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How Does The Heat And A/C Work In ECPS

The heat and A/C (HVAC) systems in ECPS and most all other commercial applications are a very complicated system. Most people try to relate the HVAC system in their classroom with their home system and there is very little comparison. Many homes have a HVAC system that uses Freon to heat and cool the spaces. This is done by compressing Freon and using it to transfer heat or cooling across a coil that air flows over. When the unit is cut off the Freon is stabilized within a couple of minutes and can easily be switched from heat to cool or vise versa.  Most large commercial applications use water to cool or heat space. This is a more efficient way to condition a larger area. As you can imagine, it takes a lot of energy to heat or cool several thousand gallons of water but when it is conditioned it is more efficient to maintain the water temperature. After the water temperature for heat is at 180 degrees, it could take as long as two days before the water cools to a temperature low enough to start the cooling process. This is one of the reasons that we can not heat a building in the morning and cool it in the afternoon like a home owner can. This is also why when we change over from heat to a/c or vise versa it stays there until the next season. There is no magical date this happens. It is up to the Principal to determine when it is changed over with the understanding that it can not be switched back and forth.
Most all of our units are controlled by direct digital controls (DDC). These are computerized controllers that operate boilers, chillers, air handlers, etc. Despite what a lot of people think, the HVAC is not controlled at the Central Office. All controllers are located at the schools. It is basically a computer network at each school so that the server located on site can communicate with all the HVAC units. Programs are written for each unit to operate within parameters set for that particular unit. Being on a computer network, it can be monitored and adjusted remotely at any location that has a computer on the ECPS network. This also allows a lot of equipment that has alarming features to be able to use the DDC to call out to the maintenance office and/or to the technician pager if something goes wrong. A lot of times a boiler will fail for some reason and with the alarming feature, we will have it back up and running before the school knows there was a problem.
One of the biggest things that the DDC looks at is outside air temperature.  During the summer and also the winter, the outside air usually does not control a lot but during the spring and fall, it does. An example of that is a day starts out with a temperature of 45 degrees but by lunchtime it is 65 degrees. The DDC will start the boiler up in the morning but as the temperature keeps rising it will shut it off when it get to a preset set point. Another misunderstanding is that if it is hot outside and the building is hot that the Central Office has it cut off. The easiest way to look at this is if it is cold outside and it is cold in your area, there is a problem. We need a work order. The same if it is hot outside and your area is hot, there is a problem. The ECPS Board of Education Policy is that we have a cooling set point at 75 degrees and a heat set point at 70 degrees. If your room is not in that range please submit a work order so it can be checked out.
ECPS is committed to saving energy but that comes with no compromise on student and staff comfort.
Danny Owens is shown servicing an air
cooled screw chiller.
Sherwood Webb is shown troubleshooting a
 boiler through DDC.


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