The best chiller fit for application

The best chiller fit for application

Undoubtedly, reasons for the installation of a chilled water system are numerous and the options are just as plenty. Here are a few that you can choose to fit your project. 

Packaged air-cooled chiller

An outdoor, air-cooled packaged chiller has all of its components located outside, in one package: the condenser, evaporator, compressors and pumps (although the pumps can be, and often are, installed indoors).

So, why choose a packaged chiller?

Lead time

Most manufacturers have a packaged chiller stocking programme. Check with the manufacturer how soon product will be received.

Space

A packaged chiller is typically installed on a roof or on the ground, where ‘real estate’ is not typically at a premium. To a business owner, this means more indoor square footage to generate more revenue for their business.

Maintenance friendly

Packaged chillers are generally the easiest to maintain compared to the other chiller options.

Noise

Assuming the chiller is not installed directly over a noise sensitive area, getting the compressors and condenser fan motors out of the indoor space can be a huge benefit.

Price

Packaged chillers are generally the lowest upfront cost.

Waterside economiser option

Since the chilled water loop is already outside, this gives an owner the option to add a waterside economiser. This option adds chilled water coils to the condenser section of the chiller and allows the chiller to run in ‘free cooling’ mode when the ambient temperature starts to fall below the design leaving water temperature. It can be an expensive upfront option, but it typically pays for itself in three to five years. Most manufacturers will require a glycol solution for this option, so be careful when designing your system to make sure you have enough capacity.

chill 002Image shows an example of a chiller evaporator barrel. This is located indoors on a split system chiller and exchanges the heat between the water loop and DX loop. Image credit: Air Cooled Modular Chiller

Disadvantages

Since the water leaves the comfort of the building, freeze protection must be considered. Which means adding glycol to the system, never shutting off pumps, or planning to drain the system every year. The life expectancy is also shorter since the entire system is exposed to the elements.

Split system chiller with an air-cooled condensing unit

A ‘condensing unit’ is the high side of a split system that has compressors built-in to the unit. A ‘condenser’ does not have compressors – it is just the condenser coil and condenser fans in a box. So, why would you choose this option?

Since the evaporator is installed indoors, we don’t need to worry about freeze protection. This means no glycol, no draining of the system, no freezes, no need to run pumps all winter long.

Noise

This is similar to a packaged unit. As long as you are careful about where the condensing unit is located, lower indoor noise could be experienced.

Life expectancy

This gets a small boost, but it’s not as good as a water-cooled chiller. Since the evaporator (and the controls) are located indoors, this section of the chiller should last a lot longer. However, the high side is still located outdoors, which might have a shorter life cycle.

Disadvantages

The biggest one is the refrigerant piping component. On a packaged chiller, the unit comes pre-charged and ready to go. But on a split system, the contractor must install copper refrigerant lines (liquid and suction lines) from the evaporator to the condensing unit. This just adds another layer of complexity during start up and service. Also, careful consideration must be made for sizing the DX refrigerant piping before installation. For a good mechanical contractor this is no problem. But it is still adds extra steps to the installation and the servicing of the chiller.

Design consideration

When you are designing a split system chiller, make sure your condensing unit has the correct capacity at the desired suction temperature. Some condensing units are designed to be connected to a chiller evaporator, and some are designed to be connected to a DX air coil. What is the difference? Approximately 15% in the system capacity. For example, a 100-tonne condensing that is rated for a DX coil, will have a 100-tonnr capacity at a suction temperature of about 45-50 degrees. But if you run it as a chiller, and you want 44-degree water, your suction temperature will need to be 35-38 degrees. Which will de-rate your condensing unit at about 15%.

chill 003Image of an air-cooled condenser. These are typically on stands and have an open bottom, as opposed to the condensing unit. Image credit: Westermeyer Industries

Split system chiller with air-cooled condenser

Not nearly as common as the other three types is the split system chiller with an outdoor air condenser. Remember, this means the compressors are located indoors with the chiller evaporator, and the outside unit is just the condenser coil and fans.

Same as the split system chiller with a condensing unit, the water stays inside, so no freeze protection is required.

Noise

Now that the compressors are inside, noise could be a problem if the compressors are located in the wrong place. If you are designing a new system, be careful where you decide to locate the indoor portion of the chiller.

Disadvantages

Just like the split system condensing unit option, we have to deal with DX refrigerant piping. Although, instead of a suction and liquid line, we have a liquid and hot gas line. But we still have to think about everything that goes into managing the refrigeration. Also, this option starts to take up a decent amount of precious indoor space.

chill 004An indoor water-cooled chiller has a longer life expectancy compared to its counterparts. Image credit: ArchiExpo

Indoor water-cooled chiller

This chiller type has all the components indoors with the exception of a cooling tower or ground loops. So, why would you pick a water-cooled chiller?

This option does not require freeze protection on the evaporator side, nor the expense of glycol. However, you still need to think about possible freeze protection on the cooling tower side, like an immersion heater.

Non reversing heat pump: At least one manufacture that we know of has this option. On a 4-pipe system, when you might have some zones calling for both heating and cooling, you can change the chiller to ‘heat pump’ mode and control the chiller based on condenser leaving water temperature. This hot condenser water can be sent to the hot water side to assist the boiler for heating.

Life expectancy

Of all the chillers discussed today, this option has the longest life expectancy since all of the components (less the cooling tower) are installed indoors.

Disadvantages

Water cooled chillers are generally the most expensive upfront option, however, since the life expectancy is typically longer than the other options, this can be a smart investment. The other disadvantage is maintenance. If the condenser is connected to an ‘open-loop’ evaporative cooling tower, there will be an increased amount of service that will be required due to mineral build-up and other foreign materials that find their way into the system.

Source: Contracting Business 


 


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