eaton Contactor , QT7.5

[youdevon]

the issue seems a bit odd ..I posted here about it originally http://garagejournal.com/forum/showthread.php?t=340791&page=2

so I got a guy to check it out , he got it up and running somewhat.. he disconnected one of the wires off the relay , (the red wires) and manually pressed the contactor in and the machine started up as its supposed to, then he attached the wire back and it continued to run. but when the wires are set an u turn the power on there is a flash in the contactor and a very rough turn over , seems like the contactor is not holding .... any ideas ???

 

[wyliesdiesels]

the issue seems a bit odd ..I posted here about it originally http://garagejournal.com/forum/showthread.php?t=340791&page=2

so I got a guy to check it out , he got it up and running somewhat.. he disconnected one of the wires off the relay , (the red wires) and manually pressed the contactor in and the machine started up as its supposed to, then he attached the wire back and it continued to run. but when the wires are set an u turn the power on there is a flash in the contactor and a very rough turn over , seems like the contactor is not holding .... any ideas ???

It may not be fulling actuating because the coil is not getting full voltage especially when the motor kicks in due to in-rush current causing voltage drop. The flash is the contacts not making full contact.

If youre seeing 224v idle, I bet its dropping close to 200v during in-rush which the coil wont like and will cause the motor to use more current than its designed for as well.

Try replacing the contactor to see if the problem sill occurs. If it does then u know its not the contactor.

 

[youdevon]

I got the electric company to fix my line , so I'm getting about 234v now.. This is the second contactor , a guy did mention the fact that its maybe dropping low when it kicks in.. So now I'm looking for solutions to this issue

 

[matt_i]

You might have to try to find a buck/boost transformer for the control wiring. That's a transformer with multi-tap windings setup to slightly increase or decrease the voltage, depending on which set of windings are chosen.

An alternative would be a contactor rated for 208/240vac on the coil....not sure if Eaton has such an animal. But, if available, that would be an easy cure for the proper magnetism during the startup voltage sag.

I would also spend time making darn sure all the other wire connections are good on the control side of the circuit (with power turned OFF!). One good way is to physically pull or tug on the connection with low-medium hand force. A connection that pulls apart cannot be a good electrical connection.

Along those lines one can troubleshoot for a very short period of time by bypassing the pressure switch contact with a jumper or wire nut. No more than a few seconds before you open the breaker as there's now no signal to shut the compressor down when target tank pressure is reached. Same thing for the overload contact (if present). It can be temporarily jumpered to troubleshoot the motor starting. If either of these tests improve the operation greatly, then you have identified the bad component or high resistance contact in the circuit. Proceed with great care doing these things and restore everything to normal before proceeding. Take cell phone pics and label wires with electrical tape or paint pen so they all get back to the proper places. "red wires" can all start to look the same if the circuit diagram isn't crystal clear in your head.

 

[Dagny]

New contactor

 

[TheEquineFencer]

FWIW...Several years ago a buddy with a shop near his house, separate service, same property, had a reoccurring problem of his compressor burning motors and contactors. Long story short, no pun intended, the POCO had undersized the wire from the transformer to his meter base. He was getting a heck of a voltage drop at start up. The POCO up-sized the feed cable size from the transformer to the meter and the problems went away.

If I saw this correctly, the OP is in Canada? What is your normal Voltage and Hz for the area you are in?

If you have a meter that records hi/lo like a Fluke 87V, set it to record the incoming voltage, then start the compressor and see what the voltage drop is.

 

[wyliesdiesels]

FWIW...Several years ago a buddy with a shop near his house, separate service, same property, had a reoccurring problem of his compressor burning motors and contactors. Long story short, no pun intended, the POCO had undersized the wire from the transformer to his meter base. He was getting a heck of a voltage drop at start up. The POCO up-sized the feed cable size from the transformer to the meter and the problems went away.

If I saw this correctly, the OP is in Canada? What is your normal Voltage and Hz for the area you are in?

If you have a meter that records hi/lo like a Fluke 87V, set it to record the incoming voltage, then start the compressor and see what the voltage drop is.

The OP is in the Caribbean...his voltage should be 240v 60hz

 

[youdevon]

yep Caribbean I am , suppose to be 240 which sometimes is 220 and below .. but I have currently about 234v coming in .. I attached a pic to the main post of the wire we disconnected from the relay , so now when we manually push the contactor In it engages an when engaged if u attach the wire where it suppose to be it works perfectly thru that cycle . but if we set it to stock , there is a lot of flashing an knocking in the contactor.. so I'm looking for ways to remedy this ..

 

[wyliesdiesels]

yep Caribbean I am , suppose to be 240 which sometimes is 220 and below .. but I have currently about 234v coming in .. I attached a pic to the main post of the wire we disconnected from the relay , so now when we manually push the contactor In it engages an when engaged if u attach the wire where it suppose to be it works perfectly thru that cycle . but if we set it to stock , there is a lot of flashing an knocking in the contactor.. so I'm looking for ways to remedy this ..

Do u have a multimeter that has a min max avg function?

If so, then u should hook it up to the line terminals on the starter set the meter for minimum and voltage and then turn on the compressor. Imcurious how low the voltage drops.

Even if u have 240v before u start the motor, if the transformer, service wire and/or branch circuit wire isnt large enough to handle the momentary in-rush current u will have voltage sag which can cause the coil to not fully engage and thus have sparks at the contacts.

 

[TheEquineFencer]

Do u have a multimeter that has a min max avg function?

If so, then u should hook it up to the line terminals on the starter set the meter for minimum and voltage and then turn on the compressor. Imcurious how low the voltage drops.

