Module: ASHRAE901PRMFan

Included in:
ASHRAE901PRM
Defined in:
lib/openstudio-standards/standards/ashrae_90_1_prm/ashrae_90_1_prm.Fan.rb

Overview

A variety of fan calculation methods that are the same regardless of fan type. These methods are available to FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust

Instance Method Summary collapse

Instance Method Details

#fan_standard_minimum_motor_efficiency_and_size(fan, motor_bhp) ⇒ Array<Double>

Determines the minimum fan motor efficiency and nominal size for a given motor bhp. This should be the total brake horsepower with any desired safety factor already included. This method picks the next nominal motor catgory larger than the required brake horsepower, and the efficiency is based on that size. For example, if the bhp = 6.3, the nominal size will be 7.5HP and the efficiency for 90.1-2010 will be 91.7% from Table 10.8B. This method assumes 4-pole, 1800rpm totally-enclosed fan-cooled motors.

Parameters:

  • fan (OpenStudio::Model::StraightComponent) —

    fan object, allowable types: FanConstantVolume, FanOnOff, FanVariableVolume, and FanZoneExhaust

  • motor_bhp (Double) —

    motor brake horsepower (hp)

Returns:

  • (Array<Double>) —

    minimum motor efficiency (0.0 to 1.0), nominal horsepower



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# File 'lib/openstudio-standards/standards/ashrae_90_1_prm/ashrae_90_1_prm.Fan.rb', line 16

def fan_standard_minimum_motor_efficiency_and_size(fan, motor_bhp)
  fan_motor_eff = 0.85
  nominal_hp = motor_bhp

  # Don't attempt to look up motor efficiency
  # for zero-hp fans, which may occur when there is no
  # airflow required for a particular system, typically
  # heated-only spaces with high internal gains
  # and no OA requirements such as elevator shafts.
  return [fan_motor_eff, 0] if motor_bhp < 0.0001

  # Lookup the minimum motor efficiency
  motors = standards_data['motors']

  # Assuming all fan motors are 4-pole ODP
  search_criteria = {
    'template' => template,
    'number_of_poles' => 4.0,
    'type' => 'Enclosed'
  }

  # Exception for small fans, including
  # zone exhaust, fan coil, and fan powered terminals.
  # In this case, use the 0.5 HP for the lookup.
  if fan_small_fan?(fan)
    nominal_hp = 0.5
  else
    motor_properties = model_find_object(motors, search_criteria, capacity = nil, date = nil, area = nil, num_floors = nil, fan_motor_bhp = motor_bhp)
    if motor_properties.nil?
      OpenStudio.logFree(OpenStudio::Error, 'openstudio.standards.Fan', "For #{fan.name}, could not find motor properties using search criteria: #{search_criteria}, motor_bhp = #{motor_bhp} hp.")
      return [fan_motor_eff, nominal_hp]
    end

    # If the biggest fan motor size is hit, use the highest category efficiency
    if nominal_hp > 9998.0
      OpenStudio.logFree(OpenStudio::Warn, 'openstudio.standards.Fan', "For #{fan.name}, there is no greater nominal HP.  Use the efficiency of the largest motor category.")
      nominal_hp = motor_bhp
    end

    # Round to nearest whole HP for niceness
    if nominal_hp >= 2
      nominal_hp = nominal_hp.round
    end
  end

  # Get the efficiency based on the nominal horsepower
  motor_properties = model_find_object(motors, search_criteria, fan_motor_bhp = motor_bhp)

  if motor_properties.nil?
    OpenStudio.logFree(OpenStudio::Error, 'openstudio.standards.Fan', "For #{fan.name}, could not find nominal motor properties using search criteria: #{search_criteria}, motor_hp = #{nominal_hp} hp.")
    return [fan_motor_eff, nominal_hp]
  end
  fan_motor_eff = motor_properties['nominal_full_load_efficiency']
  nominal_hp = motor_properties['maximum_capacity'].round(1)

  return [fan_motor_eff, nominal_hp]
end