Sequences of Operation (Guideline 36)

Learning objectives

• >Explain trim-and-respond reset and the role of requests in Guideline 36
• >Describe AHU supply air temperature reset, static pressure reset and economizer logic
• >Describe chilled-water plant pump staging, DP reset and minimum-flow bypass
• >Write a plain-English sequence of operation and critique it against Guideline 36

Sessions

Three 2-hour weeknight sessions plus a weekend block. Check each one off as you finish it.

1. SESSION 1· 2 h Register for ASHRAE free read-only access. Read the Guideline 36 overview and the trim-and-respond logic
2. SESSION 2· 2 h G36 VAV AHU sequences: supply air temperature reset, static pressure reset, economizer
3. SESSION 3· 2 h G36 plant sequences, including the hot-water plant addendum
4. WEEKEND· 4 h Exercise: write a primary-variable chilled-water plant pumping sequence, then compare it with G36. Field visit #1

Answer in your notebook first, then reveal the answer and grade yourself honestly.

1. Q1Explain trim-and-respond in one sentence.

   [ reveal answer ]

   The setpoint is trimmed a little at regular intervals and raised (responds) when enough zones or valves report requests.

   ✓ I got it ✗ Missed it

2. Q2In Guideline 36, what generates a 'request' for a higher pump DP setpoint?

   [ reveal answer ]

   For example, a chilled-water valve that is nearly fully open (above about 95%) for a sustained period generates a pressure request.

   ✓ I got it ✗ Missed it

3. Q3Why does resetting duct static or loop DP save so much fan or pump energy?

   [ reveal answer ]

   Fan and pump power scale roughly with the cube of speed, and lower setpoints reduce throttling across valves and dampers.

   ✓ I got it ✗ Missed it

4. Q4In a primary-variable chilled-water plant, what is the minimum-flow bypass for?

   [ reveal answer ]

   It keeps chiller evaporator flow above the manufacturer's minimum.

   ✓ I got it ✗ Missed it

5. Q5Name one economizer problem that well-written sequences guard against.

   [ reveal answer ]

   Examples: high-limit lockout so warm outdoor air isn't used, coordination of the dampers with mechanical cooling, and freeze protection.

   ✓ I got it ✗ Missed it