ltucker
Model 0057440 (20kW; 200AMP)
ATS P/N: 0G6389B

I am a good DIY person, respect electricity, and know the basics of residential electric systems. A couple months ago right after a storm, I thought I was losing a leg of power from the utility feed. I manually turned off the utility breaker (@the ATS) and the generator fired up and ran the whole house, no problem. The power company came but found the utility feed was fine when they got there. I flipped the utility breaker back and power was there on both phases. It had been a couple months, but I lost a leg/phase yesterday. It wasn't until yesterday that I realized it wasn't the power company or the utility feed. I took a voltmeter to the ATS and realized that the right phase had power, N2 through the utility breaker but not on the other side of the transfer switch at T2 which is the feed going to my main breaker panel in the house. T1 had 120V and half my house had power and all the 240V was half powered. 

When I flip off the utility breaker in the ATS box, and transfer to the generator, and then back, it starts working again off the utility. I think high draw of power causes this malfunction. I have a Tesla which wasn't plugged in yesterday when I lost the leg. It was plugged in a couple hours before the leg went out. I think I had the dryer going, probably both AC units, and the Tesla a couple hours before it happened. Again, when the phase went out, I did not have the Tesla charging. This morning, I plugged the Tesla in and it happened. I think anytime there is enough of a draw of power, whatever malfunctions in the ATS. I have had the Tesla about 8 months. I hope it doesn't have anything to do with it other than being something that draws a lot of power, enough to trigger the fault. It charges on a 240V, 60amp circuit at a max of 48 amps. If my house were pulling more than 200AMP, wouldn't I pop a breaker before something malfunctioned in the ATS?

It's stable right now, but I am afraid to charge my car or do anything that draws a lot of power. 

https://photos.app.goo.gl/aNd8PCzroXNaTMFR8 link to a photo showing my ATS and where I do and don't have power when the fault happens.  

Thank you for reading!
Quote
ltucker
Also, just to clarify, when I am talking about losing power at T2, I am talking about behind the bars where the generator would put power into the feed for the house. I know I don't get 120V on the bars that source from the generator when that is not running. 

see pic: https://photos.app.goo.gl/A4gRugbvjMkXoCsZ6
Quote
78buckshot
Carefully remove the small metal spring clip from the transfer mechanism, then remove the brown/red perforated guard. You will see a series of horizontal steel plates on the lower and upper halves of the mechanism, these are arc suppressors. With insulated long nose pliers you can pull them out. Now you will be able to see the contacts within the switch, the switch and terminals are live so be careful. I have found stink bugs and earwhigs in the switches that will prevent the contacts from making-hopefully that is the issue. If you find the switch is clean then I suspect one of the utility lugs on the top of the switch has been overheating due to a loose lug from the factory-it will cause the plastic to melt and the switch will bind and make poor contact.
Quote
JayH
Somewhere between the utility feed and the T2 terminal there's an intermittent connection. Do a thorough visual inspection looking for overheated parts or lugs. If you have or can borrow a FLIR camera or phone attachment it's a very handy tool for finding overheated connections. An IR laser thermometer can also be useful.

During a failure condition, measuring voltage from the open connection to neutral can be deceiving, so look for voltage drop along the failed path.

Observing safety, when it's failed first measure across both hot sides of the utility input breaker. It should be approximately 240 volts. If not, you have a problem between the meter socket and the utility input breaker. This is unlikely as the condition would cause a generator start and transfer. 

Next measure from the N2 utility feed into the utility main breaker across the breaker. Voltage drop through the breaker should be near zero volts. If not, your utility breaker is defective. This is unlikely as the condition would cause a generator start and transfer.

Then measure from the utility feed into the breaker to the N2 lug on the transfer switch. It should also be near zero volts. If not, the connection on either the cold side of the breaker or the N2 input on the transfer switch is loose.

Last measure from the N2 terminal on the transfer switch to the T2 terminal which should also be near zero volts drop. If not, the trouble is within the transfer switch itself. As others have suggested it could be insects but this is far more common on the generator side as the utility is normally closed.

