Custom flue pipe retrofit works wonders in a tight space
Like many buildings of its era, the 47-year-old CHA Flannery Senior Apartments were due for a mechanical retrofit in 2009 when Primera-Hill landed the big Chicago Housing Authority contract. Just one of over a dozen CHA buildings in a group that were slated for an energy efficient makeover, Flannery posed a special challenge because of its narrow, existing flue.
With samples obtained and successfully presented to Primera-Hill, Steam Sales, an Oswego, IL manufacturer’s rep, was hired to supply the material for venting and to offer design assistance. Steam Sales solved a complex design problem when its president, John Greenwood, created with a simple, hand-drawn sketch on the spot.
Darren McCuaig, sales manager for Steam Sales, said “John had the general vision. A 15-in. diameter custom chimney liner - two side-by-side stacks - was the only thing that was going to work.” The complex boiler room retrofit needed to vent emissions from five heating boilers and two domestic water heaters - all into a narrow, 18- by 32-in. chase rising nearly 160 ft through the 16-story, vintage building on Chicago’s Near North Side.
Could the manufacturer that Steam Sales represents build a custom-size chimney liner? And could they prepare and ship proto-type samples right away, over the weekend?
FACTORY SUPPORTThe call went to Selkirk, a division of Hart & Cooley’s Commercial Products Group (CPG) in Carol Stream, IL.
“Selkirk had never built a 15-inch diameter flue gas pipe before,” said Greenwood. “Our design depended on having two side-by-side, 15-in. round stacks to fit into the existing 18- by 32-in. chase.” He adds, “We calculated that our design would work if Selkirk could make the non-standard 15-in. diameter liners,” which also had to include smaller, custom flanges, he noted. Fortunately for the project, there were green lights all the rest of the way.
Arriving at a specific plan to route breech pipe in the boiler room was the next big hurdle. Greenwood’s sketch involved multiple direction changes, rolling 90s into 45s, and changing direction and elevation all in the same movement.
“We did not want to relocate gas or electrical lines,” Greenwood recalled. “In the end, all we knocked out was a small section of wall in the boiler room about 24 by 38 in., and we relocated two, small, 1.5-in. diameter pipes there, too. Nothing substantial.”
CALCULATING TRICKY PRESSURESEmission pressures for five heating boilers and two domestic water heaters were handled by three separate draft controls, to split the positive and negative pressures of the two distinct hot water systems between the two flue gas stacks.
There was no way to combine all of these appliances into one riser and account for all of the variations in outlet pressures. Two overdraft systems onto one common vertical stack system were needed.
Stack system #1 needed to support two 2,000 Mbtuh heating boilers and two 750 MBtuh domestic hot water boilers. Two modulating overdraft dampers systems (MODS) were specified - one to isolate the -0.02 to -0.04 in. wc static pressures coming from the two, stacked water heaters; and a second MODS to maintain a constant -0.012 in. wc static pressure in the line coming from the two, positive draft 2,000 MBtuh heating boilers. These larger boilers were respectively equipped with balancing baffles on the appliance side of the MODS to provide the outlet pressures specified by the respective appliance manufacturers.
Stack system #2 was less complicated. A single MODS was needed to isolate the two 2,000 MBtuh heating boilers and one 1,500 MBtuh heating boiler. A total of three over draft dampers - all Model MODS with EBC30 modulating draft controls with XTP pressure sensors - were specified and used in the twin-stack project.
TEMPORARY STACK ARRANGEMENTA temporary stack arrangement was put in place to direct water heater flue emissions through a side wall for two weeks while Primera-Hill worked to upgrade the boiler room. The dual-stack lifting and securing operation took less than three weeks. According to Pat Klee, the field sheet metal superintendant, “The building was only off the main stack system for six weeks.
NINETY DAYS START TO FINISHWork on the Flannery building’s flue and boiler system began on June 15th and finished, on time and under budget for the design/install part of the budget, on September 15th. A large, Chicago-based energy savings and control company took on the performance contract for CHA, with Primera-Hill and its subs doing the work as outlined.
Klee ultimately raised 159 ft of dual stack Selkirk Model “G” U.L.-listed, single wall 304 stainless steel chimney liner, of the custom 15-inch-diameter size, inside of the narrow, 18- x 32-in. chase opening.
According to Primera-Hill senior project manager Mike Slazas, a rig on the roof lowered stack hoisting equipment down the chimney. Internal lifting hooks added to the first piece of liner allowed the installation team to build and lift a 5-ft-high, side-by-side, dual unit of chimney liner. Each additional 5-ft pair was built and connected to the one above it. The growing section was lifted and pulled upward, one additional dual-unit at a time, to make a full, 70-ft section of chimney liner.
The first, long section of dual-stack liners was lifted the rest of the way and anchored at the top and at the middle of the chimney. Then, a second section was similarly constructed, lifted, and joined to the first section at the midpoint at the ninth-floor level of the Flannery building, thus completing the build-and-hoist job.
When asked about the degree of difficulty of the CHA Flannery Senior Apartments, John Greenwood rates the job as a seven on a scale of one to ten. “We’ve done multiple stacks before,” he says, “but this was the first time we ever had two stacks in a single chimney with a special diameter of liner.”
“I love it when a job comes together,” Greenwood says of Flannery. “Because we had made samples in advance, our specifying the custom-size liner did not add any lead time to the project. We have Selkirk to thank for that.”