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NORA Oilheat Technicians Manual

Chapter 6—Draft and Venting 6-15 Another alternative is to use a draft inducer, Figure 6-13. Draft inducers are electrically powered fans installed in the flue pipe. They help to pull the air from Figure 6-13: Draft inducer the unit and push it up the chimney. They can also be used to boost the draft if the natural chimney draft is too weak. A draft inducer can also solve the loss of draft from the rapid cooling of combustion products in the chimney. Poorly insulated metal flues and oversized or unlined chimneys can cause a rapid cooling of combustion products and lead to a loss of draft. A draft inducer can offer a reasonable temporary solution but the ideal solution is to line and insulate the chimney. Induced draft has the advantage of developing controlled draft under most conditions. It can help to provide a clean start with no rumbles and it can provide adequate draft in a chimney that is too small, too low, or too large. Installation of a pressure or draft-proving switch is required by codes and is strongly recommended with an induced draft installation. See Figure 6-14, the draft proving switch is DIP-1. Alternative venting systems In recent years, manufacturers have created alternative forced draft venting Figure 6-14: Draft inducer with draft proving switch, typical installation systems that do not use a chimney for oilfired heating systems. The technology takes two different approaches: power- venting and direct-venting. Power-venting: a fan is attached to the flue pipe at the exit terminal from the building to pull the products of combustion out of the heating unit. Power-venters do not need a chimney and are usually sidewall vented. Direct vent: the static pressure created by the burner fan pushes the combustion gases through the heat exchanger and out of the building. A direct-vented system is a positive pressure system. No chimney is needed with a direct vent system. The advantages of alternative venting systems are: • More positive control of draft • No chimney warm-up problems • Lowered cost in new building con struction and electric to oilheat conversions (eliminates the chimney) • There is a significant reduction in burner noise with direct venting Chapter 6 Draft and Venting


NORA Oilheat Technicians Manual
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