Sometimes change isn’t a bad thing.
That certainly was the case with the Monarch Plaza office building in Atlanta. The 16-story structure was built in 1983 and age was starting to catch up with it, specifically when it came to energy and water costs.
“The building was constructed with 1983 technology and wasn’t energy-efficient anymore,” Monarch Plaza Chief Engineer Ralph Kowalke says.
Monarch Plaza is part of the Monarch Centre property on Peachtree Road in the center of Atlanta’s trendy Buckhead neighborhood. Monarch Centre features two Class A high-rise office buildings.
With sustainability at the forefront, Monarch Plaza ownership set out on a progressive multi-phase retrofit that resulted in the nearly 370,000-sq.-ft. facility earning the U.S. Green Building Council’s LEED Silver designation. Both the Monarch Plaza and the Monarch Tower buildings — connected by a covered walkway — have Silver certification.
One of the chief goals of building management is to make sure tenants are occupying space that is properly climate-controlled no matter what time of the day it is.
“There are tenants that work after hours,” Kowalke says. “With the chillers that were in there before, we had to run a lot of flow. For only one tenant we potentially had to run seven floors just so that particular tenant could have after-hours air conditioning.”
The solution to the efficiency quandry was to specify two varying-size Trane chillers. “We wanted dual sizes,” Kowalke says. “We wanted one that could go down to a lower capacity and one larger chiller. The smaller one is a three-stage chiller that can unload to 118 tons and has an overall rating of 317 tons. We also went with a two-stage chiller that goes up to 633 tons.”
The decision was made to change the chiller plant from a series to a parallel system. “We gutted the plant and took all the previous piping out,” Kowalke explains. “A heat exchanger was put in back in 2006 and we were able to keep that. We expanded the heat exchanger to handle the higher capacity coming online in the building.”
Three chillers are in the building. Kowalke notes one of the old series chillers was retained. “The old series (York) chiller isn’t necessarily efficient, but it works well in the setup we have,” he says. “It doesn’t get in the way and it’s a great idea to keep as an emergency backup. We’ve already used it due to maintenance and routine servicing.”
The upgrades have taken the building from two stages of cooling to five. “We started with two-stage cooling with one or two chillers and then went to three stages of cooling with the plate heat exchanger and now we have five stages — plate heat exchanger, plate heat exchanger with chiller assist, small chiller, large chiller and both chillers,” Kowalke says. “We’ve spread out our capacity to reduce the amount of energy needed to maintain the temperature and provide comfort in the building.”
Pump up the pressure
A major concern with the original building was the inability to get proper water flow to the upper floors.
“Water flow was a critical issue,” Kowalke says. “We couldn’t circulate water well enough to get it to the top of the building. I experienced it firsthand. With the previous setup, the condenser pumps would circulate water, but if only one was working it had to flow through all three chillers. We had a lot of pressure drop when we got to the upper floors. The pumps were designed to move water at the plant level and the pumps were much smaller. The old motors were 40 hp and required two pumps running to maintain flow due to pressure drop through the three series chiller setup, so they were real slow in circulating water that came through the online chillers.”
To solve the pumping problems a host of Bell & Gossett pumps and accessories were specified. Condenser water pumps, primary chilled water pumps and secondary chilled water pumps were installed. All pumps are equipped with Bell & Gossett suction diffusers and triple-duty valves.
“Instead of running water to each chiller, this is where the pumps come in,” Kowalke explains. “We went to a booster pump system. As water comes out of the chillers and before it goes back to the building, these pumps pick up the water, boost the pressure and pump it all the way to the top.”
There are three booster pumps; one is a backup but generally only one or two are needed at a given time. Based on demand and static pressure when air-handler loads are up, variable-speed drives help to increase the amount of water flow. The backup pump automatically will go online should one of the primary pumps fail.
Three condenser pumps also are installed and again only one or two are generally needed.
“We created a tonnage where we didn’t have enough cooling tower capacity. We were short 200 tons,” Kowalke says. “To make it fit within the roof parapet wall, we put two 100-ton self-cleaning cooling towers online to handle the additional capacity.
“The large chiller equals what we put online before. We brought the cooling towers up to 1,100 tons. Now, we’re controlling the water flow going through the cooling towers. We have three 300-ton towers connected together and two 100-ton ones that are connected with a common return. We literally isolate a tower and use only what is needed online. The variable-speed condenser pumps provide additional flow so we never have water through the loop.”
