Article 645

[jcrew]

Trying to understad the intent behind Article 645.4(D)(3). Ventilation in the underfloor for IT rooms shall cease upon activiation of smoke detector upon detection of ire or products of combustion. It seems if there is smoke below the raised floor then the HVAC system will shut down but there is no mention of shutting down the power. Especially if the fire is caused by smolderling power cables or fault.

The IT rooms are designed with significant cost to protect equipment (its intended purpose thus complying wiht NFPA 75). It seems that this section of code allows for a false alarming to trip cooling to the space without warning and not solving the problem of smoke below the raised floor. Shutting the HVAC will only prevent from exapanding but the casue can possibly be still there.

Appreciate any thoughts and inputs.

 

[charlie]

Re: Article 645

This subject is way out of my expertise but it seemed to me to be a question instead of a proposal to the 2008 Code so I relocated it from the proposal section. If I am wrong, let me know and I will move it back.

This question concerns 645.4 in the 2005 Code which is 645.2 in the 2002 Code. This section was relocated to 645.4 with no changes from the 2002 Code so if wish to address it, you may use the 2002 Code for reference.

 

[ron]

Re: Article 645

This requirement which was inserted into the NEC in 2002 for the first time, is a nightmare for reliability. I have not reviewed the original proposal or comments, but it is tough to swallow, but my designs have been compliant.
Always keep in mind that this is only required, if you choose the utilize the leniencies in 645. If you can live with the requirements of the first 4 chapters of the code, then you don't need to do anything required in 645.2 (2002).

 

[steve66]

Re: Article 645

But there is nothing to prevent you from providing a warning or shutting off power. I have seen one system designed where a warning is sent to security, and they have a couple of minuites to get to the room and reset the alarm before power goes off. This prevents false alarms from shutting down the power, yet protects equipment by shutting off the power after a delay.

My feeling is that this is of a design issue than a safety issue, and should not be in the NEC.

 

[sandsnow]

Re: Article 645

I'm not up to speed on the 2002 req's, but in the codes were on the Fire Dept. has the alarm system shut down the power and hvac upon alarm activation. Our IT rooms get pretty involved with halon and double interlocked sprinklers.
What I do know is the intent of having the power shut down in case of fire is because if it is an electrical fire ( and ALL fires are electrical in origin ), you want to remove the source or cause of combustion.

 

[ron]

Re: Article 645

The requirement in question is for the fire alarm to shut down airflow below the raised floor. The fire alarm is not required to shut down power.

 

[paul]

Re: Article 645

I have always seen the HVAC shut down on 2nd alarm only. The only time I've seen a power shut down was via the EPO (Emergency Power Off) button located by the exits in older setups. Other than that, let the halon fly and keep the computers running.

NO OUTAGES!