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Heating Issues – Solving the Client Equation

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After 12 years in business, one of my biggest fears is still running into a technical problem that I could not resolve. It’s yet to happen, we have somehow managed to tackle all the mechanical problems thrown our way.

The curveball that I did not anticipate was the “people” problems that you run into. Everyone has a different viewpoint and way of looking at things. I have found these problems to be much more difficult to resolve and requires a different skill set and proficient communication skills to fix.

Here’s What Happens
Every fall, as the weather begins to change, we have chilly nights where the temperature dips into the 30s, but mild, sunny days where the temperature quickly rises into the 60s. The call will come in from a client: “That new boiler you just installed is not working. We have no heat! Get someone out here as soon as you can.”

Here’s how one call went. We had just installed a new condensing gas boiler and indirect DHW tank. It replaced a 40 year old cast iron beast and tank-style water heater. It was tied into an existing high mass radiant floor heating system. The boiler had an integral outdoor rest control and we had the curve dialed in to an optimal setting.

The morning after the first cold night, the client called me with a “no-heat” complaint. I decided to handle this one myself as I was sure this was not a mechanical problem. The first thing I noticed when I walked into the boiler room was that the pipes were hot. The boiler had just cycled to satisfy a call for DHW, so I knew the boiler was working. The house was split into three zones. Two of the zones were satisfied. One zone was set for 70 and the actual temperature in the zone was 69. My first thought was that this was hardly a “no heat” situation.

I checked to see that the thermostat signal was reaching the zone control and that the zone valve had opened. The zone pump was on and boiler pump was on. The modulating boiler was operating on low-fire and the supply water temperature was about 90. As the ambient temperature was now 53, this was dead on to the reset curve we had selected. The system was operating exactly as designed.

I tried explaining this to my client, but he was having none of it. His elderly mother lived in the house and he wanted her to be warm. After failed attempts at trying to convince this homeowner that this system was operating properly, I gave in. Against my better judgment, I bumped up the reset curve to provide more heat into the radiant system. The boiler responded and settled in to a supply temperature of 105. Everyone was happy and I packed up and left.

The chilly morning turned into a beautiful fall afternoon with temperatures peaking in the mid-60s. Then I received the call. The client called back to say that there was a problem. The thermostat was still set to 70, but the indoor temperature was now 76. Of course it was! We had injected way too much energy into the high mass slab. Between the time lag of the high mass concrete slab and the solar gain from the sunny day, the indoor temperature had overshot the thermostat set point.

I returned to find the boiler off and the pipes cold. I returned the reset curve to its previous setting. The boiler settings were right the first time. My failing was not technical, but in my ability to explain the operation of the system in a way my client could understand.

Two Solutions
Two technical solutions come to mind. One would have been to use a more sophisticated control that employs an indoor sensor to provide feedback to the boiler control and adjusts the reset curve accordingly. This would take into account the slow response of the concrete slab, as well as internal loads created by people, appliances, and solar gain.

One boiler we use has a simple way of dealing with heat loads at the upper end of the reset curve. It uses a “boost” feature that can be activated if desired. If a heat demand has not been satisfied after a programmed period of time, typically set at 20-25 minutes, it boosts the supply water temperature until the heat demand is satisfied. It then reverts back to the programmed reset curve. This is a simple solution to this dilemma.

I wish I had done a better job explaining how the new system would operate at the time it was installed. Since the new system operated differently than the old system, the client incorrectly concluded it was not working properly. The issue was strictly communication, not mechanical.

Dan Foley

Posted In: ACCA Now, Hydronics

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