Not everyone will have experience with this but your opinion is important.

An arc flash study can take quite some time to complete. During new construction, the new electrical equipment may be installed and ready for initial startup BEFORE the arc flash study has been completed and labels have been applied.

This week's question is about energizing new equipment BEFORE the arc flash labels have been added.

Are you OK with NEW electrical equipment such as panels, switchboards, switchgear etc. being energized BEFORE arc flash labels have been installed?
Yes
No
It Depends
Comments are Welcome! We would love to know your views!

If the project is being done properly, there should be plenty of time to complete an arc flash study of the new equipment prior to energization. I always add new equipment to my studies before project commissioning.

Interesting question. One could argue that this is properly installed and assumed properly maintained since it is new and simply operating the equipment - i.e. energizing, should be "normal operation". However on the other hand, how does one know the equipment will function properly without going through a startup. And during the startup if something is missed and goes wrong, you would not want PPE to be considered in hindsight. One other consideration, to stop the commissioning because a study is not completed could reverberate up and down the line. There are many factors to consider on this one. Curious about what others think.

Re-energizing after changes to wiring, such as re-work and installation, is probably one some of the riskiest tasks performed.
This is when PPE is most likely going to be needed.

I agree with Voltrael. There should be time to complete the study before energization. An arc hazard study on a new installation is not nearly as difficult as on an existing facility because you don't need the field data gathering. The system should be modeled already for load flow and protective coordination anyway.

You will often need to work on the equipment after initial energization, and you need to know what PPE to wear when measuring voltage to confirm de-energization.

Start up is where a lot of complacently can take over. When, in fact., this could be the riskiest time. A good proactive step/habit, to get into, is to insure you do the arc flash study before the equipment arrives or at least before main power is applied. Also, it is a best practice to program protective devices before system power is applied. If you can't set the protective settings in the relays at a FAT then at least write into your specification the ability to provide remote 120V test power to the control circuits so that the protective relaying can be programmed prior to system power application.

So often I have seen people setting up protective relays with the power bus active and minimal PPE. "Once I set this relay the incident energy level will be lower...". Another common misunderstanding, especially for main or incoming sections, is the local protective O/C relay setting provides some control of the IE at the incoming point- when in reality is an upstream protective device. Contractors need to be given a full briefing on the power one line diagrams before any work is done- outlining to them the various sources of energy and the potential risks involved in commissioning a system for the first time. If there are no labels the highest PPE needs to be considered. This too does not guarantee anything though if the PPE does not match or better the IE at the point in the system. Without a study you will not have any valid data!

You do not need a study to determine what level of PPE to wear. You do need to do fault study (which should have already been done as part of the design), that with the breaker trip curves will give you enough information to use the table in NFPA 70E. At a previous employer we designed and built manufacturing/processing plants and would do a two step study. The building is always ready to be energized prior to the competition of the process installation. We would have a preliminary study for the building electrical system and then a final study to include all the process equipment. As for data gathering I would agree that yes having a new system does make this easier. I would usually have the system modeled based on submittal data. But there still needs to be a verification step as quite often I would get control panels on site that were different than designed/submitted by the manufacturers. Also verification from the electrical as to how the system is installed (wire, conduit, sizes, lengths, etc.) needs to be done. Proper safety practice starts with making sure every one understands that you NEVER SHOULD WORK ON ENERGIZED EQUIPMENT. If you need to than you go through the proper steps to determine how to do it safely and what safety precautions/procedures and protective equipment is necessary. Have a plan in place before you start.

Startup is fine if you use the table method. If no label is present you have no choice but to use the tables and the new equipment is required to have the generic arc flash hazard warning label installed. I concur that all the projects should include having the assessment done before commissioning, but a lot of companies out there not only have not done the assessment on any of their equipment mainly due to finances in the first place. Most electricians in the field unless they are labeled industrial have not even been to an arc flash or NFPA 70E class. It is a sad thing, especially to the ones that continue to be involved in arc flash events and have not had any training. Use the tables in this case and get the assessment done on the next code cycle or ASAP to at least get up to code for what has to be on the labels.

The best time to get correct sizing on cables, busses, breaker/fuse sizes/settings is while equipment is installed. You can't often get details until it arrives, even if you ask, and its often wrong. For instance transformer impedance is built to a target but can't be checked until just before it ships.

Qualified persons should be able to determine the hazard from the available fault current on the one line. The arc flash study should not be done in the design stage because their are typically changes that affect the study. Customers do not want to pay for a study twice and updates are rarely free. However, personnel must have enough information to safely do their job but it does not have to come from the arc flash study.

During the construction phase, I don't worry about it as much because de-energization to perform work on electrical equipment is routine and kind of expected before substantial completion. So it's not as big a deal to shut things down, for the most part, they just schedule work around it in the morning briefings.

The real question is what's going on with the construction temporary power panel that they bring in before the facility power system is up and energized. Most of the time, the electrical contractor will work it out with the utility and not involve the engineer.

On nearly any job larger than a single panel, most electricians will give the engineer a few weeks notice prior to energization and ask for the protective device settings. If I haven't done the arc flash study already from the shop drawings, I'll complete it at that time.