Some may think that the Air Conditioning Contractors of America’s (ACCA’s) Quality Installation (QI) Standard deals mainly with cooling systems, but that would be an incorrect assumption. The specification also deals with necessary steps for the safe and efficient installation and operation of fuel-fired heating equipment, as spelled out here.
The standard pulls both the heating and cooling sides together with necessary information on controls, airflow, and last but not least, owner education.
ELECTRICAL REQUIREMENTSElectrical operation is critical for jobsite, operational, and building owner safety. It must be connected according to codes and the manufacturer’s requirements.
The contractor has to document the following:
• For single- and three-phase equipment line and low voltages - the percentage (or amount) higher or lower than nameplate values are within original equipment manufacturers’ (OEM) specifications and/or code requirements.
• For single- and three-phase equipment amperages - the percentage (or amount) higher or lower than nameplate values must be within OEM specifications and/or code requirements.
• Line and low-voltage wiring sizes must be in accordance with the National Electric Code (NEC) or equivalent.
• Grounding/bonding must be in accordance with NEC or equivalent.
The contractor must verify measurements against the nameplate and over current protection criteria.
FUEL-FIRED EQUIPMENTThe contractor has to ensure that the on-rate (Btuh input during steady-state operation) for gas- or oil-fired equipment is at the equipment nameplate value.
For gas-fired equipment, the contractor has to prove that the firing rate is within ±5 percent of nameplate input for gas equipment (or per OEM specifications). The contractor also has to prove that the temperature rise is in accordance with the nameplate.
Acceptable procedures include the use of clocking the meter or another fuel input measurement, and measuring the temperature rise at steady-state conditions (furnaces only). Note: Combustion analysis may be necessary in some cases.
For oil-fired equipment, the contractor has to ensure that the nozzle flow rate, spray angle, oil pump pressure, and temperature rise are correct per nameplate input and OEMs’ specified values.
The contractor needs to verify nozzle or alternate input nozzle per OEM installation or oil burner instructions; adjust oil pump pressure with a dial or electronic gauge designed for oil pressure measurement; and measure the temperature rise at steady-state conditions per OEM installation or oil burner instructions. Combustion analysis is necessary when setting up an oil burner. Additionally, new oil-fired equipment no longer standardizes the pump pressure at 100 psig. Hence, incorrect pump pressure may result in an incorrect input rate for the equipment.
COMBUSTION VENTINGIt’s up to the contractor to ensure proper sizing, design, material selection, and assembly of the combustion gas venting system.
The contractor has to prove compliance with one of the following:
• Category I vent system sized per OEM instructions and the National Fuel Gas Code (NFGC), NFPA 54;
• Category I vent system sized per OEM instructions and the International Fuel Gas Code (IFGC);
• Category II, III, and IV vent system sized per OEM instructions; or
• Category II, III, and IV vent system sized per required local code.
The contractor has to use one or both of the following acceptable procedures for fulfilling the design criteria:
• Comparison of the actual installation to appropriate fuel gas venting tables for Category I vent systems; and/or
• Comparison of the actual installation to appropriate OEM instructions, for Category II, III, and IV vent systems.
SYSTEM CONTROLSProper selection and functioning of system operational and safety controls can affect a system’s performance (e.g., incorrectly selecting a single-stage heating and single-stage cooling thermostat for a heat pump). Examples of operating controls include thermostats, humidistats, and economizer controls. Safety controls include temperature limit switch, airflow switch, condensate overflow switch, furnace limit switch, and boiler limit switch.
To be in compliance with the QI Spec, the contractor must ascertain the following:
• Operating controls and safety controls are compatible with the system type and application, and the selected controls are consistent with OEM recommendations and industry practices.
• Operating controls and safety controls lead to proper sequencing of equipment functions, with all controls and safeties functioning per OEM or customer design specifications.
DUCT DISTRIBUTIONDuct-related elements of the installed HVAC system have been overlooked for a long time. That is starting to change.
