Bryan is joined by Eric Mele to investigate A Strange Contactor Issue.
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and find our handy calculators at https://www.hvacrschool.com/
All right, so what we're gon na be showing here is a really weird problem that we had with a contactor that was intermittently tripping a breaker, and I know you're gon na say that's not what was causing it and we would have agreed, but eventually we source The problem to the contactor and we're gon na show you how hard this thing was to diagnose and then we're gon na try to pull it apart and see if we can figure out what the heck's actually going on inside this thing, it's gon na be exciting And I've got air in here with me all right, so Eric's gon na demonstrate we're gon na start with the field piece and we're going to just leave it in megaohm scale and we've got the screws a little bit back down because that's how it was when We on its oldest when we first checked it, we're like no, it's not shorted but then tighten screws down like they would be when the system was an operation. I remember this was an intermittent problem, so we show up breaker be tripped. We reset the breaker and we really couldn't figure out what was going on still still when I've shown anything previously when we tightened down, we actually did. But we're not thing to consider here is when you're, using a typical multimeter, it's using pretty low voltage in order to travel in between to actually make the path.
And this is why, in some cases, you won't find a short-circuit with a regular meter on say a compressor or motors or switch gear, and now we're gon na use. The 1587 will start as insulation test mode right now. Does that where you want to start a list of it's fine, it will start there and we'll start with 50 volts, so we're gon na change, the range to 50 volts and now we're gon na do insulation test and see what we get and we're reading 55 Mega ohms, which, if you do the math on that really shouldn't, be enough to even really show up and then the current that would be present over 55 mega ohms. I don't want to do the math, it's not very much.
Do you know that you know that math off the top of your head Ellen yeah? Could you think yeah? That's that's a lot so now we're gon na switch you to. Are you gon na go to 500 well 500, because the peak of 240, because to 40s that have rain, it would be around 500 volts. So this is what be your people here? What sine waves right? You can hear it yeah! You can hear the thing arcing in there, so it started off and now it's now it's after the are cap and then the megaohms went up a little higher. Let's, let's take it up to a thousand volts watch your eyes.
You could really hear yeah. You can hear it now. You can see the arc yeah where's. It happening a super strange.
So now we're gon na try to pull this sucker apart and see. Why that's happening now again. Remember this one! This isn't just theoretical. This represents a real fault and feel take your top end off.
First, I'm having Eric do this for me, because I don't know how to actually use tools in real life, better, get real technician to pull the contactor apart. Maybe you know you might be onto something there. Is there like a little sawing tab holds these in then I have to depress. I can't aim with the screwdriver. We did clean up this area with contact cleaner before because there's that carbon tracing it I've heard of before - and I don't know exactly why that happens - are you familiar with carbon tracing? Well, every time the contacts make an you know, the arc and pieces of it are going everywhere, but I might just have to bend this out of the way, because I can't get the tab to depress where we see we were actually seeing it right there underneath That contact right. This is where you were saying it. If we can pull out the bar such a pain, yeah, it's got these tabs right here and I couldn't it's just a one-time deal. Do you have absolutely on the left side outside we've got not just any fires? Oh yeah them have expires.
These pliers smell funny yeah. I think the bars got a couple tabs that do it too. So I'm trying to not destroy the contactor as it comes apart, but well we might destroy okay. There we go so we got the bar out yeah, I don't see anywhere, it could have been touching.
I mean it would have had to bend this this or this. Well, we would see it to here because the thing was clearly arcing and it's not there's nothing on this side, because it was only showing a short between these sides. With the contacts open, I mean, I think it was literally just it had to be Andrew - that carbon yeah. That is weird because you also think if carbon is being an insulator, maybe but it does illustrate interesting, even with it being cleaned up, I mean I don't see a heavy build up here.
That would that I would think would conduct electricity spontaneous disassembly, strong, strong in public. I don't know my own strength, yeah, that's very, very interesting yeah. I don't know I think so I mean, if anything, it indicates that the higher the voltage, the more necessity there is to actually keep your contacts clean right, more likely you're gon na have, I can't remember, even seeing it on a 480 contactor yeah. I know I just gave a quick credit to Gary McCready, because I know he did a video on overage fees.
