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Dear group,

After many days of digging through documentation and tweaking my model, I'm having trouble resolving a couple of issues related to some of the (autosized) VAV reheat coils in my model: 1) the supply temperature from the VAV box (as indicated by the variable "single duct VAV reheat supply inlet") to a few of the perimeter zones on the sizing day is below the zone air temperature (and the zone air temperature is below the heating setpoint). So basically the zone is underheated all day. All HVAC system capacities (flow rates, output levels, etc.) are autosized. But I did notice the coil heating rate and delta T across the water side of the problem coils seem to be reaching some inexplicable limit. 2) the design capacity for said VAV reheat coil (as per the summary table) is about 75% as big as its heating design day heating rate. I'd have expected that the sizing period simulation would have led to a coil capacity that is adequate to prevent underheating. 3) I have reason to believe that the sizing period may not be accounting for the ventilation-related loads, as I expect. I can only get core zone VAV reheat coils to be big enough (or non-zero actually) if I crank up the People Per Zone Floor Area to ASHRAE standard levels (0.054/m2). In contrast, the whole premise of my model (being used for research purposes) is to explore lower occupant densities.

Perhaps these things are related to each other - perhaps not. In any case, advice would be greatly appreciated!

Here's my model: https://www.dropbox.com/s/ws3girq93vb1u1d/LargeOfficeForAutosizingReplacedValues.idf?dl=0 and weather file used: https://www.dropbox.com/s/0q8azvl4v9kz6tq/Toronto.airport%202016.epw?dl=0

Thank you in advance,

Liam O'Brien

Dear group,

After many days of digging through documentation and tweaking my model, I'm having trouble resolving a couple of issues related to some of the (autosized) VAV reheat coils in my model: 1) the supply temperature from the VAV box (as indicated by the variable "single duct VAV reheat supply inlet") to a few of the perimeter zones on the sizing day is below the zone air temperature (and the zone air temperature is below the heating setpoint). So basically the zone is underheated all day. All HVAC system capacities (flow rates, output levels, etc.) are autosized. But I did notice the coil heating rate and delta T across the water side of the problem coils seem to be reaching some inexplicable limit. 2) the design capacity for said VAV reheat coil (as per the summary table) is about 75% as big as its heating design day heating rate. I'd have expected that the sizing period simulation would have led to a coil capacity that is adequate to prevent underheating. 3) I have reason to believe that the sizing period may not be accounting for the ventilation-related loads, as I expect. I can only get core zone VAV reheat coils to be big enough (or non-zero actually) if I crank up the People Per Zone Floor Area to ASHRAE standard levels (0.054/m2). In contrast, the whole premise of my model (being used for research purposes) is to explore lower occupant densities.

Perhaps these things are related to each other - perhaps not. In any case, advice would be greatly appreciated!

Here's my model: https://www.dropbox.com/s/ws3girq93vb1u1d/LargeOfficeForAutosizingReplacedValues.idf?dl=0 and weather file used: https://www.dropbox.com/s/0q8azvl4v9kz6tq/Toronto.airport%202016.epw?dl=0

Thank you in advance,

Liam O'Brien O'Brien

After many days of digging through documentation and tweaking my model, I'm having trouble resolving a couple of issues related to some of the (autosized) VAV reheat coils in my model: 1) model:

1. the supply temperature from the VAV box (as indicated by the variable "single duct VAV reheat supply inlet") to a few of the perimeter zones on the sizing day is below the zone air temperature (and the zone air temperature is below the heating setpoint). So basically the zone is underheated all day. All HVAC system capacities (flow rates, output levels, etc.) are autosized. But I did notice the coil heating rate and delta T across the water side of the problem coils seem to be reaching some inexplicable limit. 2) limit.

2. the design capacity for said VAV reheat coil (as per the summary table) is about 75% as big as its heating design day heating rate. I'd have expected that the sizing period simulation would have led to a coil capacity that is adequate to prevent underheating. 3)

3. I have reason to believe that the sizing period may not be accounting for the ventilation-related loads, as I expect. I can only get core zone VAV reheat coils to be big enough (or non-zero actually) if I crank up the People Per Zone Floor Area to ASHRAE standard levels (0.054/m2). In contrast, the whole premise of my model (being used for research purposes) is to explore lower occupant densities.

Perhaps these things are related to each other - perhaps not. In any case, advice would be greatly appreciated!

Here's my model: https://www.dropbox.com/s/ws3girq93vb1u1d/LargeOfficeForAutosizingReplacedValues.idf?dl=0 model and weather file used: https://www.dropbox.com/s/0q8azvl4v9kz6tq/Toronto.airport%202016.epw?dl=0

Liam O'Brienused.

After many days of digging through documentation and tweaking my model, I'm having trouble resolving a couple of issues related to some of the (autosized) VAV reheat coils in my model:

1. the supply temperature from the VAV box (as indicated by the variable "single duct VAV reheat supply inlet") to a few of the perimeter zones on the sizing day is below the zone air temperature (and the zone air temperature is below the heating setpoint). So basically the zone is underheated all day. All HVAC system capacities (flow rates, output levels, etc.) are autosized. But I did notice the coil heating rate and delta T across the water side of the problem coils seem to be reaching some inexplicable limit.

2. the design capacity for said VAV reheat coil (as per the summary table) is about 75% as big as its heating design day heating rate. I'd have expected that the sizing period simulation would have led to a coil capacity that is adequate to prevent underheating.

3. I have reason to believe that the sizing period may not be accounting for the ventilation-related loads, as I expect. I can only get core zone VAV reheat coils to be big enough (or non-zero actually) if I crank up the People Per Zone Floor Area to ASHRAE standard levels (0.054/m2). In contrast, the whole premise of my model (being used for research purposes) is to explore lower occupant densities.

Perhaps these things are related to each other - perhaps not. In any case, advice would be greatly appreciated!

Here's my model and weather file used.

After many days of digging through documentation and tweaking my model, I'm having trouble resolving a couple of issues related to some of the (autosized) VAV reheat coils in my model:

1. the supply temperature from the VAV box (as indicated by the variable "single duct VAV reheat supply inlet") to a few of the perimeter zones on the sizing day is below the zone air temperature (and the zone air temperature is below the heating setpoint). So basically the zone is underheated all day. All HVAC system capacities (flow rates, output levels, etc.) are autosized. But I did notice the coil heating rate and delta T across the water side of the problem coils seem to be reaching some inexplicable limit.

2. the design capacity for said VAV reheat coil (as per the summary table) is about 75% as big as its heating design day heating rate. I'd have expected that the sizing period simulation would have led to a coil capacity that is adequate to prevent underheating.

3. I have reason to believe that the sizing period may not be accounting for the ventilation-related loads, as I expect. I can only get core zone VAV reheat coils to be big enough (or non-zero actually) if I crank up the People Per Zone Floor Area to ASHRAE standard levels (0.054/m2). In contrast, the whole premise of my model (being used for research purposes) is to explore lower occupant densities.

Perhaps these things are related to each other - perhaps not. In any case, advice would be greatly appreciated!

Here's my model and weather file used.