HPAC Fastrack

Johnny Tundra--Cold Weather Engineer

"Your problem isn't in that electronic brain; it's in that butterfly valve!"—Johnny Tundra

By Ronald Wilkinson

Johnny Tundra knew from the sound of his cell phone that it was trouble. Nobody would call him at 5:30 p.m. on a Friday except somebody who was in trouble with a legislature in session at the state capitol in Helena, Mont.

Johnny's old pal Hank Hoovestahl, the supervisor of Capitol Facilities Maintenance and Operations, had started a new job with the state only a year before, operating and maintaining the capitol complex buildings in Helena. Because it was the capitol, and close to the center of the state leadership, the buildings in the area had seen more than their share of energy measures and mechanical modernizations. The capitol building had just undergone a major facelift aimed at providing air conditioning for the 100-year-old landmark.

Johnny had just pulled off Highway 12, into Townsend, and was headed toward the Mint Bar for a cold one with his faithful hound, Gas Train. He backed off the throttle and let his 1964 International Harvest Scout coast down to sixty while he retrieved his cell phone from under the capacious folds of Gas Trains' flaccid jowls.

"Tundra here," he barked into the phone, as he coasted into the Mint parking lot, still hopeful the emergency could wait until the next day.

"Johnny!" Hank said. "Boy, am I glad to get a hold of you. I am in a pickle this time, and Lester says he will have me tarred and feathered if I don't get this chiller running by tomorrow at noon!"

"Now just hold on there, Hank," Johnny replied, as leverage got the best of Gas Train who fell, after his ample chops, onto the front floorboards of the braking Scout. "Lester who? And, what's he in a twitch about?"

"Lester Heapleach, that's Lester who--the Senate majority leader!" Hank replied. "He tried to be an engineer once and says, 'If I don't get some cooling into these meeting rooms for the public hearings tomorrow, he'll cook my goose in boiler #2.' They just spent $20 million on this capitol remodel and they expect it as cool as a cucumber in those chambers.

"We've been getting free cooling out of the closed circuit tower so far this winter. But, it's getting warm, and tomorrow is supposed to be a real cooker. We'll need that chiller for those interior spaces. Especially when they are crammed with concerned citizens and confused legislators.

"We've tried to start the chiller a dozen times. It runs for about a minute and then trips out. The factory representative in California is headed this way but won't get here until tomorrow afternoon. By then it will be too late. Lester wants to sue!"

"Okay," the lanky trouble-shooter said. "I was just about to head into the Mint down here in Townsend, but if you'll give me a half hour, I'll come on up and eyeball the situation. My bet is we can get you cooled down soon enough."

Johnny cruised north through the Elkhorns, dropped down through East Helena past the lead smelter, and into the capitol parking lot. He heard the telltale fan noise from the cooling tower, hidden in the depths of the boiler plant, which confirmed that the tower was cooling with the chiller off line. As he started toward the plant door, Hank burst out in a tizzy.

"What took you so long?" Hank said. "You ride that hound of yours?

"Johnny, this chiller has got me up a tree. All I can figure is that the controller is bad. The factory can fly another one up tomorrow, along with the start-up technician, but it'll cost $15,000 for the rush service. I can't afford to take it out of the maintenance budget, but I'll have to anyway. Come on and take a look."

Hank showed Johnny the new chiller, closed-circuit cooling tower, and three-way-valve arrangement for the chiller and "strainer-cycle" circuits. The return chilled water from the capitol could be routed to the cooling tower, the chiller, or both. The closed-circuit cooling tower was run with no spray, with the sump drained and spray pumps off, during the winter. The cold outside temperatures provided ample cooling without having to run the chiller, saving substantially on the power bill.

However, when the outside temperatures topped 40°F, the tower could no longer handle the job alone and the chiller had to be brought on line. When the chiller was started, the three-way valves routed the cooling-tower water through the condenser, and the building water went through the evaporator to provide the necessary 42°F chilled water.

Johnny gave the piping a quick once-over as the chiller sat idle. He traced the cooling water piping from the tower, through the three-way valve, past the manual shut-off gate valve, and to the chiller condenser connection. The three-way-valve arrangement consisted of two butterfly valves linked together with a common actuator. The linkage closed the valve to the condenser, as it opened the valve to the cooling tower.

"Okay, start it up," the Big Timber bull-whacker said. Hank punched a few buttons on the BAS operator workstation and the two watched as the three-way valves changed positions to route tower water and building water through the chiller. Droplets of condensate on the uninsulated gate valve shook loose as the actuator turned the valve shafts. The chiller ran for a few moments, wheezed, and coasted to a stop.

"See?" Hank exclaimed. "And look at the fault message." He pointed to the chiller control panel. The message read: "Surge--High Suction Superheat."

"High suction superheat? What's that supposed to mean?" Hank questioned. "There's no load on the chiller yet. The return water temperature is 46°F. How can there be high superheat? There's probably no superheat at all. This controller has got to be bad."

Just then a voice boomed out of the doorway. "Hoovestahl, did you get that chiller running yet! If not, I'm going to sue that chiller company for all they're worth and run you out of town on a rail!" It was Lester Heapleach, and he was fuming mad. "Don't worry, Senator," Hank replied. "It's just a bad controller. I'll get another one flown out here as soon as possible."

"Hold on just a minute both of you," Johnny said. "You can fix this problem for a lot less time and money than a new controller. Your problem isn't in that electronic brain; it's in that butterfly valve!"

"What are you talking about, Tundra?" Heapleach asked, recalling his refrigeration theory. "Obviously there can't be any superheat problem with no load on the chiller. The controller is belly-up!"

"On the contrary, Senator Lester," Johnny said. "It's the valve linkage that's the problem. The tip-off is that condensation on the gate valve to the chiller condenser, downstream of the automatic butterfly valve.

"The condensate on the body of the isolation valve means cooling-tower water is leaking past the butterfly valve and through the chiller condenser when the chiller is off. Over a couple of weeks, this causes all of the refrigerant to be drawn into the condenser because it's the coldest place on the machine. When the compressor starts up, there is no liquid refrigerant in the evaporator to cool the suction line and the compressor impeller. So the suction elbow heats up, and the sensor trips the superheat safety.

"All you have to do, Hank, is close that manual isolation valve for a few hours, stop the flow of cold water through the condenser, and let the refrigerant re-distribute itself between the evaporator and the condenser. Then open the manual valve and start up the chiller normally. As soon as condenser water flow is proved, it'll start up and run like a dream. You can adjust the linkage any time."

"I have to hand it to you Johnny, you are one smart cookie," Lester ejaculated. "Come on over to Jorgensen's for a cold one on me! And bring your dog, too!"

"Don't mind if I do, Lester," Johnny replied. "But Gas Train better stay in the car. The last time we were there, he got into the lutefisk and couldn't come into the house for two weeks!"