Module 8 - CAZ.pptx

STRAND Energy-Star Training CAZ © 2023 STRAND Dallas I Texas 972 620 8204 Configurations of Combustion Appliance Zones Appliances should be installed in a zone or room that can be sealed from the indoor space and communicated to the outdoors through openings in the wall or ducts that connect t...

STRAND Energy-Star Training CAZ © 2023 STRAND Dallas I Texas 972 620 8204 Configurations of Combustion Appliance Zones Appliances should be installed in a zone or room that can be sealed from the indoor space and communicated to the outdoors through openings in the wall or ducts that connect to the outdoors. This room could include: A mechanical closet that opens or vents to the outdoors. A separate room open to the outdoors. © 2023 STRAND Dallas I Texas 972 620 8204 Option 1. Combustion air vertical ducts through floor and ceiling Combustion air can be drawn through vertical ducts in the floor and ceiling (see Figure 1) with one duct through the floor to the vented crawlspace and one duct through the ceiling to the vented attic. The duct into the attic terminates above the attic insulation. The interior openings should be within 12 inches of the ceiling and within 12 inches of the floor. The minimum net free area of each opening should be one square inch per 4,000 Btu/h of the total input of all the appliances in the zone. Be sure to account for louvers, screens, or grilles. © 2023 STRAND Dallas I Texas 972 620 8204 Option 2. Combustion air vertical ducts through attic to vented ceiling – Figure 2 shows two vertical ducts through the ceiling to the vented attic. One hole is located in the ceiling with the duct terminating above the insulation. The second duct extends from a point within 12 inches of the floor and extending up through the ceiling and terminating above the insulation in the attic. The minimum net free area of each opening should be one square inch per 4,000 Btu/h of the total input of all the appliances in the zone. The same duct opening calculation is used for Figure 2 as for Figure 1. Be sure to account for louvers, screens, or grilles. © 2023 STRAND Dallas I Texas 972 620 8204 Option 3. Combustion air horizontal ducts through exterior wall – With this option shown in Figure 3, both openings are through an exterior wall, with one opening near the top of the wall and one near the bottom of the wall and total input BTU/h is divided by 2,000 BTU/h. Be sure to account for louvers, screens or grilles. © 2023 STRAND Dallas I Texas 972 620 8204 Option 4. Single duct through exterior wall – When a single combustion inlet is used in an exterior wall as shown in Figure 4, the opening should be within 12 inches of the top of the zone. The minimum net free area of the opening should be one square inch per 3,000 Btu/h of the total input of all the appliances and not less than the sum of all the vent connectors in the space. © 2023 STRAND Dallas I Texas 972 620 8204 For any of these options, the openings must be a minimum of 3 inches in width or height. If the opening is covered with a grille or louver, you must compensate for the area covered by the grille. Use the manufacturer’s labeled free area when provided or, if unlabeled, assume that wood grilles or louvers have 25% free area and that metal grilles or louvers have 75% free area and increase the size of the opening to meet the minimum calculated free area required (NFPA 54, Section 9.3.7). © 2023 STRAND Dallas I Texas 972 620 8204 Option 5. Combustion air horizontal ducts through interior wall (not recommended) – Although this option is not recommended, this situation may be encountered in some older homes or retrofit projects. If this method is used, it is strongly recommended that the contractor refer to a document titled “Measure Guideline: Combustion Safety for Natural Draft Appliances Using Indoor Air (https://basc.pnnl. gov/library/measure-guidelinecombustion-safety-natural-draft-appli ances-using-indoor-air).” Combustion dilution air can also be taken from the main building volume or CAZ, if adequate room volume exists, not counting rooms with closable doors © 2023 STRAND Dallas I Texas 972 620 8204 How to Test the Combustion Appliance Zone If outdoor air is used to provide combustion air to the appliances. There are two test conditions for the combustion appliance assessment: equipment-off and equipment-on. With the equipment off, verify that the CO level in the zone is below the alarm limit and that there is no natural gas leakage. Also verify that the vent system installation is compliant with the –NFGC, Chapter 12 for installation and Chapter 13 for sizing. As mentioned above, verify that the combustion air openings are free of blockage and meet the code requirement for net free area. Finally, inspect the appliance for visual signs of deterioration and clean or repair as needed. © 2023 STRAND Dallas I Texas 972 620 8204 If connecting the CAZ to building space through an interior wall, two openings or ducts should be located in the wall, one duct within 12 inches of the ceiling and the second duct within 12 inches of the floor. The area of each duct opening in square inches is calculated as the total input BTUH divided by 1,000 BTUH for each duct. If the opening is covered with a grille or louver, you must compensate for the area covered by the