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Refrigerant Piping Design Basics

MEP Academy Instructor
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Refrigerant Piping Design Basics

Refrigerant Piping Design Basics. Refrigerant piping design is an important aspect of any air conditioning or refrigeration system. Proper design of the refrigerant piping system ensures that the system operates efficiently and reliably. Here are eight key factors to consider when designing refrigerant piping.

If you prefer to watch the video of this presentation, then scroll to the bottom or click the following link. Refrigerant Piping Design Basics

1. Refrigerant System Layout

The layout of the refrigerant system should be designed to minimize the length of the piping and the number of fittings and inline components required. This reduces pressure drop in the system and helps improve efficiency. The total length of the refrigerant piping must not exceed the manufacturers requirements as this could result in a loss of capacity.

2. Refrigerant Pipe Sizing

The diameter of the piping should be chosen based on the required refrigerant flow rate and pressure drop. The wrong size piping can cause excessive pressure drops, leading to reduced system efficiency and capacity, while increasing power consumption. 

Liquid lines that are installed larger than required will increase the amount of refrigerant in the system, which could create additional problems. While under sizing liquid lines can cause the refrigerant to flash before it reaches the expansion valve, which will starve the evaporator and cause a loss in capacity, and the possible frosting up of the coil.

If the suction line is oversized then there could be problems with the return of oil to the compressor. And, if they are undersized there can be a loss of capacity and an increase in superheat.

3. Refrigerant Type

Different refrigerants have different properties, such as pressure, temperature, and viscosity. The refrigerant type should be considered when designing the piping system, and the system should be designed to accommodate the specific characteristics of the refrigerant used.

4. Refrigerant Piping Materials

The materials used for the piping should be compatible with the refrigerant and should be able to withstand the pressure and temperature of the system. ACR type Copper tubing is commonly used for refrigerant piping in the HVCAR industry.

Checkout Refrigerant Piping Products here

5. Refrigerant Piping Insulation

Proper insulation is necessary to prevent refrigerant lines from losing their cooling capacity. The thickness of the insulation should be chosen based on the temperature difference between the refrigerant and the surrounding environment. Insulation thickness requirements can be found in the various codes that regulate the installation of the refrigerant piping. See our video on the proper methods for insulating refrigerant piping.

Checkout Refrigerant Insulation Products here

6. Refrigerant Piping Support

Refrigerant piping should be supported at regular intervals to prevent sagging and vibration, which can cause leaks and reduce system efficiency.

7. Expansion and Contraction

The refrigerant piping should be designed to accommodate the expansion and contraction of the piping due to temperature changes. Long lengths of piping can cause problems when temperature changes with the piping vary. The piping length will grow when heated up and contract when cooled down. Some method of compensating for the variable of expansion and contraction must be considered. 

Copper Piping Expansion = Delta-Temperature in piping x Piping Length x Coefficient of Expansion

8. Refrigerant Oil Management

Oil will be circulated around the system with the refrigerant and must be returned to the compressor where it’s needed to provide lubrication of bearings and moving parts. For this to happen it’s important that the refrigerant piping is sized correctly including the refrigerant velocity.

As refrigerant changes from a liquid to a vapor in the evaporator, the oil is separated out, which requires the correct velocity to ensure that the oil returns to the compressor. It’s important that refrigerant oil return to the compressor at the same rate at which it leaves.

Refrigerant Carrying Capacity of Piping

Refrigerant pipe sizing will also dictate the quantity of refrigerant required, as the larger the liquid line pipe size, the greater the volume of refrigerant required. We’ll look at the liquid line because it holds more refrigerant per linear foot than that of the same size suction line. We’ll compare the difference between 100 feet of pipe for various sizes using standard pressure in a R22 and R410A system.

R22 (100 feet of Liquid Line)

1/2” Pipe = 7 Lbs.

5/8” Pipe = 11.3 Lbs.

Difference in 4.3 Lbs.

So, by upsizing your liquid line from a 1/2” to a 5/8” line, the system would require approximately 4.3 Lbs. more of R22 refrigerant.

R410A (100 feet of Liquid Line)

1/2” Pipe = 5.8 Lbs.

5/8” Pipe = 9.2 Lbs.

Difference in 3.4 Lbs.

