Forum / A-C, Heat Pumps & Refrigeration / Honeywell economizer

## Honeywell economizer (3 Posts)

• ### Honeywell economizer

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
• ### Some Economizer Information

Even when conditions are ideal for "free cooling", buildings require (Under ASHRAE 62) that outdoor air be supplied to the structure for ventilation purposes. In many cases, this minimum air requirement is in the 10% range.

In Central Islip, for example, we use 85 degrees as the design temperature for our cooling systems. So, for a 75 degree return air temperature, we will have a mixed airstream that is made up of 90% 75 degree air and 10% 85 degree air. By mixing these two air streams, we will get:

0.90(75 degrees) + 0.10(85 degrees) = 76 degree mixed air.

The A, B, C and D settings on the economizer control are very similar to the settings on an outdoor reset control; they tell the control which set of "instructions" to follow.

The A, B, C and D settings determine the temperature at which the economizer will return the dampers to the minimum (outdoor) position. Typically, there is a 10 degree range between the A and D settings and often range from about 60 degrees (setting A) to about 70 degrees (setting D).

The calculated mixed air value will be a good starting point for setting the economizer. In the example provided, the mixed air temperature is 76 degrees, so the setting closest to 76 degrees should be used.

Let's say we have the following values for A, B, C and D:

A: 62 degrees
B: 65 degrees
C: 68 degrees
D: 72 degrees

In this case, we would set the economizer control to "D".

At any temperature above 72 degrees, the economizer will move the outside air dampers to their minimum position.

Hope this helps.
Eugene
• ### Dear "Some Economizer Information" -er.

I love how you do that , Professor !
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