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Discussion Starter · #21 ·
I didn't make it clear, JS; the shield was only for my safety while I was working. I wouldn't dream of filling my panel with combustibles.

Why will it cause a meltdown? The breaker makes full contact, just as it did before. I checked and measured. I should have taken a picture. If you ask, I will go back in and do so.

$150 plus labor is very expensive, to me. The breakers were all I could manage.

I got a very "Microsoft" reply from GE tech support: Yes it fits, and if it doesn't, buy a new panel. It is to laugh.

SUMMARY
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Old-GE HO's who want/need to replace a breaker have three lawful options:

1. Replace 50-year-old TQL with other 50-year-old TQL
2. Install THQL, Issue UOxxx or older (NOS only), not Issue RT-xxx (current)
3. Replace the panel

In other words, you're screwed. :surrender:
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If you don't feel so lawful :whistling2::

4. Install QP or BR
5. Modify the panel per my small contribution to our collective knowledge

If I had infinite time and energy, or infinite wealth, I would replace it, sure.
As it is, I don't see a stab-check in my lifetime.* Let the next guy bite the bullet; I'm tired.

Dave

* He might glance at the panel, see GE, and call it good. If he says, "Wait a minute, those shouldn't fit," I'll drop dead from astonishment.
 

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The melt down could come from poor contact. It depends how the buss was filed down and how much. If any breaker isn't gripping well that connection could arc/overheat causing the buss bar to melt or the plastic to catch fire.

Also, keep in mind this is a split buss panel. If a stab began to heat up over time to the point the insulating material behind the buss failed the buss bar could short to the metal back pan. In the sub main section the breaker would catch it, but in the main section the fault would continue until something from the POCO stops it. What that is and how long is unknown but a worst case scenario is the service conductors literally melting.
 

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Discussion Starter · #23 ·
It grips as well as it did before the mod. It simply grips a different patch of stab. The portion removed played no electrical role. It never touched the contact patch of the breaker's fingers, except to swipe past during insertion. The only effect of the removed portion (before it was removed) was to mechanically prevent full seating.

The buss insulation is Bakelite, as far as I can tell, same as the breaker case. Or some kind of thermoset anyway. You gave me an idea. I will pick a heavily-used stab and check its temperature now and then. If it gets uncomfortable, then the case is closed, and new THQL is out, period. Being realistic, I don't expect anyone to do what I did, but many many people would just bolt the cover on even if it didn't fit.

Since GE (or at least its representative de jur) is unaware of the incompatibility, I am not sure that they considered new THQL's use in old panels. We know they didn't test it! Therefore they may have inadvertently equipped it with contacts which are, in fact, inappropriate to old stabs. The old stab, stamped from copper sheet into a corrugated shape*, is quite different from modern solid aluminum(?) ones. The RT-xxx fingers contact a smaller area of stab than UOxxx and previous. (QP and BR have a large contact patch too.)

* Measuring from peak to peak of the corrugations, the old stab is the same thickness - 3/32" - as the modern solid stab, but old-style fingers touch more peaks.

At the same time I argue my case, I acknowledge that modification of equipment is beyond the pale, unthinkable in the ordinary course of business. I did it because, of the two options that are real options for me, it is less likely to be detected. (Also, I have the designer's outlook, where everything is raw material and opportunity. Changing things so they work is my hobby.)
 

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Discussion Starter · #25 ·
Thank you for getting my ornery streak going. I did the temperature run -- FAIL! After an hour at 40A per pole, the stab was up to 80 deg C (75 degrees rise) and the breaker did a thermal trip.

Issue RT THQL breakers employ a smaller contact patch. This patch is short enough that it does not span from one peak of old-stab corrugation* to the next, resulting in insufficient area and pressure. Issue RT's are TOTALLY INCOMPATIBLE with old GE panels, and my proposed modification is out the window. (Issue UO and older are okay and don't require the modification but they are only available on the secondary market.)

I stuck the old TQL's back in and continued the load run. After a half hour it stabilized at 35 degrees (only 30 degrees rise). I don't care if they are old, they are staying put. I'm sorry I ever conceived this misbegotten "project", except for the knowledge gained.

Dave

* For the record, old-panel stabs are .050" copper sheet, about .085" peak to peak including the corrugation. New stabs are solid aluminum (I think) and measure .093" .
 

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All of them. The old breakers still fit, and run cool.
Far from ideal... but if you are 100% certain the old breaker tabs grip the same area of metal... it will be fine. But the key is 100%.

I am going to be honest, you should have asked here before sawing off the tabs. I would have told you to just put the older breakers back and return the new ones. When DIYs go ahead and do things without running it by a pro hazards are introduced, some dangerous.

For the time being, keep an eye on the heat. Make sure those stabs are indeed working as designed.
 

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Discussion Starter · #29 ·
Yes, they grip the same. With these corrugated stabs, it's not area per se, rather, how many peaks are contacted. I didn't remove a peak. The material I removed did not touch the finger. Going one hour at 40A (plus another 18A from the other breaker on the same stab), I see 30 deg C rise on a thermocouple touching the stab.

