New shunt-trip breaker failed - should I pay for the replacement?

[Mr. Serious]

Sorry, I brought up too many issues and confused everyone. The problem is just that the breaker won't reset. However, before I replace with a new one, I want to also make sure we have the shunt trip voltage applied properly. The site is a 1 hour drive the opposite direction from everywhere else I normally go, so I have not taken the time to go down there and verify if the shunt trip voltage is momentary or continuous.

Checking to make sure the shunt coil doesn't have voltage when trying to reset the breaker: yes, we did that. I had someone disconnect the shunt wires completely, and it still wouldn't reset.

Here is what I'm going to do: I'm going to ask the supplier nicely if they'll cover a replacement, and if not I'll buy a new one. The issue of fault current only came up because I was thinking I might buy a lower-rated one to save money. But I prefer to keep the panels fully rated to 22k as they are now, instead of installing one lower-rated breaker.

 

[curt swartz]

I just skimmed through all the replies so may have missed this. Your last post said you did disconnect the shunt trip wires. Did you also disconnect the load wires?

Normally if there is a fault on the circuit the breaker will emit a very audible pop when trying to close but I have had them trip out with no pop sound.

 

[xformer]

I just skimmed through all the replies so may have missed this. Your last post said you did disconnect the shunt trip wires. Did you also disconnect the load wires?

Normally if there is a fault on the circuit the breaker will emit a very audible pop when trying to close but I have had them trip out with no pop sound.

Could this issue also be caused by inrush?

 

[ptonsparky]

I strongly suspect he knows how to reset the breaker. No reset means no current flow.

 

[curt swartz]

I strongly suspect he knows how to reset the breaker. No reset means no current flow.

Who suggested they didn't know how to reset the breaker? If there is a fault, high overload or as xformer suggested a high inrush a breaker will trip immediately when trying to close it.

 

[ptonsparky]

I don’t know of any breaker that i could not tell when it was closed onto fault current.

 

[curt swartz]

A high inrush or major overload will cause a trip without any obvious signs.

 

[Mr. Serious]

I just skimmed through all the replies so may have missed this. Your last post said you did disconnect the shunt trip wires. Did you also disconnect the load wires?

Normally if there is a fault on the circuit the breaker will emit a very audible pop when trying to close but I have had them trip out with no pop sound.

The breaker feeds directly into a bus in a panel, but we turned off every other breaker in the panel in addition to disconnecting the shunt wires, while trying to reset it. Also had the panel cover off, so would have noticed anything shorting out the bus.

 

[Mr. Serious]

My supplier has reached out to GE and they will probably warranty it, but don't know for sure yet.

 

[petersonra]

You should not be paying to fix something unless you broke it

 

[Mr. Serious]

Well, I guess I'm honestly not sure if I broke it or not, or whether to take the blame for it, because I was unaware that I have to watch out and make sure the shunt trip voltage does not stay on after the breaker trips. When it failed, I started to ask myself, did I do something wrong? That's when I did the research and realized that a shunt trip breaker is not designed to withstand a continuous application of the current through the shunt trip coil.

As of now, I believe that GE will provide the replacement under warranty. When I get it and install it, I'll make sure to check the operation of the system, and re-wire as necessary so that the coil voltage is turned off after the breaker trips.

 

[ptonsparky]

Well, I guess I'm honestly not sure if I broke it or not, or whether to take the blame for it, because I was unaware that I have to watch out and make sure the shunt trip voltage does not stay on after the breaker trips. When it failed, I started to ask myself, did I do something wrong? That's when I did the research and realized that a shunt trip breaker is not designed to withstand a continuous application of the current through the shunt trip coil.

As of now, I believe that GE will provide the replacement under warranty. When I get it and install it, I'll make sure to check the operation of the system, and re-wire as necessary so that the coil voltage is turned off after the breaker trips.

I think it was suggested already, but arrange your control so when the breakers off, so is the control.

Let GE eat it if they will, but otherwise they go well with Steak, Shrimp and beer.

 

[wc86]

Did you resolve this? We just did a Kitchen hood like this. There were probably like 9 shunt breakers that the hood had to trip. 2 of them wouldn't shunt at all and 1 wouldn't reset like yours until after a few tries. I notice if i let it sit for a bit in the off(not tripped) position it would reset. The 2 that wouldn't shunt we're going replace. The control panel on the hood uses the the circuit that feeds it to deliver 120v to the shunt breakers and maintains that voltage while under an alarm condition. I think it's a saftey feature so no one can reset anything under the hood when they aren't suppose to.

 

[kwired]

Oh. I would consider that a bug then. I don't think that's how it was originally intended to operate, because the picture appears to show cables in series, one panel after another. It gives the correct result of cables in series if you do a single-phase calculation instead of 3-phase.