Electrician-rated insulating gloves, insulated tools, safety glasses are a must, even for just taking measurements. If you must replace or tighten any utility side connections, don't try this live. Turn the generator off on the control panel, turn off the generator MLCB and utility breakers, then pull the electric meter.

Never attempt a transfer with covers off. I'd turn off the MLCB in the generator to make sure you don't have a situation where the transfer switch might operate any time you're working on it.
Quote
ltucker
I did take off the arc suppressors earlier and took some pictures. It looked fairly clean in there. I should have taken some more measurements while I was in there, like JayH said, but I had everything powered down, so I guess I wouldn't have measured anything. I did tighten one bolt but it didn't feel loose enough to be the problem (bottom of N2; top of the transfer switch). I manually transferred it back and forth (with the power disconnected at all sources) to see if I could see anything fishy, but I didn't notice anything. 

I am going to see how it does now. It did drop that phase while I was away from the house earlier today, and the only things running would have been the 2 ACs. That's when took off the arc suppressors and did all the above.

Here are pics from when I took out the arc suppressors:
https://photos.app.goo.gl/zdzraepTkWG2FfeU7

Thanks for the suggestions. I will report back. 
Quote
78buckshot
The contacts on the right leg look slightly more pitted than the others but nothing that would cause the issue you are having. Do you smell anything out of the ordinary, hot electrical/plastic odor? The problem I have seen is on the back side of the switch were N1 and N2 are connected to the transfer mechanism, they use a small phillips head screw to hold the lug in contact with the "buss" bar and I have found those screws loose or cross-threaded and unable to carry the current which then causes the lug and buss to overheat. In order to get to the screws you have to kill all power, remove the transfer mechanism and tighten the screws from the back side.
Quote
Cobranut
While you're in there, I'd use a drop of blue or purple lucite, whichever is appropriate to the screw size, on the threads.  Be sure it doesn't get between the lug and contact though, as loctite is an insulator. 
Quote
ltucker
So those screws looked good and nothing stood out to me other than what I am about to describe. I didn't see anything burnt or smell anything. I did notice that the left switch bar (name?) of the right phase didn't seem to be making a good contact with the bus bar (name?). I shifted the bus bar down when I reinstalled the transfer switch. Hopefully one of these pictures I doodled on will help make sense. I snapped a few more just in case anyone sees anything that I missed that I should look into. 

I am going to see what happens as I made the fix this morning. It did trip again about midnight last night. I "metered" a few things then, and it seems feasible that I could have found the problem. At midnight, I shifted it over to the generator and it always seems to work fine when on the generator. That makes sense even more that it was a poor connection on one of those switch bars at the utility connection as that switch bar was making a good connection when it was down on the generator bar. 

https://photos.app.goo.gl/eTmRGht3FRSV7edSA

Thanks for all the ideas and support!
Quote
78buckshot
It sure looks like the right side leg has been overheating, the color of the braided conductors and the screws look like they have been hot. When I put them back together I clean up the contacts with a mill file and put some NO-ALOX on all of the connection points. hopefully you have it aligned better than it was from the factory, time will tell. I don't like to argue but I don't recommend any locktite, those screws are difficult enough to work with due to being phillips head, I wish they had a better design for the lugs.
Quote
Kim Barton kmbartosz
I've seen loose lugs on the bottom of main breaker twice now check them
Quote
MacL
Unfortunately, you need a new contactor assembly.  These 200 amp switches are not rated for 200 amp continuously.  Cleaning the contacts usually makes them worse.

A voltage drop test will tell you how bad it is.  With the utility on and feeding the house, put your vom in ac volts and put one probe on the bottom of the breaker and the other probe on the load lug  on the same side.  You should read 0 volts.  10, 20 or 30 millivolts may be acceptable.  When you start seeing 1/4 volt or 1 volt, then there is too much resistance across the contactor.

You can then transfer it (generator running and load connected) and read voltage drop from the generator lug to the load on the same side.  But the problem is most often on the utility side as it's in use 99% of the time.  

