This house call was straight out of a modern-day ‘Dragnet’

BY PAUL ROHRS,

contributing writer

I got the call on Thursday. It wasn’t good. The house was overheating, and the homeowner’s relatives were coming over on Saturday. The lady of the house was rattled. I understood. She started talking about her soufflé and the dinner party, but I said, “Just the facts, Ma’am.” She understood. I made a note of that.

My name is Friday, and I wear the hydronic contractor’s badge. My sidekick’s name is Tuesday. He is a good man, except for being late every other Wednesday. He and I set out to the address the lady had given us.

We knocked; she answered. This is standard operating procedure for us. The house was normal enough. It was built in the 1950s. The homeowner’s name was Sarah. She said she was sweating, because the boiler wouldn’t shut off. The house was hot, so the story checked out. The boiler was in the basement; the original had been replaced with a modulating and condensing boiler. She took us down to the basement. I tripped over something; it may have been Sarah’s cat. I made a note of that. Tuesday brought down some lights and some tools, and we started looking for the culprit.

The newer mod-con boiler looked okay on the outside. I made a note of that. We pulled the cover off the boiler and started our forensic search. This was a constant flow system. When it got cold enough outside, the zone pump turned on and started redistributing heat throughout the house. When the thermostat called for heat, it signaled the boiler to fire. The boiler checked its outdoor sensor and generated a target water temperature. This temperature was constantly being monitored, and the boiler’s firing rate would typically modulate until it reached its target temperature.

When the system reached its target temperature, the boiler cycled off, but the zone pump continued to extract heat from the loop and distribute it all through the house. As the house lost heat and the temperature dropped below the thermostat’s differential, the thermostat called for heat, the boiler fired again and modulated up towards the target water temp.

The zone pump was running and sending hot water out to each of the radiators. We made a note of that. There was vent pipe; we were relieved. Relief valve, safety devices, thermometers, circulators, flanges -- they were all there. We had good gas pressure and did not exceed the allowable pressure drop through the gas valve on startup. The rectification probe was rectifying. There was a strong micro-amp signal; we were pleased and knew we had a good earth ground. The system pressure was good.

I disconnected the thermostat. Nothing happened. The boiler continued to run and then shut off after achieving the target temp. The next safety device was a manual reset high limit, and it would have locked out the boiler if it had shut down after surpassing the target temp.

Tuesday was sweating. He should have been; it was getting hotter. We had to find out why the boiler wouldn’t shut off under normal operating conditions. The zone pump was putting the boiler’s heat out into the zone, even though the house didn’t need it. The thermostat wasn’t calling for heat any more. The target temp didn’t require the full firing rate; it didn’t even need the minimum firing rate. There was no buffer tank. We made a note of that. The boiler’s minimum firing rate of 20% was still providing too much heat and was running up on its limit, and the on/off cycle would continue. We were on to something, and we knew it. Hot house, company coming, soufflé in the oven, Tuesday sweating, thermostat not ending the boiler’s call for heat; it was all becoming clear.

Most of the wiring looked good. We found an extra wire in the boiler room that led down the hallway. Strange, I thought. I asked Sarah what it was. Her face contorted. Her soufflé fell. She said she was going to try her torte recipe. We were getting nowhere with Sarah; she was hot, mad and had company on the way. We had to solve this caper, and fast. Family coming over, fallen soufflé, house getting hotter; we understood.

We still needed to find out where that extra wire went. Who put it there? What was it for? Why? These were our questions.

We started tracing down the extra wire. We followed it down the hallway. It led into Sarah’s son Mitch’s room to the “Pre-Out Terminals” on a new Fender amplifier. The amp was turned on. You could hear the hum of the amp wafting through the room. The volume was turned up. We now knew where the extra wire went, but why did it lead back to the boiler room?

We went back to the boiler room. We had to; that’s where the cable started. The amplifier cable led to the boiler’s control board. The two wires were plugged into the boiler’s external modulation input. Some boilers offer a feature that allows external controls to ramp the boiler’s firing rate up or down. The amplifier volume was now controlling the modulation and the boiler’s firing rate.

Turns out that Mitch had a few too many energy drinks. He had plugged his amp into the boiler. He had turned the amplifier up while playing Deep Purple’s, “Smoke on the Water.” Good tune. The kid had taste; maybe it was a tribute to steam boilers. We disconnected the amp from the boiler. The boiler modulated down and shut off. Caper solved.

We told Sarah what we found. She mumbled something about a soufflé and Mitch needing to wait till his father got home. She thanked us. We understood. Company was arriving; it was time for us to go.

Another case solved. Tuesday was still sweating; I made a note of that. My name is Friday. I wear the badge.                   

Paul Rohrs is a radiant heat contractor in Lincoln, Neb. Paul can be reached at paulr@biggerstaffradiant

solutions.com.