Air compressor contactor/wiring problem. Need help please!

[dalmatiangirl61]

I built my own phase converter, everything made sense when I assembled it. 15 years or so down the road I decided to upgrade it with new components as a few of the capacitors started leaking. The wires looked like a big plate of spaghetti with no sauce. Thank God I saved my original design drawings, they were good to refresh the memory. It seems the older you get the longer it takes to get your head back in the game.

All the more reason to draw it out! I see it as a logic train, if this happens here, the electrons flow to here, then go here, no wait, thats not right, they need to go here...

 

[CITIZEN F16]

Can you get a picture like #2 in the first post orientated right from different distances?

 

[dalmatiangirl61]

Attached is a rough sketch of your control circuit connections. Your power wiring is connected correctly since you can manually get the motor to run manually, as long as the generated/wild leg stays on L2.

The voltage readings supplied by the OP indicate that L3 is the generated leg, not L2 as he states.

 

[CITIZEN F16]

When testing refrain from testing to ground, this is mostly irrelevant as none of the controls or motor are referenced to ground. You need to do all testing from line to line, namely L1 and L3 in your case.

How are you going to determine the wild leg without testing to a ground or neutral? The wild leg should be on L3 in most circumstances. It needs to be kept out of the control circuit. Also why fuse a control circuit on a machine
without any circuit boards? I am all ears. I see this as a mess that needs to be simplified. I have run a similar compressor without all the crap this thing has with no issues for 25 years and I got it used.

 

[SAF]

If That's the case he needs to correct it. L2 needs to be the generated leg for the way the control circuits are tapped currently.

 

[CITIZEN F16]

The voltage readings supplied by the OP indicate that L3 is the generated leg, not L2 as he states.

Agreed, I think we have 2 people calling the generated leg # 3 you and I, two people calling it #2. Can someone chime in and break the tie, ha,ha.

 

[CITIZEN F16]

If That's the case he needs to correct it. L2 needs to be the generated leg for the way the control circuits are tapped currently.

Are you seeing something I am not? The generated leg should be used as the 3rd line to the motor and nothing else. It needs to stay out of the control circuit. The point to me is he needs 240v to the coil and no way to get it. I think it is time to just take two separate 120v sources and energize the coil with it and see what happens.

 

[13engines]

Post #18 shows the starter with the white wire in the number 2 terminal. Terminals 1 and 3 have control circuit wiring coming out of them. Terminal 2 or the center terminal does not. Hence the suggestion that #2 has to be the RPC generated leg.

The trick here is not to get hung up on a wiring number sequence, but only to keep track of which leg is the RPC generated one. I ran an elaborate system in my garage where the middle terminal or #2 was my generated leg. As long as he knows that and keeps it the same for every connection here on out, what does it matter what number it is?

 

[dalmatiangirl61]

Post #18 shows the starter with the white wire in the number 2 terminal. Terminals 1 and 3 have control circuit wiring coming out of them. Terminal 2 or the center terminal does not. Hence the suggestion that #2 has to be the RPC generated leg.

The trick here is not to get hung up on a wiring number sequence, but only to keep track of which leg is the RPC generated one. I ran an elaborate system in my garage where the middle terminal or #2 was my generated leg. As long as he knows that and keeps it the same for every connection here on out, what does it matter what number it is?

In post #32 he shows voltages to ground, and unless he has a major incoming power off the pole problem, it would indicate L3 is the generated leg.

 

[SAF]

I didn't thoroughly read all of the prior posts, mainly the pictures to produce the sketch.

By code the wild leg is required to be identified with orange wire or tape. Since he has undersized wire connected that should be corrected when he wires it permanently. He will likely have more issues once he installs the belts and puts a load on it. Were just discussing how to get the controls working at this point.

Also the code requires that the wild leg be place on L2 in all cases, except for utility meter cans. This is why the factory starter control connections are tapped from L1 and L3, even provides an extra lug hole, only there for the purpose. Its standard procedure.

The fuse is also required for any control conductors that leave the control enclosure, such as the pressure switch and the low oil switch. The supply circuit should be on the order of a #6 or #8 wire, the breaker to provide the circuit protection, is too large to protect #14 control wiring circuits, once they leave the enclosure.

The starter is wired correctly from the factory to comply with code, its the field wiring that leaves something to be desired.

 

[13engines]

In post #32 he shows voltages to ground, and unless he has a major incoming power off the pole problem, it would indicate L3 is the generated leg.

