INSTALLING CCTV SYSTEM IN A METAL BUILDINGS

[MikeR86 0]

I recently installed a DVR in a decent sized metal building. For the most part all the wiring is run in PVC conduit. Some of this conduit is zip tied to EMT that has one electrical wire run inside of it. The only part of the wire that is exposed is at the end where the RG-59 connects to the camera and in the small office building where all the wires run down and out a sheet rock wall connecting into the DVR. I have four high resolution cameras... that can run off either 12VDC OR 24VAC, I chose 12VDC being that this is the process I am most familiar with and have given each camera their own power supply adapter that plugs into a wall next to the DVR suppling 12VDC 800mA to each camera. I have run many siamese wires without conduit ziptied to EMT or anything unprotected in metal buildings and never experienced the problem Im about to describe. As soon as I plugged in all my equipment like I have done so many times before, I experienced a shock when touching the DVR and the BNC at the same time... it was a nice little jolt... like a telephone block gives off (45volts). I forgot to mention... originally I had a power supply box that supplied power for all cameras. This is when I was experiencing the shock when touching the DVR and BNC. It was a very nice jolt. After putting all the cameras on their own power adaptors replacing the power supply box the shock was gone and non existent. All the four cameras came up working properly with no problem. I come back four days later to port forward this DVR for remote access and the DVR is dead! The power adaptor for the DVR which is a 12VDC 5A supply was reading 0.00 on my meter and even after trying another adaptor that produced 12.5 VDC it would still not power the DVR up. What did I do wrong? I called the manufacturer of the DVR and determined that power supply in the DVR was damaged... but when I did have have the cameras on a power supply box... some of the cams wouldnt come up and the others appeared to have a ground loop problem. But after putting each camera on their own adaptor this fixed the problem. Everything was working fine, what could have caused the DVR to go out? Any advice on running CCTV in metal shop buildings? also what could have caused the DVR to shock me... this has never happen before and was VERY UNEXPECTED!

[MikeR86 0]

No one has anything to say regarding cabling I'm a metal building?just looking to strike us a discussion.. Always looking for good advice and opinion

[SectorSecurity 0]

This sounds like an electrical problem, possibly bad wiring, was everything plugged into the same outlet? I would have an electrician check it over, sounds like someone has mixed up some wiring, seen this before where someone has gotten the positive and negative wires backwards, or there is arcing in the box.

[the toss 0]

While I'm not familiar with Canada's electrical system, it does sound like an electrical wiring fault as Sector has already indicated. In Australia we use the MEN (multiple earthed neutral) system which provides the electrical earth (neutral) as well as a safety earth. These are tied together at the service point (fuse box) so the difference in potential within a building "should" be negligable. If the metal building is relying on a local earth (earth stake etc) then large voltage differences can develop if the local earth becomes compromised which is why it is very poor practice to not have the bonded earth to neutral. Remember that the electrical neutral is actually the earth from the power station.

This is the principle for earth leakage circuit breakers. The current in the active & neutral should always be the same. When an electrical fault develops this balance is upset by current in the "protective" earth which causes the breaker to trip.