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Supply air temperature reset
Supply air temperature reset

Standard control strategy for air handling units has been a constant-temperature discharge. In many healthcare spaces, air change rates determine airflow, rather than loads. So, even in a VAV system, minimum airflows are often greater than needed for cooling. Thus, even VAV systems require reheat in many zones most of the time. If we reset supply air temperature based on actual cooling demand, we can reduce the need for reheat for space temperature control.

SATR has been required by energy codes and has been a known good idea for many years, yet it seems to often be disabled, or relatively ineffective. Why is that? What are the keys to effective SATR? What are the pitfalls that keep us in reheat mode?

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Rogue Zones

I've watched a 20,000 cfm air system run at 55 degF 24/7 - even though we had SATR implemented in the control sequence. Why? Because "someone" buried the thermostat in an IT closet. With the thermostat set on 62, the... (More)

SATR v. Static Pressure Reset

I often hear that there is a conflict between SATR and supply fan Static Pressure Reset (SPR). SATR tends to raise the SA temp, causing an increase in airflow, while the goal of SPR is to reduce pressure (and fan... (More)