So, by upsizing your liquid line from a 1/2” to a 5/8” line, the system would require approximately 3.4 Lbs. more of R410A refrigerant.

When to Use Soft Copper

This is bound to create some controversy, as the ease by which soft copper can be installed is compelling from a labor standpoint, but practical engineering guidelines should be considered. Keeping soft copper installation to a maximum of a 50-foot roll is a prudent engineering request. Long lengths of soft copper tend to sag, and oil could be trapped where sags occur in the suction line.

Purging

When brazing refrigerant piping it’s important that a constant nitrogen purge be used to keep the system clean from the formation of copper oxides.

Refrigerant Pressure Drop Guidelines

The compressor will need to work harder for added pressure drop in the refrigerant piping design which considers pipe size, equivalent piping length which includes inline fittings, and components. Components may need to be oversized to compensate for excessive pressure drop in the system. By installing piping that’s too small there will be an increase in pressure drop and velocity, and a reduction in system capacity. It’s important that the overall equivalent pipe length be considered when selecting refrigerant pipe sizes.

Total pressure drop in the refrigerant piping system is determined by many factors including the pressure, velocity, and friction through pipe, valves, and fittings. And as previously stated, there is a loss in capacity of the system if the suction line is undersized. Smaller pipes have greater pressure losses, so ensuring the correct size is important for meeting design capacity.

Refrigerant Volume

It’s important to have the correct mass of refrigerant to achieve the design capacity of the system.

Sizing Refrigerant Piping

The process of sizing refrigerant piping begins with measuring the distance between the outdoor condensing unit and indoor fan coil while counting all the inline fittings and components. The routing should minimize the length of piping and number of fittings required, as each fitting or valve increases the overall pressure drop of the system. Upsizing the liquid line one size will increase the refrigerant carrying capacity by about 50% more, for example a 1/2” liquid line carries approximately 5.8 lbs. of R410A per 100 feet, while a 5/8” liquid line carries about 9.2 Lbs./100 feet.

If the pressure drop is too great in the liquid line, then it’s possible that the pressure drops below the saturation temperature of the refrigerant causing it to flash into vapor. This cause a loss in capacity and explains why the correct sizing of the piping is important, and why you should avoid additional fittings or too small of a liquid line. 

When the condenser is below the air handler than the Liquid Line requires “Vertical Lift”, and when the condenser is above the air handler than the suction line requires “Vertical Lift”. This is easy to determine if you think about the work the compressor must do, and where the compressor is located when running. If it’s on the bottom then it must push up, and if it’s on the top then it must pull up. Depending on where the compressor is in relationship to the air handler it either must push the liquid up or pull the suction gas up.

Summary

Overall, the refrigerant piping design should be carefully considered to ensure that the system operates efficiently and reliably. A well designed system will ensure that the suction, liquid and discharge piping is large enough to prevent excessive pressure drop, yet small enough to ensure that the velocity will carry the oil back to the compressor crankcase. It’s recommended to consult with a professional HVAC engineer to ensure proper design and installation.

Refrigerant Piping Design Basics

How Indirect Evaporative Coolers Work

MEP Academy Instructor
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How Indirect Evaporative Coolers Work

We’ll learn how indirect evaporative coolers work. By using indirect evaporative cooling some buildings can eliminate mechanical refrigeration-based systems while reducing environmental impact. Indirect evaporative coolers use air to air heat exchangers to optimize approach temperatures. We’ll show you four systems that use the indirect evaporative cooling method.

If you prefer to watch the Video of this presentation than scroll to the bottom or click the following link. How Indirect Evaporative Coolers Work

The difference between a direct evaporative cooler and an indirect evaporative cooler is that a direct evaporative cooler will add moisture to the air, thereby increasing the humidity, and the indirect evaporative cooler doesn’t add moisture to the space. 

Checkout these Indirect Evaporative Coolers here

When water evaporates from a liquid to a vapor by the process of the heat of vaporization, sensible heat is absorbed from the air causing the air temperature to drop.

Indirect evaporative coolers use two separate air streams separated by the heat exchanger walls. The secondary air stream uses the evaporative process where water trickles down over air being exhausted from the building or by the use of outside air. This causes some of the water to evaporate and absorb heat from the primary air stream through the heat exchanger wall.

