Multiple breakers tripping and hot to the touch

[brantmacga]

I could use another opinion here.


In a restaurant with electric equipment, the customer states the breakers feeding electrical fryers and grills will trip and are very hot to the touch. They've also experienced RTU breakers tripping.

Customer says they have to wait up to half an hour before breakers will reset and hold.


This happens once every few weeks, and I've yet to see it happen personally.

A visual inspection didn't show any problems, and we're not seeing anything overload or abnormal voltages.


I had the utility install a monitor recently, and the engineer says they show no voltage problems.


They did tell me they have found blown capacitors up the line during one visit. None of the surrounding businesses I talked to said they have experienced a problem.


My best guess at this point is a problem in their secondary. If we disconnect to test with a megger, and a problem exists, the utility obviously will not reconnect. The capacitors blowing seem to be revealing an underlying problem as no one else is having this issue.


The customer is willing to shut down for a night to replace the secondary, but I don't know 100% that it will fix their problem.


At this point, I'm leaning towards having thermography done on their gear to look for internal problems. I've torqued the breakers already and found nothing out of the ordinary.

Thoughts? Thanks


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[don_resqcapt19]

What are the actual currents on the breakers? Have you checked the breaker to bus connection? Have you tried reading the voltage drop between the bus and the load side of the breaker with the loads on? What is the ambient temperature where the panel is located? Are the breakers that are tripping adjacent to each other?

This sounds like a problem with one or more of the breakers.

 

[mikeg976]

I experienced this in a bar I wired a kitchen up for the owner and his deep fryers would trip about every other week and breakers would not reset.
Come to find out it happened on the days they changed there oil in the fryer do to a lot of use and putting frozen foods in hot oil it would cool then fryers would heat up and so on witch caused the breaker to get hot with the two on each side to get warm .
Hope this helps .

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[jim dungar]

The hottest part of a properly functioning breaker is usually its operating handle. The inability to touch the breaker is not really indicative of anything, without knowing the current flowing through the device and the ambient temperature of the room.

Can you move the breakers around in the panel so that there is some air space around them?

 

[mivey]

Old equipment? You may have degraded wiring in the equipment creating fault currents. I have seen some nasty stuff in old kitchen equipment. Scary sometimes.

 

[mivey]

Thermal scan would help find weak connections susceptable to higher loads so I like that idea too.

 

[kwired]

My money is first on looking at breaker to bus connections. Can start with only one connection going bad but over time heats up more bus and spreads to other breakers. If this has happened you need to replace both bus and breakers, if you only replace one or the other they will not last very long as the other has been compromised.

I had this problem one time and was easy swap because new loadcenter interior still fit the old loadcenter cabinet, but isn't always that easy.

 

[brian john]

What I would do

1. Measure the current on the loads, be there when they change the fat in the fryers (based on others comments)
2. Perform a Fall of potential on the circuit breakers at load.
3. Take temperatures of the CB's and check to see if the problem from below (heat rises) is causing problems above with other CB's.

We had a case where an overloaded CB was resulting in the CB above to trip that was at maximum load. The lower CB was way overloaded but the customer was not willing to arrange an outage for this MDP as it fed critical UPS as well. They did the old cover off fan thing for a few weeks while the system was upgraded.

 

[kwired]

What I would do

1. Measure the current on the loads, be there when they change the fat in the fryers (based on others comments)
2. Perform a Fall of potential on the circuit breakers at load.
3. Take temperatures of the CB's and check to see if the problem from below (heat rises) is causing problems above with other CB's.

We had a case where an overloaded CB was resulting in the CB above to trip that was at maximum load. The lower CB was way overloaded but the customer was not willing to arrange an outage for this MDP as it fed critical UPS as well. They did the old cover off fan thing for a few weeks while the system was upgraded.

Don't you like it when they are not willing to plan an outage, but when the thing fails unexpectedly (though they knew it could fail at any time) you can not make repairs fast enough?:roll:

 

[don_resqcapt19]

...They did the old cover off fan thing for a few weeks while the system was upgraded.

There was a story in the original EC&M magazine some 30 years or so ago about going a step beyond an open door and a fan. It was a critical breaker for some data center, and the put people there with CO2 fire extinguishers and they gave it a shot of CO2 every minute or so....that is about -78°F.

 

[JFletcher]

Intermittent problem sometimes is caused by intermittent operation. Do they have the breakers trip during a busy Friday lunch or dinner when everything is in operation? How long has this problem persisted? You cant assume the breakers or wiring is sized correctly for the loads.

Lower end IR cameras are not terribly expensive; it may be worth it to buy your own rather than sub it out.

 

[brantmacga]

Intermittent problem sometimes is caused by intermittent operation.

I did ask that the first time they called, and it's happening at all hours of the day.

You cant assume the breakers or wiring is sized correctly for the loads.

Yeh everything is sized correctly. We've built dozens and dozens of these buildings and service about 40 of them in our area, and everything is the same.


Thanks everyone for the response.



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[brantmacga]

Old equipment? You may have degraded wiring in the equipment creating fault currents. I have seen some nasty stuff in old kitchen equipment. Scary sometimes.

I think this one is probably 20 years old at least.

It's Siemens gear, which I see a much higher failure rate on compared with the same buildings using square d gear.


I was checking the work we had done prior to this problem starting, and we replaced several of their BL miniature breakers in the lighting panel that failed.

The breakers that are tripping now are VL series in the MDP.


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[brantmacga]

What are the actual currents on the breakers? Have you checked the breaker to bus connection? Have you tried reading the voltage drop between the bus and the load side of the breaker with the loads on? What is the ambient temperature where the panel is located? Are the breakers that are tripping adjacent to each other?

This sounds like a problem with one or more of the breakers.

35A load max on 50A grill breakers, and about 38A max on 60A fryer breakers.

Yeh checked the connection on bus also.

Ambient temp is never above 75 degrees; gear is in the stockroom.

And yes, they're all adjacent.


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[Cow]

And yes, they're all adjacent.

I like Brian John's advice. If all his tests check out, would it be possible to move the breakers around to get at least a single pole air space between all of them to dissipate heat?

 

[Strathead]

One thought that occurred to me...

The fryers are almost purely resistive loads. If the RTU's are having their problem now, the may be electric heat and so the same. what is the customer had a perfect storm. The Utility company is delivering power at the high end of their tolerance, the breakers are old and weak at the low end of their tolerance and the original installation was right on the edge allowing for little variation? Just a thought.

For the average person here, (who is way above average) no more. But for someone who is more just following. A heating element that is resistive has voltage and resistance directly proportional. More voltage equals more amperage equals more more wattage, equals more heat. All per Ohm's laws.

 

[Dennis Alwon]

I would also check the bus bar and see if there is corrosion on it.

 

[brantmacga]

I like Brian John's advice. If all his tests check out, would it be possible to move the breakers around to get at least a single pole air space between all of them to dissipate heat?

Not possible.


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[brantmacga]

I would also check the bus bar and see if there is corrosion on it.

I pulled the breakers to look for problems on the bus bar and found none.


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[kwired]

I pulled the breakers to look for problems on the bus bar and found none.


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"Corrosion" is not so likely to be found, you need to look for discoloring, which would indicate overheating. Once this happens the material has lost it temper so to speak and will never be the same again. When replacing such damaged bus you need to replace the component that plugs onto it as well as both are likely compromised.

Again make sure you don't have 100 amp bus where you need 200 amp bus or something of that nature, or have exceeded maximum load on a individual pole space(es).