Motorized Elbow · 24 Vac · Spring Return

HAC-E
Motorized Elbow
Damper

Damper control built into the elbow — for installations where a standard inline HAC won't fit.

  • ✓Blade integrated directly into the elbow fitting — no straight duct sections required upstream or downstream
  • ✓Same patented Hoyme 24 Vac spring return drive as the standard HAC
  • ✓PO or PC spring return — specify at order, cannot be changed after installation
  • ✓Proving end switch available on all sizes — confirms physical blade position
  • ✓No relay option — motor code 10 on all sizes
  • ✓Sizes 5"–9" — 2-year electrical / 10-year mechanical warranty
Is this the right product?
✔ Right product if
You need a motorized damper for fresh air or ventilation control and there isn't enough straight duct for a standard inline HAC — the control point is at or near a duct elbow, sizes 5"–9".
✗ Not this product if
Adequate straight duct is available before or after the control point → use the standard HAC inline damper — easier to install and far easier to service.

Specify the HAC-E only when the elbow is your only realistic control point.
⚠ Plan Before Roughing In
Actuator clearance and service access must be confirmed at the elbow location before the duct is roughed in — not after. See Section 4 for the full pre-installation checklist.
Hoyme HAC-E Motorized Elbow Damper — elbow body with actuator mounted
Hoyme HAC-E installed in tight mechanical room at elbow location

What It Does — and When to Specify It

When the inline HAC won't fit — motorized damper control built into the elbow itself.

The HAC-E is a motorized elbow damper for round duct applications where space constraints prevent installing a standard inline damper in the straight duct run. The damper blade is integrated directly into the elbow fitting itself — you get 2-position open/close airflow control at the elbow without needing straight duct sections upstream or downstream of the control point. Same patented Hoyme 24 Vac spring return drive as the standard HAC. Same PO/PC configuration.

The HAC-E exists for one reason: installations where the duct layout makes a standard inline HAC impractical. In a tight mechanical room where the fresh air duct immediately turns an elbow at the only viable control point, installing a standard HAC would require adding straight duct sections before and after the damper — which may not be possible within the available space. The HAC-E eliminates that problem by putting the control function in the elbow itself.

That said, the standard HAC is always the preferred product when straight duct space is available. Specify the HAC-E when the elbow is your only option. When there's room for the HAC, use the HAC.

HAC-E installed in tight mechanical room — elbow as the only viable control point
If the standard HAC fits — use the standard HAC. The actuator on a standard HAC is mounted on the inline body with clear service access from any direction. On the HAC-E, the actuator is mounted on the elbow body itself — service access must be planned at rough-in, because the elbow location is often in a corner or against a structural element. A standard HAC serviced in place is a ten-minute job. A HAC-E in a tight corner with limited clearance is a harder service call. Specify the HAC-E only when the elbow is your only realistic control point.

HAC vs. HAC-E — Which to Specify

The decision is determined by one site condition: is there adequate straight duct at the control point?

✔ Use standard HAC when…
✓Adequate straight duct is available before or after the control point
✓Preferred for all new construction — easier to install, easier to service
✓Sizes 2"–9" — wider size range than HAC-E
✓Relay option available on 4"–9"
✓Full ADP relay adaptor compatibility
✓Motor serviced in place with clear actuator access
→ Use HAC-E when…
→Elbow is the only viable control point — no straight duct available
→Tight mechanical room or utility space with space constraints
→Retrofit where existing duct layout only permits control at an elbow
→HRV/ERV fresh air connections where the elbow is the first practical control point
→Control point is at a direction change in the duct run
Service access — plan before roughing in: The actuator on the HAC-E is mounted on the elbow body. Its position is fixed by the elbow geometry and cannot be reoriented after installation the way an inline HAC's actuator can. If the actuator is inaccessible after installation, a motor failure means opening up the space — drywall, ceiling tile, or ductwork — to reach it. Plan service access at rough-in. If access cannot be guaranteed, reconsider whether a duct layout change to accommodate an inline HAC is worth the upfront effort.
Where It's Installed
·Tight mechanical rooms and utility spaces where straight duct at the control point isn't available
·Fresh air intake runs where the duct changes direction at the same location where damper control is required
·HRV and ERV fresh air duct connections where the elbow is the only viable control point
·Retrofit fresh air additions where the existing duct layout only permits control at an elbow
·Any round duct application, 5"–9", where space constraints prevent installing a standard inline HAC
ADP relay adaptor compatibility: The HAC-E works with the ADP-0241-S5A for fresh air damper + furnace fan sequencing when the proving end switch variant (SPO) is ordered. The ADP confirms the blade has physically reached the open position before allowing the furnace fan to run — the proving end switch, not the motor run signal, is what the ADP reads. See Section 3 for the proving end switch explained in full.