Primary and Secondary Air in a Evaporative Cooler Heat Exchanger
Primary and Secondary Air in a Evaporative Cooler Heat Exchanger

The heat exchanger keeps the wet air stream separate from the primary dry air flow to the space. Indirect evaporative coolers work best in low humidity areas with design wet bulb temperatures below 70F, allowing for an energy savings over mechanical refrigeration cooling.

The use of air conditioners contributes to the largest consumption of peak demand on the US electricity grid and is the primary cause of blackouts and grid failures. The problem is increased on high ambient temperature days when air conditioners are least efficient and the demand for cooling is the greatest. Indirect evaporative coolers use less energy than Variable Air Volume or Direct Expansion (DX) rooftop packaged units.

How indirect Evaporative Coolers Work

There are various configurations that can be used with indirect evaporative coolers, including additional stages of cooling using direct evaporative cooling and chilled water or DX cooling for additional capacity. We’ll explain the basic Indirect Evaporative Cooler only application.

The secondary air can be Return air from the space or outside air that enters the indirect evaporative cooler and passes over a wetted Heat Exchanger medium where the water is evaporated before its discharged outdoors. On the primary side the Outdoor air is brought into the indirect evaporative cooler where it crosses the Heat Exchanger medium without mixing with the return air and is indirectly cooled by encountering the cool heat exchanger before being supplied to the space. 

If additional cooling is required, then a second or third stage of cooling can be added with an direct evaporative section and a chilled water or DX coil to drop the supply air temperature further. Since the primary air never mixes with the secondary wet air, the humidity of the space is not increased.

Indirect Evaporative Cooling in a Data Center

An indirect evaporative cooler can be used to cool a data center while saving large amounts of energy. See our video on Data Centers for a better explanation of the systems used for cooling data centers. Hot air from the servers is captured in a Hot Aisle and brought into the indirect evaporative cooler where it travels through the primary side of the heat exchanger where it gives up its heat to the secondary side. See our video on Heat Exchangers for a better understanding of Plate and Frame Heat Exchangers. 

Indirect Evaporative Cooler in a Data Center
Indirect Evaporative Cooler in a Data Center

The cold air is then sent back to the data center through an underfloor distribution system. The cold air exits through floor grilles and travels back into the server racks where it picks up the heat of the servers and begins the cycle again. On the secondary side of the indirect evaporative coolers heat exchanger, there are fans mounted on top of the unit that pulls outside air through the heat exchanger as water is sent trickling down causing the water to evaporate and absorb heat through the walls of the heat exchanger. 

Checkout these Indirect Evaporative Coolers here

If the indirect evaporative process can’t meet the load because of unfavorable outdoor ambient conditions, a second phase of cooling can be added. This secondary cooling can be achieved by using a DX or Chilled Water coil.

Indirect Evaporative Cooling of Air-Cooled Chillers

Indirect evaporative cooling is also used to cool down the condenser coils of an air-cooled chiller.

Air-Cooled Chiller
Air-Cooled Chiller

Panels containing wetted medium can be attached around the air-cooled chiller, effectively closing off the pathway for the condenser fan inlet air. This causes the condenser inlet air to travel through the media which is sprayed with water based on the ambient temperature and the compressors liquid line temperature.

Air-Cooled Chiller with Evaporative Cooling
Air-Cooled Chiller with Evaporative Cooling

This precools the incoming air before it travels over the warm condenser coils, allowing for increased energy efficiency. Before attaching the panels the condenser coils should be cleaned to ensure the best performance.

Packaged Air Conditioners and Indirect Evaporative Cooling

This is another method of using indirect evaporative cooling to pre-cool air before it enters the condenser coil of a packaged DX unit. This also allows for increased efficiency.

Packaged Unit with Evaporative Cooling Pads
Packaged Unit with Evaporative Cooling Pads

Indirect Evaporative Cooling using a Fluid Cooler

There is another method of providing indirect evaporative cooling by providing a fluid cooler that feeds a cooling coil within an air handler. The fluid cooler provides indirect cooling by spraying water over an enclosed coil that circulates water through an air handler. The coil in the air handler absorbs heat from the space or outdoor air and circulates it to the tower where it gives up its sensible heat to the cool moist air. The water circulated in the Indirect Evaporative Cooler never mixes with the water circulated in the air handler coil.