Voltage drop has to be read only on a closed circuit that also has current flowing in it.  You can read this across a circuit breaker as well as across any suspected resistance.  

We see these overheated contactors on houses that have heavy normal electric loads such as 2 or more electric furnaces, electric water heaters, multiple air conditioners.  You have to keep your utility load down to prevent this overheating of the switch.  If you can't keep the everyday load down, then a 400 amp switch is the only solution and that's expensive.

A contactor should last about ten years, but 2 or 3 in ten years will need a bigger switch.  That movable blade that is not in contact with the upper contact is because the plastic has melted that holds that blade due to temperatures caused by sustained high ampere loads

That or you'll just have to turn off your grow lights.  

I'm pretty sure the part number will be 0L2911
State your problem, not your diagnosis.
Quote
Geoff Z
MacL wrote:
Unfortunately, you need a new contactor assembly.  These 200 amp switches are not rated for 200 amp continuously.  Cleaning the contacts usually makes them worse.

A voltage drop test will tell you how bad it is.  With the utility on and feeding the house, put your vom in ac volts and put one probe on the bottom of the breaker and the other probe on the load lug  on the same side.  You should read 0 volts.  10, 20 or 30 millivolts may be acceptable.  When you start seeing 1/4 volt or 1 volt, then there is too much resistance across the contactor.

You can then transfer it (generator running and load connected) and read voltage drop from the generator lug to the load on the same side.  But the problem is most often on the utility side as it's in use 99% of the time.  

Voltage drop has to be read only on a closed circuit that also has current flowing in it.  You can read this across a circuit breaker as well as across any suspected resistance.  

We see these overheated contactors on houses that have heavy normal electric loads such as 2 or more electric furnaces, electric water heaters, multiple air conditioners.  You have to keep your utility load down to prevent this overheating of the switch.  If you can't keep the everyday load down, then a 400 amp switch is the only solution and that's expensive.

A contactor should last about ten years, but 2 or 3 in ten years will need a bigger switch.  That movable blade that is not in contact with the upper contact is because the plastic has melted that holds that blade due to temperatures caused by sustained high ampere loads

That or you'll just have to turn off your grow lights.  

I'm pretty sure the part number will be 0L2911


+1...Larger loads and a lot of switching creates heat and can shorten life. You are correct on the part number.
Quote
Peddler
👍 with MacL, seen it several times but the contactor needs to be replaced.  I also agree if you push toward 200 amp draw actual on a regular basis you need to go to a 400 amp switch.
Quote
Goofy4TheWorld
I am curious, if this guy's problem is that he's running super-heavy amps on a regular basis and causing the switch to heat up, then why isn't he also having issues with an overloaded generator?  Looking at his pics I just assumed the contactor was a little loose from the start, and then got a little hot, then more loose, then more hot.  If it's overloaded (mostly via 240 loads) I would think both sides of the switch would show distress, but the heat damage is concentrated on just one of the four wires.  Isn't it possible he just had a weak switch from the get go and replacing the switch (as linked above) will fix him up?
Quote
ltucker
To update all...

I see that the plastic melted/warped, and that is why that one contact bar wasn't quite contacting like it should. I think I provided a temporary fix that might last for a little while longer, but I will go ahead and order another switch to have on hand for replacement. 

I have been checking my loads on each leg, looking to see if it's balanced. I haven't seen more than a 15 amp difference so far. If it was that different, I would think that would be the reason that side shows more evidence of overheating. Even though I have that electric car that can charge at 48 amps, I normally only charge at 30 amps at night when my power usage is normally only my heat/AC, 2 units. I am thinking the generator and transfer switch are probably 10 years old or more (there before I bought the house 5 years ago). So I am guessing I have gotten my money's worth out of the one I have. I doubt I am pulling too many amps on a consistent basis. When it's on the generator, I am careful not to charge, run the dryer, etc. I have one HVAC that is gas heat and the hot water is also gas. Gas stove... I have 95% LED lights and don't keep a lot of them on all the time. 

Thanks again for all the advice and ideas! 
Quote
JayH
ltucker wrote:
To update all...

