No Overhead Obstructions

Here’s another of example of something you would not normally expect to see.


This building has power lines running the entire length of the C side of the structure. Not only do the lines run across the back, but look closely at the second picture. The lines break off and go to a weather head style service drop in the middle of the roof. In smoky conditions there is a good chance you may not see the first set of wires, and end up throwing a stick against them. If you were fortunate enough to avoid them while making the roof, hopefully your luck would not run out while making you way across the roof.

22 thoughts on “No Overhead Obstructions

  1. ... says:

    Checking the roof now means checking the air above it. Talk about an obstacle. That is one building that would really test your knowledge, safety, and skill.

  2. Nate DeMarse says:

    A great photo showing potential hazards to firefighters.

    I think the best bet for access would either be an aerial ladder to the parapet and under the wires. The members ascending will have to be very careful not to come into contact with the wires.

    Another option is to throw the portable ladder to the roof like you are laddering a window sill for entry. Drop the butt of the ladder at the level of the parapet. While the normal 3-5 rungs is always preferred, but impossible here without potentially hurting yourself.

    Nice find

  3. N/A says:

    If the caption is true in saying that the wires are only on the C side then laddering the building from the other sides should not be a problem. That is of course if you do not need ladders on the C side. In that case you would need to take one of Nate’s approaches. As he mentioned though the ascending firefighter would need to be very cautious. Overall this building would be very hazardous during any type of smoke conditions and during the night.

  4. Jon says:

    A good Outside Vent Man would see this immediately. And usually and based on the photo he would beat the roof man to his assigned position and be able to give the heads up before he makes a shocking mistake! This building must have some heavy machinery to be using that kind of power. It also looks like the rear is below the grade of that parking area (look at the cars and the top of the rear entrance). I think it could be a stretch with the 24 in the back there, only cause of that parapet wall.

  5. Patrick says:

    I agree with the comments about avoiding the C-side all together and just make the roof in a position well away from the wires. Also looking at this building and seeing the amount of power going into it the questions of “Is there anything to be gained by entering and/or vertically venting this building?” has to be asked and answered quickly.

  6. Nate DeMarse says:

    Patrick,

    I agree with you fully.

    My answer would be that vertical ventilation must be done (at least attempted) to allow the engine company to quickly advance and extinguish the seat of the fire.

    I don’t think that there is anymore power going into this building than any other commercial taxpayer. The only difference is, it is blatantly visible, obvious and in an odd location.

  7. Jon says:

    Nate, our buildings dont need 3 phase plus here in the city. They usually have 220 at most at their disposal. 4 wires means a heavy draw of current/need for voltage.

  8. Patrick says:

    Nate,

    As Jon points out that kind of power tips me off to something industrial and with the multiple visible HVAC units on the roof from just two ground pics I would approach this with alot of caution. My read of this is something industrial/commercial that if I have to order multiple lines into and am thinking of ordering a vertical vent on this taxpayer, and we all now the roofs of taxpayers in our areas, I would probably be looking more defensive. If all occupants are accounted for/building unoccupied at time of arrival I would porbably order the front and rear to be opened up as much as possible and master stream in the front. Knock down the fire and do my best to make sure all my guys went home. This is the kind of building that kills and I would have no problem in letting this become the latest Mecca of Urban Renewal. As usual just me $0.02.

  9. Drew Smith says:

    In 1999 while investigating an electrical problem at the Northbrook, IL Niemann-Marcus store, Assistant Chief Wayne Luecht of the NBFD and an electrician were severely burned in an electrical arc flash fire. Burned over 90% of his body, A/C Luecht died after about a two-week fight for his life. One factor in this incident was the 480V AC electrical service. More info on this incident is available at http://firechief.com/mag/firefighting_firefighter_death_spurs/

    In the late 1990s when I tried to apply my knowledge and experience with residential electric to a temporary fire station we were setting up, I and another member inadvertently caused the destruction of more than $1,000 in computer, fax and TV equipment.

    These two incidents led me to go out and learn more about the difference between residential and commercial/industrial electrical services.

    What I learned was:

    Almost every single family home and small apartment building uses single phase 120/240V AC service. This is characterized by three wires from the pole to the meter, either buried or overhead. If overhead, the three wires can be twisted (Triplex) or three parallel wires (open wire). In both cases, the wires are rarely insulated but covered with a weather-resistant material. Open wire service may use bare wires.

    In Triplex, the two covered wires are hot to the touch and not a problem because they are at the same potential. The bare or uncovered wire is not a ground but rather a neutral. It also serves as the messenger cable supporting the overhead service. A broken neutral should always be considered hot. The two hot wires each carry 120VAC. When combined they produce 240VAC.

    When operating at commercial/industrial occupancies it is any guess what combination the service may contain. It is not uncommon for there to be multiple services for a single occupancy or in the case of a strip mall, a variety of services-one for each occupancy’s needs.

    Commercial/Industrial services will usually have 2 or 3 pole mounted transformers or a single pad mounted transformed. With pad mounted transformers you have no idea how many transformers are in the case. Never open the case as you subject yourself to possible electrocution.

