Items Tagged with 'hydronics'

For boilers operating on natural gas or propane, flue gas condensation begins at inlet water temperatures below about 130 ºF. Boilers operating on low sulfur #2 fuel oil have lower dewpoint temperatures in the range of 110 ºF.

The homerun system is a simple technique for connecting multiple heat emitters using two runs of small flexible tubing (such as PEX) for supply and return. In North America, the standard size is 1/2-inch, but 3/8-inch tubing can be used with proper design and compatible fittings.

An owner, who has never been satisfied with the performance of his heating system, decides that the boiler must be the root cause of all the performance issues. Not wanting to spend any more than necessary, he makes several calls looking for the lowest boiler replacement price.

Many of the ratios used in the HVAC industry are just some “desirable output” quantity divided by the “necessary input” quantity. One example is the coefficient of performance (COP) of a heat pump. The desirable output quantity is Btu/hr of heat output. The necessary input quantity is the electrical input power needed to operate the heat pump. The latter is typically measured in watts or kilowatts.

Around 25 years ago, I developed a design that sends high-temperature water to a remote manifold for low-temperature floor heating, mixing it with returning water to achieve the optimal supply temperature, regulated by a variable speed pump. Can you identify a problem with this approach or propose a better one?

At a supply water temperature of 103 ºF, the heating capacity of the heat pump is the same as the total heat dissipation ability of the distribution system. That’s where this system achieves thermal equilibrium. The floor heating zone is fine at this condition, but the output of the air handler is significantly lower than what was planned for based on the assumption that 120 ºF supply water would be available.

These are common design pitfalls that may seem effective as they are. Review them and identify changes that could enhance the layout.

Millinocket is near utility-scale wind turbine farms where strong winter winds can lead to over-generation of electricity, surpassing local grid demand. While it might seem intuitive to shut down some generation equipment during such times, the process is not as simple as flipping a switch.

Some hydronic heating systems use slab-on-grade floor heating combined with an air handler or fan-coils in other areas of a building. This approach is also used for heated basement floors combined with a “hydro-air” delivery system for the main living areas.

One concept that’s getting increasing attention among HVAC engineers is “resilient design.” It refers to approaches that - ideally - allow systems to remain operational under very abnormal conditions, or minimize effects that could cause major damage to systems when and if they are otherwise rendered inoperative.