VRF an Efficient, Adequate Zoning Solution for Methodist Church
St. James United Methodist Church’s mixed-use nature required a versatile comfort fix
St. James United Methodist Church in Raleigh, North Carolina, is blessed, architecturally speaking. Stained glass, vaulted ceilings, and curved gables give the impression of age beyond its actual years. The church, which was built in the 1960s, includes a main sanctuary, offices, numerous classrooms, and a small chapel.
Until 2014, almost the entire structure was served by an underground network of steel spiral duct for heating and cooling. As time passed, and the duct deteriorated, it wasn’t uncommon for the system to flood after a heavy rain. This created a rash of problems, not the least of which was poor IAQ.
The south side of the building, including the chapel, a kitchen, and cafeteria, was most affected by the flooding. The church moved quickly to abandon the ductwork serving those locations. They explored a number of different options in the spring of 2014, hoping to solve the issue before North Carolina’s stifling heat and humidity set in.
Their search put them in touch with Alan Stephens, owner of Raleigh’s Eco-Green Air. Though the company installs and services everything from boilers to geothermal, its specialty is mini-split and variable refrigerant flow (VRF) technology.
“Mini-splits make up about 75 percent of our business,” said Stephens. “Last year, we installed 200 units.”
FLEXIBILITY IS KEY
Because of the mixed-use nature of church buildings, broad range of room sizes, and long vacancy periods punctuated by short stints of high occupancy, many congregations, especially those exploring retrofit projects, have turned to mini-split heating and cooling technologies in the past decade. More recently, commercial VRF systems have added even more capability, simplicity, and efficiency to the already vast number of possibilities offered by ductless technology.
When Stephens visited the site for the first time, it was quickly apparent that the system tapped for the south corner of the church would need to boast extensive flexibility.
The chapel’s vaulted ceiling and continuous stained glass was a limiting factor. The cafeteria was a challenge, too. One wall is fully flanked with full-height windows while another side is open to the kitchen. The third wall is composed of wooden doors that open to the hallway. The remaining wall is made of block and separates the space from an adjacent classroom. The hallway between the cafeteria and the chapel also required additional heating and cooling.
“Based on space limitations and the block construction, I knew ductless would be a good solution for the retrofit,” said Stephens. “Given the difference between the rooms, we needed a variety of evaporators, so I bid the project based on a VRF design.”
With help from Jackson Willis, Mid-Atlantic sales engineer for Fujitsu General America Inc., Stephens designed a system around Fujitsu’s Airstage VRF technology.
A pair of 2-ton wall-hung units was placed above the entry doors in the rear of the chapel while a floor-mount unit was hidden behind the organ in the front. A 2.5-ton ceiling cassette unit now serves the kitchen and cafeteria. A smaller wall-hung unit heats and cools the hallway.
A single 8-ton condensing unit mounted on the roof serves all five indoor units.
“This was the first VRF system we’ve installed,” said Stephens. “We’re a Five-Star Fujitsu dealer, so the Airstage system was the natural choice when we began looking at VRF.”
The congregation’s main concern during the installation was that the noise level from units in the chapel would be distracting during service or prayer. As it turned out though, the sound levels were almost unnoticeable and far below that of the original ducted system.
Everyone was happy with the Airstage system. Throughout 2014, the areas it served were quieter and more comfortable than the rooms still conditioned by ductwork of various ages. Church members expressed keen interest in using the same technology as part of a large renovation of the building’s classroom wing. Early this spring, Eco-Green Air hired more technicians and tackled phase two. The company now has 12 employees and is still growing with awareness of ductless technology.
This past winter, Stephens worked again with Willis to design a VRF system to serve 12 rooms. The classrooms and library are served by compact ceiling cassettes. A small wall-hung unit cools a remote server room. All indoor units tie to one of two 8-ton Airstage condensers on the flat roof above.
Because of limited ceiling space, line sets were run across the roof. Each line is double-insulated, painted white, and suspended above the roof deck. One roof penetration — sealed and sleeved with polyvinyl chloride (PVC) — was provided for each room.
The installation drew to a close in late April. Willis visited the site to help tie the new Airstage units into the Fujitsu control installed during phase 1.
“Jackson was a great resource during design and commissioning,” said Stephens. “These systems are very simple to operate, but, being that we hadn’t used them before, there was a learning curve. He got us over that quickly.”
The main Airstage central remote controller, located in the cafeteria, allows all of the indoor units to be operated from a central location. Individual room control is accomplished simply via a wall-mounted controller.
“Eco-Green Air will soon be connecting a bit more indoor equipment to the phase-two outdoor units,” said Willis. “Right now, there’s only 6 ton of load on each, so they’ll be adding three more ton to each system in order to maximize their capacity.”
“Because of zoning and the assumption that not all spaces are simultaneously going to demand 100 percent, these systems can be designed for an approved oversize of 130 percent,” explained Stephens.
In a newer section of the building, two conventional split systems with vertical air handlers are nearing the end of their service lives. These will be replaced with Fujitsu’s newly developed vertical air handlers. The new units will serve the existing in-wall ductwork.
The new systems will serve a choir room, bathrooms, a nursery, and a few small classrooms much more efficiently in both summer and winter.
Church members have been pleased with the new system, and everyone is glad that a much larger portion of the church will have real air conditioning this summer. If last winter’s propane bill was any indication, the savings should really stack up over the following year when a much bigger chunk of the property will be served by VRF.
“St. James Methodist has been a continuing source of work for us,” said Stephens. “We initially got the job in part because of the outstanding warranty we were able to offer through Fujitsu. Adding VRF to our product offering has definitely allowed us to expand.”
The new systems have been so well received that a third phase is planned for 2016. The plan is to install a 10-ton Airstage system equipped with heat recovery to serve the church’s largest hall, main kitchen, and some small office spaces.
Publication date: 2/8/2016
Information courtesy of Fujitsu General America Inc. For more information call 888-888-3424 or visit www.fujitsugeneral.com.