Modulating · 2–10 VDC · Spring Return
HAC-43
HAC-43
Belimo TFB24-SR-T
Inline Damper
Proportional Blade Positioning · 24 Vac/dc · Spring Return Fail-Safe · 6"–20"
✓
2–10 VDC analog input — proportional blade positioning from 0 to 100% open
✓
Spring return fail-safe — blade moves to action-code position on power loss
✓
24 Vac or 24 Vdc supply voltage
✓
OPO (spring-open) or OPC (spring-close) — confirm action code with engineer before ordering
✓
End switch available on all sizes for BAS position feedback
✓
No heat bypass — not applicable to modulating control applications
✓
Factory-mounted Belimo TFB24-SR-T — ships ready to install
Is this the right product?
✔ Right product if
Your BAS or DDC controller outputs a 2–10 VDC analog signal and needs proportional blade positioning — anywhere from 0 to 100% open — with spring return fail-safe on power loss.
✗ Not this product if
On/off is sufficient → HAC-40 (TFB24) — simpler, less expensive
3-wire open/stop/close → HAC-34 (CMB24-3-T)
Modulating, hold last position → HAC-60 (LMB24-SR-T)
Line voltage only → HAC-44 (TFB120) for on/off
3-wire open/stop/close → HAC-34 (CMB24-3-T)
Modulating, hold last position → HAC-60 (LMB24-SR-T)
Line voltage only → HAC-44 (TFB120) for on/off
Control Input
2–10 VDC Analog
Supply Voltage
24 Vac / 24 Vdc
Fail-Safe
Spring Return
Sizes
6"–20" even
Action — Confirm Before Ordering
OPO (spring-open) · OPC (spring-close)
What It Does
Proportional blade positioning via 2–10 VDC. Spring return fail-safe. For BAS and DDC analog output control.
The HAC-43 pairs Hoyme's inline damper body with the Belimo TFB24-SR-T spring return modulating actuator. The blade tracks the 2–10 VDC analog signal continuously — 2 VDC holds the blade at minimum position, 10 VDC drives it fully open, and every point between corresponds to a proportional blade position. On power loss, the spring return moves the blade to the fail-safe position set by the action code, regardless of where it was in the modulating range.
Action Code — Confirm Before Ordering: OPO vs. OPC determines both the fail-safe direction and the signal-to-blade direction. The wrong action code means the blade modulates in the wrong direction relative to the control signal. Confirm with the mechanical engineer or DDC controls designer before ordering — this cannot be changed after installation.
Do I Actually Need Modulating Control?
On/off works for most fresh air applications. Modulating is only required when the control strategy demands proportional positioning.
An on/off damper has two states — fully open or fully closed. That is sufficient for most fresh air intake, make-up air, and zone control applications. Modulating control is required when the strategy demands proportional blade positioning:
| Application Strategy | Why Modulating Is Required | Product |
|---|---|---|
| Demand-controlled ventilation (DCV) | CO₂ sensor drives damper proportionally to measured occupancy | HAC-43 |
| Mixed air temperature control | Damper modulates to maintain supply air temperature setpoint | HAC-43 |
| Building pressure management | Damper modulates to maintain pressure differential | HAC-43 |
| VAV fresh air tracking | Fresh air damper tracks variable flow setpoint | HAC-43 |
| Fixed-cycle open/close ventilation | 2-position is sufficient — on/off is simpler and less expensive | HAC-40 (on/off) |
HAC-43 vs. HAC-60: Both accept 2–10 VDC. The TFB24-SR-T (HAC-43) has spring return — blade moves to fail-safe position on power loss. The LMB24-SR-T (HAC-60) has no spring return — holds last modulating position on power loss. Use HAC-43 when a defined fail-safe position is required. Use HAC-60 when holding last position is acceptable.
Belimo Series — Control Type Selector
All Belimo-actuated HAC variants. Select by control type and voltage.
| Model | Actuator | Control Type | Voltage | Spring Return | Link |
|---|---|---|---|---|---|
| HAC-40 | TFB24 | On/Off | 24 Vac/dc | Yes | View |
| HAC-44 | TFB120 | On/Off | 100–240 Vac | Yes | View |
| HAC-43 ← You are here | TFB24-SR-T | Modulating 2–10 VDC | 24 Vac/dc | Yes | — |
| HAC-60 | LMB24-SR-T | Modulating 2–10 VDC | 24 Vac/dc | No — holds last | View |
| HAC-34 | CMB24-3-T | Floating point 3-wire | 24 Vac/dc | No — holds last | View |
| HAC-30 | LMB24-3-T | Floating point 3-wire | 24 Vac/dc | No — holds last | View |
| HAC-35 | CMB120-3 | Floating point 3-wire | 100–230 Vac | No — holds last | View |
| HAC-70 | LMX120-3 | Floating point 3-wire | 100–230 Vac | No — holds last | View |
| HAC-90 | FSLF24 US | Fire & Smoke (UL 555S) | 24 Vac | Yes | View |
| HAC-80 | FSLF120 US | Fire & Smoke (UL 555S) | 120 Vac | Yes | View |
Configuration Guide
Select size, action, and end switch. Confirm action code with the mechanical engineer or DDC controls designer before ordering.
