Summer and winter schedule

Jbeard

Member
Join Date
May 2019
Location
Tn.
Posts
14
I have a bunch of twido plc's sitting around and I would like to put them to some good use. Im new to ladder logic but I'm learning fast, I would like to place the plc's in some of my boiler rooms to control building loop pumps , boilers and a few cooling tower fans. I already have a small program written to control the boiler on/off , loop pumps and cooling tower fans on/off. My problem is when cooler weather comes around my boiler will want to come on to keep my building loop at a set temperature and then my cooling tower fans will want to come on to lower that set temperature. Is there a way to make a summer and winter schedule with like a 6 degree difference so that my boiler and cooling tower fans don't fight each other?
 
Do the Twido PLC's keep track of the date?

If so it shouldn't be that difficult to check the date and change parameters appropriately.
Poet.
 
Yes you can program them that way. I guess I can just program them using time to change over the settings.
 
This change-over happens twice a year, I would do it manually. Some winters are short, some are long, when do you change-over?



Have two sets of parameters, but the actual change-over from one to the other should be manual.


I work with boilers, the ones that are used for domestic heating often have temperature compensation. Higher temperature when it is cold outside and vice versa.
 
I may be wrong on this, but.

your location is Tennessee, so boilers are inspected and licensed by the state.
these boilers already are licensed by the state and as such their controls are also approved by the state as well. any modification of the controls will require the state to be notified and extensive testing to be done on the system.

as I said, I can be wrong, so please double check with engineering, safety, maintenance manager in regards to your plans. I would hate for you to d the install and have the state shutdown the boiler for safety violations due to the controls.

james
 
Hi James,


Speaking for our systems, the actual burner control usually lies in a dedicated combustion manager, we change temperature setpoints and send start/stop signals. The actual safety, timing and safety ratio's are independent.
 
Sounds like he is doing some type of building Heating/Cooling systems. Turning on Loop pumps etc.. Not sure about Tenn. but in some states, the standard regulations start at a certain size, say 15HP. Anything below the minimum, no operators license needed, no annual inspection, etc...
 
If it was me, I'd add a temperature (and humidity) sensor from the outside. If it's cold outside, the cooling towers will be more efficient, so then set the cooling tower (and boiler) setpoint higher (possibly with the 6 degree differential that you suggested); if it's hot, the towers are less efficient and you need less heat, so lower both setpoints.

With a sensor, you don't need to worry about dates, the weather outside will take care of everything for you. If you add in humidity, then you can get fancy and calculate the wet-bulb temperature (= ~"Real Feel"), for even better environmental control.
 
As said before I just want to turn the boiler on and off, the boilers safeties will take care of the rest. I think I'll just put a outside temp sensor to control the boiler and cooling tower fans.
 

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