What is an economizer in hvac

So, the other day, I was having a conversation with a colleague and he couldn’t stop complaining about the outrageous bills he has to pay on electricity at the end of every month because of his HVAC system, so I advised him to get an Economizer. But to my surprise, he said he was hearing that for the first time.

Just like my colleague, people all around the world always look for ways to reduce the running cost of their HVAC systems. If you also find this challenging, you might also be wondering “what is Economizer in an HVAC system?”. Well, the good news is, I was able to help my friend achieve his goal and I intend to do the same for you with this article, so keep reading.

What are HVAC Economizers

Derived from the word Economize which means to reduce wastage or extravagance. An economizer in HVAC is designed to help facility managers and homeowners reduce the energy consumption rate of their HVAC system. It is usually positioned on the top of the HVAC system or facility and helps to reduce the general workload of the HVAC system by making use of air drawn from outside to cool or heat the building.

Is Economizer a heat exchanger

Yes, Economizer is a heat exchanger. A heat exchanger works by transferring heat between fluids either in gaseous, liquid, or vaporized form at differing levels of temperature. On the other hand, an HVAC economizer work by transferring air from the outside to the interior of a building, in as much as the outside temperature meets the preset standard for the HVAC system. Therefore, it is safe to say an Economizer is a form of the heat exchanger.

How do HVAC economizers work

An HVAC system is usually equipped with a temperature sensor and a logic controller. The temperature sensor measures the outside temperature to be taken indoors, while the logic controller compares the outdoor temperature with the preset temperature standard for the HVAC system.

If the outdoor temperature matches up with the preset standard, then the external damper of the HVAC will open up and the compressor of the cooling system will be automatically shut off so that the air drawn from the outside can be taken in and used for cooling the building. But if the outdoor temperature or humidity falls short or is higher than the preset temperature standard, then the damper will remain shut so that the outside air is not taken in.

HVAC Economizer requirements

The international energy conversion code (IECC) prescribed in 2018 that a building is required to use an economizer based on the cooling capacity. The cooling capacity of a building depends on two factors – the climate and the number of occupants. This requirement aims to see that economizers are put in the place where they are needed the most so that optimum results can be arrived at. An economizer is best used in areas with arid temperatures.

In the united states, while some cities like New York require that economizer must be installed to all HVAC because of the temperature, some cities like Florida which usually experience high temperatures most of the year do not require that an economizer be installed.

In states where it is mandatory to install economizers, it is required that the total net capacity of a building (usually in btu) must not be lower than the value given for building occupancy. For example, if the cooling capacity of your building is 500000 btu and the value given for your building occupancy is 600000, then you are not required to use an economizer.

Note: The figure here is just an abstract and therefore, you must check with the appropriate authorities within your state/city for the actual figure.

HVAC economizer sequence of operation

An HVAC economizer sequence of operation determines how energy efficient the device will be when put to use. Below is the highlight of what the sequence of operation of an HVAC economizer should be.

  1. The sequence should begin with what needs to be controlled which in this case is the Mixed air temperature.
  2. Add the proportional integral derivative (PID) or comparative logics and setpoints.
  3. Determine what output will be controlled by the logic.
  4. Input an enabling logic or instruction of what is required when the loop is disabled.
  5. Provide details about input and output as well as the parameters.

What is an additional benefit of an economizer on an HVAC system

The major reason why Economizers are designed is to help reduce energy consumption. However, there is more to it and that is why in this section, I will also tell you other benefits you are going to enjoy if you use an economizer.

1. Energy efficiency

In the course you running an ac unit, a lot of energy is usually consumed, and operating them for long hours ( especially in commercial or large residential areas) will only lead to an increase in electricity bills. Economizers compare indoor and outdoor air for compatibility. Once the outdoor air matches the indoor air, the ac unit will be shut off and the outdoor air will be used to cool the room. When this happens, energy the energy that is supposed to be consumed by the ac unit is saved.

