Snap-On compressor wiring

[bashr52]

I just purchased an older Snap-on BRA7180v model compressor. The body shop I purchased it from had the control panel wiring all hacked together. I've got the wiring all run to it and everything back together the way it appears to go, but it wont fire up. I think I'm missing a wire off the pressure switch, as there is one screw missing, and the other is loose.

Does anyone have one of these compressors and could send me some pictures of the way the wiring is run on your compressor?

Thanks

 

[DieselDent]

I have the same compressor post some pictures of your situation and ill try and see whats goin on, I wont be home for a few days to get pictures of mine.

 

[bashr52]

I think I have it figured out. There should be a neutral and hot leg going to the automatic shutoff valve, which would be why there are two places where wires are missing. Those then run up to the relay which powers the motor.

I'm going to try it tonight and see what happens.

 

[LS6 Tommy]

If it's a 120V unit and there are only 2 terminals on the switch, putting N and L1 on them will be dead short. L1 should go on one terminal and one wire from the contactor coil on the other. The othe contactor coil line should go to N... Pics would be a great help.

Tommy

 

[G_P]

Google says thats an 80gal 7HP compressor. It has to be 240v, not 120v.

http://buy1.snapon.com/catalog/item.asp?item_ID=643128&group_id=681243&supersede=&tool=all

Take some detailed pics of the wiring and connections and we can get it figured out.

 

[LS6 Tommy]

Google says thats an 80gal 7HP compressor. It has to be 240v, not 120v.

http://buy1.snapon.com/catalog/item.asp?item_ID=643128&group_id=681243&supersede=&tool=all

Take some detailed pics of the wiring and connections and we can get it figured out.

Either way, you only have 1 leg on the pressure switch if it only has 2 terminals...

 

[bashr52]

Yes it is 220V. There are 4 terminals on the pressure switch. The two existing wires are black and white and go to the L1 and L2 positions on the motor relay. I believe I need to run a neutral and hot leg to the corresponding open terminals on the relay to match. It apears the pressure switch cuts off both the neutral and hot leg to the main relay, instead of just one like I'm used to.

 

[pattenp]

If 220V there should not be a neutral. The white is a hot. L1 & L2 are the 2 hots coming in and T1 & T2 are the 2 hots going out to the motor.

 

[LS6 Tommy]

If 220V there should not be a neutral. The white is a hot. L1 & L2 are the 2 hots coming in and T1 & T2 are the 2 hots going out to the motor.

Yup. Beat me to it...

Tommy

 

[bashr52]

Yup. Beat me to it...

Tommy

Yes this is how the main compressor relay is setup. This relay is separate from the smaller relay on the pressure cut off side of things, which I believe is 120.

 

[pattenp]

What is the purpose of the relay that you believe is 120V? I'm failing to think of its purpose unless someone wired in a switch to cut off the compressor.

 

[bashr52]

Heres the main contactor. I belive it should be wired:
A1 energizing live
A2 neutral
1 permanent live
3 supply neutral
2 switch live
4 load neutrail
View media item 47267
View media item 47268
Here's the contactor on the pressure side
View media item 47269
I believe I need to tap into the neutral and one live wire and send 110 through it to trip the msin contactor

 

[Trey T]

If that contactor/relay is C25BNB230B, then you don't need to have a neutral on the relay coil or the switch. Another word, if that relay is 240V, then you don't need the neutral wire.

You can run 120v or 240v through most, if not all, pressure switches out there.

One side of the relay contact will be hot all the time and the other one will have the pressure switch b/t it, like a light switch.

 

[bashr52]

The wires on the pressure switch come off the side terminals on the main relay, which are isolated off the main relay lugs, so there is no power being sent to the pressure switch. The neutral wire I just have tied direct to the neutral on the motor (green). The white and black wires from the motor are both tied to the incoming hot legs. Both wires on the pressure switch are isolated from each other as well, no matter if the switch is tripped or not.

 

[redmondjp]

What is the purpose of the relay that you believe is 120V? I'm failing to think of its purpose unless someone wired in a switch to cut off the compressor.

It's a 2-pole contactor, controlled by the pressure switch.

I have this same exact compressor. They cut corners on the motor controls, as a 7HP motor really needs a proper motor starter with overload heaters in it. Mine, in addition to the contactor and pressure switch, also has a 40A 2-pole circuit breaker factory-installed. I suspect this is their cost-cutting way of achieving some sort of overload protection for the motor, but I haven't looked at the motor and breaker time-current curves to see if it actually will or not.

