Revision history [back]

Let's get back to the (real-world) basics:

• A PTAC, or Packged Terminal Airconditioner, is a through-wall device where you have DX cooling and non-DX heating, typically via electric resistance (electric PTAC) or a hot-water coil^[1] (hot water PTAC). There is a blower fan to blow air across the coils. The unit is inserted in a wall sleeve, on the inside you have the evaporator coil, the heating coil, and the fan. On the outside you have the condenser coil, a fan and the compressor. There's usually an outside air damper included in the unit too (which may or may not actually open)
• A PTHP, or Packaged Terminal Heat Pump, is exactly like a PTAC except that it has DX heating too: it is a reversible system, the same coil is providing heating in winter and cooling in the summer. There is often backup electric resistance heating for cold climate operation (typically under 35°F/ 1°C, electric resistance is used either alone or in conjuction with the DX heating (mixed-mode))

As far as how to model this type of systems in openstudio (or energyplus in general for that matter), it's been covered before here: you can either use a ZoneHVAC:PackagedTerminalHeatPump (or PTHP) or a VRF system: if your refrigerant flow is actually varying, it'll better capture the performance of your unit.

^[1] There are also some PTAC units with steam coils, such as in the formerly Remington and now McQuay Type J and Type K, but I'm not sure you really encounter them much outside of NYC and maybe another couple of US cities in the North East that have a history of steam heating.

You also can encounter some PTAC with gas heating coils, but since that requires piping a gas line to each unit, I personally haven't seen them much.

Let's get back to the (real-world) basics:

• A PTAC, or Packged Terminal Airconditioner, is a through-wall device where you have DX cooling and non-DX heating, typically via electric resistance (electric PTAC) or a hot-water coil^[1] (hot water PTAC). There is a blower fan to blow air across the coils. The unit is inserted in a wall sleeve, on the inside you have the evaporator coil, the heating coil, and the fan. On the outside you have the condenser coil, a fan and the compressor. There's usually an outside air damper included in the unit too (which may or may not actually open)
• A PTHP, or Packaged Terminal Heat Pump, is exactly like a PTAC except that it has DX heating too: it is a reversible system, the same coil is providing heating in winter and cooling in the summer. There is often backup electric resistance heating for cold climate operation (typically under 35°F/ 1°C, electric resistance is used either alone or in conjuction with the DX heating (mixed-mode))
• Split system: I've covered that in How can I model a ductless split HVAC system? already.

As far as how to model this type of systems in openstudio (or energyplus in general for that matter), it's been covered before here: on the same question I just linked: you can either use a ZoneHVAC:PackagedTerminalHeatPump (or PTHP) or a VRF system: if your refrigerant flow is actually varying, it'll better capture the performance of your unit.

^[1] There are also some PTAC units with steam coils, such as in the formerly Remington and now McQuay Type J and Type K, but I'm not sure you really encounter them much outside of NYC and maybe another couple of US cities in the North East that have a history of steam heating.

You also can encounter some PTAC with gas heating coils, but since that requires piping a gas line to each unit, I personally haven't seen them much.