Floor Register Fire Dampers

[gerry_g]

I have installed a stove in my basement family room (one story ranch). I'm having a nightmare with fire safety codes and distributing heat around the house. My fire department only does comercial construction and my building inspector is not familiar with the topic.

A few things I know, many I don't:

- since the family room is "conditioned space" (warm air) I can do anything with the kitchen stairwell door leading to the the family room. No door is even required. I'm replacing it with a louvered door which solves one area.

- I can add a metallic return from the family room to my furnace return and meet code. I am duct size constricted due to headroom in the basement where the furnace is located (unconditioned space), thus metal all the way. I intend to use a booster fan which comes on when the furnace starts. Currently the "return" os just a plain floor register to the upstairs, using a single hallway return register, no fire damper. This is "grand fathered" but I may replace it anyway.

- The big problem is rooms above the family room with the stove. I plan on picking up ceiling air, using variable speed fans, metal duct and floor registers. My inspector says I need a fire damper (I agree) but has no clue on how to install one. He will approve just about anything I do if it has a fire damper.

Currently I'm planning on a simple setup, floor register, metal register boot, duct fan and a round fire damper at the entrance to this "pickup". I have a non fire rated suspended ceiling to hide all of this (meets code) so I'll add some grills in the suspended ceiling to let air freely move to the pickup.

This seems to make sense to me, the floor opening is just as any heating duct in my home and is cut off should a fire occur via the damper. The fire dampers only have instructions for passing trough a fire rated wall, no information for a setup such as this where they just are picking up room air.

How does such a setup sound? Any references would be appreciated!

gerry

 

[LLigetfa]

Better duct fans have a high temp cutoff thermostat.

 

[gerry_g]

Better duct fans have a high temp cutoff thermostat.

That has nothing to do with fire codes regarding passing trough a floor. A fire damper completely closes the duct blocking any flame path. Stopping a fan does not stop the convection path.

gerry

 

[Crabbypatty]

a fire damper is designed to seal off a duct passing through a fire wall or demising wall or floor in case of a fire. if the damper is in a wall it can be gravity actuated via a fusible link which melts at a determined temperature, 165* f is common. if it is in a floor it needs to be spring actuated. the fire damper should not be in the middle of a room, but where the duct penetrates the wall or the floor. may i also suggest upgrading your thermostat to a honeywell 8000 touchscreen or a similar model which allows for intermediate or circulate on your furnace fan control. IE fan on for 20 min off for 20 min. good luck with your project.

 

[LLigetfa]

That has nothing to do with fire codes regarding passing trough a floor

It is possible in theory for a passive vent to have temperatures that would require a B vent by code. A fan in theory would mix enough cooler air to keep the temp down negating the need for a B vent.

In my former home I had a weighted butterfly damper that would only open under the force of the fan and would close if the fan stopped. The fan had a high temp cutoff in case the temps exceeded the code requirement for a B vent.

I am not familiar with the various fusible link registers and whether or not a fan could overpower the closer. I wouldn't want to find out the hard way.

 

[gerry_g]

Thanks for the reply.

It seems that would mean attaching the fire damper to the register boot since the floor is only 1 1/4", then extend duct to where ever I choose to pick up the air. The spring loaded round fire dampers I have looked at appear to be installed in a sleeve. Every diagram I've seen shows a "sleeve" passing through a wall. In this case it will be in free air between joists over the suspended ceiling.

a fire damper is designed to seal off a duct passing through a fire wall or demising wall or floor in case of a fire. if the damper is in a wall it can be gravity actuated via a fusible link which melts at a determined temperature, 165* f is common. if it is in a floor it needs to be spring actuated. the fire damper should not be in the middle of a room, but where the duct penetrates the wall or the floor. may i also suggest upgrading your thermostat to a honeywell 8000 touchscreen or a similar model which allows for intermediate or circulate on your furnace fan control. IE fan on for 20 min off for 20 min. good luck with your project.

 

[Crabbypatty]

FYI i am a tinknocker by trade, i have put in a couple hundred fire dampers.

 

[gerry_g]

I am not familiar with the various fusible link registers and whether or not a fan could overpower the closer. I wouldn't want to find out the hard way.

I'm looking at a spring loaded Phillips-Aire S3 Round Fire Damper designed "For Use where Square, Rectangular and Round HVAC Ducts Penetrate Partitions with a Fire Resistance Rating Less than 3 Hours, Low Pressure HVAC Systems Damper Closes Automatically Upon Elevated Temperatures" (165F).

It appears to me that a duct booster fan is intended for and does not exceed low pressure HVAC pressures.

 

[LLigetfa]

It appears to me that a duct booster fan is intended for and does not exceed low pressure HVAC pressures.

Your OP made three references to fans, once in the plural form and one reference to a variable speed fan, so it was not entirely clear what pressure this/these fan/fans will produce.

 

[gerry_g]

It is possible in theory for a passive vent to have temperatures that would require a B vent by code. A fan in theory would mix enough cooler air to keep the temp down negating the need for a B vent.

