In 2003, I had the opportunity to attend ISH in Frankfurt, Germany. Two things of concern: We had just begun bombing Baghdad and were told to not speak unless necessary (our English revealing we were Americans); and the SARS outbreak was fast emerging, which put a damper on international travel. It didn’t help matters that we were flying Singapore Air, the very same airline that had seen one of its jets SARS quarantined just a week prior to our departure!

ISH is as much theatrical as it is a trade show, and the awesome displays are well lighted; products positioned for optimum visual impact; booths expansive in square footage; and most of the 55,600 exhibitors had some form of liquid refreshment as well as a snack or full-blown sit-down restaurant — in several cases, with impeccably dressed wait-staff. Think of it as a cocktail party for 2.3 million visitors that’s held in 10 buildings covering 5,123,664 square feet! 

A different kind of trade show

At ISH, manufacturers traditionally roll out new products. Unlike American trade shows, ISH is geared towards selling products and negotiating two-year contracts for purchases. Monday through Friday, ISH is restricted to contractors who visit various manufacturers to be wooed, wined and dined as they negotiate their best deal. Also permitted entry are architects and engineers. By week’s end, it is quite common to see contractors disappearing into small cubicles with a manufacturer’s representative to ink the two-year deal. For smaller items, such as a combustion analyzer, you’ll see intense negotiations taking place for single units.

The boiler hall was so stunning; it took me a few minutes to fully comprehend its scope and magnitude. Trade show booths encompassing thousands of square feet with several two stories tall! After rebooting my overwhelmed mind and senses, I began to delve into the hydronic systems proffered. By systems, I literally mean the whole enchilada. All components that make up a hydronic system were available to contractors as a bundle. As the week progressed, contractors began negotiations in earnest and manufacturers were doing their best to convince contractors theirs was by far the best value. 
What a difference between our U.S.-based procedure for cobbling together a hydronic system and the ISH method! Our European counterparts were set for the next two years with full knowledge of their wholesale costs for the system, while we had to request quotes from wholesalers for all the various components with each bid.

A foreign concept

That was not always the case here in the United States. When I first entered into the trades in 1972, there was the Edwards boiler system. Boiler, manifolds, zone valves and control — all carrying the Edwards logo. On one of my first encounters with an Edwards boiler, the B&G 100 circulator had stopped working and its impeller section was horribly corroded. 

Although Taco had brought forth the first wet rotor circulator around 1958, wet rotor circulators were not yet widely available, and I installed another B&G 100 circulator. I was back that night to correct my mistake: I had installed the circulator on what I assumed was the return pumping towards the Edwards. Pipe at base of boiler means return, right? Pipe leaving top of boiler means supply, right? Wrong! Edwards was a counter flow boiler. A first for me, and the reason why so many mechanical contractors despised the Edwards boiler — because it was a foreign concept.

I came to really like working on Edwards boilers and, as a result, other contractors sent that work my way.

Another way in which the Edwards system was ahead of its time? The circulator was pumping away from the thermal expansion tank! That also meant pumping towards the zone valves, and those who did not “get it” and replaced zone valves using another brand often found that while closing, the zone valve would chatter or exhibit a loud bang as it closed. They incorrectly assumed the Edwards cast iron manifold with its multiple zone valves was the supply instead of the return. Easy fix by reinstalling the zone valve in correct orientation to flow.

Recovering circ-aholic

Zone valves, in the early 1970s and 1980s were far less reliable than circulators, and I kept several Edwards zone valves on my service truck. By the mid-1980s, many Edwards boilers were reaching the end of their lifespan. So how do you replace a counter flow boiler with a conventional boiler? Bear in mind that every Edwards system I ever encountered was connected to baseboard radiators. Since baseboard doesn’t have a one-way flow, it doesn’t care which way the water flows, and those return-side cast iron Edwards manifolds became the supply-side of the system.

John Siegenthaler labeled me a circ-aholic many years ago because I wouldn’t use zone valves: Once bitten, twice shy! (As a recovering circ-aholic, my systems now — and for the past decade plus — have one ECM circulator and 1-watt zone valves).

The old Edwards supply became the return with an isolation and purge valve while the old thermal expansion tank, air scoop and water-feed valve were replaced on the now supply line that connected to the old cast iron Edwards manifold. As a circ-aholic, the Edwards zone valves were replaced with wet rotor compact circulators. Wet rotor circulators in the 1980s had become the predominant choice for retrofitting into older hydronic systems, as well as for new system installations. 

Although Dan Holohan had not yet written his life-altering book “Pumping Away,” the old Edwards systems were doing just that, and, once purged, never became air bound because the circulator’s differential pressure was added to the highest elevation within the heat emitters causing and air bubbles to shrink in size, enabling them to be carried back down to the air elimination device. A very happy ending and farewell to my old friend, the Edwards boiler.

I wanted to locate literature and pictures of the Edwards counter flow residential boiler and various components for this article. When I came up empty, I turned to Dan Holohan and John Siegenthaler only to discover they had no knowledge regarding the Edwards, nor did they remember the boiler. I tried contacting Edwards Engineering per Siggy’s recommendation, but never heard back from them. I turned to several private contractor groups I belong to and received more than a few recollections with comments not fit for printing!

Bill Bearse responded on Oil Tech Talk’s site with a picture of a new Edwards aquastat with the comment, “I don’t know why, but I have one on a shelf in my shop.” One thing Siggy said that sparked a memory was something to the effect of counter flow would raise significant concerns regarding sustained flue gas condensation. Edwards had that covered by having an aquastat that would not allow the circulator to run until internal water temperature was hot enough to prevent flue gas condensation. I have to believe the counter flow would have increased the Edwards rate of fire-to-water transfer of thermal energy, just as does counter flow in a flat plate heat exchanger.

Looking back to look forward

More and more, we see manufacturers who offer additional components that can turn a boiler or tankless combi unit into a much more complete system. With engineered components, we contractors can have full confidence about them working seamlessly together. Many incorporate primary or secondary piping as an optional accessory. Life is good. 

You can reach industry icon Dave Yates at