Many times fire alarm techs get stuck with a bad situation…. When the tech comes in and install the fire alarm, only to discover that the SLC loop line is also in the same pipe as the AC power. Now a few years ago, that might not be a problem, but today I can assure you that is a problem especially if Art. 250.94 is violated. If you have 120V sine-wave bleeding over the SLC loop line of less than 24 volts, you can find a phantom voltage exceeding 34.4 volts. This phantom voltage does not have current. So to attenuate this phantom voltage it is possible. The use of surge suppression can help, but it only caps it off at 34.4 volts. The FA30BH, on the other hand will attenuate the phantom voltage even more….or should I say almost squash it. Not kill it, but to a very livable situation. In cases where there is a violation of Art. 800, (see Art. 250.94) that phantom voltage can bring radio, white noise and all sorts of nightmares.
I believe….to mitigate grounding differentials to comply with Art. 250.94, always specify a # 14 Gauge stranded copper ground wire which should go through the pipe as well. I find it will come in handy especially when corners are cut and the buildings are not bonded together. You can use this wire to accomplish the same thing called a jumper wire. It is not a perfect ending, but it is a solution to passing current and noise issues.
There is a story to this. I got a call from a tech in California about this very thing. He did an install on an E-3 panel, only to have elevated voltage issues. He was on the verge of loosing the customer to another security company. That security company was going to replace the entire panel with a different brand panel. It was going to cost the customer big bucks. He took a last ditch effort and called me based on a referral. I tried to tell him what the issues were, and what violation it was and so forth, but he was only interested in my solution. A $100 dollar solution is far cheaper then words of wisdom. Anyway he ordered both the FA30VB and the FA30BH to accomplish two tasks. One to clamp the hell out of the voltage and the other one to attenuate the signal. His customer facing a huge expense, opted to try this low cost Band-aid. Thank God it is California, not the Lightning Capital of North America.
If you need further assistance in the area of surge suppression, lightning protection and grounding for fire alarms….I am available. Some techs don’t like to spend a lot of time on the phone….but it will be worth it if you did with me. I have a lot of experience to pass on and in most cases, you will learn a lot. Surge Suppression is not the answer to all things and I don’t want to give you the impression that if you call, you will have to buy something. Sometimes an Engineer like myself, just might help you solve something with lip service. That has been known to happen. In those cases, I don’t make a dime, but I gain your trust.
727-823-6100 x 1 Stormin Protection Products Inc. John Pecore, BSEET, MBA, Power Quality Engineer for the Life Safety Industry.