The two pictures below show two electric panels that I took while the installation was in progress. The small panel on the far right is actually the telephone DP.
Picture 1 – Electric panel installation for a typical floor at a high-rise office building
RELATED ARTICLES: Conduit to trunking connections | Cable ladder pictures | Electrical conduits and trunking pictures | Electrical panel under water pipes | Electrical busduct installation pictures | Electric conduit installation pictures | Electric trunking installation pictures | FR electric cable installation pictures | Multi storey building electric closets | Underfloor trunking pictures | Site-fabricated electrical trunking | Electrical Services Color Codes | Light switch installation pictures | Electrical installation pictures
About the author: http://www.linkedin.com/in/electricalengineerforhire
Or visit: https://www.facebook.com/Freelance.Electrical.PE
Picture 2 – The front view of the electrical panels
Why would I want to show the readers these pictures?
There was something wrong with this panel installation. The telephone DP is not a problem, but the installation of the electrical panels was not acceptable.
The high-rise building electrical system
This building was a high-rise office building. At every floor there were a number of electrical panels to serve all the lighting and power requirements on that floor including the lighting, switched socket outlets, toilet exhaust fans etc, etc.
Some areas of the office used an open floor office systems so under floor trunking was also used here.
A few of the panel were located inside the riser room of each floor. However, since each was a large area some panels needed to be located at the office area. Wiring directly from the electrical riser would be unnecessarily too long.
Therefore, the electrical consultant locates these electrical panels along the corridors throughout the building. The design architect was requested to provide small rooms to house the panel.
Alternatively, small electrical cabinets with lockable doors and sufficient work access and ventilation would be acceptable.
The Client-Consultant Meeting
Four months before I took these pictures, during a weekly site coordination meeting, the design architect asked me if they could just house the electrical panels inside cabinets but the doors would not be provided with locks and keys.
You see, this was a design-and-build contract.
In a design-and-build contract, the main contractor employed all consultants. So all design consultants were obliged by contract to assist the main contractor in any effort to optimize the design (to save more money actually).
They call this “value engineering”.
I was the site supervision engineer on behalf of the electrical design consultant in this project.
Okay, back to the meeting I mentioned earlier. The design architect asked me if they could just house all the electrical panel in the office areas in small cabinets but the doors would not be provided with locks.
They had no budget for the locks. The design architect said he did not know they needed to lock the electric panels.
If locks were provided, the main contractor might decide to deduct the consultant’s design fees to cover the cost of the locks. “The consultants should be responsible for any omission from the design”. Those were the words.
I said NO.
The discussion and arguments about this matter went on for more than half hour.
I maintained my position that the electrical panels should be housed in enclosures with lockable doors and access provided to all the electrical trunking in and out of the panels.
The basis of my position was that all those panels were designed to be housed in side a protected enclosure. That was why all panel doors were not provided with locks.
I defended my position and in the end the architect and the main contractor’s project manager gave in. I won.
The Value Engineering trick
However, supervising a construction work under a design-and-build or turnkey contract was never easy.
The main contractor is not afraid of the consultants, or the resident engineers, which are the consultants’ representatives at site.
Four month after that meeting, the contractor’s M & E Manager told me they have made a mock-up of the electric panel enclosures and they wanted me to check and see if it was acceptable.
I went to see the mock-up with the M & E Manager.
Surprise! You can forget about the locks and the keys. The electrical DB’s were not even housed in a cabinet, let alone a DB room or something.
I told him that I rejected the mock-up and took a few pictures (Picture 1 and 2).
He argued that they do not have enough time because the building must be handed over to the owner in six weeks, failing which there would be LAD imposed to the main contractor by the building owner.
A few days after, one after another of the main contractor’s site people came to see me and asked me to approve the mock-up enclosure for the panels.
Now a new round of arguments came up. I maintained my position, of course.
In the end, which was the next day, the Project manager told me they would proceed to comply with my requirements but I needed to submit to them the codes that were the basis of my position.
IEE Wiring Regulation Sixteenth Edition 1991
I was not in the mood to write any Site Memo, so I just went out and took the IEE Wiring Regulation Sixteenth Edition from my car.
I photocopied Page 25 and Page 30.
Page 25 was the content page for Chapter 41: Protection Against Electric Shock, while Page 30 contained the detailed regulations relevant to the issue at hand, which were: (a) Regulation 412-03 - Protection by barriers or enclosures; (b) Regulation 412-04 – Protection by obstacles; and (c) Regulation 412-05 – Protection by placing out of reach.
