Compare zone loads, ventilation, and exact catalog points to check terminal flow, pressure, and capacity margins.
Concepts behind this calculation
Compare documented single-duct VAV candidates across cooling, minimum ventilation and hot-water reheat, including sensor range, pressure, capacity and catalog sound limits.
A cold-primary VAV terminal with hot-water reheat must handle cooling, neutral operation and peak heating. Cooling airflow follows the zone sensible load and the room-to-primary temperature difference using the entered density and specific heat. Heating airflow must carry the net zone load without exceeding the discharge-temperature cap. Coil duty also includes warming the cold primary air, so it is larger than the zone heating load alone.
The configured minimum is constrained by primary ventilation, the project minimum, controller limits and the pickup’s valid signal floor. Those constraints can govern even when thermal load is small. Selection then needs exact flow and package-pressure rating support for all three states. Sensor differential, minimum terminal drop, coil drop and bare-terminal acoustic rating pressure describe different boundaries and cannot be substituted for one another.
How to use this calculator
Complete Terminal, controller, coil and rating reference and Ventilation, sequence and project-limit reference; establish the candidate and project basis.
Enter the zone sensible loads, cold primary and room temperatures, Maximum permitted heating discharge temperature, Actual air density and Air sensible specific heat.
Enter Required primary ventilation airflow, Additional configured minimum airflow, the three project airflow caps, state-specific available terminal-plus-coil differentials and both catalog NC limits.
Add Candidate rows and exact-condition Rating rows, choose Candidate selection objective and review every state’s sensor, pressure, coil and acoustic margins.
Calculation method and applicability
Sensible factor=60ρcp. Cooling CFM=zone cooling load/[factor×(room−primary)]. Heating CFM≥net heating load/[factor×(maximum discharge−heating room)]. Minimum=max(primary ventilation, project minimum, controller minimum, K√minimum signal). Peak coil duty=net zone heat+factor×heating CFM×(heating room−primary); neutral coil duty=factor×minimum CFM×(neutral room−primary). Match exact source flow and bare pressure plus coil drop.
ρ = actual density (lbm/ft³); cp = compatible mass specific heat (BTU/(lbm·°F)); sensible factor = 60ρcp. Thermal loads and coil duties are BTU/h, temperatures °F and terminal flows CFM; K√signal follows the documented pickup units.
Input definitions and units
Terminal, controller, coil and rating reference
Required: ID-to-model/controller/coil mapping, source revisions, sensor label/calibration and units, entering air/water and water flow, pressure boundaries, lining/accessories and acoustic rating basis. Source notes do not authenticate a complete assembly.
Ventilation, sequence and project-limit reference
Required: source of primary ventilation requirement, selected control sequence, project flow/temperature limits and any applicable code edition or exception. Outdoor-air volume must be converted to required primary supply by the appropriate system analysis before use.
Candidate and project basis established?
Confirm cold primary air with modulating hot-water reheat, matching controller/sensor data and exact rating conditions. The example is constructed from separate component points; it does not certify the combined package. Choices: Not established — withhold comparison; Documented for this limited comparison.
Zone sensible cooling load (BTU/h)
Use the corresponding zone sensible load, not equipment nameplate capacity. Coil duty includes additional primary-air reheating separately.
Zone net heating load (BTU/h)
Use the corresponding zone sensible load, not equipment nameplate capacity. Coil duty includes additional primary-air reheating separately.
Cold primary air entering the terminal (°F)
Common entering air condition for all three stated scenarios. Warm-primary central heat is outside this model.
Cooling room design temperature (°F)
Cooling airflow is load divided by the actual primary-to-room temperature difference.
Neutral-state room temperature (°F)
Neutral mode reheats the configured minimum cold primary airflow to this temperature; no net zone heating is assumed.
Heating room design temperature (°F)
Peak heating coil output includes both zone heat and warming primary air to this room temperature.
