Sprinkler proximity to AC diffuser etc

[AZsprink]

I'm having trouble finding anything in NFPA13 regarding heat zones etc. for QR or SR SSP pendants
Any help would be appreciated, thanks

 

[SprinklerDesigner2]

Table 8.3.2.5(a) Temperature Ratings of Sprinklers Based on Distance from Heat Sources

 

[b1ueshift]

I know there is a minimum spacing for smoke detectors from diffusers (so the air flow doesn't affect their opperation), but I've never heard of a similar requirement for sprinklers.

I don't think there is any rule that stops you from putting a sprinkler next to a diffuser (although it will likely take longer to go of in a fire with cold air being blown on it).

 

[NJ1]

I dont think anyone here is talking about cold air being blown on the sprinkler. The original comment is reference to heat zones.
Then sprinklerdesigner2 referred his comment to NFPA 13:
Distance from sprinkler to heat sources

AZsprink needs to elaborate a little more so we can properly comment on his question.

 

[AZsprink]

Sorry for not being more clear, My original question was referring to the minimum distance a sprinkler can be placed next to a ceiling heat diffuser.

I know that most tyco residential heads have to be at least 2 ft. from vertical AC diffusers and 3 ft. from the front and 2ft. from the side of horizontal diffusers (according to the TYCO residential design guide)

I wasn't sure if the requirements are different for commercial heads, looks like they are, for commercial heads you can be 1 ft. from vert. diffuser. "maybe residential heads are more sensitive to temp. changes than commercial heads"

Thanks

 

[b1ueshift]

I think in practice you will be 2' from a heating outlet unless you want to use intermediate temperature (yellow or green) heads next to outlets. For convenience, you probably want red bulb sprinklers throughout.

 

[stookeyfpe]

AZsprink:

I suspect (and this is purely my opinion) the increased distance is necessary because residential sprinklers have an RTI <= 50. Most likely the manufacturers are concerned with HVAC air flow interrupting the hot gas plume and ceiling gas layer during the fire's growth from incipent to pre-flashover.

 

[bksprinkler]

Be aware that the more restrictive requirements (2'-0" from ceiling diffuser instead of 1'-0", etc.) found in table 8.3.2.5(c) apply to ALL types of sprinklers installed in residential areas, not just to residential sprinklers.

 

[b1ueshift]

@Stookey,

Perhaps NFPA should be concerned about interupting the gas plume the way you described, however the way NFPA 13 is written, the requirement only addresses diffusers used for heating not for cooling.

The requirement seems to address unwanted discharge of sprinklers caused by overheat, but doesn seem to address reduced response time caused by blowing cold air on a sprinkler as diffusers that only have cold air are exempt.

 

[cdafd]

So what would you do about a 20000 sq ft freezer storage room and delay in sprinkler response???