What does Condensing Mean?

Condensing
ability is a feature you can see in both traditional and tankless water
heaters. Condensing water heaters absorb almost all the heat in the fumes
produced by the burning of propane or natural gas to the point that the water
vapor in the fumes actually condense instead of going out of the venting very
hot. This is achieved by letting the hot fumes travel through a secondary heat
exchanger where it transfers its remaining heat to the incoming cold water. As
a result, condensing water heaters are more efficient than non-condensing
units. An average tankless water heater with no condensation feature has an
energy rating of about 0.8 whereas condensing tankless water heaters usually
boast energy factors of 0.95 or above. Efficiency is the most important benefit
of getting a condensing unit and there are also other good things about them.
Because the
exhaust gases in a condensing tankless water heater are cooler, such a unit can
be vented with the more economic PVC unlike the mid-efficiency devices that
need an expensive stainless steel venting system to dump the very hot fumes
without suffering any heat damage. A condensing tankless water heater is a few
hundred dollars more expensive in comparison to a plain tankless unit with
similar features and from the same brand name but part of this extra cost is
compensated with cheaper venting appliacation. In other words, condensing
tankless water is not as expensive as it looks.

More Differences

Condensing
tankless water heaters usually have two ventillation pipes, one of outgoing
fumes and one for incoming fresh air while plain tankless water heaters generally
have concentric vents where the outgoing fumes go through an internal pipe
surrounded by a larger fresh air pipe. It is hard to say which one is better
but a point that deserves a mention is that Rinnai condensing tankless water
heaters are unique because they allow for both dual vent and concentric.
Finally,
condensing water heaters have a drain pipe that takes the condensed water to a
drain. In some cases, neutralizers are installed on the drain pipe to prevent
the outgoing water, which can be mildly acidic to damage the drain system. Note
that Rheem condensing tankless water heaters have a built-in neutralizer.