2. Improved ventilation

By comparing both indoor and outdoor air and substituting the indoor air for the outside air, natural ventilation is being utilized and this will increase the quality of air circulating throughout the building.

3. Prevention of wear and tear

When you run your ac unit uninterruptedly for long hours, there are chances that they will wear out earlier than expected because the more you use them, the more the unit’s components are used and become tired. But when the air conditioner is interrupted by the economizer, its lifespan will be extended because it will be working lesser. Therefore, an economizer does not only save money for electricity bills but also helps to save the cost of maintenance and repairs.

How much does an HVAC economizer cost

The cost of an HVAC economizer depends on the capacitor of the compressor and their prices are compared in the table below.

The capacity of compressor in ton Average cost ($)
Lower than 10 $500
Higher than 10 up to 20 $900
Higher than 20 up to 30 $1100
Higher than 30 up to 60 $2500
Higher than 60 up to 100 $4000

Note: If you are adding Economizer to an existing system, you will be charged an extra cost of $1000 for installation.

Is the HVAC economizer worth it

Yes, the HVAC economizer is worth it. If you are worried about the cost of acquiring an ac unit with an economizer or retrofitting an existing one, I can assure you that you will pay much more on electricity bills if you let the cost discourage you from buying it, so it is worth it.

Do I need an HVAC economizer

No, you do not need an HVAC economizer if it is not mandated by any authority in your state that you have one because its absence does not mean your ac unit will not function optimally. Nevertheless, I would advise you to get one so that you can save lots on your electricity bills.

Best economizer for HVAC system

There are three types of Economizer for HVAC systems. We have the Dual or differential enthalpy Economizer, Dry bulb Economizer, and the Single or wet bulb enthalpy Economizer. It is hard to choose the best because people look for a specific quality when shopping for an economizer. While some people may be considering one with low cost, some might be bothered about the efficiency level.

In terms of price, the Dry bulb Economizer is the cheapest, although is not as efficient as the other three.

But in terms of efficiency, the Dual or Differential enthalpy Economizer is the best because it is equipped with sensors which means that temperature will be more accurately calculated. However, it is the most expensive of the three.

The Single or wet bulb enthalpy is an upgrade to the dry-bulb Economizer. More efficient but expensive than the Bulb economizer. But cheaper and less efficient compared to the Dual or differential enthalpy Economizer.

How to check if my HVAC have an Economizer

If you live in an old building, there is a higher chance are that your AC unit does not have an economizer. With that being said, not all modern HVAC system is equipped with an economizer too. To know if your HVAC system has an economizer, check the gas stack outlet of your HVAC boiler. It is usually located close to the place. Just have it in your mind that you are looking for an object that looks like a  stacked vent.

How to install economizer in HVAC

Follow the steps below for instructions on how to successfully install an economizer.

  1. Unpack the disassembled parts of the economizer from the box without leaving any behind. Cross check every with the list of contents in the installation manual.
  2. Arrange all the hood assembly, following the guidelines provided in the instruction manual ( don’t worry, it’s pretty simple).
  3. Remove the readily installed blue/yellow bypass and fit the plug into the control area and connect the existing harness to the economizer.
  4. Place the jade controller and the ground wire on the controller.
  5. The economizer plug should be disconnected from the main terminal ( usually the blue board)
  6. Fix the harness removed earlier in step 3 into the tenth – male adapter that is connected to the Jade controller.
  7. Check for harness connected to the Jade controller (labeled Econ) and put it in the Econ section of the main terminal board.
  8. Check for another harness attached to the economizer and connect it with the fourth pin – male adapter attached to the Jade controller and run the harness into the blower.
  9. Look for a pink/purple harness with the spayed end in the blower and connect to the controller you run earlier into the blower section.
  10. Place the mixed air temperature sensor on one side of the blower case and connect to the ground orange wire usually at the end of the harness that ran into the blower.
  11. Straighten out all the wires and power the equipment.

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