Open-blade pressure drop vs face velocity
Specification text
Equipment schedule
Data basis and assumptions
Ratings (max pressure, max velocity and leakage at 1 in w.g. by section width) come from Ruskin's control damper quick product selection (May 2022). Each section is rated at the next published width up (12, 24, 36, 48, 60 in). When the closed ΔP or velocity is too high for a width, the tool splits the damper into narrower sections. CD44, CD45 and CD46 ratings and torques come from the Kele catalog page (2,000 fpm at 2.5 in w.g.).
Models: CD44, CD35, CD45, CD46, CD36, CD40, CD60, CD50, CD51, CD403, CD50V, CD60V, TED40, CD40X2, TED50, TED40X2, TED50XT, TED50V, CD36CE, CD60SS and CD60CE. Equivalent variants (CD355, CD356, CD504, CD50DC/GS/CE/IF, CD60DC/GS, TED50DC/GS/CE, TED50VXT) are noted on their base model. Round, oval, zone mixing and balancing dampers are not included.
Sizes: Ruskin's quick reference doesn't list single-section maximums. CD60, CD50 and TED50 use 60 × 72 in, and V-groove models use 48 × 72 in. Other models take the size of the closest family member or the widest published width, and their cards say so.
Leakage at the design ΔP is the published 1 in w.g. leakage × √(ΔP / 1 in). Class 1A is defined only at 1 in w.g., so a 1A requirement means 1A at 1 in plus Class 1 at the design ΔP. CD44 has unsealed blades and no leakage rating.
Pressure drop uses loss coefficients fitted to TED50 published AMCA 5.2, 5.3 and 5.5 data, interpolated by section perimeter-to-area ratio and corrected for air density. Other airfoil models use the same curves (estimate). V-groove blades use 1.5× and flat blades 1.2× (estimates).
Torque: CD60 family 5 in·lb/ft² opposed, 7 parallel; CD50, TED and other aluminum models 7; CD36 and CD35 5 opposed, 7 parallel; CD44 2.5, CD45 5, CD46 7. The tool applies the safety factor and matches common actuator sizes of 35 to 270 in·lb.
Relative cost ($ to $$$$) is an indicative ranking used to pick the recommendation. Confirm it against current pricing.
Authority = damper ΔP open ÷ (damper ΔP + branch ΔP). Auto blade action picks opposed below 0.25 authority for modulating service and parallel above it, or for two-position service.
Ratings come from Ruskin's life safety damper quick selection guide and model spec sheets. Every model is rated 2,000 fpm and 4 in w.g. at 350 °F. FSD60, FSD60-2 and FSD60-3 carry higher ratings at 250 °F: 4,000 fpm and 8 in w.g. on assemblies up to 48 × 48, 96 × 24 or 24 × 96 in, and 3,000 fpm and 6 in w.g. up to the full multi-section size (FSD60 and FSD60-2). FSD60-3 higher ratings apply to select sizes only, so the tool flags them for confirmation.
Sizes: FSD60 single section 32 × 48 vertical, 30 × 48 horizontal; multi-section 120 × 96 (144 × 96 horizontal with pneumatic actuators). FSD60-3 single 30 × 48; multi 120 × 96 vertical, 144 × 96 horizontal. FSD36 single 36 × 48; multi 126 × 96 vertical, 120 × 96 horizontal (144 × 96 pneumatic). FSD35 and FSD37 are assumed to share FSD36 sizes. FSD60-2 is assumed to share FSD60 sizes. LP models run up to 36 × 14 in. FSD60V is single section up to 48 W × 32 H.
Leakage shown is the maximum allowed by the UL 555S class at the design pressure (Class I 8, Class II 20, Class III 80 cfm/ft² at 4 in w.g.; 11 / 28 / 112 at 8 in; 14 / 35 / 140 at 12 in), interpolated and scaled by √P below 4 in.
Pressure drop uses the control-damper loss curves scaled so a 24 × 24 damper shows 0.03 in w.g. at 1,000 fpm (AMCA 5.3), the maximum stated in Ruskin's FSD specifications. Treat it as an upper estimate.
Actuators: UL 555S requires factory-mounted actuators. The tool counts one actuator per section. On multi-actuator assemblies, wire all actuators to a common point for simultaneous closure. LP models cannot take internal-mount actuators. Modulating service needs an FSD60M or FSD60-3M, limited to 2,000 fpm and 4 in w.g.
