Community College Shores Up Its Boilers
While the beautiful grounds of SCC are truly unique, the issues of deferred maintenance and improper system design are all too similar to other colleges around the country. By 2003, over 40% of SCC's boilers had completely failed or burned out. Contributing to the problem were small boiler rooms plus clogged ventilation and combustion air louvers, which caused the boilers to suffer from incomplete combustion, flame roll-out, overheat, and flame impingement conditions.
The design/build firm of McKinstry Co. was contracted to review the problem, and its engineers subsequently helped the school obtain a new system that improves boiler operating efficiency by more than 20%. Additional energy improvements are guaranteed to provide more than $80,000 in annual utility savings and qualify the school for gas and electric utility rebates of nearly $90,000.
One of the biggest benefits to the college is that the guaranteed annual utility savings will cover the principal and interest on a 10-year low-interest loan from the State of Washington treasurer's office. Only 35% of the project's $1.2 million cost was funded from the college's capital budget.
Getting StartedSCC's main challenge was - and is - maintaining its equipment. Compared to similar colleges, SCC has a large number of small buildings, and a very high concentration of HVAC and boiler equipment. The college's 21-plus boilers are spread out over 13 boiler rooms, and there are over 50 HVAC units (e.g., air handlers, condensing units) in various campus buildings. Relative to the modest size of the maintenance staff, it is difficult to properly maintain the equipment on the campus.
The old boilers had been installed in 1985, and the previous design called for staging multiple, small cast iron boilers to meet the load. The existing boilers had very low return water temperature, which caused condensation problems at the flues and inside the boilers. This condensation corroded the sheet metal skins of the atmospheric boilers, which had no combustion fans. Subsequently, if the combustion air intakes became dirty and the exhaust fans failed, incomplete combustion at the boilers resulted, overheating the rooms.
King Tang, P.E., project director at McKinstry Co., noted, "We worked with 19 cast iron boilers in six of the boiler rooms, and these were the worst of the worst. A lot of the boilers actually had combustion problems in that they were starving for air. In cases where the boilers were still functioning, carbon monoxide levels in some of the boiler rooms were very unsafe, which is an efficiency issue and, of course, a cause of health and safety concern."
Brent Irwin, P.E., senior engineer with McKinstry Co., added, "Probably half the boiler rooms were adequately sized but of the other half, three or four of those rooms were just extremely cramped and difficult to get into and out of and obviously maintain, because there's very limited clearance and in some cases, not enough clearance to meet today's manufacturer requirements. A lot of the rooms had inadequate combustion air openings."
McKinstry Co. clearly had its work cut out for itself. In addition to the project having to be completed under tight budget constraints, the compressed time schedule meant there would be little "wiggle room" during construction. Final approval of the project was not received until late June 2003, and the new system was required to be operational by the beginning of the new school year, which was only 10 weeks away.
According to Randy Stegmeier, SCC's director of facilities and capital projects, it was the team approach - combining the focused efforts of the design/build contractor, the knowledgeable local rep agency, and key manufacturers - that made it possible to complete the job on time. "The multiple project design meetings, full cooperation of everyone involved, and routine jobsite visits all played a critical role."
The Choice Is MadeMany of the boilers rooms are sandwiched between classrooms and did not meet today's fire code. "The code issues were a bit of a challenge," said Irwin. "It was very clear that the existing rooms were not meeting current code for one-hour ratings, not by a long shot. We helped the college navigate the rather stringent fire code and brought them up a long way."
To that end, the McKinstry team worked with the City of Shoreline's Building Department to improve these rooms. Improvements included the installation of new fire doors, fire dampers, and the sealing/caulking of existing wall penetrations to improve the integrity of the room envelope. Increased combustion air was also brought in through ducted supply, and ventilation air was increased to ensure the boiler rooms do not overheat. Many of these new combustion and ventilation air ducts were also provided with rated enclosures to protect the integrity of the rated boiler room enclosure.
Choosing which boilers to install was not a simple task, as Greg Angus, SCC's maintenance supervisor, initially wanted only cast iron boilers as replacements for their perceived advantage in lower maintenance. "I was concerned about the complexity of the newer boilers compared to what we had before," said Angus. In addition, the project manager for SCC wanted to evaluate very high efficiency condensing boilers.
"We went through a selection process for the boilers, looking at several different technologies that included cast iron, condensing, and copper fin design. Our selection process compared total installed costs, footprint, ease of routine maintenance, and energy efficiency," said Tang.
