This page describes how to fix a bug in the dll of !EnergyPlus 6.0.0, build23 that may occur when exchanging a large amount of data in each time step. 
The error message that !EnergyPlus writes to its {{{.err}}} file is
{{{
 ExternalInterface starts first data exchange.
 Error: No digits were found in getDoubleCheckError.
 Further characters after number: 
 Sending EXIT_FAILURE = : 1
 **FATAL:Error in ExternalInterface: Check EnergyPlus *.err file.
}}}

To fix the bug, proceed as follows:

= Windows =
 1. Install the BCVTB version 0.8.0
 1. Copy the file {{{bcvtb/lib/util/bcvtb.dll}}}, where {{{bcvtb}}} is the top-level directory of the BCVTB installation, to the !EnergyPlus directory, such as {{{C:\Program Files\EnergyPlus-6-0-0}}}. This will replace the existing file with the same name.


= Linux =
 1. Install the BCVTB version 0.8.0
 1. Copy the file {{{bcvtb/lib/util/libbcvtb.so}}}, where {{{bcvtb}}} is the top-level directory of the BCVTB installation, to the !EnergyPlus {{{lib}}} directory, such as {{{/usr/local/EnergyPlus-6-0-0}}}. This will replace the existing file with the same name.

= Mac =
 1. Install the BCVTB version 0.8.0
 1. Copy [[http://simulationresearch.lbl.gov/bcvtb/releases/0.8.0/dll/mac/32/libbcvtb.dylib|this file]] to the !EnergyPlus {{{lib}}} directory, such as {{{/Applications/EnergyPlus-6-0-0/lib}}}. This will replace the existing file with the same name. (Do not use the file from {{{bcvtb/lib/util}}}, since this is a 64-bit version, but !EnergyPlus requires a 32-bit version.)