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 WE NEED HELP with a number of problems left over from a new addition,” the homeowner told me over the phone. “It’s a slab on grade radiantly heated room that overheats, and it takes forever for us to get hot water in the master bathroom.”Further conversation revealed that the builder and his mechanical subcontractor had vanished into thin air after having made numerous attempts to correct the problems. If nothing else, the owners sounded pleasant over the phone and I wanted to see how the radiant system had been installed. Upon arrival, I found the owners had been told that their oil-fired boiler had to be relocated to within a few feet of the addition’s radiant system in order to work properly. The mixing valve serving the floor circuits was allowing 150°F water to pass into the concrete slab, which was causing it to overheat the room. A picture taken during construction clearly showed the tubing was installed on 9-in. centers. They now had a long wait for domestic hot water from the boiler’s coil. This was understandable, given the fact that the boiler was no longer in the basement directly under the master bathroom risers — and that the 12-in. copper hot water line running from the coil was buried in the concrete slab without being insulated. The boiler exhausted through a power venter to a sidewall. A great deal of soot residue was evident around the boiler’s flue and had been ground into the new concrete floor surrounding the boiler. I checked the exterior termination and found heat damage to the vinyl siding and that soot had darkened a substantial area. There were numerous fresh-air openings through the sidewalls, but the homeowners told me that there had been none at first! Not only would this boiler have been starved for proper combustion air, the power venter would have ensured negative pressure within this attached mechanical shed.
The oil tank was installed (well, stuffed would be more accurate) inside this all-too-small shed, which caused it to be adjacent to the boiler and well within 5 ft. of the burner, a National Fire Protection Association code violation. The power venter was suspended over the oil tank and had a penchant for tripping off on overload, which required crawling over the tank to access the reset button.
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The owners complained that they could no longer keep their windows open during the summer due to the exhaust fumes being drawn into the home from the lower level flue termination. They did not have air conditioning.
