Load shedding for demand control and temperature control remotely 1

[Poorboy]

I have a customer that has 14 Rooftop units. 10 kw of heat and 9.4 amps for compressor. They are strip heat with conventional compressors. They want to control the 14 thermostats from their home office over the internet. I am looking for a solution where they provide charting, adjustable set points and demand control without having to write code for all the functions. I have checked with several big name companies that want to do performance based contracting but that's not what the customer wants

 

[waross]

Look at Omega Engineering (omega.com).
As an example,

http://www.omega.com/ppt/pptsc.asp?ref=CNI_Series

The iSeries devices can serve Web pages over an Ethernet LAN or even over the Internet making it possible to monitor and control a process through a web browser (such as Microsoft Internet Explorer) from anywhere in the facility or anywhere in the world.

This is just one of many internet addressable controllers. You may be able to use a controller with multiple inputs and outputs.
The controller would directly control the A/C unit. The head office would have the ability to view the temperatures and settings of the unit over the internet and change set-points as desired. This may be done manually or automatically.
This is a place to start your research.

Bill
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"Why not the best?"
Jimmy Carter

 

[Poorboy]

I talked to the folks at omega and they don't appear to offer demand control per se. The controllers could be programmed through activex to do this but I'm hoping to find an off the shelf product designed for this purpose and hopefully integrated with thermostats.

 

[waross]

Be very careful with demand control. I worked for a division of an large international company who pioneered demand control years ago. They had an installation years ago where the demand control would juggle loads to keep the demand low. On hot days, the system would keep everything low, losing ground until it overloaded and all the loads came on at once. This gave a demand peak the like of which had never been seen.
The owners made an offer: Put the system back the way it was and return all monies and we will not sue you for all monies paid in extra demand charges and the cost of putting the system back the way it was and the return of all monies paid.
We did not do demand systems after that.
There are applications for demand control. An example may be a compressor station where starting a second compressor would trigger a demand charge that would never be met by revenue, much less extra revenue. A friend remembers a station where the compressor start button was called the $20,000 button due to the penalties involved with starting a second compressor. Probably an exaggeration but any amount that may be exaggerated to $20,000 is a lot of money.
Back to Omega. My thought was that your central computer could be programed to control and alarm the A/C systems. I would concentrate on alarms and detecting user abuse of the settings. You may also find it valuable to track and trend run-times and investigate unusual trends. Another technique that may offer savings is to raise set points a few degrees on extremely hot days. This will reduce the load without the dangers of arbitrarily reducing the demand.

Bill
--------------------
"Why not the best?"
Jimmy Carter