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You should see two sets of design loads: one labeled Base for the existing building one labeled Selected for building with proposed measures in place. If that is not what you are looking at, then please post a screen shot.
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When the thermal boundary is the attic floor, then it is modeled on the Attic page. Model this surface for the base building, but set the improved Area to zero.
When the thermal boundary is the roof deck, then it is modeled on the Ceilings (Vault/Flat) page. Model this surface for the improved building, but set the base side area to zero.
Both the Attic and the Ceiling (Vault/Flat) measures must be selected for the conversion to be effective. Total cost and savings of moving the boundary can be seen by summing the two measures.
Here is another post describing how to appropriately model more that 3 HVAC systems: https://optimiserenergy.com/forums/topic/number-of-hvac-systems/
Once you have modeled the systems as described in that post, you can get a fourth duct sealing job to register by following these steps.
1. Go to one of the cooling systems interfaces
2. Setting the Shared control to Separate
3. Set the remainder of the Distribution controls identically system to which it was previously linked.Hi Christine,
I’m working with some of the APS/SRP program administrators to determine the preferred method for handling this. I will get back to you soon.
Sorry for the delay in our response. Our notification system was inadvertently disabled during a website upgrade.
You can change the load split as part of the upgrade. Specify the improved system in System 1 and change the % Total control to 100 on the improved side.
OptiMiser is limited to single zone modeling. You have two options for dealing with this.
1. You can model the zones as though they are separate units of a multi-unit building. This requires using multiple project files. The Multi-Family controls allow you to remove the boundary between the two zones from the thermal boundary.
2. You can calculate weighted averages for the thermostat set-points, using the % Load for each system as the weighting. In you case this would still specify a setback thermostat, but the setback would be reduced.
Hi William.
Dual fuel heat pumps are modeled as two separate systems in OptiMiser. You model the furnace and heat pump components as separate systems that each handle a portion of the annual load. You can estimate the split yourself or have OptiMiser do it using the Advanced heat pump model. The Advanced model will also estimate the actual HSPF for the heat pump using the dual fuel configuration.
- Specify the two systems in the main interface, assigning the load in any way you want
- Make sure the total load assigned to the two systems is the load that will be met by the combined dual fuel system
- If you are using an existing fuel fired system as backup, then be sure to set the improved system to No Improvement
- Use COP and EER units for the heat pump efficiency, if you have those value. Otherwise, use HSPF and SEER
- Click the Advanced button to open the popup
- Change Model Setup to Live, unless you need to use the advanced model for multiple heat pumps
- Set the Backup control to the correct heating system and specify the Heating Threshold temperature at which the backup will switch on
- Click the Copy Result and Close Window button and OpitMiser the correct % Load for the heat pump and backup systems
Note: If you need to use the advanced model for more than one heat pump, then set Model Setup to “Calculator”. When you do this, then OptiMiser will copy the calculated annual efficiency values back into the main interface, rather than connecting the advanced model directly to the main energy model. If you do this, then it is very important to complete all other aspects of the building model first to ensure that the advanced heat pump model is working with correct hourly loads.
Sorry for the delay. Our notification system went out of service, when we switched to the new website.
Someone else just brought this to our attention. We intend to address it soon. The workaround that you propose is a good one.
1. Yes, put the Propane on additional fuels
2. Yes, check the Zero fuel base load box, if you are entering Fuel Oil on the detailed interface. This box is used to assist the regression analysis and won’t impact the normalization of the annual totals entered on Additional Fuels. If you are just entering an annual total for Fuel Oil, then it won’t have any impact.I assumed that this NREL document would be consistent with the RESENET HERS Standard that we used in development of our program, but it appears that on the subject of Conditioned Floor Area it is not. I’m a little puzzled by this. The HERS Standard references ANSI Z765-1996 for measurement of Conditioned Floor Area and the ANSI standard specifies exterior finished surfaces as the boundaries.
I also have the impression that most publicly available sources for conditioned area of buildings (e.g. assessors records) have been calculated to exterior dimensions.
The most important dimensions for model accuracy are the surface areas of exterior envelope components both standards agree that these should be calculated using exterior dimensions. We use the conditioned floor area to make initial estimates of other exterior surface areas, so it is most convenient for it to also be calculated with exterior dimensions.
The blower door CFM50 number is what is used in the infiltration calculations, so volume is not a critical dimension. The default Volume calculation in OptiMiser is essentially floor area multiplied by wall height plus conditioned crawl space volume. We also attempt to also estimate the volume of the joist area between conditioned floors. We do not attempt to estimate the impact of vaulted ceilings. This is basically impossible without a detailed geometric layout.