After reviewing all the options, McKinstry Co. and SCC decided on copper fin boilers manufactured by Laars. The low lifecycle cost of copper boilers was the main reason behind the decision, because while no boiler can work trouble-free without maintenance, the newer design of copper fin boilers appeared to be the best choice. In addition, the copper boilers could utilize most of the existing flues, so the installed cost was far less than forced draft cast iron and condensing boilers.
Angus still wasn't completely convinced that the new boilers would be easy to maintain, so he arranged to take a factory tour of the Laars facility in Moorpark, CA, to review the equipment. "We took a tour of the factory, so we could see the manufacturing process of this new product," said Irwin. "We could see the copper boilers had some very nice maintenance features, and for the maintenance supervisor, that was a big selling point."
These maintenance features included the fact that a lot of the parts on-board the boiler were non-proprietary, so it would be possible to purchase off-the-shelf replacement parts. Also, it was easy to access the control panel and run diagnostics from a single access point. In addition, these new boilers were stackable. By stacking the boilers, McKinstry Co. would be able to eke out a little more maintenance space in the fairly cramped boiler rooms.
New Equipment Is InstalledMcKinstry Co. ended up replacing 21 of the existing boilers with 15 copper-fin low-NOx boilers manufactured by Laars. "It was nice that we were able to downsize the quantity of boilers," stated Irwin. "In several cases where there were four existing cast iron boilers in a room, we went to two larger copper boilers. That downsized the footprint quite a bit, and we were able to re-use a lot of the existing pads, so there weren't any major structural changes."
The final boiler selection included stage-fired boilers (in sizes ranging from 500 to 1,000 MBtuh) and fully modulating boilers (1,200 Mbtuh). The ability to stage or modulate individual boilers enables the systems to efficiently meet varying heating system loads.
The existing distribution system was upgraded as well. The old system employed a single loop, single pump configuration, while the new system utilizes a primary/secondary loop with dedicated boiler-mounted pumps. All the main circulation pumps were also replaced.
New boiler controls were also required, as SCC's existing BAS could only monitor the boilers but not actually control them. Now each boiler has an on-board controller in order to maintain minimum boiler temperatures, reset temperatures, and to fire only the required number of stages, or boilers, to meet the demand.
Outdated pneumatic HVAC controls were also replaced with new DDC for more precise system control and temperature accuracy. This upgrade provided major boosts to overall system operating efficiency and the greatest reduction in energy consumption. The boiler controls are factory-equipped with alternate start/stop and a setback capability to provide additional energy savings.
The installation went smoothly, with only a few glitches that took place at start-up. As Irwin noted, "On the controls side, the BAS was trying to do a little more than it should've been. Basically there were some overlapping controls that we needed to clean up so that two control systems weren't trying to tell the boilers to do the same thing."
Several control and HVAC-related problems that affected boiler operation were caught during the first heating season. The team found that the outside air temperature lockout point that locks out the boilers during warm weather was mistakenly changed at SCC's BAS. "As soon as spring hit and the temperatures started going up, the outside air trip point turned off the boilers," said Angus.
The outside air trip point was increased from 58°F to 75° to solve the problem. The factory also performed a six-month inspection. The inspection team found that frequent cold starting of the boilers had caused some condensation, which in turn, caused some igniters to fail prematurely. The team also found that the existing HVAC units and the heating loop were equipped with only two-way valves. In that configuration, if all the HVAC units were not calling for heating, the HVAC system secondary piping system would not recirculate water even when the primary boiler pumps and the secondary heating water pumps were running, and the water in the secondary loop could cool down.
Based on these observations, the team performed a thorough cleaning and replaced the igniters at several boilers. As an added assurance to prevent condensation inside the boilers, the boiler manufacturer's representative, Columbia Hydronics, also provided three-way valves at the boilers, which will maintain a boiler return water temperature above 130° whenever the boilers operate.
Although every project has its idiosyncrasies, Angus believes that there are many positives that came from this project as well. "Initially we just had boiler money, and McKinstry was able to maximize the energy savings and increase the size of the project. That process was very, very good. This allowed us to bring forward needs that no one would ever pay attention to, such as lighting issues and getting rid of all our pneumatic devices."
Those changes alone will bring about much-needed energy savings, as well as contribute to the ongoing improvement of SCC's facilities. ES