Out With the Old?
Converting a 1980s wood-framed office building to a private school was not going to be easy, but it could be done. Money was tight, but most of the building's existing mechanical and electrical systems could be reused. Keeping four main sets of toilet rooms intact also would save a lot of money.
On the architect's first set of floor plans, all of the existing mechanical space and toilet rooms had been eliminated. New mechanical space and toilet rooms were shown elsewhere on the plans. This approach clearly was not consistent with the concept of building to a budget. It was going to cost a lot of money to demolish all of the equipment and toilet rooms and then essentially rebuild them a few yards away.
A few e-mails and phone calls later, I received revised floor plans. This time, about half of the existing infrastructure remained in place, but the plan still called for demolishing one core section that included two sets of toilet rooms and two mechanical/electrical rooms, only to rebuild two new sets of toilet rooms about 30 ft away.
“Why can't we reuse the existing toilet rooms and mechanical space in Area B?” I asked the architect. “That would save a lot of money, and you know money is tight for this project.”
“Gee, I wish we could, but we can't use those toilet rooms because they don't meet the code for handicap accessibility,” he said.
“You're right,” I said. “Those toilet rooms aren't handicap-accessible, but they don't need to be. You don't have to make every toilet room handicap-accessible as long as there are other handicap-accessible toilets nearby. We can meet all of the fixture and accessibility requirements by adding a new toilet room. Besides, we can design the new toilet rooms with enough space for fully accessible toilets without having to squeeze them into the existing toilet rooms. We need additional toilet fixtures anyway — a school needs more toilets than an office building — so we can use the new toilet rooms to meet accessibility requirements.”
A few weeks later, the final floor plans came through, reusing the existing mechanical space and toilet rooms and adding more handicap-accessible toilets. The school might never realize how much money we saved them, but I was pleased that we found a way to save money without sacrificing function.
Energy Economics Inc.
Newton Centre, Mass.
Take Nothing for Granted
The newest chilled-water plant at our facility includes 450-, 250-, and 70-ton chillers and a free-cooling plate-and-frame heat exchanger. The primary and secondary flows are decoupled with a traditional bridge arrangement. Multiple secondary pumps are distributed at each of the large air handlers or groups of smaller loads.
While preparing to teach a class on chilled-water systems, I decided to have a look at the plant. On that particular day, the free-cooling heat exchanger was operating. While tracing out the piping in the plant, I happened to notice thermometers labeled “chilled-water supply” and “chilled-water return” on the main pipes leaving the plant. Interestingly, the supply water being delivered to the loads was 8 to 10°F warmer than the return water. This seemed to be an intriguing problem that deserved further investigation.
There were at least four possible scenarios that would explain why the supply water was warmer than the return. First, could the piping at the thermometer locations simply have been mislabeled? After tracing out the piping and confirming it was labeled correctly, the values displayed at the building-automation system were checked. They corresponded to the thermometer readings.
Second, because the weather seemed cool enough to support air-side economizing, it was possible that the “chilled” water was flowing through coils that had air passing over them cold enough to cause the water to lose heat rather than gain heat. As the weather warmed up, however, it became clear from the temperature readings that this was not the problem.
The third scenario involved the free-cooling heat exchanger. Could the cooling-tower water have been warmer than the chilled water, causing the exchanger to act as a heater? This was ruled out after looking at the temperatures across the exchanger.
The fourth possibility was that one or more cooling coils and/or entire piping branches had been connected backward to the mains. This would mean that water was being pulled from the return main, sent through coils, where it picked up heat, and then deposited into the supply main. The operator mentioned that a new piping branch recently had been put online, which sounded suspicious. Tracing out the piping on the new branch revealed that this scenario was the source of the problem. Shutting off flow to this branch caused the temperatures to straighten out immediately. Plumbers were called in to reverse the connections for this branch. Once again, the truth of the phrase, “Take nothing for granted,” was driven home.
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