It's a New Age for Hydronic System Performance
If you'd dial your transporter beam back to, say, 1991, and aim your arrival for the hydronics industry, you'd quickly find a sad and forlorn marketplace. Just 15 years ago, manufacturers were barely treading water, cranking out replacement boilers at a slower pace each year. The burgeoning new construction market wouldn't have anything to do with hydronics. It was a pretty dismal scene.
Today, the hydronics industry has emerged with an extreme makeover-moving at warp speed with confidence and clear direction. New equipment and market conditions have driven manufacturers to new levels of engineering excellence.
Without question, market forces-chiefly, the push for higher and higher energy efficiencies, and demand for equipment to go where no equipment has easily gone before-are driving the pace for new and innovative hydronic solutions.
The newest generation of equipment-such as condensing technology that extracts heat from condensate within the system-has pushed combustion efficiency into the 95% to 99% range. That's smart use of energy. Add new and sophisticated commercial controls to the picture, as well as system integration with building automation systems, and you begin to see how quickly this market is moving. With performance like that, building owners are now at attention. When the design engineer can calculate a three- to four-year payback for new equipment (or perhaps even shorter than that in some instances), there's real incentive to install new technology.
To help explain this phenomenon, we've tapped the experience and expertise of several industry experts, including:
- Bill Root, vice president of sales and marketing, Laars Heating Systems Co.
- Mike Chiles, president and general manager, Watts Radiant.
- Tony Radcliff, building services product segment manager, Grundfos Pumps Corp.
- Tim Rosen, P.E., Concept Mechanical.
- Mark Olson, CEO and general manager, Caleffi Hydronic Solutions.
- Joan Mishou, manager of applications engineering, Laars Heating Systems Co.
You'll learn that high-performance hydronic heating and volume water heating depend on the interrelationship of the following six key facets of the boiler system.
1. System EfficiencyHow effectively the boiler relates to the total system is determined by its capacity to deliver heat either quickly, or slowly, depending chiefly on the needs of the system and the ability of the boiler to adjust to changes in the system's demand for heat. The common term is "to size to the load."
2. Combustion Efficiency & Thermal EfficiencyJust a few years ago, many of us in the industry considered combustion efficiency and thermal efficiency to be the most important factors in determining overall system performance. That's not the case today.
According to Root, transferring heat from a boiler into a total system-and in just the right amount and at just the right time-is a truer measure of system performance.
Manufacturers today put a lot of engineering effort into maximizing heat transfer to water-and that efficiency is a critical aspect of a boiler's performance. The only thing to keep in mind is that many applications do not call for the highest levels of combustion efficiency (condensing equipment) because the water temperatures are too high. Designing systems with staged firing, modulation, and/or multiple boilers can often produce higher system efficiency than trying to use a single condensing boiler that claims higher combustion efficiency.
3. Information ExchangeHow well does the boiler act as part of a system in terms of both accepting and responding to external sources of information? "Information exchange,"
4. Installation and ServiceabilityHigh on a field technician's or building maintenance supervisor's wish list will be:
- Easy access to all components;
- Easily accomplished field wiring of thermostats, field interlocks, accessory equipment and BAS control;
- Convenient access to water, gas and electric at different sides of the boiler;
- Combustion air that's filtered, with filters that can be washed and reused; and
- Options that include sidewall and vertical venting, as well as a boiler's installation outdoors.
5. Multi-Speed CirculationOne of the most important facets to optimal circulation for hydronic systems is for design engineers and installing contractors to match a pump's performance or flow characteristics to the specific job that it needs to perform within the system.
According to Radcliff, a single-speed pump has one performance curve. But new multi-speed circulators, such as Grundfos' SuperBrute, and the larger VersaFlo, offer a much broader range of performance. With the flick of a switch, various speeds can be chosen, easily changing head and flow to meet the specific needs of the system.
"We've standardized on multi-speed circulators because we feel they do the best job,"
Enhanced Piping SolutionsAnother advanced device combines a hydronic separator and distribution manifold. Called the HydroLink, from Caleffi, the unit is attached to hydronic heating or air conditioning systems to permit different heat adjustments for multiple zones when there is only one boiler or chiller.
Its configurations are compact and can easily be designed into any type of hydronic circuit. According to Mark Olson of Caleffi, the key operating principle is that when a single system contains a primary generating circuit with its own circulator and a secondary circuit with one or more distribution pumps, conditions may permit interaction between the circulators, creating unwanted flow rate and pressure abnormalities.
The device provides a low-pressure loss zone, enabling both primary and secondary circuits to be hydraulically independent of one another. Yet the unit combines both a low loss header and a distribution manifold. A low loss header is critical for high-flow-resistant low-mass boiler installations because it moves the point of lowest pressure drop from the boiler to the unit's low-pressure chamber. The distribution manifold has closely spaced tees that connect the secondary circuit to the primary loop internally, so that flow in the primary loop has very little tendency to induce flow in the secondary circuit.
"Because the unit's openings are so close together, there is almost no pressure difference between them, thus the pressure differential across the internal headers is close to zero,"
6. Heat DistributionThe hydronic industry's renaissance is, in part, due to the reemergence of the radiant heat industry. In the commercial sector, large radiant heat systems place unique demands on a boiler, or series of boilers. According to Mike Chiles of Watts Radiant, these systems were historically characterized by cold starts with long boiler run times, high water volume, high mass, cooler required supply water temperatures, and short boiler cycle-times when the mass is at temperature.
Of course, large radiant systems require a boiler or boilers with high output. A key advantage is that when the thermal mass of a floor or heated surface has reached temperature, shorter and less frequent boiler cycle-times are required. Better yet, a boiler system with modulation permits the heating, and later, heat-maintenance of the heated surface. Either a fully modulating burner, or the lead-lag staging of boilers, would allow a system to meet ever-changing load requirements for optimal system efficiency. Another option is to add mass to the piping system to increase boiler run times during periods of low demand. For this, water tanks can easily add mass to a piping system.
"Snowmelting systems pose a different challenge: high demand and high mass with extremely cold water/glycol temperatures,"