Economizer Operation

What’s an economizer?  Merely put, it’s a mechanical gadget that’s designed to scale back the consumption of power, whether or not or not it’s gasoline, electrical energy, or different. In accordance with Wikipedia, the primary economizer was patented by Edward Inexperienced in 1845.  It was used to extend the effectivity of stationary steam boilers. 

On this article, the dialogue will revolve round air facet economizers.  You’ll sometimes see them as an adjunct constructed into rooftop models used for the aim of “free cooling”.  Free cooling is a humorous time period as a result of it isn’t truly “free”, the fan motor and econmizer controls should be powered with the intention to function, which devour power.  The time period merely demonstrates the truth that much less energy consumption is going down because of the truth we’re using outside air to chill an area fairly than using a compressor or compressors.  Economizers additionally supply the added function of offering recent air to the constructing and it is occupants.  A carbon dioxide sensor may be built-in into the arrange.  As CO2 ranges enhance throughout the constructing, the outside air dampers are commanded to open, filling the house with recent air.  As CO2 ranges drop off, the dampers return to their minimal place. 

The Guts of an Economizer

The economizer arrange employs a number of components with the intention to function accurately.

1) A set of outside air dampers which might be immediately linked to the return air dampers are used to manage air circulate.  They transfer collectively as one, because the outside air dampers start to open, the return air dampers start to shut and vice versa.

2) An outside air sensor.  This sensor is accountable for figuring out if the outside air is suitable at no cost cooling.  Typically, there might be an possibility between a wise temperature sensor or an enthalpy sensor.

Wise Temp Sensor – Measures dry bulb temperature of the air.

Enthalpy Sensor –  Measures warmth content material throughout the air measured in btu/lb.  This sensor takes dry bulb temperature and moist bulb temperature under consideration for complete warmth content material.

3) An indoor air sensor, this sensor reads smart temperature and is accountable for sustaining combined or discharge air temperature.  The damper meeting will modulate in accordance with feed again from this sensor to keep up a pre-determined combined or discharge air set level.  On newer economizer controls, just like the Honeywell Jade for instance, you’ll be able to set the combined or discharge air temperature as desired.  

4) The damper actuator, which receives a sign from the economizer management board and strikes to the assigned place to keep up the combined air or discharge air set level.

5) When utilizing free cooling you could keep in mind that you’re introducing recent air, this added air into the house could cause optimistic stress points inside a constructing.  To eleviate this downside economizers normally can have a built-in barometric reduction damper or energy exhaust system.  

6) The management board is the guts and soul of the operation.  The management board receives sensor enter indicators, internally calculates the following step and relays the output indicators to the damper actuator and energy exhaust motor if utilized. 

Order of operations

To maintain it easy, the next instance might be based mostly on a single stage cooling rooftop unit full with an economizer bundle.

On a name for cooling from the thermostat or BAS (constructing automation system), the Y1 terminal might be powered.  Typically, the sign will first transfer via the rooftop management board and over to the econmizer management.  At that time, the econmizer management will then resolve whether or not to proceed with free cooling or mechanical cooling based mostly upon the outside air circumstances both utilizing smart temperature of the air or the warmth content material of the air measured in enthalpy.  If the outside air will not be appropriate at no cost cooling, the management sign might be then relayed again to the primary management board of the rooftop and provoke mechanical cooling (compressor operation).  If the outside air is appropriate at no cost cooling, the outside air dampers will modulate from their minimal place (damper minimal place is ready up throughout commissioning to keep up fixed recent air to the constructing and occupants) to keep up the combined air or discharge air set level till the house temperature is reached.  As soon as the thermostat or BAS has been happy, the decision for cooling will stop. 

Most air facet economizers generally, work as defined above.  It’s best to contact the producer of the tools you might be engaged on for technical recommendation or when points pertaining to that system come up.  

Take a look at this video of an onsite break down of a Honeywell Jade Economizer

Gary McCreadie