Sorry Scott I missed this thread.

Many of the buildings we do have some such system, the complexity varies greatly.

I have never heard of EMCs (other than the company EMC) around here it is EMS (energy management systems), must be a local thing. [Linked Image]

The system I like the best is made by Comptrol, we install these in the supermarkets we wire, the system consists of 'satellite' electronic boards spread out all over the building networked back to a central touch screen in the front office.

This system handles lighting, HVAC, and refrigeration.

These are 80,000 sq ft stores with a temp sensors located about every 8' in anything refrigerated.

Then using the touch screen you can map and graph anything the system monitors and they monitor everything, a check meter on the main service to keep an eye on the POCO bills, compressor head temps, head pressure, oil pressures, emergency generator status, (block temp, oil pressure, exercise etc)

Once in a will they will use VFDs on the compressors to maintain constant pressure depending on the cooling load this system will control the VFDs.

Remember for the whole store there are only about 15 compressors and dozens of different refrigerated cases, depending on how many solenoids are open calling for refrigerant will change how many or how fast the compressors must turn.

For lighting it uses a photometer which measures the light level instead of a photocell which is on or off.

The touch screen is great with a map of the store that you touch to zoom in to get more detail and levels of info.

Anything that is outside the parameters generates an alarm to the main help desk and techs. are dispatched most times without the knowledge of the store.

Another customer that has large department stores uses a similar system, one of the strangest things is the key switch at the door the last person leaves from.

Turn the key and the store goes 100% dead, not an exit sign not a night light even the plugs on the sales floor go dead.

This means interconnection to the fire panel to bring up the lights if the panel trips.

To save money the Air Conditioning shuts down before the store closes and they 'coast' form there, at about 3 or 4 in the morning the roof units start pumping cool outside air into the building and will take the store down below the normal target temp before switching to mechanical cooling.

There are indoor and outdoor thermostats and humidistat's that the controller uses to 'make decisions' on the timing of these events, the controller 'learns' how the building responds daily.

Sorry for the rambling, ask some specific questions and I will try to answer, I know about the hardware not much about the software.

Bob

[This message has been edited by iwire (edited 04-10-2004).]

Bob Badger
Construction & Maintenance Electrician
Massachusetts