The air-handler’s coil size on each floor was increased by one-third during the renovation, Kowalke adds. “One challenge was the pipe size of the chilled water pipe that was not changed during the upgrade that ran from the mechanical room to the upper floor,” he says. It needed to accommodate the upgrades. The pipe going to the floor was 8 in. and it needed to be 10 in. The new booster pump setup allowed for higher pressure to get the proper flow needed for the air-handler units on each floor.”
Kowalke is glad the days of water-flow headaches are over. “Before, we had to go up and manually throttle down the water flow going into the coils going into the lower floors,” he says. “They would steal all the water and there would be very little water flow to the upper floors. We were doing this in July and August, which are peak cooling months. With the Bell & Gossett pumps, we have real good flow now. There have been no issues with these pumps.”
Other Bell & Gossett upgrades include the installation of a thermal expansion tank and the use of auto-flow valves for flow regulation on air-handling units.
The mechanical upgrades are far from the only sustainable solutions employed at Monarch Plaza. The amount of outside air brought into the building has been tripled. “The building was operating under 1983 standards with the amount of fresh air required,” Kowalke says. “We installed variable air volume boxes on each floor to control the amount of fresh air makeup being delivered to each floor. The building exhaust system also was upgraded during this time by adding variable air volume boxes to the building exhaust duct allowing us to control the pressure within the building.”
Water conservation played a large role in the building earning the LEED Silver designation. “Some of the water-saving methods are very simple,” Kowalke says. “We put in 0.5-gpm aerators on all the sinks and that’s worked great. No one even noticed the change.”
Urinals were replaced with 0.5-gpf touchless models with rechargeable flush valves. Kowalke says the building is in the process of replacing the toilets. To date, 40% of the old 3.5-gpf toilets have been replaced with 1.6-gpf models and starting this year with 1.2-gpf models (due to new regulations).
“The toilets were one of the biggest things we did for water and energy conservation,” he says.
Kowalke adds caution had to be exercised with the toilet retrofits due to the age of the building and its plumbing system. “We had to be very careful,” he says. “The reason we didn’t go to a more water-efficient toilet is the building dates back to 1983 and the slope of the drain line is an issue. Because of the slope of the pipe, there may not have been enough water flow to clear the lines. We went the safe route with the 1.6-gpf models. Hopefully there won’t be any issues with the 1.2-gpf models. The degree and slope of the existing drain lines can’t be changed.”
The building also employs a condensate recovery system, further adding to its sustainable footprint.
“This building had to make a lot of changes and condensate recovery was one of them,” Kowalke says. “A couple sinks connected to the drain had to be removed from the condensate drain line and we are now collecting water from all the air handlers. We collect the water and treat it and sanitize it and put it in a recovery tank and then use a high-pressure pump to pump it back into the condenser room. In a recent month we collected 47,000 gal. of condensate water. At my other building that has been online for three years now, we’ll reach 1 million gal. this year.”
The recovery system has been a huge success for both the building and the city of Atlanta, Kowalke says. “We’re reducing the amount of bleed-off since the water we are collecting has no minerals in it,” he says. “There is the potential for a 2-to-1 ratio where for every gallon we collect, we’re saving 2 gal. of city water having to be added. It took a couple years for building ownership to agree to it, but it paid for itself in the first year.”
Other green initiatives include the use of CO2 monitoring on every floor and switching from the use of incandescent lamps to CFL models. In fact, the building provided tenants with free CFL lamps to help smooth the lighting transition. “We used to have change out the MR16s every three of four months,” Kowalke says. “The LEDs cost us a lot more, but we already have our money back because we haven’t had to change them yet.”
Motion sensors in storage areas, corridors and stairwells have reduced energy consumption as well. Special window film was installed to better handle the sun’s glare and increase the building’s ultraviolet rating.
“As a team, we pulled in a lot of green elements for the building and the landscape,” Kowalke says. “We have steadily improved the assets of the building.”
He estimates energy and water usage is down in the 5% to 10% range on a yearly basis. “This year we are again operating below projected utility costs due to additional cost-saving projects implemented since the last submitted budget,” he says. “I will again be lowering the utility cost for the 2014 budget year.”
Kowalke and his team don’t have plans to stand pat for too long when it comes to sustainability at Monarch Plaza. “We keep looking for ways to reduce our energy and water consumption,” he says. “We’ve taken out all the big chunks and now we’re working on the smaller ones. All those little steps keep adding up.”