Flue Pipe Considerations

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Brendan Dalton
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1 Flue Pipe Considerations Objective The application summary outlined here will communicate the necessary flue piping arrangement for EnergyLogic (EL) furnaces and boilers and give a fundamental understanding of the restrictions. Also, tools will be introduced that help alleviate draft concerns and make installations more flexible. Description For a waste-oil furnace, the air-to-fuel ratio is critical. If the combustion air flow is lower than required to fully combust the oil, the used oil will not only pool in the bottom of the chamber causing post-combustion smoking, but will mix with fly ash and form coke. Coking can present a quick down-hill slide for the combustion as it negatively impacts atomization. As such, it is necessary that the combustion air flow be held constant at a flow rate above a minimum threshold (above 25% excess air for EL furnaces and boilers). The combustion air flow rate is dictated by two factors. On the burner end, the rotation of the burner squirrel cage and the air shutter inlet setting induce a pressurization of air at the burner head. On the exhaust end of the furnace, the exhaust gases rising out of the heat exchanger create suction through the furnace. The combination of induced draft at the burner and natural draft from the exhaust gases yield the overall furnace draft. This total draft sets the combustion air-flow rate. Natural draft is primarily a function of the installed flue pipe. If the flue pipe is installed incorrectly, the overall furnace draft will be compromised and the combustion air flue rate will be low. Low draft will result in, at least, shorter and more involved maintenance intervals and hard light-offs. At most, low draft will result in smoking and coke build-up in less than 100 hours of run-time. Problem Avoidance To run properly, the EL furnace and boiler should maintain a minimum of 0.05 inch WC draft. A few key guidelines are presented in the Flue Pipe Installation Guide that will help insure a proper draft is achieved: 1 of 2

2 Flue Pipe Considerations Straight Vertical Stack (Figure 1) 1) Install flue pipe of appropriate diameter for the EL boiler or furnace that is being used. For an EL-140H, EL-200H, EL-200B or EL-340H, the appropriate diameter is 8 inches. For an EL-500B, the diameter is 10 inches. 2) Flue stack recommendations should run a minimum of six feet and should extend four feet above the roof and any point within 20 feet of the flue. Note: For additional requirements, refer to NFPA guidelines and your local codes. 3) The Flue Pipe Installation Guide provides other specifics for an appropriate vertical stack installation. Stack Offsets without Inducers (Figure 3) At times, it is necessary to jog the flue stack slightly to hit an existing roof penetration or to place the furnace in a more desirable location. The suggestions below will aid in those circumstances: 1) Offsets should be no greater than 45 o from vertical. 2) The overall vertical flue length should be twice the length of the horizontal run. 3) The total horizontal length should not exceed 10 feet. 4) If the barometric damper is set at an angle, the damper pins must be parallel to the floor. Special Applications In most installations, the above restrictions should be held. Since achieving 0.05 inch WC draft is the goal, the installer may find that he is able to achieve a sufficient natural draft without strictly following these guidelines, but without careful attention and a systematic approach, an installer will eventually find himself with a furnace that will not run per specification of draft. It is not uncommon for a customer to want the flue stack to exit out a sidewall and not to penetrate the roof. With very low ceilings, it is impossible to position the furnace eight feet above the floor and still run a 45 o bend through the sidewall. For these installations that necessitate a 90 o elbow, EL offers an in-line draft inducer for supplementing the natural draft. Figure 2 and 4 outline two options to induce draft. In Figure 2, the draft inducer is intended to supplement the natural draft. Upon exiting the building, the stack must still terminate above the roof-line. While a roof penetration is shown, the stack can exit a sidewall. EL offers a draft inducer kit (PN ) for installations like those shown in Figure 2. Figure 4 illustrates a direct vented application using a QuickDraft Q8 draft inducer. It generates considerably more draft, but is significantly more expensive than the EL version. 2 of 2

3 For questions, visit or contact EnergyLogic Technical Services at Flue Pipe Installation Guide Vertical

4 For questions, visit or contact EnergyLogic Technical Services at Flue Pipe Installation Guide 45 Angle to Vertical

5 For questions, visit or contact EnergyLogic Technical Services at Flue Pipe Installation Guide Horizontal to Vertical

6 3' Draft Inducer Flue Pipe Installation Guide Horizontal Flue For questions, visit or contact EnergyLogic Technical Services at

APPENDIX "B" November 5, 2002 Page 1 of 6 BOILERSMITH LTD. STACKS AND BREECHING

APPENDIX B November 5, 2002 Page 1 of 6 BOILERSMITH LTD. STACKS AND BREECHING APPENDIX "B" November 5, 2002 Page 1 of 6 BOILERSMITH LTD. STACKS AND BREECHING NOTE The Stack and Breeching shall be installed in conformance with national, regional and local codes and standards and/or