My point was only that with his current connection scheme pictured, he needs to make sure the white wire at #2 terminal is the generated leg. What was indicated down or upstream was not under consideration.

Nice to hear from SAF that I accidentally had my system done to accepted standards... by accident! :-)

 

[dalmatiangirl61]

My point was only that with his current connection scheme pictured, he needs to make sure the white wire at #2 terminal is the generated leg. What was indicated down or upstream was not under consideration.

Nice to hear from SAF that I accidentally had my system done to accepted standards... by accident! :-)

OK, then he needs to change some wires at the rpc connection, or move the red wire to the L2 terminal. Sounds like your elaborate system for keeping track of generated leg is just like mine, orange tape!

 

[13engines]

...Sounds like your elaborate system for keeping track of generated leg is just like mine, orange tape!

My scheme was using two black wires, and a red one for the RPG leg. Didn't know about the orange tape thingy...

 

[SAF]

For reference.

110.15 High-Leg Marking. On a 4-wire, delta-connected
system where the midpoint of one phase winding is grounded,
only the conductor or busbar having the higher phase voltage
to ground shall be durably and permanently marked by an
outer finish that is orange in color or by other effective means.
Such identification shall be placed at each point on the system
where a connection is made if the grounded conductor is also
present.

230.56 Service Conductor with the Higher Voltage to Ground.
On a 4-wire, delta-connected service where the midpoint of one
phase winding is grounded, the service conductor having the
higher phase voltage to ground shall be durably and permanently
marked by an outer finish that is orange in color, or by
other effective means, at each termination or junction point.

Part VI. Motor Control Circuits
430.71 General. Part VI contains modifications of the general
requirements and applies to the particular conditions of motor
control circuits.
430.72 Overcurrent Protection.
(A) General. A motor control circuit tapped from the load
side of a motor branch-circuit short-circuit and ground-fault
protective device(s) and functioning to control the motor(s)
connected to that branch circuit shall be protected against
overcurrent in accordance with 430.72. Such a tapped control
circuit shall not be considered to be a branch circuit and shall
be permitted to be protected by either a supplementary or
branch-circuit overcurrent protective device(s). A motor
control circuit other than such a tapped control circuit shall be
protected against overcurrent in accordance with 725.43 or the
notes to Table 11(A) and Table 11(B) in Chapter 9, as applicable

(1) Separate Overcurrent Protection. Where the motor
branch-circuit short-circuit and ground-fault protective device
does not provide protection in accordance with 430.72(B)(2),
separate overcurrent protection shall be provided. The overcurrent
protection shall not exceed the values specified in
Column A of Table 430.72(B).

(2) Branch-Circuit Overcurrent Protective Device. Conductors
shall be permitted to be protected by the motor branch circuit
short-circuit and ground-fault protective device and
shall require only short-circuit and ground-fault protection.
Where the conductors do not extend beyond the motor
control equipment enclosure, the rating of the protective
device(s) shall not exceed the value specified in Column B of
Table 430.72(B). Where the conductors extend beyond the
motor control equipment enclosure, the rating of the protective
device(s) shall not exceed the value specified in Column C
of Table 430.72(B).

 

[Ltk]

Attached is a rough sketch of your control circuit connections. Your power wiring is connected correctly since you can manually get the motor to run manually, as long as the generated/wild leg stays on L2.

There is likely a problem with one of the control components. Sitting in a barn can allow oxides to build up on contact surfaces and cause them to be less conductive when inoperative, as you need contact arc to burn off the oxide buildup.

When testing refrain from testing to ground, this is mostly irrelevant as none of the controls or motor are referenced to ground. You need to do all testing from line to line, namely L1 and L3 in your case.

First thing to check is the control fuse. You should test from L3 to the top and bottom of the fuse. The top should be hot 240V, the bottom should read the same, if not the fuse is blown. This is likely due to you having low voltage at the start, then later dropping to no voltage. If its blown, test for a short circuit before replacing. A chattering contactor can also blow the fuse if it is sized closely to the coil draw.

The next things to test, again from the line voltage NOT GROUND.

ON/OFF switch, Its fed from the fuse L1 power leg, so one lead to L3 the other lead to both sides of the switch.

Pressure switch, also fed from L1 leg, so one lead to L3 the other lead to both sides of the switch. ON/OFF switch must be on.