The Proving End Switch — What It Does and Why It Matters

The word "proving" is precise. It means the end switch proves the blade physically reached position — not that the motor ran, not that the wiring is energized.

What it proves
The damper blade has physically reached its open or closed position and completed the full travel — a true confirmation of blade location
Does not prove
That the motor ran, or that the wiring is energized — a motor signal would give a false positive if the blade is mechanically stuck
Why it matters
On a furnace fan interlock, the ADP relay adaptor uses this signal — not the motor signal — to confirm the damper is fully open before allowing the furnace fan to run

On a fresh air intake system with furnace fan interlock, the distinction between a motor signal and a proving signal matters in practice. The ADP relay adaptor uses the end switch signal to confirm the damper is open before allowing the furnace fan to run. If the signal is not present — because the blade is stuck, because the actuator failed mid-travel, because a duct obstruction prevented full blade travel — the fan doesn't run and the duct doesn't dump unconditioned air into the living space. A motor run signal can't do that. The proving end switch can.

How It Works in a Furnace Fan Interlock Sequence

With ADP-0241-S5A and the HAC-E SPO variant — the sequence that meets ventilation code.

ADP-0241-S5A + HAC-E (SPO) — Ventilation Interlock Sequence
Step 1
Ventilation Call
ADP receives ventilation signal from thermostat or controller
→
Step 2
HAC-E Opens
ADP energizes HAC-E — blade drives to open position
→
Step 3 — Critical
Proving Signal
End switch closes — ADP receives confirmation blade physically reached open position
→
Step 4
Fan Energizes
ADP allows furnace fan to run — fresh air delivered to conditioned space
If the proving signal at Step 3 is not received — blade stuck, actuator failed, duct obstruction — the furnace fan does not energize. No unconditioned air enters the duct system.

When to Include the Proving End Switch

The O prefix (no end switch) is sufficient for simple on/off control. The S prefix (proving end switch) is required when position confirmation feeds back to a controller or relay adaptor.

Control Setup End Switch Needed? Variant to Order
Simple on/off — no position feedback to controller No OPO or OPC (O prefix)
ADP relay adaptor for furnace fan sequencing Yes — required SPO (S prefix, Power Open)
Zone panel with damper position monitoring inputs Yes — recommended SPO or SPC (S prefix)
BAS or DDC controller needing position confirmation Yes — recommended SPO or SPC (S prefix)
Simple thermostat or manual switch — no feedback input No OPO or OPC (O prefix)
Same end switch as the standard HAC, HAC-F, and HOM. The term "proving" in the variant label emphasizes what the end switch actually does — it's the same physical component used across the Hoyme product line for the same purpose: giving a controller or relay adaptor confirmed position feedback rather than an inferred position from the motor being energized. The component is identical; the label is more precise.

Configuration + Installation Planning

Select action and end switch at order — both are factory-set and cannot be changed after manufacture. Read the pre-roughing-in checklist before cutting duct.

Variant and Configuration Reference

Four variants cover all HAC-E configurations. No relay option is available on any HAC-E size — motor code 10 on all.

Variant Code Action End Switch Part Number Example (6")
OPO Power Open No end switch HAC-0610-OPO-E
SPO Power Open Proving end switch included HAC-0610-SPO-E
OPC Power Close No end switch HAC-0610-OPC-E
SPC Power Close Proving end switch included HAC-0610-SPC-E
No relay option on HAC-E. Motor code 10 on all sizes and configurations — relay capability is not available. If a relay output is required at an elbow location, discuss with your wholesaler or contact Hoyme directly. A relay adaptor in the control circuit may be an alternative approach depending on the specific sequencing requirement.

PO vs. PC — Which Action for Your Application

PO is correct for most fresh air and ventilation applications. Confirm before ordering — cannot be changed after installation.

Action When Powered Fail-Safe on Power Loss Typical Application
PO — Power Open Blade opens Spring-closes — duct seals Fresh air intake, make-up air — standard
PC — Power Close Blade closes Spring-opens — duct stays open Applications requiring fail-open on power loss
Cannot be changed after installation. PO and PC are not interchangeable. Confirm action before ordering.

Part Number Decoder

Every HAC-E part number follows the same structure. The −E suffix confirms the elbow damper variant on every order.

