breaker tripping

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Have been trouble shooting a control circuit and the breaker keeps tripping. It controls a 'solenoid' valve. its only intermitient.

The breaker has been changed, and the hot lines (hot to neut and hot to ground comes out good) megged (getting ready to double check the neutral as well.. Also they even had the solenoid changed a few months back. Any other ideas?? I was wondering if the solenoid could be having alot of resistance when its trying to turn.
 

charlie b

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Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Solenoid valves do not "turn." They lift (against spring pressure) when the solenoid is energized, and they are pushed the other way (by the spring) when the solenoid is turned off. Which way is open and which is closed depends on the design of the valve. Has anyone checked for a problem (i.e., something sticking) in the mechanical part of the valve?
 

GeorgeB

ElectroHydraulics engineer (retired)
Location
Greenville SC
Occupation
Retired
I agree with Charlie and zbang. The most common problems with HYDRAULIC solenoid valves are a little trash preventing the spool from fully shifting (continues to draw inrush), or a bad connection causing low voltage preventing the spool from fully shifting (continues to draw inrush).

Intermittent ... I'd bet on a bad connection. Mechanical is usually more repeatable.
 

charlie b

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Location
Lockport, IL
Occupation
Retired Electrical Engineer
Intermittent ... I'd bet on a bad connection. Mechanical is usually more repeatable.
Not a bad bet. But if a valve stem (or other surface) gets scored, it might sometimes catch and drag, and might sometimes operate freely. My money is still on a mechanical problem, especially given that the breaker and the solenoid have both been replaced without making the problem go away.
 
Well this is what ive found so far. I did find that at another 'terminal block' where a limit switch (and something else )ties in its neutral with the solenoid to the home run control., no the limit switch doesnt use a neutral ;) This neutral and when megged to ground is not good, its under 1 meg.

I do not believe that would cause the 1 amp breaker to trip for the solenoid, (each has its own) but it can contribute to a problem.

Im thinking something mechanical too, and thats what i said at first, but they (plumbers') claim that its not that cause this is new.

Thanks for the tips, ill keep you updated.
 
Well, the solenoid issue is still an 'issue'. Those guys did replace the solenoid again, and it worked fine for a while then it started tripping again. I suggested (from the onset after meggering) that we get a recorder (see if there is any voltage drop at all going on. The valve is openned all the way for the solenoid from what I understand. That will be double/tripple checked too.

Just for giggles and grin, even though the wire did megg good, we will pull it out, (its a short run) and put in another #18. I still think there needs to be a recorder on this, just a gut.
 

tom baker

First Chief Moderator
Staff member
Some years ago I had a pump control panel that kept blowing a fuse, it had three pumps and many solenoids. It was suggested that I could install a larger fuse, I did so, and soon enough a motor starter coil burned up.

1A is a very small circuit breaker. If its 18 gage, you can safely go to 7 amps. 5A would be OK to test. Solenoids have some inrush. AB, for one makes different types of small CBs some are good for inrush some are not.

Its always an electrical problem- the CB trips in reaction to an overload. Swap the solenoid to another CB, does the problem stay or follow?
 

SAC

Senior Member
Location
Massachusetts
You may want to take a DMM and measure the DC resistance of the coil. Use this as a sanity check for the expected load current.

Many solenoids draw essentially a "locked rotor" current when they reach their extent, which is largely limited by the resistance of the coil. The DC calculation should be pretty close to the maximum expected draw.
 

benaround

Senior Member
Location
Arizona
Brother, did you take an amp reading on the new solinoid ? Can you find another 1amp

load to test out the c.b.. Maybe the old solinoid took a toll on the c.b.? Good Luck !
 

Doug S.

Senior Member
Location
West Michigan
I would try fusing the solenoid independently, at the devices (if possible).
As mentioned a 1a CB is really small, you should be able to jump up a couple of sizes? What else is being protected?