Maximum permitted heating discharge temperature (°F)
Project-supplied limit, not a universal energy-code or comfort default. Determines minimum heating airflow for the entered net load; neutral room temperature must not exceed this cap.
Actual air density (lbm/ft³)
Explicit constant-property model input. Source pressure/acoustic/coil ratings must match the relevant air condition; no automatic altitude correction is applied.
Air sensible specific heat (BTU/(lbm·°F))
The sensible factor is 60 × density × cp, not a universal 1.08 at every site.
Required primary ventilation airflow (CFM)
Already-resolved primary supply requirement for this terminal. This is not raw outdoor Voz, ACH or a direct fraction of cooling airflow.
Additional configured minimum airflow (CFM)
The chosen minimum is the largest of this value, primary ventilation, candidate controller minimum and sensor range floor. No universal deadband percentage is assumed.
Project cooling airflow cap (CFM)
Document the actual sequence/project/code basis. A failed cap preserves the required airflow and deficit; it does not clip the answer into a pass.
Project neutral/reheat airflow cap (CFM)
Document the actual sequence/project/code basis. A failed cap preserves the required airflow and deficit; it does not clip the answer into a pass.
Project heating airflow cap (CFM)
Document the actual sequence/project/code basis. A failed cap preserves the required airflow and deficit; it does not clip the answer into a pass.
Available terminal-plus-coil differential: cooling (in. w.g.)
Available inlet-to-package-outlet static differential after other system losses. A rating row must match bare-terminal differential plus coil drop; acoustic data use that bare-terminal pressure, not the total package value.
Available terminal-plus-coil differential: neutral (in. w.g.)
Available inlet-to-package-outlet static differential after other system losses. A rating row must match bare-terminal differential plus coil drop; acoustic data use that bare-terminal pressure, not the total package value.
Available terminal-plus-coil differential: heating (in. w.g.)
Available inlet-to-package-outlet static differential after other system losses. A rating row must match bare-terminal differential plus coil drop; acoustic data use that bare-terminal pressure, not the total package value.
Maximum radiated catalog NC upper bound (NC)
Separate comparison using the same documented catalog rating convention. This is not measured room NC or dBA, and no radiated/discharge noise sum is performed.
Maximum discharge catalog NC upper bound (NC)
Match the source pressure, airflow, lining and acoustic attenuation convention. For a source stated as less than NC10, a documented conservative upper bound of10 may be used; do not substitute zero.
Candidate selection objective
Only candidates with all three operating states supported and passing every entered criterion are ranked. A lower ID breaks exact ties. Choices: Smallest effective control maximum; Largest minimum coil-capacity margin.
Candidate rows: ID, min flow, max flow, K, min signal, max signal, heater minimum, max package pressure (CSV)
One to20 rows. Flow values in CFM; K in CFM per square-root in. w.g.; pressure signals and admitted package pressure in in. w.g. Additional heater minimum is a documented requirement, not inferred from inlet size. The example controller signal limits and2 in. w.g. package cap are constructed project assumptions; actual controller data must replace them.
Rows use CFM, three pressures in in. w.g., actual-condition coil capacity in BTU/h and separate catalog NC upper bounds. Match exact flow and package differential; no interpolation or extrapolation. Reuse a row for multiple matching states. Example values are separate Titus terminal/coil source points; their combined acoustic package applicability is not authenticated. Replace with matching complete assembly data for actual selection.
How to interpret the result
Read every candidate across cooling, neutral and heating states. Retain calculated flow deficits rather than reducing required flows to pass a cap. The ranked ID requires complete matching ratings; separate catalog NC comparisons do not predict whole-room noise.
Worked examples
Worked example
Inputs: Constructed project using separate published Titus size 8 component points: primary 55°F, cooling room 75°F/load 17,280 BTU/h; heating room 70°F/net load 12,960 BTU/h and discharge cap 90°F; neutral room 75°F. Primary ventilation 600 CFM, project caps 900/650/700 CFM. Candidate controller 90–900 CFM, K904, illustrative signal 0.01–1 in. w.g. Ratings at 800/600 CFM use bare differential 0.5 in. w.g. and coil drops 0.51/0.32, giving package differentials 1.01/0.82.
