The Longueuil Courthouse opened its doors in 1987 and brought together all the jurisdictions of the Superior Court and the Court of Québec. With a total area of 169 500 sq.ft, the building houses hearing rooms and administrative offices on 2 floors. The building is managed by Société Immobilière du Québec (SIQ).

The building’s mechanical systems were designed to allow optimum equipment use and maximum heat transfer recovery. The system is composed of a group of 9 air conditioners with a unit capacity of 240,000 Btuh (70kW), which serve the indoor zones and 20 heat pumps of 126,000 Btuh (37 kW), which supply the perimeter zones. These heat pumps are operated in cooling mode in summer and in heating mode in winter, depending on the demand.

The closed loop equipment is connected on one side of the plate-frame heat exchanger to a water tank and the heating system .The cooling towers are on the open loop side of the heat exchanger. The energy is dissipated by 2 cooling towers of 150 tons for a total
capacity of 300 tons, with recirculation flow of 450 gpm per tower.The towers operate year round down to an outdoor temperature of approximately – 10°C

 In a heating period corresponding to outdoor temperatures below –10°C, if the contribution of the internal zones and the energy stored in the water tank is insufficient, it is then necessary to provide an energy contribution through auxiliary gas boilers. This period only represents about 400-500 hours per year.

Problem
A gradual reduction of the plate-frame heat exchanger’s energy efficiency resulting from clogging the surfaces was observed, endangering the building due to the water temperature rise. The necessary cleaning operations were also increasingly long and frequent, with use of acids.This added to the buildings operating cost along with higher energy consumption.

Solution
A Vortisand sidestream water filter, Model AWT1-20-SP with 60 gpm filtration capacity was installed on the condenser water loop,making it possible to optimize the plate-frame heat exchanger’s energy performance.

No more loss of pressure on the mixed water side and a lower temperature differential (3°C instead of 4.5°C) were observed. The plate-frame heat exchanger has operated continuously according to its original design & performance, without the need for cleaning. Optimal performance has been maintained since the Vortisand was installed.
The following main points have been observed:

• An average operating temperature reduction of approximately 2°C in the 2 water circuits.
• Projected energy saving of 6% (11.4 kW) on the electrical consumption of the air conditioning units and heat pumps and 0.1 kW on the cooling towers.
• The plate-frame heat exchanger’s coefficient heat exchange has doubled.
  An overall saving of 11.5 kW has been calculated for an annual
  savings of $5,240, i.e.:

1) Power saving: $1,650
2) Saving of kWh: 8 400 hrs x 11,5 kW: $3,590
The total building optimization program reduced the chemical treatment usage, labor and downtime to clean the plate-frame heat exchanger and the entire condenser water system. Proper sidestream filtration allowed the building to operate more efficiently by removing
all the suspended solids down to 0.45 sub-micron size range. Payback period is less than 2 years.