| Variant Code | Fail-Safe Action | Signal Direction | End Switch | Part Number Example (10") |
|---|---|---|---|---|
| OPO | Spring-open on power loss | Increasing signal opens blade | No | HAC-1043-OPO |
| SPO | Spring-open on power loss | Increasing signal opens blade | Yes | HAC-1043-SPO |
| OPC | Spring-close on power loss | Increasing signal opens blade | No | HAC-1043-OPC |
| SPC | Spring-close on power loss | Increasing signal opens blade | Yes | HAC-1043-SPC |
Action code cannot be changed after installation. OPO vs. OPC sets both the fail-safe direction and the 2–10 VDC signal-to-blade relationship. Confirm with the mechanical engineer or DDC controls designer before ordering. Do not assume.
No heat bypass (−H) on HAC-43. The bypass is for on/off zone control where the damper commands fully closed. A modulating damper sets minimum airflow via the control setpoint — no blade bypass required. For on/off zone control with bypass, use the HAC with heat bypass (−H).
Part Number Decoder
HAC-1443-SPO
HAC
Product family: universal inline air control damper
14
Size (2-digit): 06=6", 08=8", 10=10", 12=12", 14=14", 16=16", 18=18", 20=20"
43
Motor code: Belimo TFB24-SR-T, spring return modulating, 24 Vac/dc, 2–10 VDC
O / S
End switch: O = no end switch | S = end switch included
PO / PC
Fail-safe: PO = spring-open on power loss | PC = spring-close on power loss
No −H
Heat bypass not available on HAC-43 — not applicable to modulating actuators
Key Specs
Sizes
6", 8", 10", 12", 14", 16", 18", 20"
Actuator
Belimo TFB24-SR-T
Control Input
2–10 VDC analog
Supply Voltage
24 Vac or 24 Vdc
Fail-Safe
Spring return to action-code position
Action
OPO or OPC — confirm with engineer
End Switch
Optional (S prefix)
Relay
Not available
Heat Bypass
Not available
CSA Status
Confirm with Hoyme
Warranty
2-yr electrical / 10-yr mechanical
Common Questions from the Counter
Answers to what comes up most when specifying the HAC-43.
Do I actually need modulating control, or will on/off work?
On/off works for the vast majority of fresh air damper applications — open when ventilation is called, closed when it isn't. Modulating is required when the strategy demands proportional positioning: demand-controlled ventilation tracking CO₂, mixed air temperature control, building pressure management, or VAV fresh air tracking. If the damper just needs to be open when ventilation is called and closed when it isn't, use the HAC-40 (TFB24 on/off) — it's less expensive and the control circuit is simpler.
What's the difference between the HAC-43 (TFB24-SR-T) and the HAC-60 (LMB24-SR-T)?
Both accept 2–10 VDC and provide proportional positioning. The TFB24-SR-T (HAC-43) has spring return — on power loss the blade moves to the action-code fail-safe position. The LMB24-SR-T (HAC-60) has no spring return — it holds its last modulating position on power loss. Use HAC-43 when a defined fail-safe position is required. Use HAC-60 when holding last position is acceptable and the lighter actuator torque suits the application.
Does the action code affect which direction the blade moves when the signal increases?
Yes — the action code determines both the fail-safe direction and the signal-to-blade relationship. This is why it must be confirmed with the mechanical engineer or controls designer before ordering. The wrong action code means the blade modulates in the wrong direction relative to the control signal. Confirm the specific TFB24-SR-T action code required by the control system against the Belimo product documentation before specifying.
Is there a heat bypass option on the HAC-43?
No — the heat bypass (−H suffix) is not available on the HAC-43. The bypass is designed for on/off zone control where the damper is commanded fully closed and the 10% bypass maintains minimum airflow. A modulating damper can be positioned at any point between open and closed — if the application requires minimum airflow, the modulating setpoint handles that without a blade bypass.
What does the controller need to output to drive the HAC-43?
The controller must have a 2–10 VDC analog output assigned to this damper — not all BAS output cards have analog outputs, so confirm before specifying. The HAC-43 also requires 24 Vac or 24 Vdc supply power to the actuator. If the controller uses 3-wire open/stop/close outputs instead of 2–10 VDC, use the HAC-34 (CMB24-3-T).
Can I replace the TFB24-SR-T actuator in the field if it fails?
Yes — the Belimo TFB24-SR-T is available through Belimo distributors. The actuator mounts to the HAC body and is field-replaceable without disturbing the damper body or duct connections.
Ready to Order
HAC-43 — Belimo TFB24-SR-T Inline Damper
Select your size, action (OPO/OPC), and end switch option. Confirm action code with engineer before ordering.
Configure & Order →
Size · Action · End Switch
Need help specifying the HAC-43?
Technical support available through your Hoyme wholesaler or direct.