He know it all, and he talked about this carbon C called a carbon tracing and it's just the first time I've ever seen it. I mean this is a residential unit. This is just 240 volts and I think there may be a combo problem. Let me because there was actually some one of the techs observed that the compressor wasn't starting at points.
I think maybe the compressor drawing consistent I start amps up could have resulted in more contact loss. You know, as the thing is making a breaking you have those big arcs, because again I mean you know it. Some of that can be metallic material too. I would imagine we got everything removed.
Goober all she's got Scotty yeah, look at there giggles. So that's like crazy high resistance. You go, I didn't know this mean reading giggles every burst before it doesn't even sound like a real thing. I think you just made that up. No, it actually says it there Giga ohms. What I learned here is that they're legitimately are, I mean we know this they're legitimately cases for megameters other parts of our industry, insulation tester, but in regular air conditioning there's never been a case where I felt like I absolutely needed it to diagnose the problem, but In this case, no, it's nice to have and have this one, because it's not just a mega ohm meter. It's a combination. You know I can do.
I use the milliamps more than anything else on this meter. You know you have millivolts which I've not really had to mess with, and you have your insulation testing when you need it. So there's our diagnosis. We have some path just through those, even after cleaning and even after I use contact cleaner on, because I was just thinking all right.
Well, maybe it's bridging through here and so I put contact cleaner, wipe it all down. I didn't get a brush and get real aggressive, but toriel thing yeah, that's really cool.
Carbon tracing is common in vehicle distributor cap where there is high voltage. Great video
I had one do this
Fluke 1587 somebody got deep pockets! Did you test to ground as well? Did not see that in video. Might have taken less potential for short to ground. Most tech if have a megger will use something like a Supco M500 that can't kick it that high.
That blue residue on the contactor looks suspect to me. I had this issue about a month ago blowing the low voltage fuse on the furnace and what I had found was that some of the cleaner I used a month before got into the control compartment and dripped down onto the contactor which eventually caused a path for the low voltage current to go to ground.
I run into this condition all the time in my side business of vintage tube amp repair. A carbon track becomes part of the molecular structure of the insulating material and cannot be removed. Happens often in power tube sockets when the tube has an internal short occur.
Bryan, hello, but I really DESPISE this CHEAP CONTACTORS , case a Carrier 460 v 3 phase , it only had a 2 pole, & the other led went direct to the compressor , were, it singlephased cooked it , but for SURE I replaced it with av3 pole one just retired the direct leg, all this is being CHEAP, like FRIGIDAIRE used lots of STEEL TUBING, also were FIRST. to use DCHRADER VALVES, those days they were same as car tube valves LONG Cheers 🇺🇸🇺🇸🇺🇸🇺🇸
wonder if there were surge voltages or if the 5 minute compressor delay wasn't functioning well
A friend of mine had a brand new contactor that would not conduct electricity through the floating bar. He measured on the bar itself and not the screws. It showed 208 (commercial job). A solid metal bar that would not conduct!!
Just replace the contactor! Its cheap and easy! Get em on EBay dirt cheap! I can have it swapped out in 10 min while you spend hours with fancy meters and troubleshooting time! Maybe even replacing a dang compressor. And who pays for that when it does not fix the problem?? Service area Barrhaven??
The only place the carbon can come from is the plastic insulators. The contacts by there very purpose have to be made of metal. The actual metal can be different based on the current and voltage for the designed application. The metal at the contacts under high current and voltage arc thereby vaporizing a small amount of metal each time. If enough is deposited a short may develop during high current high voltage use and this would start as intermittent but eventually fail as a dead short. If I see pitted contacts on any relay I replace them.
You might want to get a microscopes. It could be cheap usb type or a go a little fancier and get regular 40x inspection microscope. Then you could look at soemthing like that zoomed in and get a better idea of what is happening. It might also help when trying show small features in videos.
