Radiant & Hydronics

The Glitch and the Fix: Grounded Errors

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Tue, 05 May 2026 07:00:00 -0400

An installer is planning a multi-zone floor heating system supplied from a single stage non-modulating geothermal heat pump. Can you identify at least four design flaws or operational issues that are likely to develop if the system is installed as shown?

The Glitch & the Fix: Can you find the problems with this space heating set-up?

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Tue, 31 Mar 2026 17:00:23 -0400

Can you identify some problems that are likely with this set up, and propose an alternative design to eliminate any such problems?

The Glitch & The Fix: Troubleshooting hydronic piping mistakes in panel radiator systems

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 04 Mar 2026 00:00:00 -0500

Figure 1 shows a hydronic system that’s intended to supply four panel radiators, each with their own thermostatic radiator valve and an indirect water heater from a gas-fired sectional cast-iron boiler. The system is designed using primary/secondary piping. The primary circulator operates whenever the space heating load or the indirect water heater call for heat.

Plumbing, Heating, Cooling & Piping products increase – February-March 2026

forstern@bnpmedia.com (Natalie Forster) — Tue, 03 Mar 2026 10:24:47 -0500

The upward pricing trend that carried into the new year is continuing through February and into March, with a steady stream of plumbing, hydronic, HVAC and PVF manufacturers announcing increases. While many adjustments are landing in the low- to mid-single-digit range, several manufacturers are implementing category-specific or “various” increases, with select product lines moving higher.

How to use H-pattern bypass valves

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 25 Feb 2026 12:00:00 -0500

Panel radiators operated at low water temperatures, and with minimal fins attached to the rear of the water plate, can emit upwards of 50% of their total output as radiant heat.

AHR Expo 2026: Hydronics innovation focuses on practical execution

forstern@bnpmedia.com (Natalie Forster) — Fri, 06 Feb 2026 00:00:00 -0500

AHR Expo 2026 made it clear that hybrid systems are no longer an emerging idea; they are the answer to the ongoing balancing act of meeting decarbonization goals while remaining realistic about the grid's capacity for electrification. Manufacturers emphasized systems that combine electric technologies, gas-fired equipment, and advanced controls.

What’s it capable of? (part 2)

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 04 Feb 2026 00:00:00 -0500

In hydronic systems, the circuit usually passes through the boiler, which adds heat. When using a block heater and the boiler is off, it dissipates heat from the circuit. This heat loss must be considered when measuring the circuit's true "net" heating output.

Bewitched Btus: Understanding the hydraulic consequences of improper primary loop design

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 04 Feb 2026 00:00:00 -0500

Figure 1 shows the piping layout for an actual installation. It uses two boilers, fired in stages, to supply three areas of a building. One of those areas is sub-divided into three zones. The other two areas are handled by individual zone circulators. The "primary circulator" operates whenever any load circuit is on. All circulators are fixed speed. There's a partially closed ball valve at the end of the "primary loop."

One way to increase the ∆T of a distribution system

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Fri, 30 Jan 2026 00:00:00 -0500

Modern hydronic systems benefit from wider temperature drops, energy scavenging, and careful integration with domestic hot water.

ThermaCEILING radiant system provides net‐zero comfort in Connecticut ICF home

Fri, 16 Jan 2026 00:00:00 -0500

A case study of a ThermaCEILing radiant system in a Connecticut home.

The Glitch & The Fix: Geo-normous problems

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 07 Jan 2026 11:44:23 -0500

Single-stage non-modulating heat sources in zoned distribution systems often face short cycling, particularly with low thermal mass. When few zones are active, they struggle to dissipate generated heat quickly, causing temperature build-up and potential shutdown of the heat pump based on internal limits, with varied restart behavior depending on controls.

The Glitch & The Fix: Zone 3 failure

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Tue, 16 Dec 2025 00:00:00 -0500

Can you speculate why heat delivery in zone 3 was insufficient before the helper pump? How could the piping system be improved, considering the wasted length of PEX-AL-PEX tubing from the manifolds to the floor panels in figure 2?

WarmlyYours releases 2025 Q3 industry report

Thu, 11 Dec 2025 15:10:59 -0500

WarmlyYours reported strong third-quarter momentum, driven by a surge in Great Lakes radiant heating sales and steady gains across key product lines, signaling renewed stability in the broader housing and remodeling markets.

