HAC-0611-SPO. Six inch, relay, end switch, power open.
Once you can read that, you can spec anything in the line without picking up the phone, and you can look at a part number on a drawing or an old label and know exactly what is in the duct.
It comes down to four things. Size, voltage, whether it has an end switch, and which way it fails on power loss. Everything else is a suffix.
Reading the Number
It runs left to right. HAC is the family. The next two digits are the diameter. Then two digits for the drive, which covers voltage and whether there is a relay in it. Then S or O for the end switch. Then PO or PC for the action. Then a suffix if the job needs one.
Diameter
Just the size in inches. 02 is two inch, 06 is six, 08 is eight, 12 is twelve. The standard drive covers two through nine. Bigger than that and you are into different actuators.
Drive
| Code | What you get |
|---|---|
| 10 | 24 Vac, no relay |
| 11 | 24 Vac with a relay |
| 12 | 120 Vac, transformer built in |
| 00 | No motor at all |
You want the relay when the damper opening has to switch something else on. A furnace fan, an exhaust fan, some other control. If nothing is waiting on the damper, code 10 does the job and costs less. Relay is not available on two and three inch.
Code 12 is for when you get to the damper location and there is no low voltage anywhere near it. Just 120 Vac. The transformer is inside the unit so you are not hanging one on the wall beside it.
End Switch
S has one. O does not.
This is the one that catches people, and it catches them badly because the damper works fine and the system still will not run. The end switch is what tells the controller the blade actually got where it was told to go. Anything wired into an ADP interlock needs one, because without it the ADP is waiting for a signal that is never coming.
If the damper is just opening and closing and nothing downstream is waiting for confirmation, skip it. If anything is being proved or sequenced, you need it.
Action
PO is power open. Apply 24 Vac and it opens, kill the power and the spring shuts it. Duct is sealed when the system is off.
PC is the reverse. Power closes it, spring opens it. Duct sits open when the system is off.
Power open is what you want on most fresh air intakes, make up air, and HRV or ERV ducts. Power close is for when the design specifically wants the duct open if power drops. Neither one is a safe default and you cannot swap them once the damper is in the duct without getting at the actuator. Longer version in the power open versus power close guide.
Suffixes
- -L is the insulated body. For when the duct runs through conditioned space and you are worried about condensation on the damper.
- -H is the heat bypass blade, ten percent machined in. You need this for supply zone control on a single speed furnace, because closing every supply zone at once on a single speed system spikes static pressure and trips the high limit.
- -BPD is the back pressure damper. Automatic relief, no power.
- -F is the flue damper, which is really a different product with the opposite fail safe direction. Separate guide for that one.
Some Real Ones
All of these have shipped.
| Part number | What it is |
|---|---|
| HAC-0610-OPO | Six inch, 24 Vac, nothing extra, power open |
| HAC-0610-OPC | Same damper, other direction |
| HAC-0611-SPO | Six inch with relay and end switch. Ready for an ADP. |
| HAC-0811-SPO | Same thing in eight inch |
| HAC-0512-OPO | Five inch running on 120 Vac, no end switch, power open |
| HAC-0812-SPO | Eight inch, 120 Vac, end switch, power open |
| HAC-0210-OPO-L | Two inch insulated, 24 Vac, power open |
| HAC-0510-OPC-L | Five inch insulated, power close |
| HAC-1200-BPD | Twelve inch back pressure damper, no power |
Same logic runs through the rest of the line. MOH-0810-SPO is an eight inch motorized hood, 24 Vac, end switch, power open. BDH-0400-000 is a four inch back draft hood with no motor in it.
Building One
Fresh air intake on a six inch duct. You have 24 Vac. It is running through an ADP-0241-S5A so the damper proves open before the furnace fan kicks in.
Six inch duct gets you 06. The ADP is doing the fan switching so you do not need the relay, which makes it 10. ADP interlock means the end switch is not optional, so S. And a fresh air intake wants the duct shut when nothing is running, so PO.
HAC-0610-SPO.
Move it to an eight inch duct and it is HAC-0810-SPO. No low voltage at the location, HAC-0812-SPO. Add insulation and it is HAC-0810-SPO-L. Once the pattern clicks it goes quick.
Three Ways This Goes Wrong
No end switch on an ADP job. Damper shows up, goes in, gets wired, and the sequence never finishes. Nothing is actually broken. Somebody just ordered an O where they needed an S. Check for it before the order goes out.
Action backwards. PO and PC are identical from the outside and you will not know until it is wired and powered. The Hoyme actuator is accessible if you have to reconfigure in the field, which is not true of everything in this category, but sorting it out before ordering beats a return trip.
Standard HAC on single speed supply zones. This one does not show up right away. It shows up a few weeks later as a high limit fault, and by then the dampers are all in. Single speed supply zone control needs the -H blade on every supply damper.
Quick Reference
| Job | Order this |
|---|---|
| Fresh air intake, straight on and off | x10-OPO |
| Fresh air sequenced through an ADP-0241-S5A | x10-SPO |
| Damper has to switch on something else | x11-OPO or x11-SPO |
| No low voltage at the damper | x12 series |
| Supply zone control on a single speed furnace | x10-OPO-H or x11-OPO-H |
| Condensation risk where it is going | Add -L |
| Pressure relief with no power available | x00-BPD |
Getting One
Everything here is CSA certified for Canada and the US, two year electrical and ten year mechanical warranty.
The full nomenclature reference for every product family is in the Technical Library, along with installation instructions and colour wiring diagrams.
Hoyme is stocked at HVAC wholesalers across Canada. You can also order any configuration direct at hoyme.com with shipping across Canada and the US, which is how most buyers outside the wholesaler network get it.
If you know the application but not the part number, call 1-800-661-7382. Usually a two minute conversation.
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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.