hots (red and black) of 50 amps to the garage and the same with a 30 amp breaker to the motor.

Can you measure 240v at the compressor?

Read this thread http://www.garagejournal.com/forum/showthread.php?t=233833&highlight=240v

lg
no neat sig line

 

[b-body-bob]

Can you get to the caps to check them, or at least give them a visual once over? A bad cap will cause it to not start and trip the breaker.

Is there air in the tank? If you let pressure off, does it still balk at starting? If there's pressure on the head due to a bad check valve or unloader, it can stop the motor from starting because it can't turn the pump over against the pressure.

 

[Davefr]

I have a brand new 220v 5hp motor with twin capacitors and over heat protection which is rated at 23 amps. I can get the motor to run on 110v either leg but if I flip on both legs the 30amp breaker immediately trips. Being a capacitive start I don't believe I need a mag starter but I'm starting to think that I may need a soft starter or perhaps some other way to combat the issue? Any and all help is greatly appreciated!

Put an amp clamp on one of the legs of 220V going to the motor. Now measure the voltage. Report back with the data.

 

[scw1991]

A 5HP motor will pull anywhere from 21 to 23 amps (per leg) on 230v circuit.
.
Each 115v leg in the circuit must be 180 degrees out of phase with one another
.
A 30 amp 230v DPST breaker is more than sufficient for a 5HP 230v motor
.
A dedicated 30amp circuit is required to run a 5HP compressor
.
A 5HP motor will need a definite purpose mag starter (no pressure switch commercially available can handle that amount of amperage to start/stop a motor). Pressure switch gets wired to the mag starter 230v coil to start/stop motor.
.
Since you are trying to run a 5HP Harbor Freight compressor, what size of pulley is on the compressor and on the motor? I suspect you are overloading the motor because the pulley on the motor is too large in diameter

 

[C96]

All good suggestions above but try taking the belts off and then try again.
If same thing, then you definitely have some wire connections wrong.
Also, you do realize the motor you selected spins at 3,450 RPM; this is a bit fast for an air compressor. Most 5hp air compressors are usually somewhere around 1,700-1,800 RPM as far as the motor RPM are concerned. Regardless, the main thing is not to over or under spin the pump. With the RPM your running and that HF pump, the pulley size on the motor should be no larger than 4-3/8” or good chance you will be overloading the motor.

 

[El_Diablo]

The pulley is sized within 70rpm of the pumps maximum RPM. I'll have to run more tests when I get a chance. Unfortunately I don't have an amp clamp.

 

[scw1991]

I helped a friend restore a 60's vintage Kellogg compressor and used a Baldor 5HP 1725 rpm motor. I also sized the motor pulley to achieve recommended nameplate compressor RPM. The amperage draw on the motor was pushing 28amps near cut-off pressure of 175 psi. Nameplate motor full load amperage is 21amps. I knew if I did not decrease diameter of motor pulley, that motor wasn't going to last long. I reduced motor pulley diameter by almost 1" and maximum amperage draw never exceeded nameplate rating.

Needless to say , it was necessary to reduce compressor speed by almost 75 RPM to keep from overloading the motor.

 

[kams1973]

"A 5HP motor will need a definite purpose mag starter (no pressure switch commercially available can handle that amount of amperage to start/stop a motor). Pressure switch gets wired to the mag starter 230v coil to start/stop motor."

The motor has a thermal reset built in. Condor makes pressure switches that will easily handle the demand.

 

[scw1991]

I stand corrected. Thanks kams1973. No definite purpose mag starter is then required since motor has overload protection.

 

[El_Diablo]

The motor pops the fuse even without the belts. I checked voltage out at the sub panel and it's showing 244v.

With the square D compressor switch it looks like I need a mag starter as it's only rated at 15amps. I'll be ordering a starter tonight.

How can I check the caps or what should I check next? I didn't check voltage at the motor because this is brand new 10-3 wire and currently it's connected directly to the motor so it should be getting pretty darn close to a full 240v.

 

[kams1973]

If the motor is brand new, why not warranty it?

 

[El_Diablo]

I got a bad one already. I'm thinking I'm going to call them up again...

 

[El_Diablo]

I guess it's more at this point I'm wondering if I'm doing something wrong or if it's another bad motor.

 

[El_Diablo]

240v and 120/120 verified at the motor. Rewired the motor and it still trips the breaker. Starting to think I got another bad motor.

 

[scw1991]

I wonder if there is an issue with the centrifugal switch not opening up once motor gets up to speed.

A 30amp pressure switch is going to be much more economical than a definite purpose Square D series 8911 mag starter or a Siemens WS5-2301P 5HP mag starter. As stated above, since motor has thermal overload protection, a mag starter is not required.

Are you sure you've got 120v / 120v which are 180 degrees out of phase with each other? Something just doesn't sound right if this is the second motor to keep tripping a breaker.

 

[C96]

I got a bad one already.

I'm wondering if I'm doing something wrong or if it's another bad motor.

It’s not likely this second motor has the same problem as the first. You must have it wired incorrectly. Double check the wire taps at the motor junction box. Make sure its exactly as per the diagram provided with the motor. The diagram should be on the motor nameplate or inside the terminal junction box.

