Technician’s Guide and Workbook for Zoning Section 7: Zone Damper System Design

Mandatory Design Requirements PROTECTING THE CENTRAL HEATING and COOLING SYSTEM IS A PRIMARY REQUIREMENT!

Space Humidity Control 30% to 60%

Quiet Damper Actuation Damper Actuator

No Drafts or Stagnant Air (Caused By Zone Dampers)

Range of System Range of HVAC system must work for all components in all phases of operation. Airflow across the heat exchanger must always be maintained, and zones must be designed with excess air escape plans!

Zone Temperature Swing Range of HVAC system must work for all components in all phases of operation. 90oF 70oF 72oF VS 60oF

Simultaneous Heating and Cooling Should be avoided in the design if possible. When required the 1st recommendation is use auxiliary equipment. The second (if the above is not possible) is use a polling control scheme.

Zone Priority & Temperature Swing High Priority Areas: Occupied Areas Time of Day Low Priority Can Be used for: Dump zones Overblow

Developing A Zoning Plan (Zoning the Long Residence from Manual J8) Make a Survey: Get or draw the Plans! Get owner expectations. Produce preliminary plan using loads and duct design. Determine room CFM design requirements using Manual D room heating CFM and cooling CFM. Select supply and return outlets and locations.

Developing A Zoning Plan (Long Residence Update) Balancing CFM = 136 CFM cooling and 105 CFM Heating

Long Residence 1st Floor Plan Zone 1

Long Residence 1st Floor Plan Zone 2

Long Residence Basement Plan Zone 3

Zone 1 Long Residence Diffuser CFM H/C

Zone 2 Long Residence Diffuser CFM H/C

Zone 3 Long Residence Diffuser CFM H/C

Equipment Capacity CFM??? 1,000 CFM 1,002 CFM 40,452 BTUH 16,709 BTUH

XYZ Gas Furnace BTUH and CFM Gas Furnace 60,000 input Btuh = 57,000 Btuh output at 1,000 CFM. 57,000 ÷ 40,452 × 100 = 141% With AC: Manual S preferred 140% allowed 200% OK on heating side!

XYZ Gas Furnace 1,000 CFM & 1.5 ton AC Expanded AC data at design conditions BTUH Sensible = 15,000 BTUH Latent = 2,800 BTUH Total = 17,800 Cooling Load BTUH = 16,709 17,800 ÷ 16,709 × 100 = 107% Manual S allows for 115% so we are OK

XYZ External Static Pressure Chart For calculating the final CFM for field balancing numbers measure the OEM ESP and Interpolate the CFM value based on fan motor speed.

XYZ External Static Pressure Chart 1 Fan Speed Low ESP = 0.4 What is the CFM? 812 CFM

XYZ External Static Pressure Chart 2 Fan Speed Medium Low ESP = 0.3 What is the CFM? 1,015 CFM

XYZ External Static Pressure Chart 3 Fan Speed Medium High ESP = 0.35 What is the CFM? (1,140 + 1,089) ÷ 2 = 1114.5 CFM

Field Notes The homeowner’s callback stated the new zone system was noisy in the bedroom and they could not sleep. The Technician measured the system airflow and found it was higher than design. The OEM chart was checked and the fan speed was lowered. The bedroom zone damper was then opened and reset for the design airflow. The homeowner was satisfied with the lower sound levels in the bedrooms.