How to Read Your Part Number
HAC-0610-SPO-E
HAC
Product family: universal inline air control damper
06
Size (2-digit): 05=5", 06=6", 07=7", 08=8", 09=9"
10
Motor code: 10 = no relay — relay not available on HAC-E
O / S
End switch: O = no end switch  |  S = proving end switch included
PO / PC
Action: PO = Power Open (spring-close fail-safe)  |  PC = Power Close (spring-open fail-safe)
-E
Elbow damper suffix — confirms this is the HAC-E motorized elbow configuration

Key Specs

Sizes
5", 6", 7", 8", 9"
Voltage
24 Vac
Configuration
Motorized elbow — blade integrated into elbow fitting
Drive
Patented Hoyme spring motor — stall-protected, nylon bearings
Action
PO or PC — specify at order
End Switch
Optional proving end switch (S prefix)
Relay
Not available — motor code 10 all sizes
Warranty
2-yr electrical / 10-yr mechanical

Critical Pre-Roughing-In Checklist

Complete this checklist at the elbow location before cutting or roughing in duct. These items cannot be corrected after the space is closed.

Confirm Before Roughing In
→Actuator housing clearance confirmed at the elbow location — actuator position is fixed by elbow geometry
→Service access to the actuator planned and guaranteed — must be reachable for motor inspection and eventual replacement
→Elbow angle matches duct run geometry — confirm before ordering
→Damper size matches duct diameter exactly — 5" through 9", no field modification
→PO vs. PC action confirmed before ordering — cannot be changed after installation
→End switch wiring run planned to controller or ADP relay adaptor if SPO/SPC variant ordered
→Elbow is the only viable control point — if straight duct space is available, use standard HAC
→24 Vac control wiring run planned to elbow location
What's in the Box
Included
·HAC-E motorized elbow damper assembly — configured as ordered (action, end switch)
·Installation instructions
You'll supply
·24 Vac control wiring
·Duct connections at elbow inlet and outlet
·ADP relay adaptor if furnace fan sequencing is required

Common Questions from the Counter

Answers to what comes up most when specifying the HAC-E.

Why not just add a short straight section and use a standard HAC instead?
If you can — do. The standard HAC is the preferred product: the actuator is on the inline body with clear access, servicing is straightforward, and the damper can be repositioned or replaced without touching the duct elbow. The HAC-E is for when adding that straight section isn't practical — the space isn't there, the existing ductwork can't be reconfigured without major work, or the elbow is the only location where the control point can go. If the inline HAC fits, use it.
What's the difference between the standard end switch and the "proving" end switch?
They are the same physical component described with different specificity. The term "proving" in the variant label emphasizes what the end switch actually does: it proves — confirms beyond a motor run signal — that the damper blade has physically reached the commanded position. It's the same end switch as on the standard HAC, HAC-F, and HOM, used for the same purpose: giving a controller or relay adaptor confirmed position feedback rather than an inferred position from the motor being energized.
What happens if the actuator is blocked or inaccessible after installation?
The actuator motor is the component most likely to require service over the product lifetime. If the actuator is inaccessible after installation, a motor failure means opening up the space — drywall, ceiling tile, or ductwork — to reach it. Plan actuator access at rough-in, not after the space is closed. If access cannot be guaranteed, reconsider whether the HAC-E is the right product for that location or whether a duct layout change to accommodate an inline HAC is worth the upfront effort.
Is the relay available on the HAC-E?
No — the HAC-E uses motor code 10 on all sizes, which means no relay is included. If a relay output is required in addition to damper control at an elbow location, discuss the application with your wholesaler or contact Hoyme directly. A relay adaptor in the control circuit may be an alternative approach depending on the specific sequencing requirement.
Can the HAC-E be installed at any elbow angle, or only at 90 degrees?
The HAC-E is designed as a standard duct elbow fitting. Confirm the elbow angle matches your duct run geometry before ordering. Contact Hoyme for applications requiring non-standard elbow angles.
Is the HAC-E available in 4" or smaller?
No — the HAC-E is available in 5" through 9". For 4" applications requiring elbow control, contact Hoyme to discuss options. For 4" fresh air applications where straight duct space is available, the standard HAC covers sizes down to 2".
Related Products
HAC
Standard inline damper — use when straight duct space is available. Easier to install and service. Sizes 2"–9".
HAC-L
Insulated inline damper — for cold climate installations where straight duct space is available.
ADP-0241-S5A
Relay adaptor for fresh air damper + furnace fan sequencing with proving end switch. Use SPO variant on HAC-E.
ADP Series
Full interface relay adaptor lineup for all damper interlock applications.
Ready to Order
HAC-E — Motorized Elbow Damper
Confirm actuator clearance and service access at the elbow location before ordering. Select your size, action (PO/PC), and end switch option — then add to cart.
Configure & Order ↑
Size · Action · End Switch
Need help specifying the HAC-E?
Technical support available through your Hoyme wholesaler or direct.
1-800-661-7382