    The wiring configuration for these buildings can use three or four wires. If only three wires are seen then do not assume it is lower current. The assumption should be there is no neutral as that service supplies equipment and not 120VAC or lighting. Many 3 wire services supply 480VAC! In the four-wire service there can be more than one transformer wiring scheme. The most common scheme results in 120/208VAC. Measured across the three legs, A-B-C to neutral, the voltage is 120 but from A to B, B to C, or C to A the voltage will be 208. 208 is commonly used for motors but 240 can also be present for other applications. In some cases, the B leg may be a “high leg” and measure to neutral at 208 volts AC.

    In any case, none of this can be determined visually and only an experienced electrician with proper PPE and test equipment can make the determination.

    NFPA has a standard that dictates what PPE should be worn for voltages over 120/240 and in some cases it is some elaborate and expensive gear.

    Years ago we had reported fire in the basement of a hotel. It was a big hotel (three wings and over seven stories) and had many banquet halls in the basement. While two weddings were being held, another hall had some “DJs” running a rap concert. To power their equipment they had removed a circuit breaker panel cover and attached a massive extension cord to the buss bars using automotive jumper cable connections. For whatever reason, the panel blew and killed all the power to the basement. When we arrived, occupants had evacuated but the panel in questions glowed red like a branding iron. The electrical utility was called and determined that to kill the power to the building would require them to dig up the street. A set of fuses each the size of a 40 oz. beer can fed the entire hotel. The utility workers donned their PPE, tied a special non-conductive rope to each fuse then stood out in the hall some 50+ feet away and pulled. You would have thought it was the Fourth of July. Another good reason to not fool with this stuff.

    Getting back to some original comments, if an aerial ladder contacts an overhead service it is the members on the ground touching the vehicle or the members on the ladder who contact the wire who risk electrocution. Members at the tip or turntable when the ladder touches the wire will usually be OK similar to the bird sitting on a wire. This is because they do not complete the circuit. Any member throwing a portable ladder will most certainly be killed if the ladder touches a wire.

  10. Nate DeMarse says:

    Nice posts Pat and Drew.

    I noticed the layout of the wires and the way they were attached to the building was odd, but I didn’t think further of the occupancy. I wonder what the store/building is housing and what they are doing in there.

  11. Dennis Beck says:

    Drew,
    As a Master Electrician i have never heard such a good description of electrical services in my 14 yr fire career.

    Kudos

    If you have no formal electrical training YOU REALLY DID YOUR HOMEWORK i hope everybody else reads and understANDS THIS POST.

    ELECTRICITY IS SOMETHING TO BE RESPECTED NOT FEARED.

    STAY SAFE

    DENNY

  12. Ray says:

    Holy moly Drew! That was an excellent posting. I think I actually learned something here!! Back to the pic. It shows you where we are on the list of things to consider!!

  13. Nate DeMarse says:

    Brothers,

    Captain James Robeson of the Scranton, PA Fire Department was killed this morning while operating at a house fire. Preliminary reports indicate that an aerial device came into contact with power lines and he was electrocuted.

    Very applicable and on topic with this thread.

    Respectfully,

    Nate DeMarse

  14. Chris - Concord Engine 1 says:

    Drew,

    Fantastic post! I found it VERY educational and helpful. Thats what I love about this site… rarely any BS or infighting, just alot of knowledge being exchanged, and with the loss of so many senior guys over the past several years we can use all the help we can get to keep the skills, experiences, and traditions alive.

    You should consider working that text into an article for publication in FE or FH so a greater reader-base of firefighters can learn from it… Maybe Master Electrician Dennis would tag-team with you?

    Be safe Brothers & RIP Capt. Robeson.

    Chris

  15. Jimm says:

    I think a full length supplemental page with pictures would be in order. We’ll be contacting Drew (and Denny) to see it they are interested. Hopefully they are…
    -Jimm-

  16. Adam says:

    I would be weary to ladder the C side and go under the wires. Not knowing the voltage, an arc could jump 10 feet. Ladder A,B, and D. More escape routes, with one complete side unusable.

  17. Matt says:

    This is another example of where we should get out of the recliners and learn the buildings in our area. Something like this should not come as suprise to the first due and the information should be passed on through preplans and trainings with other companys.

  18. Tim says:

    This picture is very common in older strip mall/commercial type configurations, where there are multiple tenants in one structure, each with separate utlity services. Very often a utility will do this to avoid numerous poles, transformers, and service drops. These runs are usually utility owned to the service head. This is probably 70’s vintage. Now the norm is to go underground. The most important thing to remember here is that these conductors are considered UNFUSED, no matter the voltage. The only overcurrent protection is on the primary side of the transformer. They can only be disconnected by the utility. Utmost caution is required. 5/1000 of an amp through your heart will kill you.

    Stay Safe
    Tim
    Fire Chief
    Master Electrician
    Electrical Code Official

Leave a Reply