Imposed Load Simulation (ILS) error codes and common mistakes

ILS error codes

If one of the following errors occur on an ILS base circuit, a comfort issue is applicable. It actually means that one of the assumptions made by the ILS algorithm (see https://hysopt.atlassian.net/wiki/spaces/HRM/pages/1213726725 ) could not be realized for more than 5% of the time, implying some kind of comfort issue.

The ILS simulation result is INVALID because of that reason not reliable.
You will need to fix the comfort issue in order to create a valid and reliable simulation result!

  • error code 2
    cause : the imposed volume flow for heating for an individual dwelling was larger than the design flow
    this can occur if e.g. the supply temperature is too low, if the room setpoint temperature is higher than room design temperature (20), or if the outside temperature is lower than -10.
    solution : adapt the supply temperature, the room setpoint temperature, or modify your design conditions

  • error code 4
    cause : the imposed volume flow for heating, secondary from the heat exchanger, for an individual dwelling was larger than the design flow. This can occur if e.g. the controlled radiator supply temperature is too low, if the room setpoint temperature is higher than room design temperature (20), or if the outside temperature is lower than -10.
    solution : adapt the supply temperature, the controlled radiator supply temperature , the room setpoint temperature, or modify your design conditions

  • error code 8
    cause : the central heating setpoint configuration does not comply with the central heating diversity standard as defined in the settings page. The peak flows exceeded the flows as defined by the diversity standard.
    solution:

    • Either change the diversity standard in the settings page

    • either change the setpoint configuration (simulation parameter)

       

  • error code 16
    cause : the imposed volume flow for Domestic Hot Water for an individual dwelling was larger than the design flow, this can occur if e.g. the supply temperature is too low
    solution : adapt the supply temperature or the domestic hot water temperature

  • error code 32
    cause : the room temperature could not be realised. This can occur if e.g. the supply temperature or controlled radiator supply temperature is too low, room setpoint temperature is higher than room design temperature (20) or the outside temperature is lower than -10
    solution : adapt the supply temperature, the controlled radiator supply temperature , the room setpoint temperature, or modify your design conditions

  • error code 64
    cause : the primary supply temperature is lower than the secondary controlled radiator supply temperature
    solution : adapt the supply temperature or the controlled radiator supply temperature
    IF THIS IS THE ONLY ERROR YOU HAVE ON YOUR ILS BLOCK, THAN YOU CAN IGNORE THIS, BECAUSE IT DOES NOT LEAD TO A COMFORT ISSUE

  • error code 128
    cause : the supply temperature is lower than the Domestic Hot Water temperature
    solution : adapt the supply temperature or the Domestic Hot Water temperature

ILS error codes on individual time steps

If an ILS base circuit does NOT raise an error during simulation, that means that during less than 5% of the time, an ILS error occured. That’s a good situation, but it means that it still might happen in a few time steps that one of the ILS assumptions were wrong. In these particular timesteps, the simulation results for that timestep are invalid. It is possible to visualise the timesteps on which the ILS simulation resulted in an error code. This might help in “explaining” why sometimes during an ILS simulation you might see some short unexpected results, or spike or a glitch in a graph that you cannot explain.

As an example, here you can see the resulting return temperature of an ILS simulation.
There are two spikes which seem odd and cannot be explained.

By selecting the “ILS error code(s)”, the graph shows the moments when an error occurs.

You can see that the spikes occurred on a timestep that an ILS error occurred, making the return temperatures on these two time steps invalid.

To analyse which error code(s) occured, take a look at the resulting error code value, this value is the sum of all error codes that occured.

In the example above the value is 40, meaning that two error codes (32 and 8) occured on these timesteps.

ILS common mistakes

1. Do not control the pump, as it will conflict with the imposed flow

2. Do not use control valves, as they will conflict with the imposed flow