Want to Get Paid? Check Your Work
To be sure the contractor would see a note in the specifications covering an addition to one of our plants, the following sentences were printed in capital letters: “When a contractor notifies the plant that his work has been completed, and before final payment is made, all of the work by the contractor will be surveyed to be sure it complies with the plans and specifications. The plant will be surveyed by a representative of the plant and the contractor or his representative, and all installations will be compared to the plans and specifications.”
During the aforementioned survey, we followed a long steam line that lead to a small, isolated heating unit. A few feet before the heating unit, a steam trap had been installed on the line for the removal of condensate.
I was very surprised to see how the installer disposed of the condensate. There was no drain in the immediate vicinity. Instead, his solution was to connect the condensate drain line into the steam line between the steam valve and the coil.
I have no idea if the installer was ignorant, lazy, or both. Needless to say, his solution was not approved and changes were made before the work was approved for payment. The moral of the story: Always survey any new work before issuing payments.
Kenneth E. Robinson, CIH
It's a Dirty Job …
The office in which I began my engineering career was plagued by HVAC woes. The water-cooled chiller and cooling tower were over 20 years old. During the summer, it was warm in our office as well as in the adjoining mailroom, which was served by the same system. During the heating season, the warm air supply did not deliver its design cubic-feet-per-minute capacity to the heated spaces.
Renovations had been done over the years and partitions built in the mailroom. The hung ceiling was used as a return plenum for the office and mailroom, and it was discovered that the openings in the wall above the ceiling leading to the equipment room in which the air-handling unit (AHU) was located were not large enough to return the air to the AHU. A large louver was installed in the equipment-room door to facilitate the air return. The supply registers, diffusers, and return registers were rebalanced to ensure each space was supplied and exhausted adequately.
Next, the existing water chiller was examined. It was determined that the delta-T across the chiller was closer to 15°F instead of the design temperature difference of 10°F. The existing chiller and tower were replaced with a new split-system air-cooled direct-expansion system that included an indoor AHU in the equipment room and a remote air-cooled condensing unit on the roof above the mailroom.
When the new system was placed in operation, we still had insufficient air supply. The units were new; the refrigerant piping was properly sized, installed, and tested; filters were replaced; and air quantities were balanced. What could be wrong?
Heating coils had been placed downstream in the supply-air ductwork when the original system was installed. Because the new system had the same capacity as the old system, no design changes were made to the existing supply-air ductwork.
Finally, the maintenance department was asked to vacuum out the coils. When the maintenance man was done dislodging 20 years worth of buildup in the coils and ductwork, he was shaking his head in disbelief. He instructed us to cover all of the diffusers and supply registers with cheesecloth before turning on the AHU. Even though the cheesecloth captured dirt, both rooms ended up covered with soot. This happened several times over the next few days until all of the dirt was dislodged and blown out through the air outlets. Afterward, the units worked perfectly, delivering design air quantities and satisfying heating- and cooling-load requirements.
Salvatore Zuccaro, PE
New York City Department of Environmental Protection
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