"I have a feeling your cooling problem isn't in your unit ventilator; it's in your machine room!"--Johnny Tundra
By Ronald Wilkinson
It was an early winter in Angela, Mont. Although only mid-November, the surrounding peaks of the Judith Mountains to the west were already capped in snow. The wind kicked up vaporous wisps of powder in the crisp morning air.
Johnny Tundra was on his way home from a boiler tune-up at the Freeman Trauma Center in Jordan and decided to stop to see his old friend Thatcher McGowan, the facilities manager at the Stony End Home for the Aged. Johnny took the Angela exit off Highway 59, swerved--barely missing the deer grazing at the exit, and expertly guided his 1964 International Harvester Scout down the road to Stony End. Unfortunately, the swerve caused a shift in the capacious jowls of Johnny's trusted Bassett hound, Gas Train, and adverse leverage below the third chin toppled him off the Scout's seat and onto the floorboards.
Gas Train was still howling with dismay when Johnny pulled up to the Stony End loading dock, next to the dry ice van. His buddy Thatch (so named for the last growth of sage brush on his head) was rushing about giving directions to the delivery man who had boxes of the coolant loaded on a lift truck.
"Through the shop, down the hall, around the corner, and into the room marked 'Supply'," the harried facility manager told the deliveryman. "Make it quick and shut the door behind you, too! Oh, hi Johnny! What's up?"
"Nothing much, Thatch," Johnny said. "Just thought I'd stop by and say hi. What's with the dry ice? 10°F not cold enough for you?"
"It's plenty cold enough for me," Thatcher replied. "But, I've got a pharmaceutical storage room in here that has to be below 65°F and I can't seem to get it there. It seems like the colder it gets outside, the warmer it gets in the storage room. There's something wrong with the BAS controls that keeps telling the unit ventilator to heat the space, when there's no call for heating.
"I can lock the heating off at the BAS," Thatcher continued. "But, I still feel the warm air coming out the unit. I'll probably have to call in the factory technician from Wounded Bear, Wyoming, and you know what that will cost. The superintendent isn't going to like it. But, he told me that if we had to destroy those drugs, because they were stored out of compliance, he'd use my carcass to test the incinerator!"
"Now hold on for a minute," Johnny responded. "You just replaced that chiller last summer, and it was working fine. How can you have a cooling problem now?"
"It has nothing to do with the chiller," Thatcher said. "The chiller is locked out at any temperature below 35°F, and it hasn't been above that in weeks. The 55°F supply air to the unit ventilators is cool enough to maintain the room temperature. If the BAS wasn't telling the unit ventilator to heat the air, it would be coming out at 55°F and cooling the room just fine. But the air is coming out at more like 70°F."
"Have you checked the supply air temperature?" Johnny queried. "Could it be that the AHU is out of whack and overheating the ventilation air to the unit ventilators?"
"Yeah, I checked that on the BAS and double-checked it with a thermometer in the supply duct," Thatcher said. "The supply air is right on 55°F. Sometimes I think those control techs set us up for these problems just to get service calls."
"Now just hold on there, Thatch," Johnny said. "Let me take a look at that BAS of yours."
The two walked out of the store room and back to the maintenance shop where the BAS operator workstation was located. Johnny sat in front of the display, while Thatcher guided him to the AHU screen and showed him the indication for the supply air temperature. Sure enough, it read 55°F.
Then they went to the unit ventilator screen and checked its status. Sure enough, it was calling for full cooling and no heating. The next item in line was the chiller and its status showed simply "off."
"We don't get much information on the chiller from the BAS," Thatch explained. "The chiller is controlled by its own control panel, and the panel protocol isn't compatible with the BAS system. So, all we can monitor remotely is status."
Just then the phone rang and Thatch answered it as Johnny fiddled his way through a couple more screens on the CRT.
"Yes, sir," Thatcher explained on the telephone. "Don't worry, sir. The dry ice will keep the temperature down for a couple of hours and I'll get a technician on the way right now. We just have to check a couple of…Oh, OK, yes sir. I'll get a technician on the way right now. Yessir!"
"Boy is he steamed," Thatch moaned. "He said, 'If that room goes one degree above 65°F, he swears he’ll have my job and my hide to boot! I better get that high-priced wrench slinger here on the double."
"Just pull in those reins a minute, cowpuncher," Johnny said. "This screen says you have one pretty hot machine room. It says 90°F!"
"Well, yes, that's probably true," Thatcher confirmed. "We've been working on some piping and have some insulation off. "
"I have a feeling your problem isn't in your unit ventilator," Johnny said. "It's in your machine room! Let's go take a quick look before you call that pricey repairman!"
The two walked down the long corridor to the machine room. Opening the door, Johnny could feel the warm air of the crowded, machine-filled space. He walked up to the chilled water pumps and glanced at the units, then at the machine room unit heater hanging from the ceiling.
"Funny place for a unit heater in an overheated machine room," Johnny noted.
"That's not a heater," came Thatch's reply. "It's a cooler. That coil is connected to the chilled water circuit. But since the chiller is locked off by the outdoor temperature, it isn't doing any cooling now."
"That's just the problem," Johnny said. "It is cooling, a little. At least it's cooling enough to heat your drug storage room!
"You see that chilled water pump over there?" he continued. "It's running. I checked on the BAS and saw that the circulating pump was energized, but I wanted to come here and check it for sure. The pump is running because the BAS turned it on and because the storage room called for cooling.
"But, because of the low outside air temperature, the chiller is locked off at its own panel. The BAS has turned the chilled water pumps on, but the chiller has stayed off. As a result, water is circulating through the machine room cooling coil and heating up the chilled water loop. When the pharmaceutical storage room unit ventilator calls for cooling, all it gets is warm water from the cooling loop. The more the room calls for cooling, the more warm water it gets!
"All you have to do is throw the disconnect on those chilled water pumps. Once they stop, you should see the temperature in the storage room drop to its 60°F set point and stay there. When you get the time to reprogram the BAS, lock out those chilled water pumps at the same temperature as the chiller lock-out. That way, the pumps won't run on a call for cooling unless the chiller is also starting up at the same time. If you do that, your chilled water loop will always be chilled water--not water heated by the machine room!"
"By George, Johnny, you've done it again," Thatch exclaimed. "Thanks to you, it looks like I'll keep my job, and my hide, after all."