Overview Of Condensing Tankless Gas Water Heater - Noritz NR50-OD Service Manual

Overview of Condensing Tankless Gas Water Heater

This water heater is a high efficiency, fully condensing appliance. Unlike a traditional tankless water heater, a
condensing type captures heat from the exhaust gas and uses it to preheat the incoming cold water as it passes
through the secondary heat exchanger as illustrated below.
Conventional
Type
The condensing tankless gas water heater
discharges condensate.
When heat from the exhaust gas is collected within the
secondary heat exchanger, condensation occurs from
moisture in the exhaust gas and the resulting water is
discharged from the drain pipe (approx. 2 gallons/hour
(GPH) maximum). It is not a water leak. Do not plug or
block the drain line as it must always be allowed to freely
flow.
The condensing tankless gas water heater
tends to show white steam.
After the exhaust gas passes through the secondary heat
exchanger, it becomes low in temperature and moisture
rich which tends to produce steam at the vent discharge
terminal. This is a normal occurrence.
Exhaust
About 400°F
Combustion Gas
About 400°F
Primary Heat Exchanger
Condensing
Tankless Gas
Exhaust
Water Heater
About 120°F
Secondary Heat Exchanger
Combustion Gas
About 400°F
Primary Heat Exchanger
Drain pipe
(Installation example)
Condensate
comes out
from here.
4
Water is heated
using the exhaust
gas which is about
400°F.
During combustion, white
steam may often be seen.
This is normal.