USE OM - JANUARY 2017
68
Section 5. Requirements
5.1
Usage of Refrigerant Mass Flow Method
5.1.1.
All split systems, whether ducted or non-ducted, shall use the refrigerant mass flow method as the
secondary capacity check for all steady state tests per Section 6 of this appendix.
5.1.2
The absolute value of heat balance (HB) shall be 4.0% or less on all tests, except for H3 which may
be greater if:
Tests B and H1 are 3.0% or less, and
Subcooling leaving indoor unit is less than 3.0°F.
5.1.3
Excluded from Section 5.1.1 requirements are split system products with an expansion device located
upstream of the liquid line mass flow meter. Such as a system with a cooling expansion device in the Outdoor Unit.
5.1.4
This method shall be not be used on specific tests if ASHRAE Standard 37 Section 7.5 cannot be met.
The air enthalpy method shall be substituted in these cases.
5.2
Usage of Outdoor Air Enthalpy Method
5.2.1
All single package systems shall use outdoor air enthalpy method as the secondary capacity check for
all steady state tests per Section 7 of this appendix.
5.2.1.2
The absolute value of HB shall be 6.0% or less on all tests, except for H3 which may
be greater than 6.0% if all other tests are less than 6.0%.
5.3
For any products that meet the scope defined in Section 2, where the requirements of Section 6 or Section 7 cannot
be met, the Unitary Small Equipment Engineering Committee shall be contacted for resolution.
Section 6. Refrigerant Mass Flow Method Requirements
6.1
Pressure measurements shall be:
6.1.1
Measured at the indoor coil, per ASHRAE Standard 37 Section 8.3 and ASHRAE Standard 41.3.
6.1.1.1
Vapor pressures at the Outdoor Unit may be measured and used as an alternate to
vapor pressure at the Indoor Unit, if required, in order to achieve 5°F superheat, as long as appropriate
adjustments are made per Section 6.4.3.1.
6.1.2
Taken within 12 inches of the field connection of the Indoor Unit.
6.1.3
Taken on the top half of the tube, unless tubing is vertical in which case any side is acceptable.
Pressure taps shall not be installed such that oil may potentially fill the pressure tap line.
6.1.4
Made no closer than 10 tube diameters upstream or downstream of any bends that are greater than
30 degrees, or within 10 tube diameters of short radius bends. Tubing shall be inspected to verify there are no
kinks or restrictions.