Current products (Ruskin documents 2024–2026): Airflow-IQ AiQ-TD-50, AiQ-TD-50C, AiQ-TD-60 and AiQ-TD-60C stations with TDP05K thermal dispersion probes (0 to 5,000 fpm, ±3%, Modbus/BACnet/analog, up to 16 probes and 128 points), the TDP05K probe array, and the AMS050 velocity pressure station (300 to 5,000 fpm, ±3%, CD50 Class 1A damper). Above 2,000 fpm the AMS050 needs the RAM actuator or AMS8100 transducer.
Legacy products come from Ruskin's 2012 measuring solutions brochure and are flagged for availability: AMS, AML3, AML6, IAQ350XL, IAQ50X, EAMS060, EAMP, AMP probe kits, EFAMS fan inlet and CDRAMS round. EAMS050 is discontinued; Ruskin points to Airflow-IQ and TDP05K. Recommendations rank current products first.
Sizing: velocity = airflow ÷ face area (free area for measuring louvers, using the louver free-area fit at 45%). Both minimum and maximum airflow must fall inside the rated range. Sensing point counts for thermal dispersion use a typical area-based density (4 points under 2 ft² up to 16 at 25 ft², then 1 per 2 ft², max 128). Confirm them with Ruskin's TDP05K placement tool.
Pressure drop: AMS050 from its published 12×12, 24×24 and 36×36 data; Airflow-IQ and EAMS from the CD50/CD60 damper curve; probes, louvers and CDRAMS are estimates. AiQ-TD-60/C, AiQ-TD-50C and TDP05K-only size and temperature limits are assumed from the AiQ-TD-50 spec.
Models: ELF211D, ELF375DX, ELF445DX, ELF6375DX, ELF6350DMP, ELF6425DD, ELF6375DXH, ELF40V, EME420DD, EME520DD, EME520V, EME6625, EME6325D, XP500, XP500WD, ELF375DXD, ELF6375DXD, EME420MD, EME520MD, EME6625D, HZ850 and ACL445/645/845/1245. Depth, blade, free area at 48 × 48 in and approvals come from Ruskin's architectural louver catalog. Adjustable, combination and penthouse louvers are not included.
Free area for other sizes uses a fit to the published ELF6375DX free-area table, FA = c × (W − 3.9)(H − 2.0) / 144 in ft², with c set by each model's 48 × 48 free area. The frame allowances swap for vertical-blade models. The fit matches the ELF6375DX table within about 1%. For other models it is an estimate.
Water: the beginning point of water penetration (AMCA 500-L, 0.01 oz/ft² in 15 minutes) is published for ELF375DX (873 fpm), ELF6375DX (1,023 fpm) and EME520DD (above 1,250 fpm, used as 1,250). Wind-driven rain Class A limits for EME520DD are 673 fpm core velocity at 29 mph / 3 in/hr and 408 fpm at 50 mph / 8 in/hr. Other models are flagged for confirmation.
Pressure drop = K × (free-area velocity / 1,000)², density corrected. K comes from published intake points for ELF375DX (0.15 in at 873 fpm), ELF6375DX (0.16 in at 1,023 fpm), EME520DD (0.18 in at 1,139 fpm) and EME6625 (0.20 in at 1,528 fpm). Other models use estimates by blade type, and exhaust uses the intake curve.
Panel sizes: ELF6375DX and EME520DD are 120 × 90 or 90 × 120 in, ELF6375DXD 88 × 120 in at 150 psf, and XP500 96 in high. Other models assume 120 × 90 in. Wind load: ELF6375DX 30 psf standard, ELF6375DXD 100 to 150 psf.
This is an independent selection aid built from published Ruskin literature. It does not replace the manufacturer's selection software or submittal data; confirm final selections in Ruskin's selection software or with your representative. Sources: AiQ-TD-50 / TDP05K spec, Airflow-IQ announcement, AMS050 spec, measuring solutions brochure, EAMS050 spec, IAQ50 spec, architectural louver catalog, louver water penetration report, ELF6375DX spec, ELF6375DXD spec, EME520DD spec, control damper quick reference, life safety damper quick selection guide, FSD60 spec, FSD36 spec, FSD60-3 spec, FSD60-V spec, CD36 data, CD60 data sheet, TED50 spec sheet.