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What is max. permissible horizontal run for coal appliance venting to masonary chimney?

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I am installing a coal boiler (anthracite) in my basment.  I have a masonary, lined chimney nearby.  The ideal location for the boiler  (apart from venting issues) would place the vent about 11 feet from the chimney entrance.  Is this too far?  I have enough height to pitch the pipe 1/4" per foot of run.  The chimney is about 30 feet tall so draft should be OK...8" flue.
asked in Heating and AC by markleo (120 points)
edited by markleo
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1 Answer

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Hi Markleo,
Max horizontal vent connector length depends on a few variables and may vary between the manufacturers as well. For category 1  natural draft appliances (I'm not sure what is yours) the base requirement is 75% of the height of the vertical portion of the chimney above the connector. 
Based on the Gama venting tables it should be 1.5’ per inch of the vent connector’s diameter (additional requirements for connectors exceeding max permitted).
The following example is a recommendation from Energy King Coal Boiler Installation Manual:
Any horizontal runs of connector pipe should have a minimum rise of 1/2-inch per linear foot. Use extra support hangers or brackets every three feet if it is absolutely necessary to have a run of more than six feet, which is not recommended. 
Maybe if you give me some details about your boiler (manufacturer, model) I’ll be able to find more precise answer. Just click "comment" below.
answered by darekrudy (21,730 points)