Indirect Evaporative Cooling Using a Fluid Cooler

If this doesn’t provide enough cooling then a secondary system can be added, like an evaporative cooling section or a chilled water coil as shown here fed by an air-cooled chiller.

Benefits of Evaporative Cooling

  1. It can reduce or eliminate mechanical refrigeration or chiller usage.
  2. Overall energy savings
  3. Initial cost is less than refrigerated air conditioning
  4. Reduced maintenance cost with less skilled maintenance personnel. 
  5. Works good in dry climates
  6. Can save water when compared to a water-cooled chiller plant.
  7. The ability to increase the amount of outdoor air for improved indoor air quality. 
  8. Environmentally friendly as there are no refrigerants, CFC’s or HCFC’s.

Where are Indirect Evaporative Coolers Used

There is a wide application for the use of indirect evaporative coolers in schools, warehouses, offices, retail, industrial and some data centers.

According to a NREL study the use of a multi-stage indirect evaporative cooler there are “Three target market segments that have been identified for this technology: data center installations in ASHRAE climate zones 2B through 6B; outside air pre-conditioner retrofits for air-cooled RTUs in climate zones 2B and 3B; and new construction and facilities that do not currently have cooling systems in climate zones 4B, 5B, and 6B. In ASHRAE climate zones 1A through 7A, the increased outdoor humidity characteristic of these zones reduces cooling capacity and overall energy savings to the point that the multistage IEC will not provide a favorable return on investment.” 

Calculating the Effectiveness of Indirect Evaporative Coolers

The following calculation is often used to inform the engineer about the effectiveness of using an indirect evaporative cooler in a particular climate. Remember that these units work best in hot and dry climates. The higher the value the more efficient the indirect evaporative cooler.

EF = T (DB) – SAT / T (DB) – T (WB)

EF= Evaporative Effectiveness

T (DB) = Ambient Dry Bulb temperature

T (WB) = Ambient Wet Bulb Temperature

SAT = Supply Air Temperature

The greater the difference between the ambient dry bulb and wet bulb temperatures, the better the chances for the efficient use of an indirect evaporative cooler. 

Energy Use and Increased Temperatures

The typical air-cooled air conditioner loses efficiency the higher the outdoor temperature gets, while evaporative cooling usually gets more efficient. 

Summary

Indirect evaporative coolers use less energy than a refrigerant based system, they provide better air quality when ventilation air is increased, they avoid the use of environmentally hazardous refrigerants, and the installed cost is less, including the reduced skill level required of maintenance personnel. The main disadvantage is that they perform best in hot and dry climates only.

How Smart Thermostats Work

MEP Academy Instructor
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How Smart Thermostats Work

How Smart Thermostats Work. We’ll learn how the various features of a smart thermostat works, as the prices vary based on feature availability, and not all Smart Thermostats contain all these features so be sure to review the following list.

If you prefer to watch the Video of this presentation than scroll to the bottom or click on this link. How Smart Thermostat Features Work.

Why Should I Use a Smart Thermostat

The simple answer is that it will save you money and allow you additional conveniences over the traditional thermostat. With a smart thermostat you can control your heating and cooling unit from a smart device, such as your phone, tablet, or computer. With the use of wireless technology your smart thermostat can be controlled from anywhere you have an internet connection.

Checkout these Smart Thermostats here

The United States uses the Energy Star program to identify smart thermostat manufacturers that meet the requirements for reduced energy use as demonstrated across the country in different climate zones. By choosing an Energy Star certified smart thermostat you should be assured of its ability to save energy and enter a low-power standby mode when inactive, which saves you additional money and energy.

Where Can I Buy a Smart Thermostat that is Energy Star Certified

We will provide you with links to the top-rated smart thermostats that are Energy Star Rated in the Video Description below and will cover some of the features they may contain. The smart thermostats can range in price from below $65 to over $300 depending on the features. We’ll also provide a link to the rebate finder for possible rebates for various models. Eligibility is usually based on the replacement of an old non-smart thermostat and the smart thermostat must be on the Qualified Products List for the program.

https://www.energystar.gov/rebate-finder

The Energy Star rebate finder allows you to search by your zip code to find a local store in your area, or you can order online through the links we provide in the video description. 