Even if u have 240v before u start the motor, if the transformer, service wire and/or branch circuit wire isnt large enough to handle the momentary in-rush current u will have voltage sag which can cause the coil to not fully engage and thus have sparks at the contacts.

wyliesdiesels, let me run something by you. If he does have a voltage drop issue....in the back of my mind, I seem to remember something similar happening to a guy. I think he sort of "put a bandaid on the issue" by using a couple of 240V to 240V transformers on the incoming power. The transformers were large enough that when the voltage tried to drop, they had enough inductance in them they sort of acted like a capacitor and held the voltage up long enough for the compressor to start. I wonder if voltage drop is the issue, if a cap or something like this would work?

 

[manwithtools]

yep Caribbean I am , suppose to be 240 which sometimes is 220 and below .. but I have currently about 234v coming in .. I attached a pic to the main post of the wire we disconnected from the relay , so now when we manually push the contactor In it engages an when engaged if u attach the wire where it suppose to be it works perfectly thru that cycle . but if we set it to stock , there is a lot of flashing an knocking in the contactor.. so I'm looking for ways to remedy this ..

Insufficient voltage caused by inrush of the motor actually starting. Typically that is a result of voltage drop either caused by wire size or length of run. I'd suggest a temporary run of larger wire if that's practical (that will prove the problem), if not I'd change the coil to a lower minimum voltage version - maybe 208 - 240 rated coil.

 

[wyliesdiesels]

yeah hard to tell.

Looks like first notch is 24, then blank (28??), then 32, ....then maybe 40??

OP what amp setting is the yellow dial on the overload relay block set to?

Doubt that has anything to do with it though

 

[youdevon]

Doing this from my phone , hope the zoom in pic clear.

The wire size is rated for about 96a , it's 16 squared armored xlp cable .. So it should be more than sufficient for this run

 

[wyliesdiesels]

Pic is too blurry

 

[TheEquineFencer]

yeah hard to tell.

Looks like first notch is 24, then blank (28??), then 32, ....then maybe 40??

OP what amp setting is the yellow dial on the overload relay block set to?

Doubt that has anything to do with it though

??? If it trips the overload, wouldn't it "lockout" and you'd have to reset the switch?

 

[matt_i]

The Eaton catalog has a "pickup voltage" tolerance of 0.8 - 1.1 times Uc which is the nominal 240vac voltage. So that's 192vac...pretty low.

http://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/vol10_tab17.pdf

Also...potentially available in "Frame Size H" is a coil suffix -B which denotes 190-240vac operation. See pages 9 and 12 in the pdf.

http://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/vol09_tab02.pdf

 

[wyliesdiesels]

??? If it trips the overload, wouldn't it "lockout" and you'd have to reset the switch?

Yes thats why i highly doubt its the overload relay as the OP hasnt said anything about having to reset it.

The Eaton catalog has a "pickup voltage" tolerance of 0.8 - 1.1 times Uc which is the nominal 240vac voltage. So that's 192vac...pretty low.

http://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/vol10_tab17.pdf

Also...potentially available in "Frame Size H" is a coil suffix -B which denotes 190-240vac operation. See pages 9 and 12 in the pdf.

http://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/vol09_tab02.pdf

Its interesting u brought this up. We dont know what the voltage is dropping to during motor startup.

However, when he manually pushes in the contactor it works fine so i cant think of anything else that would cause the issue of the contacts flashing seeing as hes already tried another brand new contactor.

 

[matt_i]

Another possibility is to disconnect T1, T2 from the bottom side of the contactor and attempt to allow the compressor to "start" automatically.

In this case there is no voltage drop on the "power side" so the contacts should hit so hard it should literally scare you a little bit if your hearing is good and you are close by....

If not then there's a bad (= high resistance) connection somewhere in the control circuit that's causing voltage drop to the coil. This would be nearly certain as the control voltage should remain at nominal without the sag from the actual motor operation.

In my experience, a low voltage causes contacts to chatter and not pull in weakly....that's why I recommend some other troubleshooting and bypassing steps as in my previous post.

 

[youdevon]

What I did do is manually press the contactor jus to put air in the tank, and every time my handease off a bit, it started making nearly the name noise , so I had to apply pressure to let it maintain .. Granted that the feed I'm getting from the electric company can't handle the start up, what can I do.. That won't cost alot of money


P.s. I'm not the one actually working on the machine , I'm jus updating u guys what the info he gives me about the machine

 

[youdevon]

still has not had any kind of fix ..

I am contemplating though changing the magnetic Starter to one that uses either a 220v \60hz coil or 208 .. I am getting current about 230v on my lines coming to my house . IS there any recommendation in terms of doing such ??

I currently have the coil wire out on A2 and I manually push the contactor to start then attach the wire for the unit to full up , when its complete I disconnect the wire again, one could only imagine how fun that must be !!

 

[American Locomotive]

I think that the contactor armature has some how come out of adjustment, and is too far away for the magnetic field to properly pull it in.

 

[mm08822]

The coil is doing its job by trying to drop out on low voltage due to high inrush current at startup due to your high resistance utility supply. Matt brough up low voltage dropout at 190v. Looks like you are below that at startup. Measure the voltage before and at startup please.

Pushing the starter in by hand only masks the low voltage issue at the starter and you are slowly killing the motor.

Also measure it after startup while motor running. Let us know the #'s.

Changing the coil to 208v is only going to let you fry the motor.
Your load is too big for the service you have. If poco doesnt fix it you are chasing yourself.
Go see what that tire shop has for compressor motors. I bet they are 2 smaller units so startup inrush is lower, voltage drop is less and running voltage drop is less.

BTW, it is crazy to have 3 threads running for the same problem.