Buzzing Sound From Utility Room

[alyoshak24]

Hello Fellow Wizards,

I have a couple of troubleshooting related questions in a paramedical environment.

PROLOGUE: Client called due to hearing a "Buzzing Sound," during normal operational hours, from a utility room that houses all the load centers, electrical enclosures, disco's and pull-boxes.

While this "Buzzing Sound" occurred, client noted that it did NOT have any negative impact to their medical tools, dedicated medical equipment, lighting, outlets or phone systems.

When i arrived to inspect and troubleshoot noise, the manager on shift stated that the "Buzzing Sound" had randomly stopped (however, we all know that these type of problems rarely if ever resolve on their own, especially when they create a "Buzzing Sound" from any electrical enclosure). So the next thing i did was the following:

A. Took note of all medical equipment in continuous use during normal work hours

B. Panel these circuits and breakers are on are labeled as follows: [ Siemens P1 Panel ][ 250A Max ] | [208/120V 3Phase] installed on May 2022. Breakers are of SiemensType HBL / IAC Rating 65KA / HACR Type SWD, 40'C

B1. Total of (4x 20A SP and x1 DP 20A, all #12AWG5 stationary medical appliances/equipment that were used for 3 or more hours which are listed below:

• Boilers (x3) plugged into 20A gfi on dedicated circuit | 3.5-4.5 hours of continuous
• Vacuum System DP20A on dedicated circuit and has its own disco next to it with step down transformer | 8 - 9.5 hours of continuous use
• Duplicator SP 20A plugged into 20A gfi on dedicated circuit | 24/7 hours of continuous

The nameplates for all the equipment calculated at 125% per NEC for continous use arrive at 18A or lower so they are sized correctly.

B2. Next step was to open panel that housed all medical equipment and appliances. After inspection i noticed that 6 circuits had conductors AND breakers that were noticeably warmer than normal, like hot hot to the touch (unfortunately did not have my therm-cam) with a DP breaker (2 out of the 6) was substantially hotter than the other 4 breakers.

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QUESTION(S): My question is as follows:

A. Is it safe to say that "Buzzing Sound" was not a short or a ground fault, but the actual breaker(s) malfunctioning due to the continuous use of the medical equipment described above ?

B. If (A) assertion is erroneous, then what else could cause the "Buzzing Sound" ? (which was made from Utility Room that housed panels, discos and pillboxes)

C. if (A) assertion is agreed upon by majority consensus of wizards. then can i upsize these specific 6 circuits from 20A -> 30A and #12 - > #10AWG ?


Thank you for taking the time to read my question(s), i appreciate all your help and wisdom oh great council of Sages, Priests and Wizards.

 

[don_resqcapt19]

I would doubt that (A) is the answer and also doubt that there is any real electrical problem. My guess is the magnetic field from the 60 HZ power flow is just making some non current carrying part that is a bit loose vibrate.

 

[ModbusMan]

Any chance you could go back and amp clamp these things during load/business hours? We have IR scanning done on all our switchgear and customer load panels annually, and while some of them do get glowingly warm (at least as far as the IR camera's concerned, anyway), never have we had a 15/20/30 amp circuit feel hot to the touch.

 

[ATSman]

Anytime a buzzing sound is heard in electrical panels we go to the source. If in an MCC or control panel then we open the bucket door and look for a contactor or relay and press on the solenoid (armature) to see if the noise stops. It is usually caused by dirt/ grease on the contact surface of the solenoid.
If it is coming from a transformer (control or power) then that is another story.

 

[Fred B]

Given the "buzzing" wasn't present when you arrived, part of my questioning would have included how loud was the "buzzing"? Audible from behind the closed door of the electrical room or only upon entry into the room? This would indicated some different level of urgency.

Perception of "warm" by touch not always a good indicator the a breaker is too "warm". A "warm" breaker should first of all have it's current measured for load, is it on the higher end of it's operational limits. GFCI and AFCI breakers will have a "warmer" touch just because of the internal circuitry, and will "warm" adjacent breakers.

Would not ever suggest "C" as an option, no different than the old fuse type the guy would, after multiple fuse blows, just screw in a larger fuse until it no longer blew. If the "warm" breaker is confirmed to be related to a higher and close to the breaker load limit would split the branch circuit into multiple, thus reducing the overall load from the branch, if that was applicable.

These you list as being already individual "dedicated" circuits so have you actually metered for loads? I would also IR for actual heating, where is the breaker getting hot? Are the wires feeding also "warm"? Is the "Warmest" spot at the terminations or the body or nearest the bus connection point?

Have had "older" standard trip breakers "buzz" even with only moderately load within the breaker parameters. Replace the breaker and "buzzing" goes away. Internal spring was getting a little weak allowing the contact to "buzz" and creating heat. Confirmed when I opened the breaker an seen the arc points on the contactor.

paramedical environment.

What is this "Environment"?

You list these several loads as "Continuous" with some very significant times.

• Boilers (x3) plugged into 20A gfi on dedicated circuit | 3.5-4.5 hours of continuous
• Vacuum System DP20A on dedicated circuit and has its own disco next to it with step down transformer | 8 - 9.5 hours of continuous use
• Duplicator SP 20A plugged into 20A gfi on dedicated circuit | 24/7 hours of continuous

Boilers, Are these electric boilers? Hardly ever would a boiler be considered a "continuous" load. Article 100 definition: "A load where the maximum current is expected to continue for 3 hours or more."
Actually any of the loads mentioned would be hard pressed to fit this definition. If indeed they do then what is the motor or name plate list as the MOD, FLA etc.? Are the motors operating on the equipment rated as "continuous duty"?

 

[alyoshak24]

Any chance you could go back and amp clamp these things during load/business hours? We have IR scanning done on all our switchgear and customer load panels annually, and while some of them do get glowingly warm (at least as far as the IR camera's concerned, anyway), never have we had a 15/20/30 amp circuit feel hot to the touch.

Hi, I will be going back to take thermal images and take readings with my clamp ammeter and update you with the readings.

 

[CoolWill]

Lighting contactor?

 

[ModbusMan]

Lighting contactor?

Could be... at my very first controls-related job, I got to tail our resident wizard in looking at a very old DC-driven freight lift that was making a very LOUD buzzing noise, and tracked it down to a won out contactor. The constant start/stop of current flow might also explain the breaker heating.