Overload relay contacts, fed from L3, so one lead on L1 the other lead to both terminals of the overload contact.

Another issue that can cause chattering, to check last is the iron magnet assembly that is surrounding the coil. The contact faces can become rusty sitting in a damp location as they are raw steel lamination's. If this is the case the starter coil and magnet assembly will need to be disassembled to get the iron core out for cleaning. Clean the coil faces by lightly rubbing them against some very fine sand paper backed up with a flat piece of steel or glass. No excessive scrubbing or hand sanding. Blow the sanding dust dust off of all parts before reassembling the starter.

The coil should be good because it was trying to pull in while it was being supplied under voltage. just don't continue to let it chatter, it can overheat or continue to blow the fuse.

That should be enough to get you to the problem spot.

View attachment 343823

Okay so I tested everything you mentioned

L3-top of fuse = 244v
L3-bottom of fuse = 244v
L2-top of fuse = 244v
L2-bottom of fuse = 244v
L1 to fuse-both sides = 0.0v

L3-on switch, both sides = 243v

L3-pressure switch, both sides = 243v

L1-overload, both sides = 240v

Coil terminals 1 to 4 = 0.0v
Coil terminal 1 to ground = 120v
Coil terminal 4 to ground = 120v

 

[Ltk]

Took the coil out, anything I should check while I’m in here cleaning the contact surfaces?

I forgot who asked but I have this compressor in my detached home shop, so I’m near it every evening after 5:00 PM and plenty of time to work on it on the weekends

 

[Ltk]

Is there something I should be doing where the low-oil level protector device was plugged into the pressure switch? Jumper those 2 open terminals or leave as is?

 

[Ltk]

Thank you everybody for your help!! Especially SAF with the dirty magnet idea. Cleaning the magnet and coil off did the trick!

 

[SAF]

I don't think your done yet. From your prior voltage readings on post #32

L1-L2 = 241v
L1-L3 = 243v
L2-L3 = 243v

L1-ground = 120v
L2-ground = 120v
L3-ground = 212v

The wild leg is the one with the higher reading to ground, 212V which is shown as L3 above.
This is the leg that should be connected to L2 on the starter. This generated leg voltage will drop significantly when the motor is put under load, when the voltage drops your contactor will again start to chatter.

You need to move that wild leg to the L2 center terminal of the starter, to prevent the chatter from occurring while under load. In other words, switch supply lines L2 and L3.

Where you have 243V listed above, that is an indication of the wild leg being part of the reading.
Where the voltage is listed as 241V that is your line voltage legs, and that will be much more stable under load.

So make the change before you put load on the motor and controls, or you will have problems.

Your chattering problem was initially due the rusty armature magnet. But your 0V reading to the coil was due to a poor connection. Taking it apart and reassembling it fixed the poor connection to restore coil voltage.
I suggest you clean and check all of the other connections.

 

[Ltk]

I don't think your done yet. From your prior voltage readings on post #32

L1-L2 = 241v
L1-L3 = 243v
L2-L3 = 243v

L1-ground = 120v
L2-ground = 120v
L3-ground = 212v

The wild leg is the one with the higher reading to ground, 212V which is shown as L3 above.
This is the leg that should be connected to L2 on the starter. This generated leg voltage will drop significantly when the motor is put under load, when the voltage drops your contactor will again start to chatter.

You need to move that wild leg to the L2 center terminal of the starter, to prevent the chatter from occurring while under load. In other words, switch supply lines L2 and L3.

Where you have 243V listed above, that is an indication of the wild leg being part of the reading.
Where the voltage is listed as 241V that is your line voltage legs, and that will be much more stable under load.

So make the change before you put load on the motor and controls, or you will have problems.

Your chattering problem was initially due the rusty armature magnet. But your 0V reading to the coil was due to a poor connection. Taking it apart and reassembling it fixed the poor connection to restore coil voltage.
I suggest you clean and check all of the other connections.

I did switch those 2 legs as the motor was running backward. The Generated leg is the white wire which is now L2, I don’t mark them with orange tape but every machine in my shop is the same.

I will rewire this entire starter and pressure switch and clean every terminal up before putting this to use. Waiting on a few fittings for the pump that I had to order.

The moment of truth will be seeing if my 20hp RPC can power this thing under the 18” flywheel load and restart this compressor once pressure drops, etc. We’ll see once the fittings come in and I’m ready to fire it up!