Introduction - UTICA BOILERS UB90-50 Installation Manual

This appliance is a gas-fired direct vent hot water boiler with
cast aluminum boiler sections. A revolutionary cast aluminum
heat exchanger means better heat transfer and thermal storage
than similarly sized cast iron boilers, which results in higher
efficiency. The heating system water absorbs large amounts of
heat from the cast aluminum heat exchanger, cooling the flue
gases and causing condensation. Sealed combustion, premix
gas burner, and low flame temperature means drastically
reduced CO and NOx emissions, which contribute to a cleaner
and healthier environment.
Figure 1

INTRODUCTION

This appliance, unlike normal residential atmospheric and
induced draft units, takes its combustion air directly from
the outdoors (sealed combustion) and does not compete with
building occupants for fresh air. Sealed combustion (also
known as "direct vent") is the safest and best way to obtain
plenty of clean combustion air. The induced draft fan draws
in the outside combustion air, then takes the cooler flue gases
from the boiler unit and provides a positive removal of the flue
gases from the building through inexpensive and readily avail-
able PVC and CPVC pipes.
5