Brochure

5
Secondary HX-Stainless Steel 316L
Primary HX
Commerical-Grade
Copper
Drum
Coil
Hot Water Outlet
Bypass Valve
Cold Water
Inlet
Flow
Sensor
Flow Adjustment
Valve
Secondary Heat Exchanger 316L Stainless Steel
(Condensing Models Only)
The secondary condensing heat exchanger is made of high-quality 316L stainless steel. This is where the rest of the heat transfer occurs.
Due to the lower temperature acidic condensation occurs, and stainless steel is required in order to avoid corrosion.
For condensing heat exchangers, it is more suitable to use 316L stainless steel because of the extreme environment (heat, acidic
condensation, chloride) that the material is subjected to.
Primary Heat
Exchanger:
Copper vs.
Stainless Steel
• Heat transfers 25 times more readily through
copper than stainless steel. Consequently, for
the same amount of heat transfer, stainless
steel heat exchangers need to be larger than
copper heat exchangers, leading to a larger
pressure loss.
• At higher temperatures, it is the nature of
stainless steel to become prone to a number
of problems not usually experienced at
room temperature. It is vulnerable to pitting
corrosion and stress corrosion cracking (SCC).
• Stainless steel is NOT better for
durability because it is harder. Hardness
causes the material to become brittle.
Stainless steel will crack after numerous
cycles of thermal expansion/contraction,
especially with chloride in the water.
Copper heat exchangers are less
brittle and better suited for expansion/
contraction without cracking.
• In a dual heat exchanger design,
corrosion is not a big concern in the
non-condensing primary heat exchanger
because no condensation forms on the
exterior of the pipes. Stainless steel is
unnecessary for this stage.
Note: H3M, H3J and H3S condensing line units
use C1220 copper and do not have a bypass valve
* Diagram represents H3