Packaged HVAC Equipment

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Packaged HVAC Equipment
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Packaged HVAC Equipment

• Is the most common source for HVAC in small to
  medium commercial buildings
• Used in
• Retail Stores
• Supermarkets
• Restaurants

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Packaged HVAC Equipment

• Rooftop units, better known as RTUs, are popular
  because they are the "least cost solution" to
  heating, ventilating, and air conditioning a
  building.

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Rooftop Units

• Some of the reasons for this are
• RTUs are unitary or packaged equipment and
  require no field refrigerant piping.
• RTUs provide heating, cooling, air moving,
  outside air introduction, and a filtration
  system.
• RTUs do not take up valuable floor space.
• RTU service time is reduced because all of the
  components are together.
• Routine service does not interfere with store
  operation.
• RTU replacement is quicker and doesn't interfere
  with store operation.

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Rooftop Units

• Types of Rooftop Units
• Multi-zone
• VAV (Variable Air Volume)
• Constant Volume

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Multi-zone

• These systems are still available but are losing
  favor because of their inherent energy
  inefficiency.
• A multi-zone unit typically consists of a hot
  and a cold deck.
• There are also three deck units, the third being
  the bypass deck.
• This is more efficient because you add hot or
  cold air to the return air.
• Some additional disadvantages are
• You are limited to the number of zones
  available and the need to distribute the air
  proportioned to each zone evenly.
• Building energy codes place restrictions on the
  use of reheat temperature control.

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VAV (Variable Air Volume)

• These systems are becoming more popular for their
  ability to provide unlimited zoning control and
  ease of future reconfiguration of space and
  zones.
• VAV systems are available in the 15-ton and up
  range in cooling only or cooling with heat
  versions.
• The heating section allows for morning space
  warm-up and building temperature setback.

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Constant Volume

• Most retail outlet stores have RTUs with a
  single-zone heating and cooling configuration.
• These units have constant air volume to a single
  zone with a single thermostat controlling them.
• They are the least expensive to purchase and are
  the simplest to install and maintain.

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Roof Top Units

• A typical RTU is a manufactured piece of
  equipment that is factory-assembled, delivered to
  the site in one piece and ready to operate with a
  single-point control interface.
• In most cases, they connect to utilities such as
  natural gas and electric power.
• In some configurations, they can be connected to
  a systems hot water or steam system for heating,
  and chilled water system for cooling.
• In most cases, each unit is factory-tested to
  insure quality control.
• Having said this, it is still very important that
  a responsible contractor perform the start-up or
  commissioning service.

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Roof Top Units

• The following points are essential parts of
  commissioning
• Check operation of heating and cooling.
• Adjust the air/fuel mixture for your altitude.
• Adjust belts.
• Tighten bolts, particularly in the blower
  section.
• Remove shipping braces.
• Check for refrigerant leaks.

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Construction andInstallation

• Rooftop units are constructed of galvanized steel
  with a primer and a final UV-resistant paint
  coat.
• The exterior panels are insulated with glass
  fiber with a thickness of 1- to 2- inches.
• Units being manufactured with a solid metal liner
  are becoming more common due to IAQ (Indoor Air
  Quality) concerns.

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Construction and Installation

• Condensate drain pans are constructed using steel
  with a mastic coating, galvanized steel, PVC, or
  stainless steel.
• Deeper pans with two-way sloping to drain are
  desirable to remove condensate from the unit
  completely and prevent ponding of water, where
  algae and microbial will proliferate and reduce
  air quality.

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Construction and Installation

• An RTU mounts on a curb, which is a perimeter
  frame that supports the unit off of the roof
  deck.
• The top of the curb has a mating flange that
  adapts to the RTU. When you are replacing an RTU
  with another one having a different footprint, it
  is common to use an "Adapt-a-Curb".
• This device adapts the new RTU to the existing
  curb. Properly manufactured and installed with
  gaskets, the Adapt-a-Curb is an acceptable way to
  install a replacement RTU while not disturbing
  the existing roofing.
• Ductwork connections and gravity are usually not
  enough to keep an RTU in place during high winds.
  Straps, sheet metal screws or welding are common
  ways of fastening the RTU to the curb.

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Construction and Installation

• RTUs should be placed near the area where they
  will heat or cool.
• This saves ductwork installation and thermal duct
  losses. Location relative to exhaust air fans or
  vents, plumbing vents, and process exhaust, such
  as kitchen hoods, should be taken into account.
• Additionally, ambient, prevailing wind conditions
  affect movement of air on the roof into the
  outside air intake louvers.
• Wind conditions also affect the operation of the
  condenser fans. When not energized, the fans can
  begin freewheeling or wind milling due to wind.

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Construction and Installation

• Single-speed motors, when started, want to
  continue in the direction the fan was
  freewheeling.
• This could block air movement through the
  condensing unit. A three-phase unit will only run
  in one direction without changing electrical
  connections.
• If freewheeling in the wrong direction when
  energized, the fan will draw additional amperage
  and possibly damage the motor, fan blades, and or
  the fan supports.

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Construction and Installation

• The architect, roofing consultants, and engineer
  should consider access to rooftop equipment in
  building design.
• Wear or walk pads to the units can minimize
  future damage to the roof by individuals and
  service equipment.
• With all of the choices available in RTUs today,
  there is sure to be something that will fit your
  needs.
• Discuss the options with your HVAC provider and,
  after considering all of the options, pick the
  one that will satisfy your needs.

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Packaged HVAC Equipment

• In 2000 the U.S. Department of Energy estimates
  that rooftops and unitary air-conditioning
  equipment accounts for 62 of total energy
  consumption for cooling commercial buildings.

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Service and Maintenance of Packaged HVAC Equipment

• Packaged equipment is
• Smaller in size
• More numerous in number
• Usually not as well maintained

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Why are they not as well maintained?

• Out of sight out of mind!
• Often ignored and forgotten until they have
  degraded to a point of failure.
• Effects of failure are limited to small number
  served.
• Large buildings have so many that preventive
  maintenance would require a lot of a service
  technicians time.
• In many cases the unit is all contained within
  the unit. i.e. no chiller, no pumps, no
  additional piping, and no separate refrigerant
  piping.

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Packaged HVAC Units No Air Calls

• Control Errors 21
• Electrical Problems 20
• Refrigerant Leaks 12
• Condenser 7
• Air Handling 7
• Evaporator 6
• Compressor 5
• Cooling Water Loop 4
• Plugged Filters 2
• Personnel Error 2
• Expansion Device 2
• Cant Classify 1

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Packaged HVAC Units Service Call Cost Breakdown

• Compressor 24
• Control Errors 10
• Condenser 9
• Electrical Problems 7
• Evaporator 6
• New Installation 6
• Air Handling 5
• Refrigerant Leaks 5
• Installation/Start-up 4
• Cooling Water Loop 4
• Fan Belt 2
• Others 18