I have a question about fire alarm and signalling circuits and surge protection. Article 800 requires surge protection on circuits that leave a building. Fire alarm contractors generally follow this code because the AHJ requires them to. The problem is that the AHJ and the fire alarm contractors usually do not understand that Ground is not Ground. A ground in one building can be 100's of ohms different than a ground in a building on the other side of a campus. The fire alarm that travels between buildings with a surge protector on each end can effectively become a path to try and equalize the grounds in multiple buildings. When there is a potential between earth and the heavens there is no way for the earth to be at the same potential at all points in an area. It is for this reason that the fire alarm wire can not have that bird on a wire effect. There will alway be an imbalance and therefore a potential. Article 800 is causing damage from lightning becasue there is not one ground reference. If a large conductor was forced to be ran with the fire alarm and single ground point reference could be used then the surge protection would be more effective. How does the forum feel about buildings being connected together with regards to ground. This happens by default in buildings that share a generator back up. I have seen 10 or more buildings backed up by a generator and there is a transfer switch in each building. The ground from the generator is common to each building and therefore each building is effectively connected together. If you were wondering why more than one building is protected by one fire alarm system it is becasue of montoring. Eaach building can have its own fire alarm panel and then there is a montoring panel that is cetrally located that monitors all of the buildings in a campus arrangement. This is very common and it is also common that they get blown up all of the time. It is also common that the power provider will alos have poor grounds and actually bring surges from miles down the road so they can bounce around the campus. The question is can you ground (by code) multiple buildings together??
Multiple buildings Multiple Ground Rods Fire Alarm Systems
- Thread starter Davep007
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- Illinois
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- retired electrician
Why are you using a system that uses a connector connected to ground as part of the communications circuit? The phone company uses arresters at ever building and they do not have this issue, but none of their circuit conductors are connected to ground. If it was up to me, I would be using fiber or radio for this fire alarm communication as they do not have this issue.
As far as tying the grounds together for multiple buildings, that is very common for industrial applications and is not a code violation. It would be a very expensive attemt at correcting your problem and it doesn't always work. Find a different type communications circuit.
As far as tying the grounds together for multiple buildings, that is very common for industrial applications and is not a code violation. It would be a very expensive attemt at correcting your problem and it doesn't always work. Find a different type communications circuit.
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- Location
- Massachusetts
We have used fiber when connecting multiple fire alarms together in industrial settings.
Siemens has optical input / output modules available that install at the panels.
Siemens has optical input / output modules available that install at the panels.
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