 

[El_Diablo]

It's running off of the same 220v source as my furnace, dryer and oven (which have all always worked just fine) with the only difference being that power is first fed out to the sub panel box and then to the motor. I took the capacitor cover off and the capacitor mounts are all twisted around and almost looks like the capacitors are slighter "squashed" (ovaled) down to the capacitor cover.

I've checked wiring twice, the motor came with no actual diagram (which is bull) but the terminals are labelled L, C and H with an obvious green ground screw. I have the common hooked up to the C terminal, red leg going doing to the L terminal and the black leg going to the H terminal.

The thing is, this motor pops a fuse as soon as I throw the breaker (direct wired and free spin for trouble shooting) so it never even has a chance to get up to speed. The second the motor see's power it blows, disconnect the motor and it's fine, reconnect, blows again.

I'm hoping it's just my wiring but I'm at a loss as to what I could be doing wrong.

 

[joel63]

Have you checked the motor for grounds?

Also make sure to check the capacitors for grounds.

 

[JHAUK]

Ok so to clear things up a bit. First overload protection on the motor does not protect the contacts on the pressure switch from welding themselves together when not 20-25 amps are run through them, but more like 60-100 amps on start up. There just isn't enough metal there to withstand the heat. While it is true that most starters come with overload protection, no pressure switches come with magnetic coils. Second make sure to note the markings on the pressure switch. They will be marked line and load. Some switches pair the wires side to side some pair them top to bottom. If you are blowing breakers with the belts off, then the pressure switch is wired wrong or you have a defective motor. Oh and third if you have a 5 hp motor single phase, then you should look at a 60 amp breaker with a 40 amp fusable disconnect.

 

[scw1991]

There is not a Common lead on a 230v motor. There is a Red lead, a Black lead, and a grounding screw. That's it.

 

[Davefr]

240v and 120/120 verified at the motor. Rewired the motor and it still trips the breaker. Starting to think I got another bad motor.

Is the voltage steady at 240 VAC from startup to the point of tripping the breaker?

Is all the wiring from panel to motor sufficient for a motor of that size?

If the motor won't start and quickly come up to speed without a load then take it back to where you bought it and have them bench test it.

 

[454ragtop]

There is not a Common lead on a 230v motor. There is a Red lead, a Black lead, and a grounding screw. That's it.

X2, all you should have are 2 hot legs and a ground. The 4th wire is used in cases where you need a neutral to pull off a 115 volt circuit. Best to have them send you a wiring diagram for the motor.

 

[El_Diablo]

In that case I'm a tard. I've tried but so far the claim not to have one. I'll try calling northern up again.

 

[scw1991]

take some pics of this motor and post to the forum. I downloaded the motor manual for this Northern Tool 5HP motor p/n 29625, and this motor is to be used on a 208v-230v circuit only. This motor cannot be wired for a conventional 115v circuit.

There should only be (2) hot leads and a green grounding lug at the motor. That is it. There is no neutral wire that gets wired to this motor.

T1 lead at the motor gets wired to one side of the 115v breaker buss bar
T2 lead at the motor gets wired to the other side of the 115v breaker buss bar
bare copper wire (ground wire) gets wired to motor frame (green screw)

 

[brawls43]

So there's no picture or diagram inside the cover of the case? The motor manual doesn't have a diagram, which figures since its for 4 different versions of the motor. They do still recommend a starter in the manual. Can you post some pictures? It helps with diagnosis. Pictures of the motor, and cover panel, and the pressure switch. I think you said you were by-passing the pressure switch right now, but still.

I think its wired wrong. I think you only need to connect the two 110v legs to the motor, and ground the 3rd. But a wiring diagram would really help.

 

[C96]

Agreed, need pictures at this point. Nice clear pics of motor name plate, inside and outside of the terminal junction box, inside and outside of the terminal junction box cover and pics of the actual lead wires showing the markings on them i.e. L, C, H, etc.

 

[kams1973]

Ok so to clear things up a bit. First overload protection on the motor does not protect the contacts on the pressure switch from welding themselves together when not 20-25 amps are run through them, but more like 60-100 amps on start up. There just isn't enough metal there to withstand the heat. While it is true that most starters come with overload protection, no pressure switches come with magnetic coils. Second make sure to note the markings on the pressure switch. They will be marked line and load. Some switches pair the wires side to side some pair them top to bottom. If you are blowing breakers with the belts off, then the pressure switch is wired wrong or you have a defective motor. Oh and third if you have a 5 hp motor single phase, then you should look at a 60 amp breaker with a 40 amp fusable disconnect.

I've seen contacts on starts weld themselves closed too.

 

[454ragtop]

Should be fine on a 30 amp breaker, my 5HP Baldor has been for more than 25 years.

 

[sberry]

Is this machine stock from the mfg? If so it shouldn't need additional equipment. I would look again at motor wiring. A dead short trip should be somewhat obvious.

 

[El_Diablo]

Well, I got the motor working tonight. The issue was the common. I just moved the black wire to where the common was, the motor came to life and SUCCESS! IT RAN!!!



Right up until this happened....

 

[KinzeMech]

Can you post a pic of the motor junction box, and the nameplate?

 

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