John Seigenthaler: Renewable Heating Design

How to change the staging status of two heat sources

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Mon, 06 Apr 2026 07:00:00 -0400

What if your boiler system could automatically switch between heat sources based on energy cost? A closer look at staging logic, relays and smarter system control.

How do North American and European hydronic systems differ?

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Tue, 10 Mar 2026 07:00:00 -0400

When comparing hydronic systems designs that are common in North America with typical European equivalents, comparisons reveal details that would be beneficial in either market, but are not “traditional” in one market or the other.

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.

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.

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.

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.

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.

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.

Ten considerations for selling hydronic systems

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Mon, 07 Jul 2025 00:00:00 -0400

While I admit to not being fully informed on the latest things from Google, Apple, Chat GPT, or social media, I’m confident that I can still pass along advice to those who are new to the hydronic industry, especially those involved with designing systems

Transitions: Systems for simultaneous heating and cooling (Part 2)

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

What happens if there’s a simultaneous call for domestic water heating and cooling?

Transitions: What do I do about cooling? (Part 1)

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 28 May 2025 00:00:00 -0400

Fortunately, our industry is at a point where the question "But what do I do about cooling?" can be answered, with confidence, and by the same hydronics professional offering heating.

Versatility in direct-to-load systems, part two

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

Last month, we discussed direct-to-load hydronic heat pump systems. These systems use a variable-speed compressor and circulator to adjust heat output and flow, eliminating the need for a buffer tank or hydraulic separator.

Versatility in direct-to-load systems, part one

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 12 Mar 2025 00:00:00 -0400

A recent design approach for air-to-water and water-to-water heat pumps is "direct-to-load" piping. This method utilizes an inverter-driven scroll compressor, which operates across a wide range of speeds and can handle on/off cycling without the high inrush current typically seen in fixed-speed compressors.

When one heat pump isn’t enough — part two

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

Last month's column discussed piping for air-to-water heat pumps. A 2-pipe system allows staging but not simultaneous heating and cooling, while a 4-pipe system with motorized valves enables both modes of operation.

When one heat pump isn’t enough

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Tue, 07 Jan 2025 00:00:00 -0500

Air-to-water heat pumps, especially for larger systems, can be used in stages for efficient temperature control and flexibility, utilizing variable-speed compressors and specific piping setups to manage heating and cooling loads.

An expensive lesson in hydronic fundamentals

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Thu, 05 Dec 2024 00:00:00 -0500

A review of a flawed hydronic heating system uncovers critical errors, such as improper circulator placement and restrictive mixing valves, leading to uneven warmth and corrosion issues. This underscores the need for proper design and installation in hydronic systems.

Versatile hydronic systems leverage time-of-use energy rates

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Mon, 11 Nov 2024 00:00:00 -0500

As government electrification target dates loom in the near future, and power transmission systems get pushed closer to their limits, utility companies continue implementing ways to manage peak demand.

How to extract more heat from a thermal storage tank

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Mon, 07 Oct 2024 00:00:00 -0400

Thermal storage enhances the efficiency of renewable energy heating systems, like pellet-fired boilers and solar collectors, by storing low-cost, off-peak electrical energy for future use. It's vital for reducing energy costs and ensuring consistent heating, with auxiliary boilers providing backup when needed.

Geothermal heat pump systems with manifolded earth loops offer advantages

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Thu, 05 Sep 2024 00:00:00 -0400

Geothermal systems use HDPE tubing for closed-loop earth heat exchangers, buried several feet below the surface.

Do hydronics systems need internet connectivity?

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Fri, 02 Aug 2024 00:00:00 -0400

If your office routine is like mine, you probably type passwords into your devices all day to access essential websites and software. Sometimes you forget complex passwords and have to go through the hassle of resetting them. Financial websites may require monthly password updates.

The anti-condensation function of piping assemblies

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Mon, 01 Jul 2024 00:00:00 -0400

Biomass boilers burn various fuels and come in different designs. Water vapor is produced when burning wood-based fuels, and the resulting condensate can be acidic and corrosive to metals like carbon steel and iron.

3-way diverter valves: Part 2

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Thu, 30 May 2024 00:00:00 -0400

In last month’s column, we discussed the design and actuation of 3-way diverter valves. This month, we’ll look at several applications for these valves.

3-way diverter valves: Part 1

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 01 May 2024 00:00:00 -0400

There are many scenarios in which flow at some location within a hydronic system has to be directed along one of two possible flow paths. When a single valve is used to create this routing, it’s called a diverter valve. In part 1, we're digging into motorized 3-way diverter valves and actuator options.

Modern hydronics technology can play well with future energy markets — Part 2

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 27 Mar 2024 01:00:00 -0400

Last month, we discussed how solid thermal energy storage, combined with an air-to-water heat pump and an electric boiler, provides a platform to leverage time-of-use electrical rates in ways that can benefit customers as well as the utility providing the electricity.

Modern hydronics technology offers unique solutions

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 28 Feb 2024 00:00:00 -0500

A problem is developing with the transition to electric heating: peak demand. Learn how air-to-water heat pumps tackle seasonal needs but struggle during extreme cold, leading to reliance on electric resistance heating.

The challenge of reviewing proposed system schematics

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Thu, 01 Feb 2024 00:00:00 -0500

Discover the major flaws in a proposed heating system and learn about a makeover approach to eliminate the issues.

Complementary fuel sources

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Wed, 03 Jan 2024 00:00:00 -0500

Like most people, I have opinions and beliefs about our current energy sources, and specifically how they play into the future of hydronic heating and cooling technology.

Concepts for varying flow rate in geothermal earth loops — Part 2

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Thu, 30 Nov 2023 00:00:00 -0500

System COP is a more relevant metric of geothermal heat pump performance since the owner is paying for the electrical energy to operate the heat pump and the circulator, and their operation is always simultaneous.

Concepts for varying flow rate in geothermal earth loops

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Thu, 02 Nov 2023 00:00:00 -0400

The goal is to keep the system COP as high a possible as the operating conditions of the heat pump change. The logic behind maximum COP tracking is to continually look for an earth loop flow rate that improves the system COP.

Products that would be welcome additions to the North American hydronics market

hydronicpros@gmail.com (John Siegenthaler, P.E.) — Fri, 29 Sep 2023 00:00:00 -0400

Every year, manufacturers develop new or improved products for the North American hydronic market. Product development planning by those manufacturers depends on several factors. Here are a few of the main considerations.