At the Regulation 412-03-01, I highlighted with yellow markers the words “… Live parts shall be inside enclosures or behind barriers…” and jotted down the following hand written comments:
“The instruments installed at the front of the panel are fragile and they have not been designed for toughness. Any accidental damage to these instruments may expose the internal wiring and other LIVE parts.”
At Regulation 412-03-04 (i), I highlighted the words “ … the removal or opening shall be possible only by use of a key or tool.” And gave the following comments:
“The inside of the electrical DB’s should only be accessible by use of a key or a special tool.”
I initialed both hand-written sidebar comments and put down my Resident Engineer rubber stamp.
The main contractor's Project manager received the original copy later in the day.
The following Monday I saw the furniture subcontractor commencing works to modify the electrical DB enclosure.
Check out the photographs below to see the components that were mounted at the front panels of the electrical DB’s. I also gave a few lines of comments on the functions of the instruments for the benefits of casual readers. This blog is intended for beginners mostly.
Picture 3 – The DB voltmeter
This instrument measures the voltage of the incoming electricity supply. The two DB’s here are three phase DB but one voltage meter is provided. So, only one voltage can be read.
That is why a SELECTOR SWITCH is always provided (see Picture 4 below). You can change which voltage of the three phases (Red, Yellow or Blue phase) to read.
However, there six voltage positions there.
For the real beginners: The reason there are six voltages is because not only there are three phase circuits that you can connect you appliances to, but there are three other which are Red-to-Yellow, Yellow-to-Blue and Blue-to-Red. These phase-to-phase voltages provide 415 volt each, while the single phase (either Red, yellow or blue phase) only give 240 volts.
If you have a large steel gate at your house entrance and it is motorized, then it is probably using the 415 volt. The normal 13A switch socket outlet that you connect your washing machine to is a 240 volt supply.
Picture 4 – The voltmeter SELECTOR SWITCH
There is an OFF position, which means you would not read any voltage at this position. That is why the voltmeter in Picture 3 reads “zero” volts. The voltmeter switch is in the OFF position.
The transparent front plate of the instrument is actually made of some plastic material, and it can easily be broken by accidents.
Picture 5 – The ammeter (current meter, or Ampere Meter)
This is similar to the voltmeter except that it reads the phase currents. A selector switch is also provided (see Picture 6) to select which phase current the meter would show.
Picture 6 – The ammeter selector switch
Picture 7 – The phase indicating lights
When these lights are ON, then you know there is electricity in the electrical panel. It tells in a quick glance, from far away.
In most electrical panels, these light are connected the circuit before DB main circuit breaker.
That means if you open up the electric panel and turn OFF the main incoming circuit breaker, these lights would still be ON.
Why would we want it that way?
Because there is still electric supply in the DB and therefore it is still deadly dangerous.
You can only make the lights OFF by switching off the circuit breaker (or fuse) at the source supplying the DB.
This is an important life and death matter.
Picture 8 – Panel door screws
This the screw used to secure the door. There are two screws for each electric panel door in the picture, at the top and bottom of the door right side.
You would not need any screwdriver or other tool to turn these screws and open the electric panels. In fact, they are designed to be opened easily with the two fingers.
So anybody can open them. Do not get me wrong. There is nothing wrong with this design. It is one of the most widely used practices in electric panel design if they are intended to be housed in a protected room or cubicle.
If the designer intends to locate the panel at areas accessible to public, a lockable door with key would have been specified.
Alternatively, they can be located at a position reasonable out of reach. At some height, for example.
Picture 9 – Electrical trunking in and out of the electric panels
There are electrical trunking connecting the panels in Picture 1 and 2 at above and below the panels. But the box-up walls have hid them. Picture 9 show example of one of these metal trunking.
In future, the maintenance electrician would need to access and open the cover of the trunking in the repair and upgrading works. Therefore, a means of access is required, which was not provided at all at the mock-up unit.
That is all the time I have for this blog today. Visit this post, Electrical installation pictures, to see pictures of electrical installations.
(Update April 2010: The electrical panel box-up has been rectified. You can see the pictures at this post, Multi storey building electric closets.)
Visit the following post if you wish to see pictures of electrical injuries. However, first make sure you really want to see them. Some people do not like to see pictures of serious accidents. The pictures are here: Electric shock injury pictures
Copyright http://electricalinstallationwiringpicture.blogspot.com Electric Panel Installation Pictures