In my former home I had a weighted butterfly damper that would only open under the force of the fan and would close if the fan stopped. The fan had a high temp cutoff in case the temps exceeded the code requirement for a B vent.

I am not familiar with the various fusible link registers and whether or not a fan could overpower the closer. I wouldn't want to find out the hard way.

Since flames tend to reach the ceiling (floor above) there is no cooler air, just flames.

 

[Crabbypatty]

the damper is made to overpower the pressure created by the fan. as far as the installation they do have to be in a duct sleeve. i would install it right up against the floor above.......make sure the register neck does not hinder the operation of the damper usually the sleeve is heavier gage sheet metal (14 or 16 ga welded) than the duct (24 to 30 ga typ.) which attaches to it, therfore the sleeve has a fire rating as well. So when there is a fire the damper closes and the whole system is rated blocking off the opening in the fire rated floor regardless if the fire gets hot enough to melt or destroy the duct attached to the damper. you may have to have a sleeve made for you, by a local HVAC shop, because the dampers don't typically come with them. also i would get a square or rectangular damper to match the opening you have. FYI a type have the damper in the air stream and b type have it out of the air steram. i hope this info helps!

 

[gerry_g]

the damper is made to overpower the pressure created by the fan. as far as the installation they do have to be in a duct sleeve. i would install it right up against the floor above.......make sure the register neck does not hinder the operation of the damper usually the sleeve is heavier gage sheet metal (14 or 16 ga welded) than the duct (24 to 30 ga typ.) which attaches to it, therfore the sleeve has a fire rating as well. So when there is a fire the damper closes and the whole system is rated blocking off the opening in the fire rated floor regardless if the fire gets hot enough to melt or destroy the duct attached to the damper. you may have to have a sleeve made for you, by a local HVAC shop, because the dampers don't typically come with them. also i would get a square or rectangular damper to match the opening you have. FYI a type have the damper in the air stream and b type have it out of the air stream. i hope this info helps!

I have checked this with both my inspector, fire department and the damper's manufacturer's specifications. Heavy duty sleeves are required most but not all, situations fire dampers are used. In fire rated walls/floors and heavy duty sleeves help prevent compression/distortion and possible binding of the damper. A key distinction is I am transferring from a conditioned space to a conditioned space with ganged, hardwired fire alarms throughout the house's conditioned space. Thus things such as a stairway door to the same room are not required.

In my location, 24 gauge is all that is required for HVAC ducts and boots in residential homes not over 3 stories high. Fire dampers are only mentioned in residential code in situations such as having the furnace/heat source/AC in a garage with a garage-residence fire rated wall or ceiling. There are no references for transfers between conditioned (heated/cooled) floors. My family room already has 24 gauge ducting to main floor registers for the existing HVAC system. There is no requirement to exceed this gauge in this situation for the warm air transfer system I am planning. My inspector stated standard residential metallic duct work is acceptable. I only need a fire damper to cut off the inlet to this ducting in case of fire. Basically, the floor transfer is considered no different than any other warm air residential ducting. However, since it is not continuous to a furnace and has an opening, an automatic fire rated closure (fire damper) is required.

I can not fantasize any situation where a transfer with cut off (UL fire damper rated for low pressure HVAC) need exceed the standard HVAC duct and boot materials to my furnace since 24 gauge meets code if connected directly to my furnace. Stick a standard 24 gauge boot in the floor, add a UL low pressure HVAC damper and 24 gauge ducting and fan and the inspector is happy. Thus my "requirements" are my concerns over safety and having the inspector sign off.

I've searched extensively and can't find any code applying to this residential situation. Are you aware of any?

Given the popularity of residential stoves, this certainly seems to be an area where code and real safety should be clarified.

One issue remaining, do I need to fill the area between the damper and "sleeve". If so, with what?

Thanks for your comments,

gerry

 

[Crabbypatty]

if the insrector is happy and your insurance co is happy, then you have no worries. the fire damper is typically attached to the sleeve quite well via spot weld or mechanical fasteners; ie self drill screws. typically after install i would stuff any gaps between the damper sleeve and the fire rated wall or floor with rock wool and then fire caulk around the penatration. this doesn't seem to apply to your situation, however. i have never been required to install a fire damper in a residential building, except apartments, so i think you are allready being very cautious in doing so.

 

[gerry_g]

I think I'm ok with just standard residential ductwork plus a fire damper. I also plan on reworking the grandfathered unprotected register.

In single family homes, the fire protection (in this context) is simply to allow time for escape. The hardwired ganged smoke detectors already have been triggered. With an open stairwell, flames will tend to hug the ceiling. An open floor register would allow flames to come through the floor. In a typical "escape" one crawls on the floor if needed. Flames coming up through the floor would be a tad unpleasant.

Thanks for all the comments, it seems all fire damper code was not written for conditioned space in single family homes.

 

[PeteD]

it seems all fire damper code was not written for conditioned space in single family homes.

This sounds logical. It would be pretty hard to fireproof the open stairway, the loft, and other penetrations that exist between conditioned floor in single family residences.

Pete