Smart Thermostat Compatibility

It’s important that you verify that the heating and air conditioning unit you’re using is compatible with the smart thermostat that you want to purchase. You can consult an expert, or you can check the compatibility on the website of Smart Thermostat manufacturers, where they have a compatibility checker to assist you.

Here is the famous Nest Thermostat website that has a compatibility checker. First they request that you shutoff the power at the fuse box to avoid the possibility of an electrical shock, then remove the cover of your thermostat.

Next check for any of the following to be true, which would indicate that your existing system is incompatible.

Smart Thermostat Wire Compatibility Check.
Smart Thermostat Wire Compatibility Check.
  • Does your thermostat have stranded wires?
  • Does your thermostat have thick, stranded wires connected by wire nuts?
  • Is your thermostat labeled to be supplied with 110 or 120 volts?

Continuing to the next screen we see that there are buttons that you click to indicate which wires are connected to your existing thermostat.

Select the wires that your existing Thermostat currently has available.
Select the wires that your existing Thermostat currently has available.

If you indicate that you have connected wires “R”, “W”, “Y”, and “C”, and then click to continue, the compatibility checker informs you which Nest thermostats are compatible with your existing wiring.  As you can see they’ve listed three thermostats that are available for your system.

Nest Thermostat Compatibility Checker has determined that these stats will work with our system choices
Nest Thermostat Compatibility Checker has determined that these stats will work with our system choices

Existing Heating and Cooling System

Most heating and cooling systems installed after 1975 are compatible with smart thermostats. Some systems that use an oil burner or furnace may require an adapter. HVAC systems that have variable speed or multi-stage compressors or have zoning will probably require a professional for the installation. Baseboard heating, biofuels, or in-wall heaters are most likely incompatible with smart thermostats. With all that said, most HVAC systems are compatible with smart thermostats.

Checkout these Smart Thermostats here

Existing Wires and Voltage

If after removing the cover of your old thermostat you discover thicker wires for line-voltage control, then the chances are that your system is incompatible with a smart thermostat. Most of the smart thermostats on the market today use thin, low-voltage wires. Most of the smart thermostats operate with electrical power provided through a common wire to allow for consistent and reliable power for the Wi-Fi connection and the touch screen display. If your system doesn’t have a common wire then you may need an adapter, or a smart thermostat that can work without it if available. 

Smart Thermostat Features

The features of smart thermostats vary, so it’s important that you understand each of the features and choose a thermostat that gives you what you want.

Remote Control. From anywhere where there is an internet connection you can adjust your smart thermostat using your smartphone and a Wi-Fi connection.

Automatic Learning. This feature will allow the smart thermostat to learn and adapt to your routine and preferences for temperature and adjust temperature settings based on a schedule of when you sleep or are away.

Geofencing. If you grant permission to your smart thermostat, it can use the app on your smartphone to determine when you’re at home or away. This feature allows the smart thermostat to save energy by adjusting the temperature lower in heating mode, and higher in cooling mode when you are determined to be a certain distance from your home. This also works to inform the smart thermostat that you are approaching home and to adjust the temperature to your liking.

Vacation Mode. You can inform the smart thermostat when you’re on vacation and it will maintain the appropriate temperatures to avoid freezing water pipes or extreme heat in summer months. These temperatures will be much different then what they will be when the property is occupied. 

Automatic Software updates. This will allow the system to update the application software to ensure that you have the latest and greatest energy saving features.

Sensors. With the use of temperature or occupancy sensor technology you can manage extreme temperature differences. When there is one HVAC system serving several spaces that have differing heating and cooling load profiles, hot and cold spots can occur. The Temperature Sensor will allow the smart thermostat to adjust for these differences. Using an Occupancy Sensor allows the smart thermostat to identify highly occupied rooms and prioritize their temperature.

Voice Commands. Some of the smart thermostats are compatible with voice command programs which will allow you to tell the smart thermostat to increase or decrease the temperature setting in addition to other commands.

Play Music. Yes, some smart thermostats can stream music with an internal speaker.

Where to Locate a Smart Thermostat

The smart thermostat should be located as close to the wi-fi router as possible. Prevent from putting the smart thermostat on an exterior wall or where it will receive direct sunlight as this could give the thermostat a false reading of the interior temperature.