Injection mixing revisited (part 2)

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Mon, 08 Dec 2025 00:00:00 -0500

Last month, we reviewed the basics injection mixing. It’s a method for controlling water temperatures by regulating the flow of heated water “injected” into a circulating distribution system, while simultaneously removing an equal flow of cooler water from that distribution system. Any method that controls the rate of injection flow also controls the rate of heat transfer into the distribution system.

Injection mixing revisited: part one

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Mon, 17 Nov 2025 00:00:00 -0500

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.

Radiant roots: preserving history while powering modern comfort

Fri, 14 Nov 2025 12:19:08 -0500

Designing and installing a system for the unique venue posed challenges that demanded meticulous attention to detail and coordination. It needed to accommodate visitor needs while blending with the building's rustic character. “Introducing modern mechanical systems without disrupting its historic charm was difficult,” said Selestow.

Elegance extended: How to use the homerun system of connecting heat emitters

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 12 Nov 2025 00:00:00 -0500

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.

Overlooped: Boiler swap gone wrong

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Tue, 04 Nov 2025 00:00:00 -0500

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.

Using ratios to measure, compare and improve HVAC systems

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 15 Oct 2025 00:00:00 -0400

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.

Hindsight - From complex loops to clean headers: simplifying for reliability

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Mon, 13 Oct 2025 01:00:00 -0400

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?

How mismatched loads in a dual-temperature heat pump system can limit performance

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 08 Oct 2025 00:00:00 -0400

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.

Right & wrong: Examining common design pitfalls, and how to optimize piping strategies

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 01 Oct 2025 00:00:00 -0400

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

Methods from Millinocket: One town in Maine is leading the way in hydronics technology and transactive energy management

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Thu, 18 Sep 2025 00:00:00 -0400

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.

Balancing high- and low- mass heat emitters to prevent temperature "droop"

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Tue, 09 Sep 2025 00:00:00 -0400

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.

eBook | 2025 Radiant & Hydronics All Stars

Thu, 28 Aug 2025 00:00:00 -0400

The third edition of the Radiant & Hydronics All Stars eBook highlights the latest technologies and design trends in radiant heating. It features insights from our All-Star Roundtable on innovations and challenges, along with design trends for residential and commercial applications.

Aesthetic, efficient and resilient: hydronics outclass multi-splits in key areas

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 20 Aug 2025 00:00:00 -0400

Zoning has always been a premier benefit of hydronic heating and cooling systems. There are many zoning configurations capable of delivering heat (or cooling effect) when and where it’s needed in a building, with minimal effect on the temperature in other parts of the building. Some methods use circulators to create flow in each zone; others use either motorized or thermostatic valves to regulate flow.

No slips, no shutdowns: ensuring access with snow melt systems

baylesk@bnpmedia.com (Kristen R. Bayles) — Tue, 12 Aug 2025 00:00:00 -0400

Slip-and-fall accidents are among the most common liability claims in winter, according to AAA. Winter storms have cost billions of dollars in insured losses, just in the past few years. For businesses, that’s a major issue. In healthcare facilities where patient safety and uninterrupted access are non-negotiable, the stakes are even higher. Radiant snow melt systems can eliminate surface ice before it becomes a hazard, dramatically reducing legal exposure.

Using antifreeze vs. water in hydronic circuits

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Mon, 04 Aug 2025 00:00:00 -0400

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.

Massive snow melt system provides safety for state park

kevin.hale@rehau.com (Kevin Hale) — Mon, 28 Jul 2025 00:00:00 -0400

In a hydronic snow and ice melting (SIM) system, warm water/glycol circulates through pipes embedded in concrete slabs to melt snow and ice above. With sensors, the system automatically activates based on temperature and moisture, effectively melting snow on contact by evaporating it or directing water to drains.

Best Practices for performance, comfort and longevity

Wed, 23 Jul 2025 00:00:00 -0400

As radiant heating and cooling systems continue to grow in popularity for their superior comfort, energy efficiency, and quiet operation, the importance of proper system installation cannot be overstated. A poorly installed system—no matter how advanced its components—can fall short of expectations, leading to hot and cold spots, energy waste, or costly callbacks.