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What make the difference between PTAC and PTHP in OpenStudio?

asked 2017-04-20 06:14:15 -0600

Arthur SIU gravatar image

updated 2017-08-06 16:23:16 -0600

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.

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answered 2017-04-20 09:24:21 -0600

Adam Hilton gravatar image

updated 2017-04-20 13:16:20 -0600

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

Total Cooling Capacity - Function of Temperature

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Total Cooling Capacity - Function of Flow Fraction

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EIR - Function of Temperature

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EIR - Function of Flow

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Part Load Fraction - Function of Part Load Ratio

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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?

Arthur SIU gravatar imageArthur SIU ( 2017-04-20 10:14:25 -0600 )edit

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

Adam Hilton gravatar imageAdam Hilton ( 2017-04-20 10:25:27 -0600 )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.

rraustad gravatar imagerraustad ( 2017-04-20 11:33:17 -0600 )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.

Adam Hilton gravatar imageAdam Hilton ( 2017-04-20 11:36:17 -0600 )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?

rraustad gravatar imagerraustad ( 2017-04-20 11:54:21 -0600 )edit

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Asked: 2017-04-20 06:14:15 -0600

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Last updated: Apr 20