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Ethan, There are two ways of conditioning a Type56 thermal zone: energy rate control and temperature level control and I think that what is happening in your simulation is that the two are getting mixed. When you work in energy rate control, you define the temperature of the zone and you calculate the amount of energy that is required to meet that set point. Because you predefined the set point, you are in essence assuming that your HVAC system is able to meet that set point. When you work in temperature level control, the zone becomes just another component in the system; its temperature and humidity are a result of both ambient and the systems that try to keep them at set point. In your simulation, you have defined a set point and then are modulating the capacity of the cooling system at the same time. I think what you want to do is one of the following: Define the set point and allow the capacity to be unlimited and calculate the cooling loads, then afterwards, impose those loads on your CCU and make sure that it can meet them at all times. or Define a thermostat model (Type23 perhaps) that monitors the cabin temperature and Type56 ventilation inputs (T, RH, and ach). Have the thermostat command your CCU and pass its outlet temperature, flow rate, and RH to the Type56 model. The temperature in the cabin will oscillate around the set point a bit (as it would in reality) as it turns fans up and down. I hope that helps, David Ethan Lust wrote: Hello, I am trying to simulate the operation of a climate control unit (vapor compression air conditioner and electric resistance heater) in a small closed space. The climate control unit (CCU) (Type 202 and the accompanying DLL7) is an original component created from manufacturer's data. Prior to the heater and air conditioning code within the Type202.f code, there is a switch that keeps the air conditioner and heater from operating simultaneously. The climate control unit is operated via a PID controller (Type 23). In addition, the space also has an internal heat load due to some electronics, hence the three type 9a components and the Type 41c. If the heat from the CCU is input into Type 56 through the heating function in TRNBuild and the cooling output from the CCU is attached likewise, there are a number of points over the course of the TMY2 year at which the program "bogs down" and stops with the calculations though no error message is produced. Occasionally an error message will pop up stating that there are 6 errors (no matter how many I have set to allow within the control cards), which all relate to temperature divergence at a wall, according to the list file. I have tried increasing the convergence tolerance with no luck. If the cooling portion is removed, the program proceeds fine, with or without the internal loads attached. I have sought help for a similar problem, to which I was suggested to decrease the cooling output and/or decrease the time interval to aid in convergence. I've tried reducing the cooling input to very low values (the DLL I'm sending has it cut in half) with no luck. The current time interval is a dreadfully slow 5 seconds. I have also tried connecting the cooling output of the CCU to the Type 56 using the gain function (using a negative value as input) with the same result. Attached are the project, bui, component (fortran and proforma) files and the DLL. Please help! Thanks, Ethan Lust University of Maryland --
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