I see that the plastic melted/warped, and that is why that one contact bar wasn't quite contacting like it should. I think I provided a temporary fix that might last for a little while longer, but I will go ahead and order another switch to have on hand for replacement. 
 


Replace it when the replacement arrives. Keep the old one for an emergency. I wouldn't leave the old one in place. It's failed multiple times already and the next failure isn't likely to be at a convenient time. 
Quote
ltucker
It has been working fine since I made the repair, but...

I ordered a replacement switch from Ziller and am going to do like was said. Good idea to keep the current one as a spare in case this new one fails in the future. I had one final question. The current switch doesn't have anything on the right side. What do I connect into that, or do I connect anything into it? 

https://photos.app.goo.gl/vLRErD3UaYZJpQ9M6
Quote
Goofy4TheWorld
That is an "Auxiliary Contact Switch" and it comes mounted to the side of the switch but IS NOT USED for anything from the factory.  Some people use them to connect to their security system to monitor the status of the transfer switch (and maybe get texts from their alarm system anytime the switch moves), since that little micro switch is opened/closed by movement of the transfer switch.  You will simply ignore it when replacing your switch assembly.

Just to expand for the curious, the OEM micro switch is a single-pole, single throw switch that I think is only "closed" when the transfer assembly switches to generator power.  But if you look closely you will see that there are actually two sets of mounting holes for the installation of a second micro switch on the "top half" of the transfer switch.  The micro-switch sold as an extra are actually double-thrown, so they have a NO and a NC contact.  With these extra switches you can do all kinds of stuff, including monitoring the position of the transfer switch in either direction, or by breaking a thermostat wire you can directly stop an HVAC unit from ever running on generator without having to use any of the "fancier" load shedding devices.
Quote
Goofy4TheWorld
OH YEAH, just so nobody misunderstands anything I posted above, I was ALWAYS referring to the micro-switches on the RIGHT SIDE OF TRANSFER SWITCH ASSEMBLY!

If you look on the left side of your switch there are two identical micro-switches as well, and those are DEFINITELY used for proper function, and if you mess them up you could end up ruining your transfer switch because without those micro-switches your coils would burn up.

So be sure to treat the left-sided micro-switches gently and that all the little tiny wires go back to the same exact terminal they came off of, or you may let the smoke out of your coils!
Quote
JayH
ltucker wrote:
It has been working fine since I made the repair, but...

I ordered a replacement switch from Ziller and am going to do like was said. Good idea to keep the current one as a spare in case this new one fails in the future. I had one final question. The current switch doesn't have anything on the right side. What do I connect into that, or do I connect anything into it? 

https://photos.app.goo.gl/vLRErD3UaYZJpQ9M6


It's an unassigned switch for customer use. SPDT dry contacts can be wired to light an indicator that the load is on generator, lock out a thermostat, close an alarm contact, or whatever. If you have no use for it, leave it disconnected. There are mounting bosses to add a second similar switch that activates when the transfer switch is in the other position. It's SPDT so it can be wired to be closed on utility or closed on generator.
Quote
fb
Couldn't find much discussion of the contactor internals until I found this thread. Thanks all for contributing, and for the pics too ltucker.

Another good thread discussing a similar issue:
https://www.zillerstore.com/post/transfer-relay-not-closing-completely-9943884

I've similar problem to ltucker, but it's on the standby (generator running) side of T2 load terminal. 200A ATS (assembly 0D9618) circa 2014. E1/E2 from generator are hot as expected during standby, and E1 transfers to T1, but E2 is not transferring to T2 (T2 floats). This results in a dead leg at the load center during standby. No issues on utility side.

Are the arc/flash suppressors delicate or difficult to remove and replace in one piece? They appear to be in pieces in the pics. And does anything prevent them from pushing in and risk contacting the switch and terminals? Thanks.
Quote
Peddler
Just pull them straight out with needle nose pliers, they will stay together.
Quote
ltucker
Yeah, one of mine was brittle, but I think that was just due to the age. I was able to get it back in even though it was cracked. It will not be there for long as I have a new switch to install. 
Quote