I know of an application were we continually pick up debris at a solenoid, and it will muck things up sometime monthly. I have no idea were the debris comes from, but some day, when one of the cylinders fail, we'll have it figured out. :rolleyes:

Regards,
Doug S.
 
Brother, did you take an amp reading on the new solinoid ? Can you find another 1amp

load to test out the c.b.. Maybe the old solinoid took a toll on the c.b.? Good Luck !

Yes, I took an amp reading with 2 meters, (flukes). That was one of the first things I did. Also we did use other 1 amp breakers (that were in the control cabinet) and they did trip. I thought maybe the 1 amp breaker had went bad before and actually had a new one in there. But to be sure it wasnt a 'bad new one' we swapped with one we knew was working right.

Even took a 'resistance' reading on the coil, its about 20 ohms, both on the old and new solenoids (they had swapped the solenoid before). the name plate says 25 watts , 120 volts. So that comes out to 0.2 amps, which is what I was getting on my amp readings.

Yes its a mystery, but problems like this Ive worked on in the past manifest itself with a 'recorder'. But like I said, I will just pull the wire out and examine it and put in a new wire just for giggles and grin. Thanks for help. ;)
 

e57

Senior Member
Do you have a schematic? - There may be all sorts of other stuff on this circuit, I say that as it seems you found a few things already that you were not immediatly aware of. If not you could take the time to make one.

That said - has anyone been operating this equipment when it goes out - to question them if it happens at the same time or during the same operation. I have found that troubleshooting requires knowing much more about the principle of operation of the equipment - more so than 'this does that' one item at a time - you may find that when this solonoid operates many other things do too as well. Any other interconnection to other parts of the works could be involved. And some care should be taken megging wiring if you don't know where it goes.... Could be more harm than good.
 

KentAT

Senior Member
Location
Northeastern PA
Did you verify that when they first changed the solenoid, the installed the correct one? I only ask this because it seems you came into the picture after someone already had changed something...

Some thoughts:
1. Are you/they just changing the solenoid, or a solenoid/valve combo?
2. Is the solenoid valve rated for the application, or was it changed and it might not be correct for the application?
 

SAC

Senior Member
Location
Massachusetts
I crunched your numbers, and as far as I can tell it looks like a well power factor corrected device. I'm guessing the peak inrush shouldn't be more than about 1A - and that for only a cycle or so. It would seem that a 1A breaker should be ok. This is assuming you are using line voltage, and don't have any kind of special control device sourcing the device.

Good luck, and let us know how it turns out.
 
Did you verify that when they first changed the solenoid, the installed the correct one? I only ask this because it seems you came into the picture after someone already had changed something...?
Yes I came in AFTER they had tried to do some work on it. . Oh just for the info, The new wire made no change, It still trips. (this is what I had told the other guys, but just to keep them happy I went ahead and put in new wire).

I have seen the schematic/drawing (another one of the first things I looked at) to be sure that the 'solenoid' was the only thing on the this 1 amp breaker in the control center and it is. This is how it came from the manufacturer.

Some thoughts:
1. Are you/they just changing the solenoid, or a solenoid/valve combo?
2. Is the solenoid valve rated for the application, or was it changed and it might not be correct for the application?
They did call the manufacturer to get the right solenoid
well they have not changed the 'incomming' supply valve, (it does look pretty new so it may not need it) and I did suggest that. Also just to keep them happy at their request we put a recorder (amps) on it. I told them they NEEDED a VOLTAGE recorder too, just to be sure the voltage wasn't dropping (ie maybe bad transformer?). But they just got the amp reader. Oh well I guess they want to do this the 'long way'. and Yes according to the manufacturer the solenoid is rated for this application just incase I didnt mention it (LOL). I reminded them the 'amp' meter is only going to show that the 'amps' went over 1 amp (which we already know because its tripping LOL ). We NEED to know the WHY is what I told them. Oh well, dont want to completely listen to me, I get paid by the hour LOL. However I do like a good mystery.
 
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