Some Hoyme damper installations need an interface relay adaptor and some do not. If you are installing a combustion air or flue damper on a 24 Vac appliance, you probably do not need one at all. Read the combustion air guide for that case.
The ADP series covers the jobs where a damper has to be tied to something it cannot connect to directly: a millivolt or 120 Vac safety circuit, a 120 Vac exhaust fan, the furnace circulation fan, a gas dryer, or a ventilation timer. Every model ships with its relays installed and a colour wiring diagram for its application.
Picking the right one comes down to three questions. What is the damper interlocked to? What voltage is that circuit? And does anything have to wait for the damper to prove open?
Combustion Air and Flue Dampers
The HOM combustion air damper and the HAC-F flue damper both wire directly into a 24 Vac thermostat or aquastat circuit. Their built-in end switch is wired in series with the thermostat wire, so the appliance cannot fire until the damper has opened. On a 24 Vac system, no adaptor is needed.
- Millivolt safety system (standing pilot, thermopile or thermocouple): ADP-0MV2-S5A. This is the model rated for millivolt levels, 250 mVdc to 100 Vdc. Standard 24 Vac models will not work on these systems.
- 120 Vac safety controls (tankless water heaters, some boilers): ADP-1102-S5A.
- Two 24 Vac appliances sharing one HOM-SF1: ADP-0243-S5A, special order. For most two-appliance jobs the HOM-SF2 handles this on its own.
Fresh Air Damper and Furnace Fan
These adaptors open the fresh air damper and turn on the furnace circulation fan together. Neither one waits for the damper to prove open, so they are used with an HAC that has no end switch (OPO or OPC).
- ADP-0241-05A for a 24 Vac ventilation switch or an exhaust fan auxiliary contact. One DPDT relay turns on the furnace fan and opens the damper at the same time. In the standard wiring the damper does not open during furnace firing. The installation instructions show a power close damper with relay if it must also open when the appliance fires.
- ADP-0242-05A where an exhaust fan switch should open the fresh air damper and start the furnace fan, and the damper should also open during furnace firing.
- ADP-1101-05A for a 120 Vac exhaust fan switch. Its 120 Vac coil sees the fan circuit and operates the 24 Vac damper and the furnace fan. It does not interfere with the combustion air damper or the A/C circuit.
- ADP-1102-TWP where controlled line voltage is available from the exhaust fan and the damper should also open during furnace firing.
When the Exhaust Fan Must Wait for the Damper
Where the exhaust fan must not run until the replacement air damper has proved open, use a proving adaptor with an HAC that has an end switch (SPO or SPC):
- ADP-1102-TPX: a 120 Vac ventilation switch opens the damper, and the exhaust fan starts only after the damper end switch proves it open. The damper does not open during furnace firing.
- ADP-1103-TPX: the same sequence, and the damper also opens during furnace firing.
- RADP-1102-TPX: the same sequence for a plug-in exhaust fan, through a split receptacle.
On these models the proving step holds the exhaust fan, not the furnace fan. The furnace circulation fan starts at the same time the damper opens.
Gas Dryers
RADP-0241-S10A for a 24 Vac circuit. A manual switch with a red indicator light opens the damper and proves it open before the split receptacle the dryer plugs into becomes live. RADP-0242-S10A is the version for jobs where two dampers must both prove open before the dryer can operate. Order the damper with an end switch.
Timers and Two-Zone Fan Control
TMADP-1102-TPX adds a 24 hour interval timer with manual override for scheduled ventilation. ADP-0244-05A, special order, coordinates the furnace fan for two zone damper circuits.
When the End Switch Matters
The HOM and HAC-F always include an end switch, so there is nothing to choose there. On HAC dampers, the end switch (S in the part number) is required with the proving adaptors (the TPX models) and the gas dryer adaptors. The simultaneous adaptors, ADP-0241-05A and ADP-1101-05A, use an HAC without an end switch (O in the part number).
If the damper is already on site and you are not sure which you have, check the part number before wiring. HAC-0611-SPO has an end switch. HAC-0610-OPO does not.
What Is in the Box
Every ADP ships with the relay enclosure pre-wired and a colour wiring diagram for the model. The relays are field replaceable, so a relay failure does not mean replacing the whole assembly.
You supply the field wiring between the ADP, the damper, the fan and the appliance circuit. Wire gauge and routing per local electrical code.
A Note on BAS and DDC Systems
The ADP is the right solution for residential and light commercial installations where the interlock is not handled by a building automation system. If the job has a BAS or DDC controller with its own relay outputs, wire the damper end switch directly to the controller input and use the controller's relay output to power the damper motor. The ADP is not required in that configuration.
If you are not sure which model fits, call technical support at 1-800-661-7382 with the appliance type, the circuit voltage and what the damper has to interlock with.
Hoyme Manufacturing is a CSA-certified manufacturer of motorized dampers and airflow controls based in Camrose, Alberta. Products are available through HVAC wholesalers across Canada.