How to reduce the number of hours heating not met in DesignBulder

edit

I would try to have EnergyPlus autosize the rated capacities and airflows of your separate heating and cooling heat pumps to meet load. You can probably find a way to do this in DesignBuilder or in the IDF it generates.

If you are hard-sizing your heat pump capacities and still getting high unmet hours, look at the rated airflow rate(s). I have noticed in past models that if I increase the rated heating or cooling capacity of my heat pump coils and do not increase the rated airflows through those same coil objects as well, the desired effect of increasing HVAC output to match load and reduce unmet hours is not produced.

Another thing to investigate are the performance curves of your heat pump coil objects. The performance curves dictate how your capacity and EIR/COP degrade or otherwise change with ambient conditions. The curve values (function of temperature and flow fraction) combined with low ambient outdoor dry bulb temperatures can produce instantaneous capacities and COPs that are lower than rated, hence causing unmet hours.

The 1st thing to do here is to identify which zones have more unmet hours reported. This information is available at the Summary report "Time Set point Not met".

Then you will need to analise how the HVAC system is performing on these spaces and if the temperature setpoints are set up correctly and being met by the system.

Have also a look at this post: https://unmethours.com/question/359/w...

Its not specific to DesignBuilder software but the approach is similar.

If you have a valid DesignBuilder license then you can always contact DesignBuilder support team for assistance.