Those who evaluate the performance of HVAC source equipment such as boilers, furnaces and heat pumps have to work with a wide variety of acronyms. Some of them were spawned by government bureaucrats, mostly the U.S. Department of Energy (DOE). Others were created through a consensus process based on input from manufacturers and other industry stakeholders.
Over the years I’ve had opportunities to work with several architects. They’re interesting people who have the ability to meld art with building technology. Sometimes the result is more “art,” and sometimes it’s more “building.” In either case, their designs typically get handed off to engineers with the simple request: Figure out how to heat my creation…
Given the current upward trend and volatility of fossil fuel pricing, there’s renewed interest in heating using wood pellets. Federal incentives that currently cover 26% of some qualified equipment adds enticement toward purchasing pellet-burning stoves.
When designing hydronic circuits, most engineers focus on what’s necessary for that circuit to absorb thermal energy at a heat source, carry it along like a conveyor belt and drop it off at one or more heat emitters.
In 2012 the price of #2 fuel oil in upstate New York was approaching a previously unheard of $4 per gallon. This spurred many pending heating system projects to consider the use of cordwood or wood pellets.
As with most things hydronic, there are multiple approaches, and the “best” approach for each installation has to consider cost, aesthetics, access to the existing piping, available wall space and the goal of how the overall system will operate based on existing or newly created zones.
One of the best things about hydronic heating systems is that it’s easy to integrate some method of domestic water heating. This combination has been used for decades in systems where a boiler was the sole heat source. It’s also possible when a heat pump serves as the heat source.
I’ve covered pellet-fueled boiler applications in several past issues of PME. All of them have involved hydronic distribution systems. While such applications are certainly the prevailing way pellet boilers are used, they are not the only option. It’s possible to couple a pellet boiler to a forced air distribution system.
All hydronic systems designed around renewable energy heat sources — as well as those designed around conventional boilers — have at least one controller that measures and responds to temperature. Common examples are temperature setpoint controllers, outdoor reset controllers, mixing controllers and differential temperature controllers. Complex systems that operate in multiple modes, or use multiple heat sources, often have several temperature-based controllers.
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