For the most part, cast iron boilers are the preferred method for supplying hydronic heat, especially in the Northeastern United States.
However, if the application calls for a gas-fired hydronic appliance (natural gas or propane), copper boilers almost always hold an advantage.
For starters, copper is a much more effective heat transfer medium.
Copper heats up 30% faster than cast iron and requires 80% less surface area to transfer heat.
In addition, since copper tube boilers require less material to transfer a large amount of BTU's, the units are inherently lightweight.
Typical loading is only 600 pounds per million BTU for copper tube units and can be up to 2600 pounds per million BTU for cast iron units.
Consequently, copper tube boilers are more efficient and less costly to produce.
Also, further savings can be expected on installation costs.
Due to their lightweight nature, copper tube boilers can almost always be installed with less manpower and in less time.
Most copper tube boilers will fit through a standard 36" door, depending on the manufacturer and style of boiler (i.e. atmospheric or sealed combustion type).
However, the few units, which won't quite squeeze through a 36" opening or through a crazy labyrinth can be quickly separated into a few smaller, more manageable pieces.
Copper boilers also have several other operational advantages:
• Copper tube boilers utilize significantly smaller quantities of water to complete the same job as a cast iron boiler (reduces standby losses and increases system efficiency).
• Copper tube boilers can operate with temperatures as low as 105 degrees Fahrenheit, without risking harmful condensation.
• Copper boilers resist oxygen corrosion, especially when bronze headers are used. Cast iron boilers also are very susceptible to
oxygen corrosion.
• In a copper boiler, individual tubes can be replaced, or worst-case scenario, an entire tube bundle. Since the materials are so light, this is only a one-man job. Often with cast iron boilers, entire sections need to be replaced. Replacement is very labor intensive and many contractors opt to replace complete blocks when one section fails, because the failure is usually in the middle section.
• Copper boilers can be maintained in such a way to keep minerals in suspension, or wash away particles left behind after manufacture. Adversely, minerals tend to deposit in cast iron boilers, causing the iron to sometimes overheat and crack. Cast iron units canŐt be easily inspected for mineral deposits.
A final word. Copper tube boiler units are often stereotyped as inferior to heavy cast iron units.
Don't let the slim, trim, lightweight style fool you.
Copper units can fit into smaller spaces, or can even be stacked on top of another unit to save space.
Copper boilers can be installed outdoors on rooftops or on a pad at ground level, which reduces installation costs, and materials costs (no flue needed).
Installed properly, a copper tube boiler can last decades.
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