Appendix G guideline says 300 hours of setpoints not met is acceptable. Is
there any Tolerance for heating/cooling setpoints not met? Or the
temperatures have to be exact?
If I understand you correctly, you want to know what the temperature difference is allowed to be between the actual space temperature and the setpoint temperature to define what an "unmet hour" is. In eQUEST, for example, this parameter is called the "throttling range", with a default value of 2?F for a proportional-type thermostat. Prior posts have suggested increasing the throttling range as a method of reducing unmet hours. I think this should be done as a last resort, but if you do it, you need to keep the same throttling range for both baseline and proposed for Appendix G. Unless the HVAC design is poor, the building has unusual load characteristics, or you are trying to model something outside of the capabilities of the simulation program, high unmet hours are often the result of "problems" in the model - mistakes in simulating the zones, systems, loads etc.
Vinay,
If I understand you correctly, you want to know what the temperature difference is allowed to be between the actual space temperature and the setpoint temperature to define what an "unmet hour" is. In eQUEST, for example, this parameter is called the "throttling range", with a default value of 2?F for a proportional-type thermostat. Prior posts have suggested increasing the throttling range as a method of reducing unmet hours. I think this should be done as a last resort, but if you do it, you need to keep the same throttling range for both baseline and proposed for Appendix G. Unless the HVAC design is poor, the building has unusual load characteristics, or you are trying to model something outside of the capabilities of the simulation program, high unmet hours are often the result of "problems" in the model - mistakes in simulating the zones, systems, loads etc.
Regards,
William Bishop, PE, BEMP, LEED? AP
Thanks, Bill. That was exactly what I wanted to know.
Regards,
Vinay