Field Controls Oil Venting Systems manual Clearance to Combustibles, Diagram a, 113, 154

Clearance to Combustibles

If mounting the venting system near combustible materials, refer to Diagram A for allowable installation clearances. Clearances are based on an installation using single wall galvanized steel vent pipe. If manufactured double wall vent pipe is required or used for the installation, clearance should be based on the vent pipe’s rated clearance. Always check local code requirements for code restrictions.

Routing of the vent system and clearances for the vent pipe may be planned once the termination location is determined. Route the vent pipe from the appliance to the venter using as few elbows as possible. The horizontal section of the vent pipe should have a slight upward slope from the appliance to the venter. The vent pipe size (diameter) can be smaller than a typical chimney vented system and still overcome the higher pressure losses because the power venter mechanically creates the required draft or air flow to vent the system.

For estimating the minimum vent pipe diameter for an oil system, multiply GPH by 140,000 BTU/GAL, then divide by 12,600 BTU/sq. in. This will give the minimum cross sectional area required. (See Table 3 for area to diameter conversion.) For multiple equipment venting systems, divide the total BTU/hr. input for all appliances by 9,300 BTU/sq. in. This will give you the minimum vent pipe diameter needed for the common breaching of the vent system.

As a rule of thumb, size the vent pipe to the outlet diameter of the heating equipment for a single appliance venting system. For multiple appliance venting systems, use the outlet diameter of the largest unit and add 50%.

Diagram A

Single Pipe System

Allowable Inlet Temperature	Clearance (B)
400ºF or Less	3" min.
550ºF or Less	4" min.
550ºF or Less	3" min.*

Double Pipe System

Allowable Inlet Temperature	Clearance (A)
400ºF or Less	.5" min.
550ºF or Less	1" min.
550ºF or Less	.5" min.*

* With galvanized sheet metal liner or equivalent

METAL LINING FOR	A B	SQUARE HOLE
		THROUGH WALL
550°F-400°F INPUT TEMP.

FLOOR JOIST	B	COMBUSTIBLE
		MATERIAL
A	A
B-VENT
ELBOW

INPUT TEMP.

LOCATION

Table 3

Pipe Size	Nominal
	Cross-Sectional Area
	Sq. Inches
3"	7
4"	13
5"	20
6"	28
7"	38
8"	50
9"	64
10"	79
12"	113
14"	154

COMBUSTIBLE
MATERIAL	FLOOR JOIST		SWG SERIES
	A B	FLOOR
			POWER VENTER

INPUT TEMP.
LOCATION
OUTER PIPE
EXTENSION	BLOCK
END PIPE COVER	FOUNDATION
FROM SWG UNIT
B-VENT or
L-VENT
ELBOW

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