It's called polarizing when the insulator becomes conductive. I am a commercial tech and I have run into this many times. The plastic on the contactor becomes conductive and will create a ground fault or short. I see this mainly on older trane roof top units where there is a plastic terminal strip in the blower compartment for the blower motor connections. The terminal strip will polorize over a long period of time and ground out the blower power causing the breaker to trip. I fixed this issue on many of the same style similarly aged units by removing the power from the terminal strip and using wire nuts to make the connections. Problem solved however, knowone would ever believe me even though the problem was solved. The things we learn every day on this trade.
Damp or bugs etc could start it tracking between the two poles, its then burn up the plastic and keep tracking. Think distributor cap in you old style cars.
I have seen that issue before in field. I would of replaced the contractor by just the way it looked. No need to pull meter out when it looks like that. That would have saved a call back.
Great video!
I've seen carbon tracing on spark plugs before that caused a miss fire.. Are you in Ottawa ?
your videos are very helpful. I'm 3 years in, working in the HVACR field. No schooling just hands on this far. Please can you make a video of a time delay relay on break and make?
Also, i installed a time delay relay today to bypass a low pressure control for this walk-in freezer that we just installed. When i pumped down the system, to check cut in and cut out there was no delay…. idk hard to explain please help!
When I started out about 5 years ago, i found a unit with the same issue.
The old guys I worked with claimed it was the all the lead that “chinamen” our in their plastic.
it means your so moron idiots if you say that,, it is a strange issue in contactor,,,,, It means you dont have the hardwork, and knowledge of disassymbling and re assymbling parts of the contactors,, you dont have the hardwork of disassymbling and clean it good look like brand new,, IT MEANS HARDWORK AND KNOWLEDGE CONQUERS ALL!!! you MORONS!!!
you morons,,its easy to troubleshoot on that,,, carbons may conduct electricity,.. specially on higher volrages,, so,, the main fix of that is to dis assymble the all contacts in your conractor,, and clean it with emery cloth or sand it SMOOTH with 1200 grit sand paper,, sand it until it will look like new,, contacts,, shiny and clean, and remove all the carbons in the plastic casing inside and outside of your contactor, clean it until it will look new and clean,,, YOU CANNOT DO THIS FIX IF YOU DONT KNOW HOW TO DIS MANTLE AND REASSYMBLE parts of contactors piece by piece,, you dick heaheads in our country this kind of issue,, is so common even we have only analog multimeter we can fix it,, YOU MORONS, you want to test us? DICKHEADS!!!!!! Service area Ottawa??
Thanks for another informative video Bryan! Checkout my channel guys! Plumbing, hvac, fitness
Common on 600vac contactor see it all the time. Service area Nepean??
peak of 240 is 240……2 legs of 120 volts 180 degrees out
The coloring agent…
old style bakelite material never did this..only carbon colored thermal plastics. Do a conductive isolation test on a tan colored plastic, compare to the black version. I think it (carbon) adds strength to the materials for torqueing binding screws.
ask a senior auto mechanic about carbon tracing in the distributor caps….25,000 volts dc arc at each plug tower splattering byproduct or carbon into the area which the rotor whirling in a circle carries these particles in the same direction a million times. Eventually leaving a trail between the towers and causing a 'short' or alternative conductive path for the high voltage to use. This might be one reason of the solid state ignition and sequential timing..no moving electrode. Since this application has no whirling, I would bet it is the break down of the plastic.
As my dad once joked about the foundry work..,"if you wanted a day off, pour your black coffee into the molten metal during forming and cooling'", the coffee at 2500 degrees turns to a carbon fissure and pretty much a hole in the plate of steel.
Another thought created by Bryon again 👍🏼🤔
"It's Alive!" "It's Alive!"
If a contractor looks like that just imagine how bad the contacts are. I would have changed it regardless, especially if I’m trying to single out a direct short. Should have been changed on the first service call.
unreal
Nice find. Are you in Barrhaven ?