I totally should have asked. I was blinded by the excitement of moving forward.
I hope the record of my experience here dissuades the next eager beaver from trying it.
 

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Yes, they grip the same. With these corrugated stabs, it's not area per se, rather, how many peaks are contacted. I didn't remove a peak. The material I removed did not touch the finger. Going one hour at 40A (plus another 18A from the other breaker on the same stab), I see 30 deg C rise on a thermocouple touching the stab.

I totally should have asked. I was blinded by the excitement of moving forward.
I hope the record of my experience here dissuades the next eager beaver from trying it.
Don't try this at home kids! :)

Anyway, hopefully everything stays as is. And I agree, don't modify your panel without knowing what is correct/incorrect first.
 

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Was it code compliant in 1959 to gang single-pole breakers (no common trip) as double-pole main disconnects? I can't imagine that being permitted today.
It isn't, all 2 and 3 pole breakers have to have a common trip, don't take 2 single pole 30 amp breakers and put a finishing thru the holes in the toggles.

The last thing you want is to be inspector bait!!
 

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Not in all cases. A straight 240 volt load does not need internal common trip per code, only listed handle ties. Key is listed as you mention.
All multi-pole breakers are common trip unless specifically labeld "non-common trip". Single pole circuit breakers with handle ties are permitted for 120/240 volt circuits such as MWBC's.

Additionally, single pole breakers with handle ties may or may not trip both breakers upon a fault.

Documentation from Square D. Not sure if you can read it or not.
 

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Discussion Starter · #36 · (Edited)
Thanks for the common trip info. I was pretty sure that my 1959 install with indicating-handle-tied single-pole breakers was a cheat.

In other news, five years after my escapade, I exercised the breakers and measured voltage drop again. Voltage with a slash is before/after exercise. Calculated resistance and power is after exercise.

What I really wanted to know is the stab drop but that's not possible with all breakers in place, so instead I just measured from bus to the breaker's load lug. Resistance dropped significantly after exercise, so part of the numbers below is internal to the breaker and not related to my stab contact.

It's looking good.

CIRCUIT MV AMPS MILLIOHMS WATTS

Range 120/95 45 2.1 4.3
Sub A 140/85 35 2.4 2.9
Sub B 60 23 2.6 1.4
1 110 18 6.1 2.0
2 130 14 9.3 1.8
3 130 14 9.3 1.8
4 150/90 15 6.0 1.4
5 150/80 17 4.7 1.4
6 180/100 10 10.0 1.0
7 135 14 9.6 1.9
8 130/80 13 6.2 1.0
10 100 14 7.1 1.4
11 80 14 5.7 1.1
12 90 14 6.4 1.3
13 85 14 6.1 1.2
14 100 14 7.1 1.4
 

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Discussion Starter · #37 ·
I had wondered if I could have used Eaton Type CL breakers to replace my TQL's. Nope, the only GE breaker CL is classified to replace is THQL, and only in modern panels. (TL, TLM, TM; not TRX.) Not real useful since THQL is abundant and cheap.

JFYI,
Dave

I wanted to attach the PDF file from Eaton, but it's a bit too big. I just asked them what CL is classified for, and they emailed me the file.
 

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Discussion Starter · #38 ·
Actual stab drop in circuit 2 (late-production THQL1115) is 5.1mV at 15A, or about 340 micro-ohms, less than 4% of the total bus-to-wire resistance. The rest is inside the breaker, mostly the heating element that effects thermal trip. I removed the opposite-side breaker so I could probe the contact fork.
Measured with a Fluke 8020A set to AC 200mV.
 

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That's an interesting tale of adventure into the uncertain fix with possible unintended consequences. It's all still in range of the ordinary safe operating standards so the panel may be as safe as it ever was.

That said, I will add that it's disappointing to see the improvement after exercising the five breakers you listed. Since we can't be sure of the linearity of the time vs. change line, it's possible that all of that change didn't take place at a linear rate. Consider that it may have a cumulative effect and may eventually develop into a more accelerated rate until you become the victim of a thermal runaway that would destroy some things.

I'm just saying that to scare you and put an idea in your head that perhaps you should check it more frequently.

Happy New Year and full speed ahead! I like your style.
 

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Discussion Starter · #40 ·
It is so easy to measure drop across the breaker that there's no excuse not to do it every year. I wanted to see how bad it would get if it were left alone.

The stab contact itself maintained a low resistance that's a negligible part of the total. Most of the heat is generated inside the breaker. It would at worst precipitate a thermal trip. Resetting it would re-seat the circuit interrupting contacts.

I believe that, in day-to-day use, the panel is as safe as ever. The risk is when a tech removes breakers. If both breakers on a stab are pulled, the second one may take the clip* with it, and it could fall onto the bus and arc. I glued them in place, but my private notes include a warning to hold it down with a nonconductive tool. I would have loved to spot-weld them but I don't have the means, and anyway, the bus would be live. Been there done that not gonna do it again. =8)

* A plain brass strip folded over the corrugation to make it resemble GE's new profile.

Thanks for the encouragement.

Dave
 
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