Mike Dolt Enterprises
Mike Dolt Enterprises
User: skeshesh, Location: Los Angeles, Ca
Asked on: Wednesday, April 20, 2011 at 5:40 pm EDT
Answered on: Tuesday, May 14, 2024 at 4:27 am EDT
Question: Good day everyone, hope all is well.I have a plan check comment for a minor design we did. A new sprinkler riser is being installed at some point in a facility and tamper switch/flow switch have to be interfaced with the existing FA system. We called out monitor modules, contacts, what have you so no problem there. We received this comment: "Specify method of grounding on plan xxx clearly show point of grounding connection". I don't really understand this point. We're dealing with a 24VDC fire alarm signal here and I don't think grounding is required per 250.112(I) - we've also done plenty of FA work for various clients including schools and universities that go through several plan checking agencies and I had not encountered this comment in the past. Am I missing something here?
Consider the following points
Electrical Code Requirements
NFPA 72, the National Fire Alarm and Signaling Code, does not explicitly require grounding for 24VDC fire alarm circuits. However, some local jurisdictions or specific project requirements may have additional grounding provisions.
Grounding for Noise Reduction
In some cases, grounding can help reduce electrical noise and improve signal integrity, especially in environments with high levels of electrical interference.
Plan Clarity
The AHJ (Authority Having Jurisdiction) may request a clear indication of the grounding arrangement on the plan to ensure proper installation and maintenance.
Avoiding Ground Loops
Grounding connections at multiple points can create ground loops, which can cause signal distortion or false alarms. By specifying a single point of grounding, you minimize the risk of ground loops.
Recommended Actions
Confirm Local Code Requirements
Check with the local building official or fire marshal to determine if there are any specific grounding requirements for fire alarm systems.
Consider Noise Reduction
If the facility has potential sources of electrical noise, consider grounding the FA circuit to improve signal quality.
Specify Grounding Arrangement
Clearly indicate the point of grounding connection on the plan. This could be a ground rod, equipment grounding conductor, or another suitable grounding point.
Avoid Ground Loops
Ensure that there is only one point of grounding for the FA circuit.
Sample Response to AHJ:"The requested grounding arrangement has been added to the plan. The FA circuit will be grounded at a single point, indicated on sheet xxx. The grounding connection will be made using [method of grounding]. This grounding arrangement will ensure proper electrical integrity and minimize the risk of noise or ground loops." Flag for review