Bakelite will break down and carbonize over time when exposed to heat with high voltages. This occurs with motor contactors because when the circuit breaks, there is a voltage spike which is much higher than the rated voltage due to the induction of the motor which tries to keep the current flowing through an open circuit. Phenolic board breaks down in a similar manner. I have seen vinyl cords break down over time when exposed to mold which carbonizes the vinyl. Phenolic and vinyl can catch fire in these circumstances. Bakelite usually just smokes and glows as the carbon completes the circuit. Thanks for the good testing and analysis of this failure. Good video!
Thanks for sharing. Interesting find
From Geco piss if your wondering.
I had a similar problem with a 3/4” conduit pipe sticking out of the roof (in a condo complex) under the disconnect somehow rain water got in and filled it even dough it had “watertight fittings”.Inside the attic space it had a romex connector at the end of the pipe with a bunch of electric tape around it. I tried everything,omh’d the compressor,the fan motor,inspected and tested contactor,capacitor,wiring and it kept tripping out the breaker but intermittently,it was until I removed the tape that I noticed some dripping and then pulled the wires,it was then when it became evident that water was conducting to ground! Even when I did all testing on the wires it showed everything was good! Bottom line…if You suspect something is wrong,keep going till you find it!🥵😳🤯🤬
Crazy. I’ve had that happen with a semi hermetic compressor on the terminal block. I could read resistance with my meter from the leads to the insulator block.
DO YOU REPLACE CONTACTORS WHEN YOU DO PM MEASURING OHM READINGS?
Had that with electric stove where wires come in to a terminal strip to ground hole in Bakelite to ground.🤗int breaker trip started on fire eventually. Service area Kanata??
Had the exact same issue this spring. York rooftop blew two of the three 30amp fuses twice. First time it blew, we ohmed out everything we could and checked the wires and found nothing unusual. Changed fuses and no issue for 2 weeks. Then blew same two again. Double checked everything again, no issues found. Started it up to test, and double break 2p blower contractor began to buzz and hum like crazy. Changed it out and haven’t been back since, checked with the customer last week and no issues
Carbon is resistive dependent upon how densely it is packed. That the carbon pile battery testers. The original microphones were cups filled with carbon powder in which the diaphragm compressed changing the resistance.
An easy demo is to take a pencil (softer lead is better) rub a swath on the paper then check the resistance at various places along the length. Add more pencil lead and get less resistance.
Yes that's true
Thanks
It must have been a slow day because on a busy day, that contractor would have been labeled “dumpster food “ in about 0.005 seconds just by looking at it. Still, it’s a good learning experience, thank you guys!
Is that compressor getting over heated in seconds after turning on and trips?
Have only seen this a few times in over 20 years. Flows through carbon, but will continue even after cleaning it off. Never found a study addressing problem. Replace and good to go. Great video! Are you in Orleans ?
Thank you for the video. I would say a VERY rare find in an A/C component. See these kinds of "carbon" trace shorts in DC voltage components.
So, a true full PM (Preventive Maintenance), checklist may include:
1. OPEN service power disconnect.
2. Remove any load side 240V wires AND 24V wires from the contactor.
3. Apply MEGGER/MEGohmeter tester between contactor poles.
Good reading = restore wires to respective terminals
Bad reading = replace contactor
It's CARBON TRACKS, not carbon traces. ARCING, lays down CARBON TRACKS. In automotive, spark plugs will SHORT to GROUND, via carbon TRACKS, clearly visible, up and down the white porcelain insulator part of the plug,. Tracks are made by HIGH VOLTAGE ARCS between plug wire connector and spark plug's metal base/body. Tracks then provide easier path, for each successive arc to follow. Problem worsens, with each arc. Are you in Nepean ?
I had one of those once, same problem tripping breaker. I never tried to figure out why, but now I know. Good video!
👍👍👍
I bet the plastic is cracked in between the terminals…..
I think that contactor is not rated at 1000V, in addition to being old, dirty, wet and rusty due to environmental conditions (AC application). In the same way, the video is interesting …
Wow!!!
Interesting find. Thanks for sharing.