Fail-Safe ventilation 2

[carlosgw]

The code requires standby power for ventilation for hazardous material storage space. Exception if there is a "fail-safe engineered system". Any idea what that could consist of?

 

[mauricestoker]

Outside storage.

 

[carlosgw]

Hmm. Maybe some sort of exterior wall panel and/or gravity vent system that opens on loss of power.

 

[Ziggypump]

I think some mechanical dampers would be wise. Have them spring operated to open with loss of power. Probably one high and one low, so heavy gasses would drift out through the low opening, and light gases could escape through the high opening, and not allow the gasses to accumulate in large concentrations.

 

[DRWeig]

Ziggy, that's well thought out.

I would add a flow switch or differential-pressure switch (or three or four for redundancy) to the powered exhaust as well, so not just power outage opens the dampers. Failed exhauster (I assume you would not want positive pressure in this room) could spring 'em open as well.

To satisfy AHJ, though, it might need to be submitted as a system to somebody like FM.

Carlos, be sure and let us know how this all plays out!!

Good on ya,

Goober Dave

 

[imok2]

A ventilation system for hazardous material storage is normally controled by house power and a fail safe system consists of an engineered standby power system as a backup to loss of house power

 

[cjw81]

A suggestion-NYC code - fail safe system in the case of dampers applies to duct smoke - fire smoke dampers that on loss of pneumatic air or the fire panel sending shutdown signal the dampers will always fail to the closed position. For class "E" buildings (Hi-rise) and healthcare the dampers are mandatory. There is also code regarding fire/smoke purge panels to direct the smoke out of the building . When FDNY arrives, the ranking officer is in control of the situation.

 

[hollandhvac]

Also I would install duty standby fan to have at least a minimum amount of air flow.

 

[Ziggypump]

Just a quick question. holland and imok have stated to run a fan or go off of a standby power system. The question at the beginning is what to engineer after the power went out.

imok, you stated to tie the system into the standby power system, carl is looking for a possible solution to avoid this if he can.

holland, if he's going to install the fan on the standby power system, he won't need a fan to meet minimum standards, as the primary fan will already be sized for it.

carl, you should take these ideas and study the code as much as possible, and TALK to the local (or state) code inspector. Most of the guys (only ever were guys on my end) are more than willing to talk to you about a solution. They may not always agree, but at least you can get an answer for your question before spending too much time designing a system that will not pass code (according to the inspector) anyway.

 

[hollandhvac]

Ok, may be I went a bit too quick, I did not look at the power side of it, but I was talking about the the number of fans required. For example, if you need two fans to get sufficient air flow to ventilate the building and one fan breaks down you hav not got sufficient airflow. For this reason I wa sugesting to put a standby fan in in case of failure of a duty fan to get the requied airflow.
I hope this has clarified it.

 

[carlosgw]

I need 1 cfm/sf 24/7 and I need the fans on standby power.
To use natural ventilation I need a temperature difference (I would not count on gases being heavier or lighter than air). If the temperature is the same outside as inside no reasonable amount of dampers in any position will give me any air flow. I was looking for a way to avoid the generator. If we still had the old NY State code I could connect the power ahead of the main disconnect perhaps. I was thinking along those lines. We will just use a generator. (the case I am working on is a large industrial area so the air flow is high and the generator will be significant)

 

[DRWeig]

Agree with you Carlos, it's tough to envision a natural-ventilation alternative.

Actually, I can envision one but it's a lot like a house in a childrens' cartoon -- shaped like an A-frame, and on power failure the walls all spring away from the apex and fall flat on the ground. Suddenly it's an outdoor location for which ventilation is not required...

Good on ya,

Goober Dave

 

[daly1]

The fail safe design is to have the exhaust fan on emergency power (not a full stand by back up). Spring return open all dampers (or they fail in full open position). Fan defaults to max CFM/SP position