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8. Exhaust Venting
The SRU boiler is a high efficiency unit that requires proper venting. The boiler
must be vented to the outdoors by means of a lined masonry or a approved pre-
fabricated chimney of the size and height recommended by the manufacturer or by
a listed "power venting" unit which provides draft by mechanical means. In many
installations, particularly older interior and most exterior chimneys, a corrosion resistant
liner should be installed and may be required by code. Please consult the liner
manufacturer for the appropriate chimney liner.
The flue-gas exit of the chimney must be located at least 24 inches above any
part of the building structure within 4 feet of the chimney. Be sure the chimney and
smoke pipe won't become obstructed by rodents, bird nests, soot buildup, chimney
liner deterioration, etc.. If using a "power venter" system, it is suggested that it should
be installed on the leeward side of the house. (Please consult with the manufacturer
of "power venter" for requirements concerning clearances from combustibles and
distances from doors and windows.) The "venter" must be installed by a licensed
burner mechanic and done in accordance with local codes. This is a very low stack
temperature boiler so caution should be used when connecting to an outside built
chimney. Proper chimney sizing is important to prevent damage due to possible
condensation from low flue gas temperatures. Should you have concern that the flue
gases could condense, you should consider lining the chimney or using a listed, "power
venting" or the QHT direct vent system. If "power venting" is used to discharge flue
gases, then the power vent unit should be equipped with a postpurge control such as a
delay-off, timing control to prevent problems with fogging and nozzle post drip. If the
boiler is installed as a direct vent unit, it must be installed using a direct vent kit supplied
by QHT Inc.
The exhaust pipe connection from the boiler to the chimney should be as short as
possible, with a minimum number of elbows. The vent pipe must have a vertical rise of
at least 1/4 inch per foot of horizontal run. The vent pipe must be of the same diameter
as the flue outlet on the boiler. The chimney connector should have a minimum
thickness of 26 gauge, corrosion resistant (galvanized) steel, and be assembled with
a minimum of three (3) sheet-metal screws in each joint. In most one and two story
houses, a barometric draft control is not required as the SRU is designed to be pressure
fired. However in high draft situations which exceed the flue gas resistance through the
boiler, a barometric draft control is recommended. The over fire draft should be positive
and between 0 and .06 inches of water column. The draft at the breech should be
enough to overcome the resistance through the boiler.
