Water coil advanced controllers

asked 2019-05-09 08:35:56 -0500

Francisco Escobar
41 ●2

updated 2019-05-11 12:22:41 -0500

__AmirRoth__

4436 ●5 ●17 http://bleedinggreenna...

Hi!

I have a system which consists of a heating coil and a direct evaporative cooler connected in series. The objective is to heat the intake air to a certain point, and then cool the air with an adiabatic process, in order to ensure indoor conditions within narrow limits in terms of temperature and relative humidity. However, the coil should work only when certain outdoor conditions occur.

I would like to control the heating coil depending on outdoor conditions (coil must work only when outdoor temperature is between -1C and 25C and enthalpy is between 6 and 35 kJ/kg dry air). How should I set the controllers to meet these requirements?

answered 2019-05-11 02:42:46 -0500

ericmartinpe

2065 ●42 ●8 http://ericmartinpe.com/

Controlling the heating coil based on outdoor air temperature can be done easily with AvailabilityManager:HighTemperatureTurnOff and AvailabilityManager:HighTemperatureTurnOn using an outdoor air node as the sensor.

Controlling based on enthalpy is a bit trickier. You could either output the outdoor air enthalpy for every hour of the year, create an hourly on/off schedule based on the enthalpy, and use AvailabilityManager:Scheduled. Or the better but more complicated way to do it is using an EMS program that uses an EnergyManagementSystem:Sensor to track OA enthalpy and uses an EnergyManagementSystem:Actuator to control the coil availability. You could also just make an EMS program that uses both OA temperature and enthalpy to control the coil availability. If you're not familiar with EMS programs/controls, check out the EMS Application Guide documentation.

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Comments

Thanks a lot for giving light in this issue, Eric! Although a little bit painful, I think that outputting the outdoor air enthalpy and creating the hourly on/off schedule will fit perfectly.