Dear e-quest users,
Has anyone had success modeling 2-pipe fan coils with electric shoulder?
The system operates using the following schedule:
- Fan coils provide cooling March through December
- Fan coils provide heating December through March
- Supplemental electric heaters will provide heating during October, November, April and May when required.
I was able to model 2-pipe fan coils by connecting 4 pipe fan coil to 2 pipe circulation loop and using schedules to define changeover criteria. This model gave me a high number of unmet load hours, much higher than I expected. As I could not figure out how to model supplemental electric heat I switched back to 4-pipe fan coils and assigned availability schedules to heating and cooling. With this configuration, I tried to use electric baseboards and baseboard schedules based on outside temperature, but my unmet hours went up, offcourse this time in cooling. I tried changing capacities of baseboards and the baseboard reset schedule, all without any success. The only idea that I could think off is to manually calculate heat load and electricity consumption for spring-fall months. This is a huge building with almost hundred of FCs, and I am still hoping there is some better solution.
Any thoughts?
All ideas are greatly appreciated.
Ana
Hi Ana,
My take on your model, without seeing it, is that you should stick with the
2 pipe fan coil system since that is the system you have. Having hours
outside the throttling range is not a by product of your system selection
but rather indicates that you have some input which is not allowing adequate
heating, cooling and ventilation air to be supplied to your zones. To solve
this problem I suggest that you very methodically go through your HVAC input
screens and double check the validity of the inputs, especially defaults, to
be sure that they are what you want.
It is likely that by now, since you have been switching back and forth
between systems, trying to get them to work, you have made a number of
changes and maybe not in the best way. If you saved an earlier version of
your 2 pipe system with the crossover strategy you might want to go back to
it and start there.
Carol