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Detector Placement in Fire Suppression System 1

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IceYogurt

IceYogurt

Mechanical
Jun 16, 2021
17
I have read FSSA technical publication (DCG-01) and NFPA 72. However they doesn’t specify the detection placement methods of cross zoning detection in fire suppression system. As per DCG-01, it mentions that “historically, the industry has used an area of coverage per smoke detector of 250 square feet”. It does confuse me whether the smoke detector quantity is to be doubled in the case of CROSS zoning even when I am using 250 square feet to place the smoke detectors.

The same confusion hit me as well in the case that we are using smoke detector (Zone1) and heat detector (Zone2), two different types of detectors, in cross zone detection.
Given that the room (31.6 ft x 15.8 ft x 10 ft H) has smooth ceiling with low air flow, which detector placement method as below is more reasonable and logical in the industry?
A. Place the smoke detector by 250 square feet coverage with adjacent smoke detectors and place heat detectors by 250 square feet coverage with adjacent heat detectors.
B. Place detector (no matter smoke or heat) by 250 square feet coverage with adjacent detectors.
Generally, detector quantity of Method A is always double of Method B as indicated below.

Snipaste_2023-06-28_20-36-12_rzrum4.jpg


Maybe the two methods are both incorrect. Anyone could help me address the confusion?
 
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I've recommended using the area of coverage for each zone of the cross-zoned system, effectively doubling the number of detectors.

The detector spacing is based on providing an acceptable response time for actuation of the system, so if the spacing remains the same, but requires two detection zones to operate, the effective spacing is doubled, and the response time rises above the maximum acceptable.

The client and EPC firm accepted that argument.
 
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Hi ProSafPlant1.
Thanks for replying. It is so exciting to find someone having deep thought on the issue.
Yes, I have used the area of coverage per each detector for cross zoned system (fire suppression system) as below.

Image_20230629140114_jcb48g.png


There are still some confusion not being settle yet:
1. How to determine the reduction of area of coverage for detectors in fire suppression system? For smoke detectors, at least FSSA has recommended 250 square feet for area of coverage. But for heat detectors, I haven't found any publication or data sheet to recommend the reduction.

2. How do we place the two different types detectors evenly on the ceiling in the case that they have different area of coverage? For instance, we are using smoke detector in Zone 1 and heat detector in Zone 2. However the area of coverage of smoke detector in fire suppression is 250 square feet; the coverage of heat detector is 625 square feet. As cross zoned system always requires adjacent detectors have to detectors in anther zone, does it mean I have to place all the detectors (smoke and heat) uniformly by the minimum coverage of both detectors (250 square feet)?
 
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1. When you say zone one and zone two,,,,

Are these in the same room?

2. Why are you using heats??? Are they rate of rise?

3. Is this a clean agent system or other?
 
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Hi cdafd.
1. Yes. Same room. Cross zoned detection in one same room to activate clean agent suppression system. "Zone" here basically equals to "circuit of detectors" as my understanding. "Cross zoned detection" means two circuits of detectors to alarm and suppress the fire. (First circuit activated for alarm, second circuit activated for clean agent discharge.)

2. Heat detector is required as per IFC (information for construction) engineered by the Consultant. (I am Main Contractor btw.) The heat detector I am using is integrated with fix temperature (135F) and rate of rise (15F per min).

3. Yes, Clean Agent System (FM200).
 
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Interesting

Have not seen heats used for clean agent.

But, you do have a “Condultant”

Do you have a clean agent/ fire alarm company hired???

If so what are they telling you about your questions?

Can I ask in general… What is the clean agent system protecting???
 
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2. “”Heat detector is required as per IFC“”””

Do you happen to have that section??? And which year addition of IFC?
 
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1. "The Consultant" is the Engineer as per FIDIC.

2. We have clean agent specialists hired. However they don't have clear answer about the reduction of coverage per detector as there is no clear answer in NFPA 72 or。NFPA 2001 or any code to specify the method of detector placement in clean agent system. Actually we have more than one clean agent specialist and they have different detector layout drawings in one same room. As they are specialists and I am just an Main Contractor, I don't have sufficient knowledge and experience to judge who is right and who is wrong. That's why I am coming here for help.

3. Clean agent system generally protects electrical switch gear room, transformer room, server room, computer room etc, where there are always valuable property to be protected and cannot be protected by water based system.

4. IFC I mentioned previously means "information for construction" rather than "international fire code". They are the drawings prior to shop drawings and generally issued by the Design Consultant. Maybe they have different names in your region. Btw, international fire code has barely no information and restriction about clean agent system.
 
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I am former ahj

If two different detection devices are used, I would require normal NFPA 72 spacing for both.

I would say you want normal spacing, because with reduced, there maybe a delay in sensing the smoke/ fire.


I do not have the book, but would not do reduced spacing.

If truly valuable asset, that would put the business down for days/ weeks, I am thinking smoke detection all the way or smoke detection and air sampling.
 