grille. Assume that wood grilles or louvers have 25% free area and that metal grilles or louvers have 75% free area and increase the size of the opening to meet the minimum calculated free area required (NFPA 54, Section 9.3.7) © 2023 STRAND Dallas I Texas 972 620 8204 Equipment Needed or Testing • Digital manometer for measuring worst-case depressurization and combustion appliance draft (also, hoses and metal probes) • Combustion analyzer for measuring CO (and temperature in vent connector) • Personal CO instrument for measuring ambient CO • Digital camera • Tracer-smoke device • Flashlight © 2023 STRAND Dallas I Texas 972 620 8204 Vented Combustion Appliance Draft Types • Natural draft o No fan assisting the draft o Draft force created by temperature differences o Negative pressure in vent connector • Induced draft o Fan just inside or outside wall at point of termination o Negative pressure in vent connector • Forced draft o Fan at appliance, OEM-installed o Positive pressure in vent connector © 2023 STRAND Dallas I Texas 972 620 8204 Natural-Draft Gas Furnace, Category I © 2023 STRAND Dallas I Texas 972 620 8204 Fan-Assisted Gas Furnace, Natural Draft, Category I © 2023 STRAND Dallas I Texas 972 620 8204 Gas Water Heater, Induced Draft, Category I © 2023 STRAND Dallas I Texas 972 620 8204 Gas Water Heater, Forced Draft, Category III © 2023 STRAND Dallas I Texas 972 620 8204 Condensing Gas Furnace, Forced Draft, Category IV © 2023 STRAND Dallas I Texas 972 620 8204 Oil-Fired Water Heater and Boiler, Natural Draft © 2023 STRAND Dallas I Texas 972 620 8204 Barometric Damper on Oil-Fired System © 2023 STRAND Dallas I Texas 972 620 8204 1. Initial preparation o Envelope/appliance setup o Baseline (background) pressure 2. Determine Worst-Case Depressurization (WCD) o Manipulate vented/venting appliances and interior doors o Freeze appliances and doors at W-CD o Compare actual neg pressure with Table RA301.1(1) • Relieve negative pressure or change appliance if needed © 2023 STRAND Dallas I Texas 972 620 8204 Baseline Pressure © 2023 STRAND Dallas I Texas 972 620 8204 Find worst-case depressurization with your manometer, CAZ with reference to (wrt) outdoors o Turn on vented cloths dryer o Turn on all exhaust fans o Close any interior door that makes CAZ more negative. Use common sense. Smoke doors, if needed © 2023 STRAND Dallas I Texas 972 620 8204 If CAZ depressurization is exceeded at worst-case depressurization on Table RA301.1(1), add more combustion air or modify building so that depressurization is brought within limits of this Table © 2023 STRAND Dallas I Texas 972 620 8204 • During worst-case depressurization conditions, measure spillage, draft, and carbon monoxide (CO) starting with the smallest input vented combustion appliance first. • Cold-fire all appliances. • Then proceed to combustion appliances with larger input capacities in ascending order. © 2023 STRAND Dallas I Texas 972 620 8204 Check for spillage with Smoke, mirror, or flame. 60-second threshold © 2023 STRAND Monitor ambient CO during all testing Dallas I Texas 972 620 8204 • Where spillage test passes, test for acceptable draft in appliance vent connector o Category I, gas, natural draft: Not less than one foot, but not more than two feet downstream of draft diverter (hood) o Category I, gas, fan-assisted: Just above the induced combustion fan o Oil-fired furnace or boiler: At breech between unit and barometric damper • Record draft pressure and compare with Table RA301.1(2) • Refer to Table RA301.1(3) for pass/fail requirements © 2023 STRAND Dallas I Texas 972 620 8204 Check for draft in correct place. Best to test at steady state conditions. IECC-2015, Appendix RA is silent on the timing of the draft measurement, but it is after CO test (10 minutes after firing) © 2023 STRAND Dallas I Texas 972 620 8204 © 2023 STRAND Dallas I Texas 972 620 8204 Fire all other combustion appliances simultaneously and test again during firing for spillage, CO, and draft using procedures 3a through 3c and the three relevant Tables. Measure spillage, draft, and CO under NATURAL CONDITIONS, with the procedure outlined in Step 3 Natural conditions means all appliances that create negative pressure (exhaust fans, vented dryer, etc.) are OFF Confirm pressure difference between worst-case and natural conditions with appliances off. Repeat the process for each combustion appliance, smallest first, allowing each vent to cool between tests. © 2023 STRAND Dallas I Texas 972 620 8204 Review 1. Initial preparation o Envelope/appliance setup o Baseline (background) pressure 2. Determine Worst-Case Depressurization (W-CD) o Manipulate vented/venting appliances and interior doors o Freeze appliances and doors at WCD o Compare actual neg pressure with Table RA301.1(1) • Relieve negative pressure or change appliance if needed © 2023 STRAND Dallas I Texas 972 620 8204 Measuring Carbon Monoxide COas-measured vs. COair-free • COas-measured is percentage or concentration • COair-free is emission rate, adjusted (normalized) for zero excess-air conditions • Indoor ambient air CO must always be read asmeasured © 2023 STRAND Dallas I Texas 972 620 8204 Measuring Carbon Monoxide © 2023 STRAND Dallas I Texas 972 620 8204 © 2023 STRAND Dallas I Texas 972 620 8204 © 2023 STRAND Dallas I Texas 972 620 8204