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Air conditioning for elevator machine room

Discussion in 'Elevators' started by BayPointArchitect, Jun 27, 2018.

  1. BayPointArchitect

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    Code sections in order of relevance:
    2012 IBC 3006.2
    ASME A17.1 Safety Code for Elevators, Section 2.7.9.2
    2012 IBC 707
    2012 IBC 3002.4

    Given that local interpretation by the AHJ takes precedence over these National codes, I have come to realize that - where the code requires a machine room to have independent ventilation or air-conditioning system - we are expected to provide a small air conditioning system that is dedicated to that machine room and nothing else.

    I love my State Elevator Inspector because he provided redline drawings during his plan review. During his plan review, he added a note calling for 6,222 Btu/Hr HVAC. Regardless of whether-or-not any HVAC contractor was made to look at those redlines during construction, I have two separate projects with two separate engineers who would otherwise interpret the code and provide a 360 cfm fan connected to a thermostat inside the machine room.

    Now I know that you are about to remind me that the machine room needs to be fire rated and no openings are allowed into the machine room except for the fire-rated access door. You might even make reference to IBC Section 707 fire barriers, and Section 714 air transfer ducts requiring fire dampers, etcetera. We got that covered. Our small duct penetrations are fully equipped with fire dampers that are ready to slam shut at the slightest whiff of smoke or temperature rise. Looking at 2012 IBC Sections 3003.1.4 and 3004.3.1 (note #4) there is language that would suggest that a thermostat-controlled exhaust fan for the machine room is equally valid compared to the more expensive ($6,916) package split mini heat pump that can have small lines penetrating into the machine room and a (very awkward / inconvenient) condensing unit added to the exterior of the building.

    These elevators are located in three story buildings. According to IBC Section 3002.4 these elevators (serving only three stories) are not required to provide fire department emergency access to all floors. Obviously this building is not a high rise and therefore it does not need to serve as an occupant evacuation elevator.

    Meanwhile my code commentary and the State Elevator will reason that the temperature-controlled air inside the building may not be circulated through the machine room because that air will become so hot during the burning inferno that the machine room equipment will become disabled. At that very moment, emergency personnel - who are using the elevator inside a three level building - will become trapped inside.

    After considering all of this, would you concur that the code language should make it abundantly clear that a small air conditioning unit needs to be both independent and separately provided for elevator machine rooms?

    Thank you,

    ICC Certified Plan Reviewer
    NFPA Certified Fire Plan Examiner
     
  2. mtlogcabin

    mtlogcabin Sawhorse

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    It has nothing to do with emergency operation of the equipment. It has more to do with the day to day operation of the equipment. In my climate in you would be adding heat to the room at least 6 months out of the year. With out a mini split you could not cool that room if needed. Same for a large server room, the equipment operates better in a controlled environment.

    Machine room design
    When designing an elevator machine room HVAC system, a cooling load calculation is required to determine the BTU/hr that the AC system requires. The elevator machine HVAC system, due to its exposure to the equipment and a need to have it operate off of emergency generators, leads the designer to an independent system separate from the building HVAC system. A typical 3,000-lb. capacity elevator usually requires a 1.5-ton to 2-ton AC system depending on the machine room's location in the building and the climate for the local. ASME A17.1, “The Safety Code for Elevators and Escalators,” requires machine room temperature to be as determined by the elevator manufacturer. Most building elevator mechanics and manufacturers maintain elevator machine rooms between 60°F and 80°F with 35% to 60% relative humidity. The heating system for the machine room also is a built-in unit.





    AC systems for machine rooms
    The most common and practical AC systems for machine rooms are the ductless split type with automatic heating/cooling heating switchover (see Figure 1). This system's lifetime is approximately 10 years and costs $8,000 to $13,000 (installed). Capacities of the ductless split AC range from 6,000 BTU/hr. to 48,000 BTU/hr.



    In a survey of machine room AC systems, one manufacturer had a 60,000-BTU/hr. cooling capacity for one- or two-unit rooms. For semi-standby AC systems, it is acceptable to provide two identical split type AC systems, each handling 50% of the load. For hospitals, the standby system is designed for 100% capacity and must be interchangeable in operation bimonthly to maintain reliability through use. In colder climates, machine room systems should be specified with low outdoor ambient temperature down to 0°F because the machine room may still require cooling during outdoor winter days.

    Condensation from AC systems in machine rooms is handled by an insulated condensation waste drips into an indoor open, vented sanitary waste system. No floor drains are allowed in machine rooms and curbing from the remainder of the floor is not uncommon. In warmer climates, a dry well into the ground may be used for condensate waste discharge. A dual-condensate waste pump is recommended because machine rooms are unoccupied 90% of the time.

    While some buildings are provided with chilled and hot water systems for HVAC applications, serving the elevator machine room with one of or both of these systems is not recommended because any water leakage could be disastrous to the elevator system. Additionally, the building could be in the heating mode while the elevator machine room may require cooling.

    /www.csemag.com/single-article/hvac-and-fire-safety-for-elevator-systems/dee607f7fcc3cc1d8ccdd98877ac44e8.html
     
    BayPointArchitect likes this.
  3. BayPointArchitect

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    Thank you for the link to the CSE article. It was amusing to read from the engineer's perspective that the problem stems from architects who do not allow engineers to design the elevators. With two different engineers designing two different elevators, both of them provided these machine rooms with the mechanical means to keep the ambient air temperature between 50 and 90 degrees. That is the temperature specified by the elevator equipment manufacturer to ensure safe and normal operation. Regardless of winter or summer season, the air in the hallway is 72 degrees. And the current "mechanical means" will circulate that air through the machine room with a simple 360 cfm fan (fire dampers included). But my inspector will say that the engineers are wrong. I think these engineers read the code the same way I do. But the elevator inspector and the CSE article uses words such as "recommended" and "better" and "common". Those are not words that I commonly use to recommend what is REQUIRED to meet MINIMUM code. If I were to ask, "how can we increase the amount of money we can spend on a $200,000 elevator?", then my answer would include, "how about adding a $7,000 air conditioner?". Although a three-level building does not require an emergency generator, we might as well throw that in there too.

    As a full-time code enforcement agent, I create check lists for building permit applicants. There needs to be a cheat sheet for design teams that want to get it right the first time rather than wait for the inspector to show up after the elevator is already built. And that cheat sheet should include a note, "... and provide a dedicated HVAC unit for the machine room".

    Thanks again MtLogCabin for your help.
     
  4. BayPointArchitect

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    The cheat sheet should also include, "...no openings in the machine rooms walls other than door access into the machine room. Single door shall be side-hinged and fire-rated. No ductwork openings in the walls. Do not even think about fire dampers in ductwork. Fire dampers are only allowed within ducts where located in fire barriers that surround something other than an elevator machine room."
     
  5. Sleepy

    Sleepy Active Member

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    Yeah, it is just madness.

    Interestingly, 2012 IBC 3006.2 says "Elevator machine rooms that contain solid-state equipment for elevator operation shall be provided with an independent ventilation or air-conditioning system....." but that was changed in the 2015 IBC 3005.2 to say "Elevator machine rooms, machinery spaces that contain the driving machine, and control rooms or spaces that contain the operation or motion controller for elevator operation shall be provide with an independent ventilation or air-conditioning system..."

    So, it seems that the requirement for independent systems is expanded. Does this mean that a machine-room-less elevator with the "driving machine" in the actual elevator shaft would need the shaft to be independently ventilated or air-conditioned?
     
    cda likes this.

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