Fault Current Calculator

Let me know if you know of a better fault current calculator.

Mike Holts main site has a fault current spreadsheet calculator under the free stuff link. I've used this one for quite some time has ability to calculate current at transformer then after a length of conductor as well as after a second length of conductor in one use. Need further downstream calculating just enter the end result as the starting point on a new spreadsheet.

https://www.mikeholt.com/files/other/Fault_Current_Calculator_Orlando_2019.xlsx

note: clicking that link likely will automatically download the file at that location.

 

[Mr. Serious]

Did you resolve this? We just did a Kitchen hood like this. There were probably like 9 shunt breakers that the hood had to trip. 2 of them wouldn't shunt at all and 1 wouldn't reset like yours until after a few tries. I notice if i let it sit for a bit in the off(not tripped) position it would reset. The 2 that wouldn't shunt we're going replace. The control panel on the hood uses the the circuit that feeds it to deliver 120v to the shunt breakers and maintains that voltage while under an alarm condition. I think it's a saftey feature so no one can reset anything under the hood when they aren't suppose to.

I never found any documentation from GE confirming if their shunt trip breakers have built-in clearing contacts, like someone said the Square D ones do. Therefore, I'm working off the assumption that the GE breakers do not have such a feature, and a constant current applied to the shunt trip wires equates to a constant current through the coil in the breaker, overheating it within a few minutes. Melted plastic off this coil can fall into the mechanism and prevent the breaker from resetting (per reply #19).

As of now, this is my resolution:

1. GE has agreed to replace the faulty breaker under warranty, and the new one will ship on April 4th.
2. For now, to get the customer up and running, I installed a THQB32060ST1 instead of a THHQB32100ST1 main breaker in the panel. It has a lower amp rating and lower kAIC rating, thus it is much cheaper. The customer is paying for the breaker, but I didn't mark it up at all and I covered the installation.
3. I confirmed the control system was sending constant power to the shunt trip breaker while in alarm status. The shunt trip wires were operated directly off what they call the "fire suppression system relay," which in this case is simply an SPDT switch, that closes the normally open contact when the suppression system activates.
4. I re-wired the controls so that the shunt trip power comes from the hood lights circuit, which was the only circuit powered from the shunt trip panel that already had both hot and neutral run to the control box. I connected the shunt trip neutral to that circuit neutral, and the circuit hot to the common of a spare relay provided with the controls, shunt trip hot to that relay's normally open contact.

 

[LarryFine]

GE should be able to tell you whether the breakers open the coil circuit.

 

[wc86]

I never found any documentation from GE confirming if their shunt trip breakers have built-in clearing contacts, like someone said the Square D ones do. Therefore, I'm working off the assumption that the GE breakers do not have such a feature, and a constant current applied to the shunt trip wires equates to a constant current through the coil in the breaker, overheating it within a few minutes. Melted plastic off this coil can fall into the mechanism and prevent the breaker from resetting (per reply #19).

As of now, this is my resolution:

1. GE has agreed to replace the faulty breaker under warranty, and the new one will ship on April 4th.
2. For now, to get the customer up and running, I installed a THQB32060ST1 instead of a THHQB32100ST1 main breaker in the panel. It has a lower amp rating and lower kAIC rating, thus it is much cheaper. The customer is paying for the breaker, but I didn't mark it up at all and I covered the installation.
3. I confirmed the control system was sending constant power to the shunt trip breaker while in alarm status. The shunt trip wires were operated directly off what they call the "fire suppression system relay," which in this case is simply an SPDT switch, that closes the normally open contact when the suppression system activates.
4. I re-wired the controls so that the shunt trip power comes from the hood lights circuit, which was the only circuit powered from the shunt trip panel that already had both hot and neutral run to the control box. I connected the shunt trip neutral to that circuit neutral, and the circuit hot to the common of a spare relay provided with the controls, shunt trip hot to that relay's normally open contact.

So if your theory of the breaker is correct, will the breaker fail again if the hood goes into alarm mode after your re-work?

 

[LarryFine]

So if your theory of the breaker is correct, will the breaker fail again if the hood goes into alarm mode after your re-work?

Not if the light circuit is supplied from one of the shunt-trip breakers.

 

[Mr. Serious]

As Larry said, the breaker should not fail again as a result of leaving the shunt-trip coil on. When the breaker trips off, it shuts off the power to the coil, because the shunt-trip breaker is the main breaker supplying power to the panel that includes the circuit powering the coil.

 

[Todd0x1]

Have you put a meter on the shunt trip coil to see if its open? Have you removed the shunt trip coil to see if it looks melted and tried to close the breaker?