Helpful Hints
Refer to the October 2006 "HVACR Designer Tips" and "Back to Basics," and this month's "HVACR Designer Tips" for additional information.Design Phase
Give proper consideration to adequate duct insulation and pipe insulation based on current energy code requirements.
AHU replacements, as well as most infrastructure upgrades, are ideal candidates for D-B process because approximately 70% to 80% of the project is HVAC, approximately 10% to 15% is electrical work, and the remaining work requires a general contractor to act as a subcontractor to the HVAC contractor. An enhancement to this approach is to have the designer engineer act as the construction manager and have the builder and designer contracted directly by the owner.
Commissioning and the TAB Construction Phase
Prior to the FPT demonstration to the owner, the HVAC contractor is required to complete the PFPT, better known as equipment and system startup. This installation compliance includes signoff of completed work by the electrical contractor, ATC contractor, TAB engineer, equipment manufacturer, insulation contractor, and HVAC contractor.
The PFPT team should also include spot-checking compliance by the commissioning engineer and the facility engineer.
When demonstrating the functional performance of the AHU-1 system, the facility operators participate to receive on-the-job system training. Observing the system performance and performing FPT should include a review of the O&M manual in addition to system training (per LEED® requirement).
Those who contract for commissioning services in the construction phase of the job usually interpret commissioning as being enhanced startup. In reality, commissioning is intended to begin in the schematic phase of a building program.
When observing the AHU-1 system FPT, the commissioning firm will need to have a commissioning engineer at the building automation control panel/computer and another commissioning engineer or technician at the end devices to observe "action-reaction." In many installations, the automatic control computer software may be furnished on the unit (e.g., AHU-1 control panel CP-1) and programmed by the equipment manufacturer.
Review, test, and finalize the sequence of operation of the building system software program, prior to demonstrating the system performance to the commissioning team, to avoid retesting and the issue of who will pay for retesting.
CONFIRM AHU-1 OPERATION BASED ON NEW RETROFITTED UNIT IS OPERATING AS A VAV SYSTEM, BEGINNING IN THE ‘OFF' POSITION MODE OF OPERATION
ACTION: The commissioning engineer will confirm operating positions of the control components. The REACTION will be:
- Outdoor air minimum damper D-1A will (close, open, modulate).
- Outdoor air maximum damper D-1B will (close, open, modulate).
- Return air damper D-2 will (close, open, modulate).
- Exhaust air damper D-3 will (close, open, modulate).
- Cooling coil valve V-1 will (close, open, modulate).
- Supply air fan SAF-1 VFD-1 will be (off, on, modulating).
- Return/exhaust air fan RAF-1 VFD-2 will be (off, on, modulating).
- Smoke damper SD-1 will (closed, open, modulating).
- Discharge air temperature transmitter TT-1 will indicate (55°F, 65°F, no signal).
- Mixed air temperature transmitter TT-2 will indicate (55°, 65°, no signal).
- Return air temperature transmitter TT-3 will indicate (75°, 65°, no signal).
- Outside air temperature transmitter OAT-1 will indicate (55°, 65°, no signal).
- Supply airflow measuring station FMS-1 will indicate (flow, no flow, no signal).
- Return airflow measuring station FMS-2 will indicate: (flow, no flow, no signal).
- Static pressure transmitter SP-1 will indicate (5 in., 0.5 in., no signal).
- Differential pressure transmitter DP-1 will indicate (4 in., 0.4 in., no signal).
CONFIRM AHU-1 OPERATION BASED ON NEW RETROFITTED UNIT OPERATING IN THE ‘ON' POSITION IN A/C SEASON AT 85°F
ACTION: The commissioning engineer will confirm operating positions of the control components. The REACTION will be:
- D-1A will (close, open, modulate).
- D-1B will (close, open, modulate).
- D-2 will (close, open, modulate).
- D-3 will (close, open, modulate).
- V-1 will (close, open, modulate).
- SAF-1 VFD-1 will be (off, on, modulating).
- RAF-1 VFD-2 will be (off, on, modulating).
- SD-1 will (close, open, modulate).
- TT-1 will indicate (55°, 65°, no signal).
- TT-2 will indicate (>55°, 65°, no signal).
