Rinnai RHFE-431FA Owner's Operation And Installation Manual page 56

I CAUTIONS
1. Maximum extendable length
FOR BEST ROOM AIR HUMIDITY, KEEP WATER
IN THE HUMIDIFIER TRAY.
13 feet, 2 bends
The bend where the hose and pipes leave the body is
not counted.
The air intake hose should run along the exhaust pipe.
3. Condensed water formed by
combustion, will run back to the
unit, and may overflow from the
condensation pan if pipes are
longer then 8 feet. Therefore, pipes
exceeding these lengths should be
made to drain to the outside by
giving their horizontal portions 3˚ or
more downward and outward slope.
2. To prevent water condensation
Condensed water
may accumulate
here, and cause a blockage
preventing combustion.
CAUTION
Never allow the exhaust pipe to sag, as condensed
water may accumulate and cause incomplete
combustion.
3˚ slope(approximate)
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