Increases in energy costs are leading many building owners and facility managers to look for more cost-effective ways to heat and cool their buildings. Apartment buildings and student residences currently using electric systems are prime candidates for conversion to hydronic (warm water) heating systems, and sometimes even water-based cooling systems.
In 2016, Wilfred Laurier University, in Waterloo, Ontario, opted to retrofit the electric heating systems in two of its existing student residences. The school went with hydronic heating and cooling for one of the buildings and hydronic heating for the other. (The latter continues to use its existing, forced-air, DX cooling system.)
Johnson Controls was the general contractor for the project, with DEI & Associates performing the mechanical system design and Modern Niagara completing the mechanical installation.
The Bricker Residence is a nine-story, apartment-style residence with four-bedroom suites that feature a common kitchen, bathroom, and living room.
The project retrofit was designed to have fan coil units located in each of the suites, with a new piping system to supply heating and cooling water in a two-pipe switch-over system. The required flowrates for the fan coil units varied between 4.7 and 13.5 gpm, and pipe size calculations were based on a Delta T of 10°F for the cooling system.
The Bricker building included new boilers and chillers and a main loop installed on the ground floor, with the majority of the piping installed in the ceiling space of the main hallway. PEX risers were installed between floors to connect to each of the fan coil units. The PEX pipe was sealed with a fire-rated sealant for all floor penetrations and through any fire-rated walls. Each floor and ceiling penetration included a pipe bracket to minimize pipe expansion between floors.
The Grand River Residence is part of Laurier’s satellite campus in Brantford, Ontario. This five-story building houses 150 students on floors three through five, with classrooms and administrative offices on the first two floors.
This project was designed to have hydronic reheat coils added to the existing VAV boxes already installed in the offices, classrooms, and suites, while the existing forced-air cooling system was kept intact. Due to the configuration of the building and the various locations of the VAV boxes, each floor had its own main loop that was fed with larger-diameter risers.
Smaller-diameter PEX branched from the main loop on each floor to feed each of the reheat coils. These reheat coils varied in size and capacity to match each room’s need.
Flow rates for the reheat coils ranged from 1.4 to 9.7 gpm, with a majority of the coils landing in the 2 to 4 gpm range. The system was designed using a supply water temperature of 150°F and a Delta T of 20°F.
One of the key challenges with these two projects was to have the installations completed during a four-month period (May to August) when students were on their summer break. With such a tight window, there was no room for delays or project extensions.
This tight timeline was a key factor behind the decision by mechanical contractor Modern Niagara to use PEX instead of a rigid pipe system. Another strong impetus was the fact that both structures were existing buildings. As a result, the flexible nature of PEX proved to be advantageous in those areas.
The project incorporated a variety of pipe diameters up to and including 3 in, with larger sizes being black iron. The pipe manufacturer’s design department tackled the job of creating the piping layouts for both buildings to ensure the sizing and flow rates met with the engineer’s original design calculations and requirements.
Prior to the start of the PEX installation, Modern Niagara installers were trained by The Morgan Group to ensure everyone was familiar with the use of PEX expansion tools. Modern Niagara was familiar with PEX pipe and cold-expansion fittings from past projects, but this was the first job using larger 2-in and 3-in PEX pipe and fittings.
The installers transitioned between black iron pipe and 3-in PEX with brass threaded transitions and/or flange kits. Flange kits were also used for connecting the PEX pipe to some valves and circuit setters.
Most of the horizontal PEX installations included PEX support rails to allow for fewer hanging brackets and to help minimize pipe expansion. By using the PEX support rails, the installers were able to support the pipe approximately every 8 ft.
Where possible, larger connections were assembled at the bench level, and final connections were made in the drop ceiling spaces and wall cavities. The majority of the 1-in and larger pipe sizes used 10-ft and 20-ft straight lengths of PEX — the smaller sizes connecting to fan coils or VAV boxes used flexible coils of PEX to minimize the number of elbows and other connections.
Upon completion of each installation, the system was filled and pressure-tested to check for possible leaks, and the piping system was insulated before reinstalling the ceiling panels and sections of drywall.
The system design and the efficiency of the installation crews ensured that both projects were completed on schedule and the buildings were ready for the fall semester.