Welcome to the TRNSYS Users Forum.
The forum is a place where people can interact and have discussions about different topics involving the use of the TRNSYS software package. Here you can post topics for discussion or questions on using TRNSYS and get advice from other users or TRNSYS experts. This forum is not intended for detailed technical support. Users should contact their distributor’s hotline for such assistance.
Some tips for success on using the forum:
- Follow the Forum Rules posted in Forum Administration.
- There are categories for different types of topics and questions. Post your topic or question into the proper category.
- Before posting a topic or question search the existing topics (and the TRNSYS Users listserv archive or Post archive) to see if a similar topic or question has already been answered.
- Use a descriptive topic name. Don’t use attention getting subjects, they don’t get attention and only annoy people.
- State the version of TRNSYS and which add-ons your are using.
- Include enough specific details for your topic of question to be answered. Just posting “Why am I getting an error?” without describing the specific error and what you are trying to do when you get the error will not receive a response that fixes your issue.
- Remember when people help you, they are doing you a favor. Be patient, help people out by posting good descriptions of what you need help with, and be polite even if a response does not solve your issue.
- Moderators may edit your post for clarity or move your topic to a more appropriate category.
I am in need of a controller for an air source heat pump. I have set the upper temperature limit to 45°C and the lower limit to 35°C.
I require a controller that provides a signal based on a previous value. Specifically, when the heat pump is off and the temperature is decreasing, I need it to remain off until the temperature reaches the lower limit. Conversely, I need the signal to remain on when the temperature is increasing.
I believe the Type 165 differential controller may suit my needs, but I am unclear about its upper and lower dead bands.
Could you recommend a suitable controller for this application? I attempted to create my own using equations, but I am unsure how to store the previous temperature to compare it with the current temperature and apply a condition.
Any of the controllers with a "deadband" will do exactly what you described as far as maintaining the previous control signal while the temperature floats between the upper and lower limits of its range. Are you in need of a single control signal (heating only, or cooling only), or separate heating and cooling signals (which is what most TRNSYS heat pump Types require)?
It sounds like you probably want Type 166, the simple thermostat, in the standard Controllers library in TRNSYS18. It will produce heating and cooling signals (either heating ON and cooling OFF, or cooling ON and heating OFF, or both heating and cooling OFF) for separate heating and cooling setpoints. For example, using Type 166 with a cooling setpoint of 45 C, a heating setpoint of 35 C, and a deadband of 2 C (the default), you would get a cooling signal that turns ON when the monitored temperature is 46 or above and OFF when the monitored temperature is 44 C or below, floating at its previous control state when it's between those two temperatures. The heating signal will turn ON when the monitored temperature is 34 C or below, and OFF when the temperature is 36 C or above, again floating at its previous control state when it's between those two temperatures. Both signals will be OFF when the temperature is between 36 C and 44 C. This isn't exactly the scenario you described, but I think it may be the solution you're looking for.
If you *do* want a controller that operates exactly as you described, you could use Type 106, the basic aquastat in heating mode, with a heating setpoint (Input 2) of 40 C and a deadband (Parameter 2) of 10 C. Set up this way, the controller will turn ON if it was previously OFF and the monitored temperature reaches (40 - 10/2 = 35 C) or below, and it will turn OFF if it was previously ON and the monitored temperature reaches (40 + 10/2 = 45 C) or above, retaining its prior value as it floats between the upper and lower limits. This signal is designed for active heating only; it has no way to signal active cooling if the temperature reaches 45 C and just keeps growing.
