Detail Level to Provide for 120V Fire Alarm Power?

12/3/2020

As a consultant, what level of detail do you go into for the line voltage (120v) fire alarm plans and wiring?

The line voltage is affected by loads / fuse sizes and affects the disconnect switch size. I'm wondering about the level of detail that an engineer should be showing versus leaving the sizing to the fire alarm and electrical contractors based on their specific system layout requirements.

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6 Comments

sean

12/3/2020 10:12:50 am

If I understand you properly you are wondering the level of detail of how you anticipate the electrical load of the fire alarm equipment on the building load calculations (watts).

In my office we will kick back electrical panel schedules that don't show a dedicated circuit and for a standard building (which would only use one panel and maybe a booster panel or two) a nominal standard load. If it is a larger more complicated fire alarm system where more power needs are more complex we expect that the detail go up from there.

12/3/2020 11:08:27 am

Good info Sean. I think I read the question as coming more from the consulting / engineering side of things when drawings are being prepared for future bidding by others. How much information would the engineer show for fuse and wiring sizing understanding that each bidder may construct the infrastructure of their system in a different way?

sean

12/9/2020 08:55:12 pm

i hate the engineers who put out shit for fire protection engineering drawings. you know the ones where detection has no logic, and coverage for notification is insufficient, then the contractor puts together a design based on the bid spec. then i get the bad wrap of shooting them down and causing a change order.

If I was not another consultant I would be advising building owners this would be time to take advantage of the architect/engineers errors and omission policy hit them where it hurts, they will lose or learn to do it correctly, stop, or best bet hire someone.

sorry my rant, i would love to write a article on why your architect is costing you money and passing it off as the big bad AHJ.

Mark Harris

12/3/2020 03:48:15 pm

In most cases the fire alarm contractor excludes the 120 volt power wiring so it is important the the EE show the dedicated circuit on the electrical plan and panel schedule. Exception could be if the fire alarm supplier is a parts and smarts subcontractor to an electrical contractor.

At least in my markets there is usually locktab marked fire alarm that goes on the breaker. Not an expensive item but want it to be there before final inspections.

I would talk to a couple of the major fire alarm contractors in your market for their input.

Kyle MacKenzie

12/9/2020 06:51:20 pm

We have a lot line sprinkler installation with sprinkler piping being recessed in a furred out wall. We are concerned about pipe freeze ups. Since we are connected to the existing system that serves the entire floor it would not be feasible to do a dry pipe system or add anti freeze. Does anyone have a good calculation to determine if the piping will freeze in the wall cavity?

sean

12/9/2020 08:56:21 pm

i would recommend the section in the handbook/annex i believe it contains some equations to calc the thermal loss.

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Detail Level to Provide for 120V Fire Alarm Power?

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