How Waterside Economizers Work

MEP Academy Instructor
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How Waterside Economizers Work

How Waterside Economizers Work. In this video we will learn How Waterside Economizers work, also known as Free Cooling. We’ll learn how to connect an economizer into a water-cooled and air-cooled chilled water system. A 100% free cooling allows for the chiller to be shutoff and the cooling tower along with a heat exchanger to do all the cooling. We will show you three waterside economizer configurations using a plate and frame heat exchanger. 

If you prefer to watch the video of this presentation than scroll to the bottom or click on this link. How Waterside Economizers Work

In our previous video we demonstrated how an air side economizer is based on the ambient dry bulb temperature, and now we’ll show you that a waterside economizer is based on the ambient wet bulb temperature using evaporative cooling. The purpose of a water-side economizer is to reduce or eliminate the hours the mechanical cooling equipment must run, such as a chiller.

Integrated vs Non-Integrated Economizers

There are several methods of operating a waterside economizer. One is for it to be integrated with the operation of the chiller, hence operating simultaneously, or non-integrated, where the chiller is completely off and the economizer has full responsibility to meet the demand of the load.

Integrated Waterside Economizer

The use of an integrated waterside economizer allows for the simultaneous use of both the chillers and the reduced energy consumption aspects of a waterside economizer as required by ASHRAE 90.1

Chilled Water Central Plant before Retrofitting with Waterside Economizer
Chilled Water Central Plant before Retrofitting with Waterside Economizer

 This is a typical primary only chilled water central plant layout, where the primary chilled water pumps serve the chillers and the building load, represented here as a cooling coil.

A plate and frame heat exchanger will need to be added in series with the chillers on the chilled water side for the transfer of thermal energy between the condenser water and chilled water sides. For an explanation of How Plate and Frame Heat Exchangers Work see our previous video.

Integrated Waterside Economizer with Side Stream Pump Option.
Integrated Waterside Economizer with Side Stream Pump Option.

We will tap into the chilled water return piping and connect to the heat exchanger to precool the chilled water return before sending it onto the chiller. To do this we’ll need to add a control valve (CV-1) to divert the flow, and force the chilled water return to go through the heat exchanger.

The waterside economizer can lower the chilled water return temperature before it arrives back at the chiller for mechanical cooling.

This reduces the load on the chiller in an integrated system. When in full waterside economizer mode we need to add a bypass line so that all the water avoids going through the chillers in order to save on pump energy. We’ll add a control valve (CV-2) to open fully while both chiller control valves will be closed to prevent water from going through the evaporator coils. 

This completes one side of the heat exchanger which is the hot side. For the cold side of the heat exchanger we need to connect the condenser water piping in parallel with the chillers, and pipe the cold water coming from the cooling tower basins so that it flows into our heat exchanger, where it will absorb the heat through the plates from the chilled water return. The heat will then be carried by the condenser water to the top of the cooling tower where it will reject the heat to the atmosphere. We need to install a control valve (CV-3) to prevent the flow from entering the heat exchanger when it’s not in economizer mode to avoid additional pressure drop on the pumps.

At the same time, the condenser water pump can reduce its speed and water flow with the use of a Variable Frequency Drive (VFD) to compensate for the reduction in demand on the chiller because of the economizer, if the minimum flow is maintained through the chiller.

When the chiller is at partial load in an integrated economizer system, the condenser will require the manufacturers required minimum flow for head pressure control. The cooling tower will also have a requirement for minimum flow that will need to be adhered to.

There is the option to use a 3-way control valve instead of a 2-way valve, or an option to use a side stream pump to pull the chilled water return through the heat exchanger.

Adding a Waterside Economizer to an Existing Air-Cooled System

You can retrofit an existing air-cooled chilled water plant with an integrated waterside economizer as we show here. Here we have two air-cooled chillers with primary pumps and variable secondary pumps serving the building load. We can precool the returning chilled water temperature before it enters the chiller, thereby taking load off the chiller.

Air-Cooled Chillers in Central Plant before Retrofitting with Waterside Economizer
Air-Cooled Chillers in Central Plant before Retrofitting with Waterside Economizer

We add a plate and frame heat exchanger to the system and a pump which will pull water out of the chilled water return and send it through the heat exchanger, where it will give up some of its heat and be sent back into the chilled water return on its way to the air-cooled chillers.

