Any suggestions?

[anbm]

Existing main service switchboard (4,000A, 480Y/277V) in hospital feeds the chiller. We want to add new (1) 250A CB and (1) 400A CB into this switchboard to serve other added load. In order to do this, electrician said they have to shut down the power to the switchboard and let the hospital emergency circuits powered from emergency generator temporary.

However, the owner doesn't want to shut down power to the chiller.

Any solution to accomplish this without shutdown power to chiller? Can electrician install new CB in main switchboard without shutdown the switchboard? (i.e. they need a special license to work "lived?")

How long does it take to install those (2) CBs?

One thought is they may rent a temporary generator and feed the chiller if the main switchboard has to be down.

 

[stevebea]

Existing main service switchboard (4,000A, 480Y/277V) in hospital feeds the chiller. We want to add new (1) 250A CB and (1) 400A CB into this switchboard to serve other added load. In order to do this, electrician said they have to shut down the power to the switchboard and let the hospital emergency circuits powered from emergency generator temporary.

However, the owner doesn't want to shut down power to the chiller.

Any solution to accomplish this without shutdown power to chiller? Can electrician install new CB in main switchboard without shutdown the switchboard? (i.e. they need a special license to work "lived?")

How long does it take to install those (2) CBs?

One thought is they may rent a temporary generator and feed the chiller if the main switchboard has to be down.

Does breaker hardware need to be installed or is this already in place?

 

[anbm]

not sure...but I say no.

 

[zog]

Existing main service switchboard (4,000A, 480Y/277V) in hospital feeds the chiller. We want to add new (1) 250A CB and (1) 400A CB into this switchboard to serve other added load. In order to do this, electrician said they have to shut down the power to the switchboard and let the hospital emergency circuits powered from emergency generator temporary.

However, the owner doesn't want to shut down power to the chiller.

Any solution to accomplish this without shutdown power to chiller? Can electrician install new CB in main switchboard without shutdown the switchboard? (i.e. they need a special license to work "lived?")

How long does it take to install those (2) CBs?

One thought is they may rent a temporary generator and feed the chiller if the main switchboard has to be down.

NFPA 70E Article 130.1 Justification for work. Live parts to which an employee might be exposed shall be put into an electrically safe work condition before an employee works on or near them, unless the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations.
Energized parts that operate at less than 50 volts to ground are not required to be deenergized if there will be no increased exposure to electrical burns or to explosion due to electric arcs.

NOTE 1: Examples of increased or additional hazards include, but are not limited to, interruption of life support equipment, deactivation of emergency alarm systems, shutdown of hazardous location ventilation equipment

A "chiller" is hardly justified, so your best bet is to provide the owner with an EEWP for them to sign justifing doing the work under this article, putting liability on them. They will change thier mind quickly. I have done a ton of hospital jobs, with more critical loads than a chiller being shut down. Often we have to wait for the last surgery of the day to be done and finish before the first one in the morning.

 

[augie47]

Almost a no-brainer IMO, when you look at the potential danger plus the considerable damage that could result from attempting such an install "hot".
What does the owner plan to do if the chiller suffers an electrical or mechanical failure independent of the proposed work ?

Folks suprise me in that they want you to take risk to keep from turning off power to a piece of equipmemnt yet they survive if nature turns it off or it fails mechanically/etc.

 

[petersonra]

If you stage it right you might be able to shut the chiller down for a short enough period of time that it is not even noticed.

One of the problems with working on switchgear (or MCCs) is that an inadvertent "oops" can create a much longer outage than just shutting it down for 1/2 an hour.

I was involved in a project where the idea was to add a section to an existing MCC one Saturday night so it would be ready for use on Monday morning. The electricians did everything just right in getting it back together but somehow they managed to break off one of the conductors coming into the existing MCC. OOPS!