Can louvered walls remove requirement for exhaust fan? 4

[dmaffei]

I have an equipment room with two R123 chillers with a Toxalert leak monitor. The room is square and approximately 1500 square feet. Two of the walls are louvered. Am I still required to have mechanical ventilation in the event of a leak or do the large amount of louvers on opposite wall suffice?
thanks

 

[MintJulep]

With louvers only, you have no control of the ventilation. It is relatively simple to imagine conditions where outdoor air will enter the room rather than exit it.

 

[KenRad]

According to my knowledge of ASHRAE Standard 15 (which may have been revised since I last looked at it), the only way that you could get away with natural ventilation is if your mechanical room was detached AND greater than 20 feet away from any occupied building. Otherwise, you need mechanical ventilation.

The formula for determining ventilation rate involves the refrigerant mass in the largest piece of equipment. Refer to ASHRAE for details.

---KenRad

 

[HVAC68]

With louvers only and no provision of forced ventilation, the air movement will depend on the pressure differntial between outside and inside. There won't be any control and hence, it would be prudent to have mechanical ventilation, regardless of what the code says, from a safety point of view.

HVAC68

 

[chicopee]

Just because you have a mechanical ventilation system, it does not mean that it has to be continously energized.
This forced ventilation system could be electrically connected to the leak detection system. CFM of this unit could be based on floor area or on a time limit to lower contaminant concentration to acceptable safe level.

 

[spector]

We are preparing to upgrade our chiller plant very soon. The scope of work requires we meet the latest ASHRAE ST 15.

IAW the latest standard, we will be installing leak detect triggered exhaust fans and increasing the size of our louvers....Also the emergency ventilation controls must be mounted outside the equipment room.

It doesn't matter that our plant is 100ft from main building or regularly manned.

No, the louvers you have installed will not satisfy the code without also adding the exhaust fans, and the fans must be triggered by the leak detect/alarm system with controls mounted outside the space. The fans/louvers must also be properly sized and located.

 

[ChasBean1]

Just to play devil's advocate, at some louver size, the indoor space would become a covered outdoor space, right?

 

[spector]

Sorry, but in my last reply I was short too on time to include any refs.

Here is an condensed version of what the latest ASHRAE Sandard 15 changes include: (in brackets [], with more of my comments following)

[Safety requirements of newest ANSI/ASHRAE Standard 15-2001.

BACKGROUND:

ASHRAE 15 addresses general requirements, refrigerant storage restrictions, design and construction procedures, conformance to National electrical code, periodic testing of safety equipment for a refrigerating machinery room. The focus of this design alert is on safety of personnel operating and maintaining the equipment. The revised main requirements are:

Self-contained breathing apparatus (SCBA) requirements are deleted.
Ventilation requirements are revised.
Refrigerant leak detector to activate alarms and mechanical ventilation system.
The alarms shall be visual and audible inside the machinery room and outside each entrance to the machinery room. The alarms shall be of manual reset type with the reset located inside the machinery room.
Machinery room shall be vented to the outdoors, utilizing mechanical ventilation. The air supply and exhaust ducts for the machinery room shall serve no other area.
No flame producing device or continuously hot surface over 800 degrees F is permitted as a permanent installation in the machinery room.
Clear headroom shall not be less than 7.25 ft. below equipment situated over passageway.
The machinery room shall have a door that opens directly to the outside or through a vestibule equipped with self-closing tight fitting doors.
Walls, floor, and ceiling separating the machinery room from other occupied areas of the building shall be of at least one-hour rating.
Exterior openings, if present, shall not be under any fire escape or any open stairway.
Detectors, alarms and mechanical ventilating systems shall be periodically tested in accordance with manufacturer?s specifications and the requirements of the local authorities.

12. Emergency shutdown procedures, including precautions to be observed in case of a breakdown or leak, shall be displayed on a conspicuous card located as near as possible to the refrigerant compressor.

Following recommendations on ?Emergencies in Refrigerating Room? that are not part of the standard. They are provided for information only. In brief they are:

1. If a refrigerant detection system activates an alarm and the personnel working in the machinery room are not provided with and trained to use respiratory protection equipment, they must leave the room immediately.

2. Provide a digital readout of the detector reading outside the machinery room.

3. Provide personnel with appropriate respiratory protection in accordance with all applicable local and national regulations.

4. After donning the respiratory protection (if necessary), personnel may reenter the machinery room to fix leaks.

5. Coordinate emergency procedures with the local emergency response agencies in advance.

The standard states, donning respiratory protection is a last-resort option under most industrial hygiene regimens; it is preferable to provide engineering controls to reduce refrigerant concentration to tolerable levels by ventilating the machinery room automatically when a detector is activated. In many cases, this may be entirely adequate to reduce the concentration, and respiratory protection may not be needed.

Above emergency procedures is an example only and there are many other possibilities. This example is given when a facility that wishes to use its own technicians to handle minor problems in the refrigerating machinery room.]

As you can see, there have been several changes to the standard. The above ref fails to describe the latest standard in detail. And believe me, the details are important if you are required to meet this standard.

I suggest you get your hands on ASRAE Standard 15-2001 and any additional updates before you spend any money or effort in your attempt.

 

[spector]

ChasBean1,

Your question doesn't make you a Devil's advocate unless you are implying the new ASHRAE requirements are excessive and not achievable. But even then, it is still related to the discussion.

The whole idea of louvers AND fans as far as the ASRAE Standard is concerned, is to provide for personnel safety in the event of a large release of refrigerant.

That's why emergency exhaust fans, triggered by the leak detection system, are also required. Louvers alone, no matter what their size, cannot evacuate your equipment room in the event of a large leak or release. Louver sizes need to be no larger than needed to allow the emergency exhaust fans to rapidly ventilate the space.

If however, your boiler(s) are located in the same equipment space, then you need to calculate boiler combustion air and emergency ventilation requirements separately.