Honeywell economizer

Paul S_3

can anyone explain to me how to set up a economizer.....for example the "min pos" setting.....0 vdc-10 vdc setting, and what the a b c d setting means and what to set it at.....i kno what the economizer does as far as what it does with the compressors "y1" & "y2".....i just would like someone to explain more in depth than what the paperwork tells me thank you

               Paul S

EBEBRATT-Ed

economiser

Set the minimum position potentiometer to the minimum amount of outside air you want to maintain. When the unit is shut off the O A damper will close. Whenever the unit is running the damper will open to the minimum position setting. If the unit is calling for economiser operation the damper will open more to use outdoor air for free cooling if the outdoor air is suitable.



A,B,C, AND D ARE THE SET POINTS USED TO DETERMINE THE TEMPERATURE AND HUMIDITY THAT YOU WANT TO USE FOR THE ECONOMISER OPERATION. FOR INSTANCE A. COULD BE 70DEG AT 50% RH, B COULD BE 65 DEG AT 50% RH, C COULD BE 60 DEG AT 50%RH.

the set point determines economiser operation and changeover to mechanical cooling setpoints. refer to the paperwork for you specific controls. hope this helps

Wesman

ABCD

In the product data form 63-2528 included with the W7210 series of controls, Figure 6 shows the setting choices on a psychometric chart with corresponding temp to humidity variations. Generally the A setting would be the most aggressive choice allowing the greatest opportunity for free cooling. At midpoint of 50% humidity it would allow free cooling up to 73F. At the same A setting if the humidity fell to 10% it would still allow free cooling up to 83F. Follow the A line and you can see the tradeoff of temp to humidity as each variable changes. The down side is that there may not be much space cooling going on at the bottom of the A line at 83F and a lot of humidity entering at the top of the A line.

Alternately the D setting will permit the least opportunity with the mid point being 50% humidity at 63F and with 10% humidity 73F. Each setting has target points along the corresponding curve that combines temp and humidity and is expressed as enthalpy.

When the enthalpy is to the right side of the curve, "free cooling" would stop and the OA damper would move to the minimum position you set on the potentiometer. Whenever you are to the left side of the chosen line you are in free cooling. During times of colder weather the outdoor air (cold) and return air (space temp) dampers will modulate to maintain an approx 55F mix. measured at the C7046 sensor. This is not adjustable.

If the economizer free cooling could not keep up with space demand for cooling the thermostat would call for the 2nd stage of cooling. The economizer would continue to act as the 1st stage and the mechanical cooling 1st stage would be called upon to act as the 2nd stage.