i have a 200a 3phase 120/208 panel with a 166amp load. The panel feeds telecom equipment so during heavy traffic goes up another 20-30amps. So far nothing has happened. I asked the technician monitoring the equipment if it has always been this way and he said yes. If this continues will equipment fail at some point or is this a disaster waiting to happen. I took some temp readings and the breaker is 120 degrees and wire is the same. The panel is hot to the touch
continuous load
- Thread starter MBLES
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Looking at my post i never asked a my question. If my current continous load is 166amps and i add my 125% = 207.5amps but currently has 200amps OCP. My PAnel is rated for 225A do i need to raise my breaker size to 225AmPS? or can i leave the equipment as is and still be code compliant as far as breaker? The customer wants to add another 20amps circuit to exisint load. whats my max load and I can still be code compliant if all the load on panel is continous load? if not continous load could i have loaded it up to 225a panel rating?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
The total calculated load is the non-continuous load + 125% of the continuous load. In your installation the maximum load after that calculation is 200 amps.
petersonra
Senior Member
- Location
- Northern illinois
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- Semi-retired engineer
120 deg F is not all that hot. i would not worry all that much about it.
As long as your calculated load is within the limits of your feeder capacity I would not get real excited. The reality is that if the 166A is coming from a nameplate it probably does not use anywhere near that much current most of the time.
the 166amps per phase is real continous load. The equipment runs all day like that. the equipment being telecom during peak hours or game days actually increases by 10-15 % because its located on college campus.
yes sir i understand. the panel feeds a power bay converter system for -48v DC The system runs continuous for hours at 166amps per phase give or take all day everyday. they want to add a couple more converters to existing system and was concerned that adding another 25amps puts me over the 125% even though it doesnt actually go past OCP of 200amps
MattS87
Senior Member
- Location
- Yakima, WA
Wouldn't the calculated load be 166A x 125% = 207.5A + 20-30A for non continuous?
If so, even at 20A you are over the 225A rating of the panel
As far as upgrading the breaker, it could only be done if the wire pulled is rated @ 225A
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Yes, the 166 is continuous so it x 125% and if the new load is non continuous you would just it add it to the 207.5 for the total.
Is that what you meant?
MattS87
Senior Member
- Location
- Yakima, WA
Yep that's what I was getting at. OP said he has a 200A OCPD and panel rated at 225A so doing this calc means the panel is indeed over capacity during the "peak" times
jumper
Senior Member
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- 3 Hr 2 Min from Winged Horses
Yep. He mentioned putting in a 225A breaker, but as you noted, that would just get him legal for the existing load now. No adding more.
MattS87
Senior Member
- Location
- Yakima, WA
I guess I was just confirming calc since I wasn't sure how Rob got 200A. Unless he had a typo and meant to say IF calc gives you 200
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
- Occupation
- Electrician
Note that a Panelboard does not require the 80% derating for continous loads - that applies to conductors and ocpd's. Sounds like you might want to bump the breaker (and conductors if applicable) up to 225.
- Location
- New Jersey
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- Journeyman Electrician
- Location
- Chapel Hill, NC
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- Retired Electrical Contractor
Is the 166 amp load calculated or actual? If it is actual load and all loads are continuous then IMO you would need to upsize to 225 amps however, I am not sure what you are measuring
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Yes and you were correct in post #2.
Your wording was correct, but in a strange way it also kinda conveys that you were saying the calculated load was 200A after adjusting for continuous.
It was just some strange way it could be seen that way.
I could see it also so I understood Matt’s confusion.
I am not really explaining this well.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
OK, I think. I said:
"In your installation the maximum load after that calculation is 200 amps". That calculation refers to the 125%*continuous + non-continuous. I made that statement because of the limit set forth by the 200 amp OCPD. If I added permitted after the word maximum that may have helped.
See clear as mud.
JFletcher
Senior Member
- Location
- Williamsburg, VA
The OP has stated the load is a measured, continuous load.
You are already over the breaker's limit for a continuous load. A 200A OCPD is limited to 160A, or 80% its capacity, for loads that meet the definition of continuous. Even tho its a code violation, running it at 166A indefinitely is probably not going to cause any problems.
A 225A breaker is good for 180A of continuous load. If you truly have 166A now, you could add another 20A circuit (eta: to a 225A main) provided its loaded to 14A or less continuous. A 20A circuit can be loaded to 16A continuous.
Aside from changing the breaker size, your feeder may need upsizing too
Imo, your best bet is swapping to a 225A main breaker, pulling this 20A circuit from another panel, or trying to reduce your loads if possible.
Your 120* temp readings are no concern really; pulling a constant 160+A from what is essentially a lighting panel is going to generate some heat
You are already over the breaker's limit for a continuous load. A 200A OCPD is limited to 160A, or 80% its capacity, for loads that meet the definition of continuous. Even tho its a code violation, running it at 166A indefinitely is probably not going to cause any problems.
A 225A breaker is good for 180A of continuous load. If you truly have 166A now, you could add another 20A circuit (eta: to a 225A main) provided its loaded to 14A or less continuous. A 20A circuit can be loaded to 16A continuous.
Aside from changing the breaker size, your feeder may need upsizing too
Imo, your best bet is swapping to a 225A main breaker, pulling this 20A circuit from another panel, or trying to reduce your loads if possible.
Your 120* temp readings are no concern really; pulling a constant 160+A from what is essentially a lighting panel is going to generate some heat
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