Duct Smokes & Ductless Split HVAC Systems & Fire Alarm

[ryant35]

We have approved plans for a manual fire alarm system with notification throughout in a restaurant, A-3 occupancy.
The plans show connections to duct smoke detectors provided by the HVAC contractor & fire alarm relays for HVAC shutdown.

Today we learned that the HVAC units are ductless split system with heat pumps on the roof. The ductless system consists of a wall mounted fan coil that looks similar to a hotel wall unit and is over 2,000cfm.

Obviously we cannot install a duct smoke detector, and the only other exceptions under 2010 California Mechanical Code are total coverage area smoke detection or "Automatic Shutoff is not required when all occupied rooms served... have direct exit to the exterior and travel distance does not exceed 100 feet."

I know this is mostly a mechanical issue but we need to figure out a solution, has anyone run into these units in a commercial application before?

 

[GoldDigger]

We have approved plans for a manual fire alarm system with notification throughout in a restaurant, A-3 occupancy.
The plans show connections to duct smoke detectors provided by the HVAC contractor & fire alarm relays for HVAC shutdown.

Today we learned that the HVAC units are ductless split system with heat pumps on the roof. The ductless system consists of a wall mounted fan coil that looks similar to a hotel wall unit and is over 2,000cfm.

Obviously we cannot install a duct smoke detector, and the only other exceptions under 2010 California Mechanical Code are total coverage area smoke detection or "Automatic Shutoff is not required when all occupied rooms served... have direct exit to the exterior and travel distance does not exceed 100 feet."

I know this is mostly a mechanical issue but we need to figure out a solution, has anyone run into these units in a commercial application before?

This is not my area of expertise, but I would think that if there are no ducts, then the air handlers could not possibly introduce smoke into an otherwise smoke free area, and so there is no reason to shut anything down. Just for the less important reason of not fanning the flames, a smoke detector internal to each mini-split internal unit which can be used to shut them all down might be justifiable.

If the code does not make specific provisions for that sort of situation, it can be painful for all involved.

The cheapest thing might actually be to install some token ducts that you could put detectors into.

 

[ron]

Does it only recurculate air in the room or take in distribute air from other spaces?There is an exeption to needing a duct detector if you can spread the smoke to other spaces. Look at the section for the Mechanical code.

 

[hbiss]

They only circulate air within the room. I can't believe the little experience with these since they have become very common. No ducts=no duct smokes. And there is no option for a "built-in" smoke. I would treat the job as having no cooling or heating.

-Hal

 

[nhfire77]

This is not my area of expertise, but I would think that if there are no ducts, then the air handlers could not possibly introduce smoke into an otherwise smoke free area, and so there is no reason to shut anything down. Just for the less important reason of not fanning the flames, a smoke detector internal to each mini-split internal unit which can be used to shut them all down might be justifiable.

If the code does not make specific provisions for that sort of situation, it can be painful for all involved.

The cheapest thing might actually be to install some token ducts that you could put detectors into.

You cannot install a duct smoke, unless there is duct work. The inspector should understand that.

2009 IBC

606.2 Where required. Smoke detectors shall be installed where indicated in Sections 606.2.1 through 606.2.3.

Exception: Smoke detectors shall not be required where air distribution systems are incapable of spreading smoke beyond the enclosing walls, floors and ceilings of the room or space in which the smoke is generated.

Ok, but let's say they serve more than room or space....

606.2.1 Return air systems. Smoke detectors shall be installed in return air systems with a design capacity greater than 2,000 cfm (0.9 m3/s), in the return air duct or plenum upstream of any filters, exhaust air connections, outdoor air connections, or decontamination equipment and appliances.

What duct????

May sure the AHJ is aware of this, they still may require the units to shut down on a general fire alarm regardless, but I don't know about California

 

[ron]

You cannot install a duct smoke, unless there is duct work. The inspector should understand that.

2009 IBC

606.2 Where required. Smoke detectors shall be installed where indicated in Sections 606.2.1 through 606.2.3.

Exception: Smoke detectors shall not be required where air distribution systems are incapable of spreading smoke beyond the enclosing walls, floors and ceilings of the room or space in which the smoke is generated.

NFPA 72 does have methods shown in the Annex to reflect what to do if there is no duct. The key for the OP is the exception posted by nhfire77.

 

[nhfire77]

NFPA 72 does have methods shown in the Annex to reflect what to do if there is no duct. The key for the OP is the exception posted by nhfire77.

Is there a specific section or are you referring to the performance based concept in general? Maybe I missed it, since I'm using the '10 handbook

 

[ron]

Is there a specific section or are you referring to the performance based concept in general? Maybe I missed it, since I'm using the '10 handbook

I was thinking of FIGURE A.17.7.5.4.2.2(a) for spacing in the opening to the HVAC

17.7.5 Smoke Detectors for Control of Smoke Spread can also be considered too.

 

[nhfire77]

I was thinking of FIGURE A.17.7.5.4.2.2(a) for spacing in the opening to the HVAC

17.7.5 Smoke Detectors for Control of Smoke Spread can also be considered too.

Thanks Ron, I don't disagree with the concepts you referred to. Technically there are no 'ducts' in the appendix's example, but air is removed from the space it serves, in that case.

I am not attempting to debate, but wonder if I misunderstood and can learn something. How does that apply to a split ductless system, as in the OP's situation? The air never leaves the room it serves, just through the unit which is in, or on, the wall. The use of area detectors in the space (the occupied room) would be used to shut down the Hvac system? Ive never seen that used in a room, but in the diagram's example it make sense.

There are AHJ's in my area that allow duct smoke alarms to be supervisory and allow local unit shut down, but require a global shut down on any fire alarm.

 

[ron]

In this applicaiton, the recirc of the unit results in no detector or shutdown required.

 

[ryant35]

Thanks everybody for your replies, it looks like we have our answer above.