Some Assembly Required: Chiller installation made semi-easy
Installation can be everything. That surround sound home theatre system in your man cave will sound worse than a two-cans-and-a-string telephone if it hasn’t been put in properly. Ditto chillers. Whether portable or central, the most...
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Installation can be everything. That surround sound home theatre system in your man cave will sound worse than a two-cans-and-a-string telephone if it hasn’t been put in properly. Ditto chillers. Whether portable or central, the most critical part of any water-cooled or air-cooled chilling system is its installation. And there are a number of variables to consider, any one of which could have a major impact on efficiency and operability.
Here’s a quick primer for meeting the challenges.
Portable chillers are typically 30 tons in capacity or less, simpler in overall design, and lower in initial cost than a central system. Equipped with caster wheels, they’re easy to deploy, easy to connect, and easy to power up. Like central chillers, they offer both air-cooled and water-cooled types. “Most portable air-cooled chillers are placed indoors and send a stream of warm air directly from the condenser fan to the plant floor,” said Mike Mueller, sales manager, heat transfer for The Conair Group. “During cool weather, the warm airflow delivered by the condenser fan can supplement the plant’s space heating system and help to reduce energy costs.”
So far, so good. But indoor portable chiller installation requires careful attention to location, piping, and fluids — and the problem is, since installation is often done at the maintenance facility level without a technical representative at hand, these details sometimes go unconsidered by the user.
LOCATION, LOCATION, LOCATION
To begin, keep that famous real estate adage in mind. “The closer the chiller is placed to the process, the better,” said Alan D’Ettorre, engineering manager for Mokon Inc. “First, you limit the amount of piping going from the chiller to the process, which matters because every time you move water through pipe there are frictional penalties to be paid. Second, shorter lines can minimize the amount of ambient heat absorbed through the piping, in addition to being less expensive to fill with fluid and to insulate.”
But beware of placing the unit near a hot spot in your facility. “If the chiller is air-cooled, close proximity to a heat source such as an air compressor causes the system to pull in the heat,” said Ziggy Weibe, president of Chillers Inc. “And avoid putting it too close to the compressor room at all costs because you’ll lose efficiency. The exception is with a remote condenser, in which case the chiller can go in that hot environment because the heat is being dissipated outside.”
Another common mistake is simply positioning the portable chiller for convenience, which may mean overlooking potential air flow problems. “Air flow can be impeded if the chiller is too close to a wall or to adjoining equipment, resulting in inefficiency,” Alan D’Ettorre said.
THE POWER OF PIPING
As we’ve seen, long piping runs can affect chiller performance. Another installation no-no? “Too often processors will choke the line size down from 1.5 inches to 0.24 inches because that’s the size of the ports that are on their process,” D’Ettorre said. “The problem is, fluid can’t flow through those small diameters fast enough, causing it to back up in the system and compromise performance.”
The solution? “To optimize performance, portable chilling systems should be designed with a low pressure drop in the flow delivery,” said Ziggy Wiebe. “This is accomplished by having properly sized delivery piping systems that keep water velocities between five and seven feet per second and pressure losses to less than 3 psi per 100 feet of run. It’s also important to minimize the amount of elbows, valves, and other components such as quick connect fittings that can cause high pressure drops.”
Selecting a pump for process flow is critical for effective heat transfer. A good choice, some suppliers say, is a system design that utilizes two pumps, one allowing smooth, efficient chiller operation, and another that provides stable temperatures and fluid flow rates to the process application.
And this brings us to fluids, almost literally the lifeblood of the chilling system. Some rules of thumb: pure water gives the best heat transfer, but doesn’t supply freeze protection; glycols, meanwhile, provide freeze protection, but reduce the heat transferability of the fluid in the system.
“If the chiller is operating at 45°F fluid temperature or above, straight water can be used; below that temperature, a water/glycol mix is required,” said Alan D’Ettorre. “If glycol is necessary, industrial glycols are vastly superior to automotive glycols, which have waxes and parafins in them — over time, these deposits seep into very small flow passageways, causing clogs and other no-flow situations.”
Some technicians like to oversize a chiller to ensure reserve capacity for future system changes or to overcome the effects of glycol. But this should be done with caution. “Oversizing without regard to design limitations can cause excessive cycling, contributing to losses in energy efficiency, increased maintenance, decreased compressor life, and burned contacts,” D’Ettorre said.
CENTRAL CHILLING SYSTEM
Central chillers are generally larger in capacity, more complex in design, and may have a higher installed cost per ton than a portable chiller. A key advantage of central chiller systems, suppliers say, is flexibility: the ability to handle varying process loads at a lower electrical consumption while also handling the total production load with lower overall installed tonnage. A downside? Central systems also require a greater amount of dedicated plumbing to circulate coolant throughout the plant.