- TT-3 will indicate (>75°, 65°, no signal).
- OAT-1 will indicate (55°, >65°, no signal).
- FMS-1 will indicate (flow, no flow, no signal).
- FMS-2 will indicate (flow, no flow, no signal).
- SP-1 will indicate (5 in., 0.5 in., no signal).
CONFIRM AHU-1 OPERATION BASED ON NEW RETROFITTED UNIT OPERATING IN THE ‘ON' POSITION IN A/C SEASON AT 55°
ACTION: The commissioning engineer will confirm operating positions of the control components. The REACTION will be:
- D-1A will (close, open, modulate).
- D-1B will (close, open, modulate).
- D-2 will (close, open, modulate).
- D-3 will (close, open, modulate).
- V-1 will (close, open, modulate).
- SAF-1 VFD-1 will be (off, on, modulating).
- RAF-1 VFD-2 will be (off, on, modulating).
- SD-1 will (close, open, modulate).
- TT-1 will indicate (55°, 65°, no signal).
- TT-2 will indicate (>55°, 55°, no signal).
- TT-3 will indicate (>75°, 65°, no signal).
- OAT-1 will indicate (55°, >65°, no signal).
- FMS-1 will indicate (flow, no flow, no signal).
- FMS-2 will indicate (flow, no flow, no signal).
- SP-1 will indicate (5 in., 0.5 in., no signal).
CONFIRM AHU-1 OPERATION BASED ON NEW RETROFITTED UNIT OPERATING IN THE ‘ON' POSITION IN THE HEATING SEASON AT 35°F
ACTION: The commissioning engineer will confirm operating positions of the control components. The REACTION will be:
- D-1A will (close, open, modulate).
- D-1B will (close, open, modulate).
- D-2 will (close, open, modulate).
- D-3 will (close, open, modulate).
- V-1 will (close, open, modulate).
- SAF-1 VFD-1 will be (off, on, modulating).
- RAF-1 VFD-2 will be (off, on, modulating).
- SD-1 will (close, open, modulate).
- TT-1 will indicate (55°, <65°, no signal).
- TT-2 will indicate (55°, <55°, no signal).
- TT-3 will indicate (>75°, 65°, no signal).
- OAT-1 will indicate (55°, <55°, no signal).
- FMS-1 will indicate (flow, no flow, no signal).
- FMS-2 will indicate (flow, no flow, no signal).
- SP-1 will indicate (5 in., 0.5 in., no signal).
CONFIRM AHU-1 AIR AND WATER BALANCE BASED ON NEW RETROFITTED UNIT OPERATING AT PEAK PERFORMANCE
ACTION: The TAB engineer will confirm operating parameters by programming the BAS computer command unit to maximum flows. The REACTION will be:
- D-1A reading will indicate (minimum and maximum cfm, minimum cfm, maximum cfm).
- D-1B reading will indicate (minimum and maximum cfm, 0 cfm, maximum cfm).
- D-2 reading will indicate (minimum and maximum cfm, minimum cfm, maximum cfm).
- D-3 reading will indicate (minimum and maximum cfm, 0 cfm, maximum cfm).
- Cooling coil valve reading will indicate (gpm, pressure drop, gpm and pressure drop).
- Cooling coil reading will indicate (gpm, pressure drop, gpm and pressure drop).
- SAF-1 reading will indicate (cfm, rpm, static pressure, all three).
- RAF-1 reading will indicate (cfm, rpm, static pressure, all three).
- SD-1 reading will indicate (minimum and maximum cfm, minimum cfm, maximum cfm).
- Prefilter and final filter reading will indicate (cfm, pressure drop, cfm and pressure drop).
- SAF-1 motor reading will indicate (rated amp and voltage, actual amps and voltage, both rated and actual).
- RAF-1 reading will indicate (rated amp and voltage, actual amps and voltage, both rated and actual).
Log on to www.buildingsmartsoftware.com for the complete Commissioning 1-2-3 process and also refer to this month's "HVACR Designer Tips" for the equipment startup checklist for additional information. If you have any comments, suggestions, or questions regarding the AHU Replacement - Design Test, please contact Howard McKew, P.E., C.P.E, by e-mail at hmckew@RDKengineers.com.
