Mack Trucks Corporate Headquarters, Allentown, Pennsylvania

Hot Water Heating System

Two 1000 kW electrode hot water boilers were used to provide hot water to a hot/chilled water HVAC system for this 265,000 square foot facility. Hot water was circulated to the air handling equipment and to the 5/16" diameter panel coils n the ceiling of this six-story building. Hot water was required when temperatures dropped below 43° and chilled water was required when temperatures exceeded 55°. The system was designed to run 24 hours a day, seven days per week.

A management firm was contracted to improve efficiencies at this facility. One of the first cost savings steps was to reduce the amount of time these 1000 kW boilers were being used. Additionally, a water treatment system would allow the boilers to run more efficiently throughout the season.

The hot water boilers utilized ceramic electrodes to create a resistance type heating system. Water temperatures were designed to enter the boilers at 170° and heat to 180°. Conductivity was maintained to insure maximum performance. Up until this point, the electrodes were pulled annually and dipped into an acid solution to remove scale that had built up in the system. This was a two-day process as the scale collected on the electrodes was estimated to increase thermal resistance by as much as 20%. Over the course of the heating season this was estimated to increase the energy costs by as much as 35%.

In October 1996 the ED 2000 Anti-Fouling System was installed on the 8" feed pipe to both electric boilers. During the course of the season only one boiler was used on an as needed basis. The boiler ran at 100% efficiency. When the electrodes were pulled in September 1997 there was very little fouling. A light wash was required and they were placed back into service that day. The elimination of the scaling on the electrodes reduced thermal resistance and substantially improved the efficiency of the boiler, thus allowing the utilization of one boiler instead of two.