Hello,
I'm strugglling to set up a HVAC system which turns it self off when the outdoor ambient conditions are right. (i.e ambient between 20 and 25 degrees)I can set up windows to open and close in macro flow but i want to turn off my supply fans and heat/cool coils when the external conditions are right.
I need advise for the easiest method to do this.
Thanks.
Mixed mode systems - HVAC controls
Re: Mixed mode systems - HVAC controls
If the fan is on an independent controller, just use a dependent controller connected to your supply air (before entering the AHU) measuring its temperature, and connect it to your fan controller using an AND connection.
Now, if the fan is on a time switch instead of an independent controller, replace the time switch with an independent controller using the temperature of the supply air (before entering the AHU) as input for the controller.
Now, if the fan is on a time switch instead of an independent controller, replace the time switch with an independent controller using the temperature of the supply air (before entering the AHU) as input for the controller.
Re: Mixed mode systems - HVAC controls
Yep i've tried doing that with a single sensor but i can only make it switch on from High value onwards Or from low values only. eg. i want somthing to turn off between 20-25 degrees. i can use a proportional control to make it stay off till 20 and then make it modulate between 20-25 degrees and then go to maximum flow after 25 degrees. OR full flow below 20 degrees and modulate when it's between 20-25 and then zero flow after 25 degrees.
It seems i can only get half of the mixed mode operation correct but i need to combine the 2 control conditions to make to make it work right! basically i need to control something that does this.
max signal (on)<20(min signal or off)25< max signal (on)
at present i can only get one half of either side to work..
It seems i can only get half of the mixed mode operation correct but i need to combine the 2 control conditions to make to make it work right! basically i need to control something that does this.
max signal (on)<20(min signal or off)25< max signal (on)
at present i can only get one half of either side to work..
Re: Mixed mode systems - HVAC controls
Ok, I think I understand.
I would suggest using cascaded dependent controllers; have two dependent controllers sense the room temperatures. The first one detects a room temperature above 25°C; the second one detects a room temperature below 20°C. Use that third controller you've already created (an independent controller that controls for flowrate, I suppose), and link them to the two dependent controllers using OR connections. That way, if the temperature is either above 25°C or below 20°C, that independent controller will be active, however, if it is neither above 25°C nor below 20°C, the independent controller will be disabled.
Does that make sense for your application?
I would suggest using cascaded dependent controllers; have two dependent controllers sense the room temperatures. The first one detects a room temperature above 25°C; the second one detects a room temperature below 20°C. Use that third controller you've already created (an independent controller that controls for flowrate, I suppose), and link them to the two dependent controllers using OR connections. That way, if the temperature is either above 25°C or below 20°C, that independent controller will be active, however, if it is neither above 25°C nor below 20°C, the independent controller will be disabled.
Does that make sense for your application?
Re: Mixed mode systems - HVAC controls
Yep i figured that one out after some experimenting with the OR function. I did exactly the same thing and it works well.
Thanks.
Thanks.