RESFEN 3.1 Knowledge Base 

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Last update:05/18/05 04:59 PM

Below is a list of RESFEN modeling issues that have been discovered by users, and possible solutions. For RESFEN support, send email to RESFENHelp@lbl.gov

If you have questions or need program support, please DO NOT telephone Santosh Philip at Gabel Associates (as shown in the RESFEN Help/About screen). Instead send email to RESFENHelp@lbl.gov

CONTENTS

INSTALLATION

Installation Error -- "Error Number: 0x8002802B, Description: Element not found"

DOE2 Files for RESFEN

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WINDOW 5.0 DOE2 Report for RESFEN

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Results using WINDOW 4.1 DOE2 DAT files do not seem correct (too large a difference in results between using and not using the DAT files) 

 

WEATHER DATA
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Cannot Find Weather File, Simulation Cancelled

 

 

COST CALCULATIONS

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Gas and Electricity prices are too low

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How to Convert $/cubic foot to $/therm for Natural Gas

HVAC MODELING

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How to Model Electric Resistance Heating

KNOWN BUGS

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Window Peak Energy Results for 4 orientations

 


INSTALLATION

Installation Error -- "Error Number: 0x8002802B, Description: Element not found": 
If this error appears upon installation, do the following:
Delete the Program Files\Common Files\InstallShield\Professional folder on the target machine.


DOE2 Files for RESFEN

WINDOW 5.0 DOE2 Report for RESFEN: 
Although WINDOW 5.0 can write WINDOW 4.1 files that RESFEN can read, the gas properties are not being written correctly into the WINDOW 5.0 DOE2 Report. Therefore, DO NOT USE DOE2 files written from WINDOW 5.0 with RESFEN 3.1.

Results using WINDOW 4.1 DOE2 DAT files do not seem correct
(too large a difference in results between using and not using the DAT files)
 
When using WINDOW 4.1 libraries to specify the Window Types in RESFEN, do not give the windows in the library ID numbers between 1 and 12. These ID numbers are reserved for windows in the internal DOE2 window library, and therefore RESFEN, because it is using the DOE2 simulation engine, will also use those default values. 

Therefore, make the WINDOW 4.1 Window Library ID numbers greater than 12.


WEATHER DATA

Cannot Find Weather File, Simulation Cancelled
This message can appear when pressing the calc button under a few different circumstances, such as:

bullet Input file is not in the RESFEN program directory -- the input files must be in the same directory as the RESFEN program, and not even in a subdirectory of that directory

COST CALCULATIONS

Gas and Electricity prices are too low
The gas and electricity prices in RESFEN 3.1 may not reflect the the price of the fuels in your area, because they are limited to the following ranges, and cannot be changed:

Electricity:     $0.040/kWh - $0.150/kWh

Gas:              $0.30/therm - $1.00/therm

There are a few different ways to work around this. Both require calculating the costs with values available in RESFEN, and then doing a manual calculation outside the program based on those to convert to the correct costs. 

Method 1:

One approach is to set the electricity and gas prices to a value that can easily be multiplied by a "factor". For example, you could set the prices in RESFEN to half of the real price, and then multiply the RESFEN cost results by 2 to get the correct costs.

For example, if the electricity costs in your region are $0.20/kWh and the gas costs are $2.00/therm, both of which are higher than the maximum choice in RESFEN, you could set the prices to half those values in RESFEN, as shown here:

Electricity = $0.10/kWh
Natural Gas
= $1.00/Therm

Then do the RESFEN calculation using these "halved" prices, which gives the following results for Whole House Total Cost:

        Cooling = $63.80
        Heating = $551.21

Multiply each of the total costs by 2, to get the costs for electricity at $0.20/kWh and natural gas at $2.00/Therm, which gives the following results:

        Cooling = $127.6
        Heating = $1102.42

Method 2:

Another approach is to do the same Whole House Energy Total cost calculation that RESFEN does, which is to multiply the Whole House Energy Totals for heating and cooling by the electricity and gas rates. 

For example, if the Whole House Totals are as follows (for a gas furnace/air conditioner HVAC system):

        Cooling = 638 kwh
        Heating = 55.12 MBtu

And if the utility prices are the following:

Electricity = $0.20/kwh
Natural Gas
= $2.00/Therm

The energy cost calculations would be as follows:

For Cooling:

Multiply the cooling energy in kwh by the electricity cost in $/kwh, so:

638 kwh * $0.20/kwh = $127.60

For Heating:

Convert the $/Therm into $/MBTU, by multiplying the $/Therm by 10.
(A Therm = 100,000 Btu, and an MBtu = 1,000,000 Btu, so converting from Therms to MBtu requires multiplying by 10).

So in this case, $2.00/Therm = $20.00/MBtu

Multiply the total heating MBtu by the cost per MBtu, so:

55.12 MBtu * $20.00/MBtu = $1102.40

These are the same results obtained with Method 1.

How to Convert $/cubic foot to $/therm for Natural Gas
In order to convert $/cubic foot for natural gas into $/therm, which are the gas cost units in THERM, do the following conversion:

Multiply the cost of the natural gas in cubic feet ($/cubic feet) times 0.01 to get cost per Therm ($/Therm)

Background:

1 cubic foot of natural gas = 1,000 Btus

1 Therm = 100,000 Btus

Therefore:

1 Therm = 100 cubic feet of natural gas 
                     or 
1 cubic foot of natural gas = 0.01 Therm

Example:

$0.10 / cubic foot of natural gas = $0.001 / Therm


HVAC MODELING

How to Model Electric Resistance Heating
Using the current input values in RESFEN 3.1 there is no accurate way to model electric resistance heating. To get a rough estimate, it is possible to model the building with a gas furnace/air conditioner, and then convert the gas consumption to electricity at an efficiency of 0.70 for existing construction and 0.78 for new construction.

To convert gas furnace heating results in MBtus to kWh, multiply the results in MBtu for heating by:

205.1 for existing construction

228.50 for new construction

Background:

Conversion for Btu to Watt-hours (W-h)

1 Btu        = 0.293 W-h

1 MBtu     = 1,000,000 Btu 

                 = 293,000 W-h/MBtu 

                 = 293 kWh/MBtu

Taking into account the furnace efficiencies of 0.70 for existing construction and 0.78 for new construction:

Existing Construction:

293 kWh/MBtu * 0.70 

= 205.1 kWh/MBtu

New Construction:

293 kWh/MBtu * 0.78 

= 228.50 kWh/MBtu

Example calculation:

If the Whole House Totals for Heating are as follows (for a gas furnace):

       Heating = 55.12 MBtu

Calculate:

55.12 MBtu * 205 kWh/MBtu 

= 11299.6 kWh


KNOWN BUGS

Window Peak Energy Results for 4 orientations

The results in the tab labeled Window Peak Energy Results, which display when doing a 4 orientation simulation (clicking on the double lightning bolt icon or using the Calculate/Whole House + 4 orientations option), are incorrect for the Heating (W/ft2) row. At this time there is no work around for this error.