AFTER ALL THESE YEARS

BY JOHN SIEGENTHALER

I’ve been designing hydronic systems for over 40 years. As with most technologies, there have been tremendous changes in what a “typical” residential hydronic heating system looks like today compared with what it did in 1978.

Back then it was common to see a single cast-iron boiler—fired by natural gas or fuel oil—supplying a distribution system consisting of one to three zones of finned-tube baseboard.

The boiler usually had a “tankless” coil heat exchanger for providing domestic hot water, and the water temperature leaving that boiler was 180F (82C) or higher.

Although it’s possible to create a similar looking system today, I believe most informed hydronic system designers would likely try to talk you out of it. I know I would.

Change Is Constant

So why should anyone alter an approach that has kept tens of thousands of North American homes comfortable for decades?

The “short answer” is the greatly improved hardware and design methods that exist today. Here are a few examples I've seen during my career:

• The introduction of cross-linked polyethylene (PEX) tubing to North America and a subsequent resurrection of radiant panel heating.

• The introduction of modulating/condensing (mod/con) boilers that pushed thermal efficiency (annual fuel utilization efficiency/AFUE) from mid-80% into the mid-90s.

• Controls that morphed from those using springs, glass bulbs partially filled with mercury, and capillary tubes, to microprocessor-based controls that can manage entire multi-load systems and also wirelessly communicate with installers.

• Circulators with electronically commutated (EC) motors that can automatically adapt their operation to the pressure and flow requirements of a hydronic system.

• WiFi thermostats that let you change the temperature in a zone from almost anywhere in the world.

• A broader understanding of the importance of and methods for implementing hydraulic separation in multi-circulator systems.

Many of these introductions were a really “big deal” when they occurred. Today, most of these innovations have reached commodity status. They are readily available from multiple suppliers and used on a high percentage of hydronic system installations.