Volume air valve vs. fire dampers

[eager2learn]

My question is whats the difference between the two. Don't they work relatively the same function. I know that the fire dampers tie in to the fire alarm system with a relay or am i mistaken

 

[infinity]

VAV's are used to control air flow into certain areas and are usually located just about anywhere within the ceiling and controlled by a T-stat or BMS type system. Fire dampers, or fire smoke dampers as they're sometimes called, are located right where the ductwork passes through a fire rated wall and are designed to close under an alarm condition. These are different than VAV's which are designed to control normal airflow of an HVAC system.

 

[iwire]

I know that the fire dampers tie in to the fire alarm system with a relay

Sometimes, more often I see fire dampers like Trevor described with simple melt out links that will let the damper close by spring or gravity if the temp gets to high.

What is the application you have in mind?

 

[pgordon]

vav's sometimes have back up resistant heat in them,they come off the main
trunck line for remote offices, And yes fire dampers are usually controled by a fuseable link, and may or may not trip a the FACP.

 

[eager2learn]

VAV's are used to control air flow into certain areas and are usually located just about anywhere within the ceiling and controlled by a T-stat or BMS type system. Fire dampers, or fire smoke dampers as they're sometimes called, are located right where the ductwork passes through a fire rated wall and are designed to close under an alarm condition. These are different than VAV's which are designed to control normal airflow of an HVAC system.

thanks for this answer it makes things a lot easier to understand knowing that fire dampers are located next to fire rated walls - which would automatically close the damper controlling or limiting the oxygen in those rated walls - correct.

 

[eager2learn]

so is it safe to say that when ever there is a fire rate wall there should also be a damper

 

[infinity]

so is it safe to say that when ever there is a fire rate wall there should also be a damper

Yes that would be a good assumption if there is ductwork passing through the fire rated wall. Doesn't make much sense to have a fire rated partition and a big open duct passing through it.

 

[ItsHot]

use caution

use caution

Be careful when working around these fire dampers. The fuseable link can fail and depending on the size of the damper they can close with enough force to break your arm!!

 

[dcspector]

they can close with enough force to break your arm!!

I must agree with that.....the force that is.

 

[keesha]

If you look real close at those dampers.. You will see what a nice easy path it is for the Network guys to route their cables (and others).:roll:

 

[ItsHot]

blue wire guys

blue wire guys

If you look real close at those dampers.. You will see what a nice easy path it is for the Network guys to route their cables (and others).:roll:

You do see a lot of that. Why is it that those blue wire guys get away with anything?

 

[quogueelectric]

There are 2 basic types of smoke dampers

There are 2 basic types of smoke dampers

One type is electrically activated through a relay in the facp for which there is no fusible link. The other is a fusible link type which is not tied into the facp. Now that I think of it I have seen pneumatic types also which may or may not have status switches tied in to the facp. Almost all of the newer systems I have done are electrically driven motors.

 

[infinity]

One type is electrically activated through a relay in the facp for which there is no fusible link. The other is a fusible link type which is not tied into the facp. Now that I think of it I have seen pneumatic types also which may or may not have status switches tied in to the facp. Almost all of the newer systems I have done are electrically driven motors.

Me too, and that was the basis for my answer, motorized fire dampers. I wasn't even thinking about the dampers with the fusible link since they don't really compare with VAV's.

 

[eager2learn]

The type of dampers that we will be using will tie into the F.A.C.P.

 

[quogueelectric]

You should be very cautious with smoke dampers

You should be very cautious with smoke dampers

The most common system is a 110 volt system which is daisychained off of a relay usually mounted close to the facp. 110 volts holds the dampers open when the alarm sounds a relay breaks the feed and all of the dampers open The problem arises when the system is not designed properly because if some of the dampers close and they happen to not be interlocked to the air handlers which are pushing air through them as they close. For example lets say you had a 60 ton air handler in a big department store running full tilt and you tripped the smoke damper ckt and both the supply and return dampers slammed shut while the unit was running full tilt riddle me this batman what do you think is going to happen. How do you spell sheet metal repair?? The fan shutdown is imperative to the safe operation of these dampers

 

[randomkiller]

Fire dampers are always spring loaded and held open by a fusible link, completely mechanical in nature and they are always mounted within a wall or floor. Smoke dampers are electrically operated usually tied into the alarm system and have end switches on the operator motor that is tied into the smoke exhaust fan start circuit.

VAV boxes as previously stated reduce high static pressure air flow down to usable velocity for system zoning and often have reheat coils in them electric or hydronic.

 

[keesha]

You do see a lot of that. Why is it that those blue wire guys get away with anything?

No one checks up on them.

 

[keesha]

Many types

Many types

You do have fire dampers that seperate space for return air plenums (those I referd to).
You have fire dampers for duct returns, smoke evac and others.

Return air plenums most commonly will have the thermals (links).
The others are usualy powerd open and spring closed (open or closed what ever is called for) In any event, What ever position they are to be in during a fire/emergency situation, they will be set to that via springs. Thats' the fastest way to get them in that position. Typicaly.there are of course variables that come into play.

 

[eager2learn]

How exactly do the air handlers tie into the circiut in order to make them interlock. Do they tie in parallel with the relay that is controlled by the f.a.c.p. or will they be set alone on their own relay

 

[randomkiller]

You do have fire dampers that seperate space for return air plenums (those I referd to).
You have fire dampers for duct returns, smoke evac and others.

Return air plenums most commonly will have the thermals (links).
The others are usualy powerd open and spring closed (open or closed what ever is called for) In any event, What ever position they are to be in during a fire/emergency situation, they will be set to that via springs. Thats' the fastest way to get them in that position. Typicaly.there are of course variables that come into play.

A true fire damper (supply/return/exhaust duct) has to be able to work without power, in other words mechanically (springs and fusible links) end of story check the NFPA codes. Yes there are other types of electrical dampers.