Air Cooled Chiller Central Plant with Integrated Waterside Economizer
Air Cooled Chiller Central Plant with Integrated Waterside Economizer

Then a cooling tower is added to the system for heat rejection along with a pump to pull cool water from the basin and send it into the heat exchanger where it will pick up heat from the chilled water return system. Then it will exit the heat exchanger warmer and be distributed at the top of the tower where it will give up the heat to the atmosphere.

Non-Integrated Waterside Economizer

The use of a non-integrated economizer strategy provides for the economizer to be either on or off, there is no simultaneous chiller function. When the economizer is operating the chiller is 100% off. The condenser water from the cooling tower will satisfy the cooling load without assistance from the chiller.

Water-Cooled Chiller Plant before Retrofitting with Waterside Economizer
Water-Cooled Chiller Plant before Retrofitting with Waterside Economizer

Here we have a water-cooled chilled water plant served by a cooling tower that we can add a waterside economizer to in a non-integrated method just for you to see the difference.

We install a plate and frame heat exchanger and then tap into the chilled water return piping and connect to the inlet on the warm side of the heat exchanger. From the outlet on the warm side of the heat exchanger we connect into the chilled water supply feeding the load in the building, in this case we show one air handler, but this could be dozens of air handlers.

Non-integrated Waterside Economizer used in Water-cooled Chiller Plant
Non-integrated Waterside Economizer used in Water-cooled Chiller Plant

Next we tap into the condenser water supply coming from the cooling tower basin and feeding the chiller. This will be our inlet on the cold side of the heat exchanger. Then on the cold water outlet of the heat exchanger we’ll connect to the condenser water return piping leaving the chiller and entering the tower.

To make this all work there needs to be control valves that reroute the water when the economizer is activated. Remember this is a non-integrated economizer, so there is no simultaneous running of the chiller. This is why the piping is routed around chiller. Control valves CV-1 and CV-2 will be installed on the chilled water side of the economizer, so that when the economizer is activated and the chiller shuts off, CV-1 will close, and CV-2 will open. This allows the water from the air handler or building load to bypass the chiller and go directly to the heat exchanger.

Next there will need to be control valves on the condenser water side of the heat exchanger to bypass the chiller. Control valves CV-3 and CV-4 are installed on the condenser water supply to the chiller and the inlet piping to the heat exchanger. During waterside economizer mode, CV-3 will close preventing water from entering the chiller, and CV-4 will open allowing the flow to be diverted from the chillers condenser to the heat exchanger.

ASHRAE 90.1 (2019 Section 6.5.1.2.1)

If your local building code has adopted ASHRAE 90.1 then the use of a waterside economizer could be mandated by code under certain conditions or as one of several options to achieve energy saving goals. When the temperature drops below a set value, such as 50 F dry bulb/45 F Wet bulb or (10 Celsius DB/ 7.2 Celsius WB) mechanical cooling would shut down and 100% full waterside economizer would be active.

For those that live in the state of California, in the United States, the temperature requirement thresholds are the same as mandated in the Title-24 Energy Code. When starting up the central plant the control logic will determine whether to activate the economizer mode based on the two approach values being able to meet the chilled water supply temperature setpoint.

Important Temperatures

Some of the key temperatures to look for when determining if an economizer will work in your location is what they call the Approach Temperatures. This would take another video for an in-depth explanation but we’ll get you started with two approaches important for the integrated economizer systems we have explained in this video.

Waterside Economizer Approach Temperatures and Range
Waterside Economizer Approach Temperatures and Range

There is the Cooling Tower or Condenser Water Approach, that defines the condenser water supply temperature in relationship to how close it gets to the ambient wet bulb temperature. Then there is the Heat Exchanger Approach that compares the condenser water supply temperature to the chilled water supply temperature across the heat exchanger.

Another important value would be the temperature range of the condenser water, that’s the difference between the condenser water return minus the condenser water supply.

The three important factors in sizing the water-side economizer are the wet-bulb temperature, the temperature range, and the approach.

How Waterside Economizers Work – Free Cooling with a Fluid Economizer
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