Electrician Talk banner
1 - 20 of 22 Posts

·
Registered
Joined
·
428 Posts
Discussion Starter · #1 ·
Hey guys I have a job to install a 125a square d breaker in an mdp. We will be shutting the building down as we get the wire into the mdp and install the breaker.

My question/ concern is operating the 800a main breaker which is quite old. I'm not sure the last time it has been opened.Is there reason to be concerned about resetting this thing or am I just being paranoid.
 

·
Registered
Joined
·
15,339 Posts
Hey guys I have a job to install a 125a square d breaker in an mdp. We will be shutting the building down as we get the wire into the mdp and install the breaker.

My question/ concern is operating the 800a main breaker which is quite old. I'm not sure the last time it has been opened.Is there reason to be concerned about resetting this thing or am I just being paranoid.
You're being paranoid! I would be too. It might be no big deal, or it might never open or close. Good luck. What's the backup plan?
 

·
Registered
Joined
·
243 Posts
Presuming the 800a is also SqD, it's probable a MAL style, a fairly trustworthy breaker, obviously take readings after opening to make sure all 3 legs disconnected and have your PPE on when closing to reenergize.. I ain't a rocket scientist, but my guess would be that a 800a/ 480v arc flash could sting just a smidge.. Best of luck sir
 

·
Registered
Joined
·
81 Posts
If anything it wont open cause the contacts wont release. Just make sure you unload it as much as possible before you open it and really the worst thing that would happen (other than catastrophic failure) is a failure to open. I have had that alot with old 60's-70's square D stuff that never gets exercised.
 

·
Registered
Joined
·
428 Posts
Discussion Starter · #6 ·
Thanks for the advice I plan on turning off all of the individual mdp breakers first before opening the main. Same goes for closing it turn them back one at a time... After it closes
 

·
Registered
Joined
·
20,135 Posts
What would your procedure be for energizing a MB for the first time?

I would make sure the client knew that there is a risk of operating a vintage breaker of that size. Make sure you know who has stock and how fast you could procure one.
If it has one I would use the trip button instead of trying to operate the handle.
Then check to make sure all three phases opened.
 

·
Registered
Joined
·
5,448 Posts
Hey guys I have a job to install a 125a square d breaker in an mdp. We will be shutting the building down as we get the wire into the mdp and install the breaker.

My question/ concern is operating the 800a main breaker which is quite old. I'm not sure the last time it has been opened.Is there reason to be concerned about resetting this thing or am I just being paranoid.
What type/model/cat# is the 800A main?
 

·
Registered
Joined
·
3,450 Posts
Failure to open is bad, but it would've failed to open regardless so that's not your baby. The one that really sucks is when you get it open and it fails to close, because "It worked before you touched it!"
We have a lot of outdoor pole/post mounted metermain panels out here that are getting up in age. That is ALWAYS on my mind every time I have to shut one off. I would hate to have to do a service change because some old obsolete metermain won't close back in.....:censored:
 

·
felonious smile.
Joined
·
15,934 Posts
We have a lot of outdoor pole/post mounted metermain panels out here that are getting up in age. That is ALWAYS on my mind every time I have to shut one off. I would hate to have to do a service change because some old obsolete metermain won't close back in.....:censored:
it's not limited to outdoor panels, I banged out a ko and tripped a Murray 200 amp main that wouldn't reset. A temp job and a whole new service came to order in the following days.

Old Murray's are famous for trip, non reset, most common the I line, upside down 100 & the 200 plug in.
 

·
RIP 1959-2015
Joined
·
39,618 Posts
Hey guys I have a job to install a 125a square d breaker in an mdp. We will be shutting the building down as we get the wire into the mdp and install the breaker.

My question/ concern is operating the 800a main breaker which is quite old. I'm not sure the last time it has been opened.Is there reason to be concerned about resetting this thing or am I just being paranoid.
Make sure you know where one is available before you touch it.....:)
 

·
Registered
Joined
·
243 Posts
JPRO2 said:
I was hoping you'd chime in. I'm pretty new with big switchgear this is my first real time working with it. I'm not sure the type or model it is a square d I-Line mdp 800a
HCW... I-line board... Probably Ma or MAL main ...
 
1 - 20 of 22 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top