TAKE IT OUTSIDE
Central air-cooled chillers are typically located outside, or with the main chiller — including the critical, serviceable components — inside and the condenser outside to conserve space or improve performance. An outside air-cooled condenser sounds simple, but there are umpteen important questions to answer before installation. “The condenser requires adequate air flow, preferably six feet from a wall and not in a corner or other tight space that can hamper heat evacuation,” said Mike Sinclair, regional sales manager with Berg Chilling Systems Inc. “If placed on the facility roof, allow for radiant heat that can affect the coil sizing. Putting the condenser on the roof also involves civil verifications that the weight can be supported, which may lead to the roof needing reinforcement.”
If placed on the ground, the condenser might need bollards around it to prevent damage from trucks and other vehicles. “If vandalism of high-priced copper in the coils is a concern, either a cage or architectural fencing can be used — although the latter can also affect the air flow, so the fencing has to be a certain distance from the condenser,” Sinclair said. And condensers don’t exactly run silent, which might trouble the neighbours and/or violate sound regulations. “The condenser can be made quieter by reducing the rpm on the fan, but that also reduces the amount of air flow, which means the condenser has to be made larger,” he added. “There are very efficient low-rpm and low-noise condenser fans available.”
A fully outdoor air-cooled unit removes the problem of keeping an outdoor condenser relatively close to the main chilling unit located indoors, but doesn’t necessarily solve any other problems. “Weight is an issue because of the structural frame and compressors, so putting it on the roof mi
ght not be an option,” Sinclair continued. “It can be placed on a concrete pad which allows better access for service mechanics, but that also raises issues around security, fencing, and bollards.”
A water-cooled outdoor chilling system has the potential for trouble from the start. To begin with, the system will require glycol in the evaporator loop for freeze protection; but glycol is expensive, needs extra flow to achieve the same heat transfer as water, and will require a larger horsepower pump motor. “Also, glycol leaks are messy and very time-consuming to clean up,” Sinclair said. “The 20 per cent extra cost to weatherproof the system, plus the costs and issues associated with glycol, should make an outdoor water-cooled chiller a last resort, only if indoor space simply can’t be found. Ultimately, the risks from freezing make it an impractical option almost anywhere in Canada, except perhaps southern and coastal B.C.”
According to some chiller suppliers, a water-cooled central system is easier to bring indoors because, since it doesn’t require a fan, it doesn’t produce as much noise. But that may be where the easy decisions end. For the installation of any large indoor central system, a big problem — literally — looms at the very outset: getting it into your plastics processing facility. “Loading door size can be factor, as can bollards around loading doors that take away space,” Sinclair said. “We sometimes have to size the unit to a specific constraint to get it indoors; it might have to be built in pieces and then reassembled on site.”
Assuming you can navigate those twists and turns, other questions arise. Take Technical Standards & Safety Authority (TSSA) regulations, for example. “TSSA codes dictate that, if an indoor central refrigeration unit reaches a certain level of connected horsepower, a defined mechanical room with access doors, relief doors, and defined ventilation is required,” Sinclair said. “The processor might also need to employ licensed refrigeration operators.”
Where exactly to put the system is an issue, too, for a variety of reasons. “An indoor air-cooled central system requires adequate air flow and ventilation in the area to exhaust out the heat, which means that the ceiling height of where that unit is located has to be sufficient to avoid bouncing the air flow back at the condenser,” Sinclair continued. “It’s a common installation mistake to tuck the system into a corner or on a mezzanine, in which cases the recirculating hot air might eventually cause the unit to trip out.”
And with an indoor water-cooled system, meanwhile, location close to an outside wall nearest to the outdoor cooling tower system is a favorable position. But that’s not the end of it. “In addition to the coolant plumbing required by any chiller and process water system, a water-cooled central chiller may require installation and maintenance of additional pumps, piping, and tanks to support operation of the cooling tower,” said Mike Mueller. “If an existing tower system is in place, it may require modification or expansion to meet the additional tonnage demands of a chiller addition.”
And whether air-cooled or water-cooled, it’s preferable to place the system close to the main power feed as well as sanitary sewer and city water.
Another hint: take advantage of existing piping lines if possible. “All else being equal, it makes sense to install a central system in an area from which you can tie into existing process piping,” said Mike Sinclair.
Finally, don’t forget to take the longer view when considering the location. “If you know your plant is going to be expanded in a certain direction, locate the equipment so that it doesn’t have to be moved when that time comes,” Sinclair added.
In the end — and unlike that surround sound theatre system — installing either a portable or a central chiller probably shouldn’t be a DIY project. Bringing the equipment supplier into the setup process is a good way to avoid getting burned with your chilling.
Advantage Engineering Inc. (Greenwood, Ind.);
Chillers Inc. (Newmarket, Ont.); www.chillersinc.com; 905-895-9667
Berg Chilling Systems Inc. (Toronto); www.berg-group.com; 416-755-2221
The Conair Group (Cranberry Township, Pa.);
Dier International Plastics; (Unionville, Ont.);
Industries Laferriere (Mascouche, Que.);
Mokon Inc. (Buffalo, N.Y.); www.mokon.com; 716-876-9951
En-Plas Inc. (Toronto); www.en-plasinc.com; 416-286-3030