In the QI Standard the contractor has to ensure that the ducts are sealed and that air leakage (cubic feet per minute, cfm) is minimized. For new construction, test using any one of the four options:
1.Ducts located inside the thermal envelope can have no more than 10 percent total duct leakage (airflow cfm), or in accordance with option 4.
2.Ducts located outside the thermal envelope have no more than 6 percent total duct leakage (airflow cfm), or in accordance with option 4.
3.The EnergyStar™ Qualified Homes specification requires that ducts must be sealed and tested to be less than 4 cfm leakage to outdoors per 100 square feet of conditioned floor area, or in accordance with option 4.
4.Per local code or authority having jurisdiction if they meet or exceed the requirements of option 1, 2, or 3.
For existing construction, test using any one of these three options:
1.No more than 20 percent total duct leakage (airflow cfm), or in accordance with option 3.
2.Fifty percent improvement on existing leakage rate, or until no more than 20 percent total duct leakage is achieved, or in accordance with option 3.
3.Per local code or authority having jurisdiction if they meet or exceed the requirements of option 1 or 2.
The contractor shall test using one or more of the following procedures:
• Duct pressurization tests for commercial buildings can entail the total room supply cfm and return cfm compared with blower capability (e.g., flow hood method); blower door subtraction method; or a hybrid duct pressurization test/blower door subtraction.
• Duct leakage is measured using a duct pressurization test through a calibrated fan or orifice. Duct registers are sealed, a fan is attached to one opening, the ducts are pressurized to match the system operating pressures, and the amount of air flowing through the fan is quantified. A calibrated fan measures whole-building leakage, then the duct grilles are sealed and the house is remeasured. The difference is the amount of leakage attributable to the duct system.
AIRFLOW BALANCEThe contractor must make sure room volumetric airflow cfm meet the design/application requirements. The contractor has to ensure that:
• For new construction or the addition of new ducts to an existing structure (with doors closed): In residential buildings, individual room airflows need to be within the greater of ±20 percent, or 25 cfm of the design/application requirements for the supply and return ducts. For commercial buildings, individual room airflows are within the greater of ±10 percent, or 25 cfm of the design/application requirements for the supply and return ducts.
• For existing construction without contractor modification of existing ductwork - no additional requirements apply.
• For new or existing construction, the airflow balance is per local code, or the authority having jurisdiction if such meet or exceed the requirements of previously mentioned sections.
• The contractor has to test using flow hoods (used per specifications from the flow hood manufacturer); a traverse with anemometer (hotwire or rotary) used per specifications from the test equipment manufacturer; and/or a pitot tube and slant manometer used per procedures specified by the Associated Air Balance Council, American Society of Heating, Refrigerating and Air-Conditioning Engineers, National Environmental Balancing Bureau, or Testing, Adjusting and Balancing Bureau.
Note:The use of certain measurement instruments/devices that determine airflow based on velocity measurements may be acceptable if grille “free areas” can be correctly determined, and the instrument/device measurement tolerances are tighter than the airflow balance tolerances.
A hybrid of the duct pressurization test and the blower door subtraction methods can be used, in which a pressure match is performed in the house and the ducts and the values then compared against separate measurements of the airflow into the ducts.
OWNER EDUCATIONPart of the beauty of the QI Spec is the ability it provides for contractors to really educate their clients, reinforcing the value in using contractors who perform QI. QI contractors provide the homeowner with job documentation, operation instructions, and the education needed to properly operate and maintain their new HVAC systems.
The QI contractor is required to place copies of pertinent architectural drawings, as-built drawings, survey data, equipment submittals, equipment performance information, balance reports, equipment operation sequences, maintenance and operating instructions, and equipment/contractor warranties within easy reach of the homeowner - say, at the air-handling cabinet, or in the hands of the building owner/operator (or designated agent).
Model and serial numbers of all equipment installed needs to be kept at the contractor’s place of business.
The contractor is required to educate the owner/operator on how to both operate and maintain the installed equipment, and will promote system maintenance to help optimize the continuing performance of the installed equipment.
It’s required that the QI contractor provide contact information for warranty, maintenance, and service requirements.
For more information, the QI Spec can be downloaded from www.acca.org/quality.