 

[pattenp]

The main contactor has a 240V coil. There is no neutral. The small relay should also be 240V. Look for markings on the small relay.

Also why is there URD cable wired to the compressor? That cable is not approved for inside use. It's under ground service entrance cable.

 

[bashr52]

There is no neutral going to either of the contactors currently, it's just tied directly to the motor. The way it sits now, I've got 240 going to the main contactor, and that's it. Not sure what else I need from here.

 

[redmondjp]

There is no neutral going to either of the contactors currently, it's just tied directly to the motor. The way it sits now, I've got 240 going to the main contactor, and that's it. Not sure what else I need from here.

That's all you should need, besides the ground wire connected. That is, unless somebody has messed with the factory wiring on the unit. Does your unit have the circuit breaker on it (on mine, it's facing the floor, mounted underneath the motor support)?

 

[bashr52]

That's all you should need, besides the ground wire connected. That is, unless somebody has messed with the factory wiring on the unit. Does your unit have the circuit breaker on it (on mine, it's facing the floor, mounted underneath the motor support)?

It did, I can see the cutout and mounting holes from it. Can you look at your pressure switch wiring and maybe get me some pics of how your system is done? There were some screwy things done on this thing when I got it. It worked in the body shop until they replaced it with a rotary style.

Also, what does that red lever do that's just above the tank gauge on the side of the pressure switch?

 

[pattenp]

The red lever is for turning off the compressor by inactivating the pressure switch.

The pressure switch should have 4 wires going to it. It needs to have 240V to it. I see one open screw hole, there should be another open hole or screw for the second connection which I do think I see back behind the yellow spade connector.

 

[bashr52]

That is whats stumping me. There was one hole open, and one with a screw half way out. The fact that the wires running to the main contactor are black and white made me think it should be 110V to the main contactor (which is what I need for the contactor on my mill). So I need to tap into both the hot legs and send 240 through the pressure switch as well?

 

[pattenp]

That is whats stumping me. There was one hole open, and one with a screw half way out. The fact that the wires running to the main contactor are black and white made me think it should be 110V to the main contactor (which is what I need for the contactor on my mill). So I need to tap into both the hot legs and send 240 through the pressure switch as well?

Yes. The pressure switch needs to provide 240V to the main contactor coil. From what I can see the pressure switch is a 2 pole switch.

There are spade connectors on the constant hot side of the contactor to supply power to the pressure switch.

Check the condition of the contacts on the main contactor. If they are badly burned and pitted you should replace the contactor.

Also the supply line, if that's aluminum wire, and you haven't do so, use noalox on the ends at the connections.

*

 

[bashr52]

Great, I'll give that a try tonight. Yes that is aluminum wire, and I put that goop on all exposed ends.

 

[LS6 Tommy]

HOld it a minute... There is no reason to connect Neutral to the "green" wire in the motor. That is a ground, not a Neutral...

Tommy

 

[justsam]

Sounds like pattenp is on it to me.
Pick up constant 240VAC from the incoming side of the contactor, that goes to the two poles on the pressure switch.

The other side of the pressure switch, the switched side if you will, goes right back to the contactor coil to activate it.

I cannot imagine any neutral being used as that would normally not be expected to be available in typical 240 VAC shop wiring.

If you manually activate the contactor by using some insulated tool and pressing down on contacts, does the motor run as it should?

 

[bashr52]

Thanks guys, I will try tapping into the incoming side of the contactor and put 240 through the pressure switch and see if that does it.

I dont see any place on the compressor for the ground from the motor to be attached, or a boss for the neutal wire. I just tied the two together so the motor would be grounded right back through the box......

 

[redmondjp]

It did, I can see the cutout and mounting holes from it. Can you look at your pressure switch wiring and maybe get me some pics of how your system is done? There were some screwy things done on this thing when I got it. It worked in the body shop until they replaced it with a rotary style.

Also, what does that red lever do that's just above the tank gauge on the side of the pressure switch?

I'll try to look at the wiring tonight - Snap-on sells two versions of that compressor and one of them doesn't have the circuit breaker so it's possible that yours never came with it. I'm still puzzled as to what provides overload protection for the motor on these units.

 

[justsam]

I'll try to look at the wiring tonight - Snap-on sells two versions of that compressor and one of them doesn't have the circuit breaker so it's possible that yours never came with it. I'm still puzzled as to what provides overload protection for the motor on these units.

