Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page

What make the difference between PTAC and PTHP in OpenStudio?

What make the difference between PTAC and PTHP in OpenStudio? Can I show the setting of each to differentiate them?

Moreover, I tried a school building model, one simulated with PTAC in each thermal zone, one simulated with PTHP in each thermal zone. Why the model installed with PTHP resulted in lower energy consumption?

Thank you.

edit retag close merge delete

Sort by ยป oldest newest most voted

PTAC: Packaged Terminal Air Conditioner (Cooling Only)

PTHP: Packaged Terminal Heat Pump (Heating and Cooling)

Don't know why it's lower without looking at the inputs you're using. You can compare the wrapped object inputs to see what's different between the two.

OS Default Curves for Coil:Cooling:DX:SingleSpeed in PTAC and PTHP

EIR - Function of Flow

more

Does it means the same operation when both are used for cooling purpose only?

Is it possible and worth when PTHP only used for cooling only?

( 2017-04-20 10:14:25 -0500 )edit

No, a heat pump coil system in cooling is going to be driven by a difference performance curve than an ac coil system.

( 2017-04-20 10:25:27 -0500 )edit

Different performance curve only if the user has entered a different performance curve. @Arthur SIU, when you say lower energy consumption, is that for cooling or for everything? If everything, then PTHP heating is more efficient than gas or electric heaters. These 2 HVAC models are nearly identical.

( 2017-04-20 11:33:17 -0500 )edit

Right. In OS, there are different curve coefficient defaults for the Coil:Cooling:DX:SingleSpeed in the PTHP versus the PTAC. This is probably why the consumption is different.

( 2017-04-20 11:36:17 -0500 )edit

@Adam Hilton, I wouldn't think there would be that much difference (only the extra reversing valve in the PTHP), I'd be interested in seeing those coefficients to see how performance changes. Are these curves presented in documentation somewhere?

( 2017-04-20 11:54:21 -0500 )edit