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Sorry got lost

Smoke detectors at 250

Heats per nfpa 72
 
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May I ask which state of AHJ you were? I always feel like to hear the opinion from AHJ about the issue.

We may use air sampling detectors in the room having high air flow.

The Consultant insists heat detectors in second circuit as they concerns smoke detectors in both circuit are more likely to raise false alarm and unwanted discharge than two different detection devices. Since heat detectors may delay verify the fire, the Consultant requests tighter spacing to decrease the response time.

Btw, may I ask how do you as an AHJ judge or confirm the detection layout submitted by the property owner has complied with NFPA and state code? Do you have a detailed method of detector placement?
 
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Texas

Plan review

Look at what is submitted

Compare against NFPA standards adopted by the ahj, or if submitter requests to use a different design standard.

NFPA is just requires the minimum. So compare the plan submitted against the NFPA standard.

Some call it cookbook add this to this and out it comes.

Sounds like the consultant was brought in for some reason,,, which is good,,, as long as the owner understands what they are getting and how it works. The design sounds like it meets the standard…

The clean agent company should verify that !!!!!
 
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Hi cdafd,

Sorry to reply late. Hope you had a great summer.

Update of the above said issue:
Our clean agent system specialists don't agree with the Consultants' opinion of detector placement. And even different engineers in the Consultant have different opinions. (Most engineers in the Consultant always chose to go with the specialists, but there is an elder engineer in the Consultant having his own method to place the detectors, but no specialist agrees and no reference to verify his method. The Consultant management chose to believe the elder engineer.

Regarding clean agent equipment (detection system) suppliers such as honeywell, kidde, ansul, are not willing to verify it as they said the issue is out of their scope and it should always refer to the Consultant.

I am looking for a clear reference in international code or American code or a third party to judge the issue. No positive feedback as of yet. I have contacted with FSSA (Fire suppression system association) but no reply. So I am lost. (Crying face) Please tell me whom I should ask for the help.
 
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If allowed to design per NFPA 72,

than space per that, for each zone.

Are they still wanting to use heat detectors?
 
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Yeah they are still wanting heat detectors. In the beginning, the system specialist provided smoke detector and multi-criteria detector. Now the consultant is insisting smoke detector and heat detector as they think dusts or cigarette smoke may raise double knocks.

Regarding "zone", do you think whether my understanding about "zone" equaling to "circuit" of detectors is correct? If wrong, how should I understand "zone"?

Spacing per zone is clear and simple for the system contains only one kind of detector. But for the cross zoned system containing two kinds of different detectors, it seems impossible to unify the spacing without authoritative technical publishment because the two different detectors have two different spacing requirement. Should I go with the shorter one of the two to place all the detectors?
 
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Regarding "zone", do you think whether my understanding about "zone" equaling to "circuit" of detectors is correct? If wrong, how should I understand "zone"?

A zone
It can be a circuit of smoke detectors.

It can be a circuit o smoke detectors, that are programmed, every other one either zone one or zone two.



If using NFPA 72 as the installation standard,,, then space the heat and smoke detectors per 72.

Are you working with the clean agent company, that will install this ??


Only other I know is a Fire Protection Engineer, that has handled clean agent systems before.

 
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For "zone", ok I got your point.

We are using NFPA 72 as the installation standard, however smoke detector and heat detector have different spacings. For example, spacing of smoke detector is A, and spacing of heat detector is B. (A>B) So how long spacing should I apply in the case?
1. A
2. B
3. B/2
4. (A+B)/2
OR ANY OTHER ANSWER

We are working with the clean agent system companies which are local suppliers having the certificate from the manufacturer (Kidde, Ansul, etc).
Should one engineer who has NICET certificates on Fire Alarm or Fire Suppression be able to judge in the case?
 
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Install the smoke detectors per 72 spacing

Install the heat detectors per 72 spacing

Yes they are different distances.

I would go with the nicet on fire alarm, for any fire alarm questions, but work with the clean agent company, so the two meet and work together.
 
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Hi cdafa,

I have talked with the clean agent about the opinion of placing the different type of detectors as per their own requirement. They told me they have never seen the design as it may reach the irregular placement of the detectors belonging to one fire suppression system, not detector array or sprinkler array as commonly seen.

Finally, both parties (clean agent companies and the Consultant) have compromised that:
- For lower height room, both types of detectors have to follow the shorter spacing of the two types per NFPA 72 and FSSA (reduction of detector coverage area while using it in fire suppression system, consider the reduction factor as 0.5).
- For higher height room, detectors placement will be arranged by the Consultant case by case.

I cannot find anyone having NICET in the country where I am working. It seems like NICET is only accessible for US citizens.
I do want to get NICET of fire suppression system as I think I am very familiar with NFPA 2001 now. (kidding)
 
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Sounds like the clean agent company is your best source!!!
And normally are.
Good luck
 
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