I know nothing about the motor used in this application, but I suspect it has it's own internal thermal overload protection, and does not use external devices. Keeps it simple and low cost of production.

 

[redmondjp]

I know nothing about the motor used in this application, but I suspect it has it's own internal thermal overload protection, and does not use external devices. Keeps it simple and low cost of production.

But this is not a consumer-grade "SPL" motor we're talking about here. It's a large-frame Baldor 7HP capacitor/start capacitor/run motor that has a full-load current of 34amps. Find me any internal overload protector that can handle that kind of current. There is a very good reason why true 5HP and larger single-phase motors need a separate motor starter.

I've taken the cover off my 7HP motor and it's stuffed full of capacitors. No sign of any overload protection. No red 'reset' button anywhere on the motor either, like my "5HP" (actually about 3HP) Devibliss compressor motor has on it.

Not saying that they didn't cut corners on this motor, as they did - if you go to the Baldor website, they don't even show a 7HP motor, only 7.5HP. So they did leave out a few turns of windings and put the 7HP rating on the nameplate for this compressor manufacturer.

 

[justsam]

But this is not a consumer-grade "SPL" motor we're talking about here. It's a large-frame Baldor 7HP capacitor/start capacitor/run motor that has a full-load current of 34amps. Find me any internal overload protector that can handle that kind of current. There is a very good reason why true 5HP and larger single-phase motors need a separate motor starter.

I've taken the cover off my 7HP motor and it's stuffed full of capacitors. No sign of any overload protection. No red 'reset' button anywhere on the motor either, like my "5HP" (actually about 3HP) Devibliss compressor motor has on it.

Not saying that they didn't cut corners on this motor, as they did - if you go to the Baldor website, they don't even show a 7HP motor, only 7.5HP. So they did leave out a few turns of windings and put the 7HP rating on the nameplate for this compressor manufacturer.

While I certainly do not disagree with anything you have stated, the OP insists that there are but two control devices in play, the pressure switch and the contactor. I suppose that Snap On may have recommended a legitimate external starter and one was not used.

I wonder what the recommended breaker size is; is there little margin for in-rush or slip and that is the only form of motor protection, which is none at all.

 

[pattenp]

I don't know why neutral keep getting talked about. All I see are three feeding conductors, 2 blacks and 1 black with a yellow stripe which should be the ground. Which by the way needs to be marked as green on the ends as long as it's #4 or larger. If smaller than #4 then it needs to be replaced with a green wire. bashr52, do you have 4 wires pulled to the compressor or just 3? Again, I'm only seeing 3. Are you calling the yellow striped wire a neutral? I really don't want to go down the code road because the wire used for the feed is an improper type.

 

[redmondjp]

While I certainly do not disagree with anything you have stated, the OP insists that there are but two control devices in play, the pressure switch and the contactor. I suppose that Snap On may have recommended a legitimate external starter and one was not used.

I wonder what the recommended breaker size is; is there little margin for in-rush or slip and that is the only form of motor protection, which is none at all.

Here are the links to the compressor information from Snapon's site - they claim that a magnetic starter is included (so they are considering the 2-pole contactor as a magnetic starter which is technically not completely correct due to omitting the motor overload protection):

http://buy1.snapon.com/catalog/item...roup_ID=681243&store=snapon-store&dir=catalog

and this more expensive one:

http://buy1.snapon.com/catalog/item...roup_ID=681243&store=snapon-store&dir=catalog

Their description is a bit confusing - mine appears to be a combination of the above-two units (mine is about ten years old though) - I have the all-aluminum Chinook K30 pump, hourmeter, circuit breaker switch, but a manual tank drain.

And per the other poster above about the neutral - you are correct in that there is no neutral wire to the unit - it's two hot leads and a ground.

 

[bashr52]

It works finally! First thing I did was manually trip the main contactor to verify the motor would start and run, which it did. Then I tapped into two of the tabs below the incoming power leads and ran it through the open terminals on the pressure switch. It fired right up and ran until the pressure switch cut it off. I'm back in business now.

Yes there are 3 wires, the black/yellow wire is a ground, which is tied direct to the green ground wire on the motor. The motor lists a startup/full load draw of 34 amps, and is run through a 40 amp breaker at the box. The compressor itself is switched through a 60 amp square D wall mounted switch.

 

[pattenp]

You are welcome.