Result: Candidate 1 meets the entered three-state arithmetic checks. This is a component-based teaching fixture, not a real controller certification, complete combined-package acoustic rating, field result or energy-code approval. At800 CFM the source radiated/discharge catalog values are24/28; at 600 CFM they are20/28, evaluated separately.
Assumptions and limits
Only cold-primary single-duct terminals with modulating hot-water reheat are covered. Electric heat, fan-powered, dual-duct, warm-primary central heat and automatic full sequence/code verification are outside this model.
The controller window is constrained by documented flow limits and calibrated sensor Q=K√ΔP. Catalog typical-control ranges are guidance, especially for controls supplied by others; they do not prove an actual installed controller or transducer can measure those flows.
Primary ventilation must already be calculated for the actual ventilation system and outdoor-air fraction. This page does not implement62.1 system ventilation or equate outdoor Voz with primary supply.
Project neutral/heating/cooling caps and maximum discharge temperature require their own adopted-code/sequence basis. No universal 20%, 30%, 50%, 1,200 FPM or fixed turndown rule is embedded, and the large example primary minimum is not a recommended energy-code setting.
Coil capacity must match actual entering air/water temperatures, water flow, row count and assembly. Do not paste a 180°F/55 °F capacity for another entering condition without source correction. The page performs no water-flow or temperature correction and does not assess valve authority or hydronic design.
Radiated and discharge catalog NC are separate source-rating comparisons using a particular attenuation convention. They are not measured room NC, octave sound power or dBA and cannot be added. Bare-terminal acoustic points do not certify noise from a complete terminal-plus-coil package.
Exact actual flow/package-pressure coordinates are required for each operating state. Missing data withhold selection; no pressure, coil or sound interpolation is used. A supported rating row can be reused for matching states.
The worked example combines published component coordinates with constructed loads, project caps and controller thresholds. It verifies arithmetic only; it does not authenticate combined-package acoustics, field control performance or actual project compliance.
Titus sound tables reference ASHRAE 130-2008/AHRI 880-2011 and NC via AHRI 885-2008 AppendixE, with certification limited to marked points. No broader AHRI certification claim is made here.
The February 2016K-factor source and March 2002sensor guide disagree on the size 5 constant; no generic size5preset is embedded. The example size 8 K904 agrees, but actual label/controller calibration must still be confirmed.
FAQs
Is Required primary ventilation airflow the outdoor-air requirement?
It is the already-resolved primary supply requirement for this terminal. A separate system ventilation analysis must account for outdoor-air fraction before that value is entered here.
Why does neutral operation need coil heat with no zone heating load?
The configured minimum still delivers cold primary air. Neutral coil duty warms that air to the neutral room temperature without adding net zone heat.
Sources
Titus ESV performance and control ranges, April 2025 fileM16control guidance and selection procedure; M17/M18separate radiated/discharge sound and full-open minimum terminal pressure. Actual product-page link was followed; a stale performance filename returned an HTML error and was excluded.
Titus ESV hot-water coil dataSize 7/8, two-row, 3 GPM: 600 CFM, 28.6 MBH, 0.32 in. w.g. coil loss;800 CFM, 32.5 MBH, 0.51 in. w.g. Capacity basis 180°F entering water/55°F air; actual selection requires matching conditions.
Titus single-duct control strategiesDifferent hot-water reheat minimum/maximum sequences are described; this page implements its explicit steady three-state envelope, not a complete automatic control sequence.
Titus ESV submittal, February2,2026Product family/configuration context and nominal flow ranges; dimensions alone do not establish controllability or sound.
Nailor 3000/3100 single-duct terminal catalogIndependent manufacturer guidance separates controller transducer sensitivity, control ranges and rating conditions. No Nailor coefficient or range is transferred to the Titus fixture.
