Squeezing It All Into The Controller
Just a few years ago, when you selected an electronic control, you had a number of components that were required. There was the microprocessor-based controller with an LED display, which had a series of parameters that required programming. The control could be programmed by pressing a number of buttons until you got the set point, differential, defrost, and alarm settings.
Two temperature probes were used. One probe was for the set point to cut in and cut out the compressor. Usually, this probe was placed in the return air section. A second probe would be placed in the evaporator to determine the end temperature of a defrost cycle and maybe control fan delays.
You usually needed a transformer to drop from line voltage to the usual 12-V or 24-V control voltage. Then, finally, you would add an outboard relay to be able to handle the load of a compressor, sometimes up to 1 hp.
When compared to a mechanical system - which included a thermostat, a defrost clock, a thermometer, and maybe a separate alarm - the costs were a little higher for the electronic system.
New GenerationA new generation of electronic controls has eliminated most of the extras and squeezed most everything needed inside the controller. Now you have internal transformers and internal large relays. Call it "plug and play." Controls now can have up to three probes, with the third one used just for the temperature display.
Another feature that is now standard is what is called "digital input," which basically involves a switch detection circuit to add a door switch so you can really save energy by closing the door after the door alarm delay.
Another use for the digital input is to add a high-pressure switch that tells the controller, "Hey, I think the condenser needs cleaning; I keep getting high pressure here." Condenser cleaning is an often neglected form of preventive maintenance. Such neglect leads to many compressor failures in the field.
Another important new feature is what is called a programming key, also known as a hot key or copy card. It's a little flash memory stick that contains all of the programming parameters.
When plugged into the controller, it instantly uploads the program in a matter of seconds. There are two major benefits of the programming key. For OEMs, who may have a number of different programs for various models, it makes life quite simple. It also helps service people to restore the factory settings or make changes without having to scroll through 50 parameters to find the alarm delay setting.
There are two ways to download the settings to the program key. The first is to go ahead and manually program one control by hand and then copy or download the program to the key. Some manufacturers offer programming kits that connect to a PC. With this method, you see the whole parameter list, make the changes you need, and burn the key.
Speaking of PCs, controls are now coming with communications ports. Still an option, but with a serial RS485 bus, a network can be set up to monitor and remotely control the operation of the controller. Networks like this have been in supermarkets for a while, but now restaurants can have their own system. The most important benefit is an automatic hazard analysis and critical control point (HACCP) system to make sure federal guidelines are met.
A gateway can connect from 32 to 225 separate controls to record and store temperatures, compressor run cycles, defrosts, and fan cycles, while keeping an eye out for alarms. Information can be faxed or sent to mobile phones.
On The WebNew Web-based systems eliminate special software that used to be required to gain access. A Web browser can allow you to monitor and control the network remotely (with a password, of course).
The second is the development of a protocol by the National Association of Food Equipment Manufacturers (NAFEM). Known as the NAFEM Data Protocol or NDP, it is designed to allow various controls to talk together in order to interface different pieces of equipment in a kitchen. The NDP can be found on the NAFEM Technical Liaison Committee (TLC) Web site, www.nafem.org/resources/dataprotocol.
Rick Cartwright, current chairman of the TLC and engineering manager at ITW Food Equipment Group (Hobart/Traulsen), said, "We have made many of our reach-ins' blast chillers, even dishwashers, NDP compliant, and while the concept was first promoted by the large chain restaurants, we are seeing the early adaptors as being institutional operators such as schools, hospitals, and prisons."
Integration with point of sale (POS) systems is also in the works, so when French fry sales slow down, the network will tell the fryer to go into standby mode.
Weiss is with Weiss Instruments Inc. He can be reached by e-mail at email@example.com. Many of the new developments outlined in this article will be showcased at the IKK Expo in Nuremburg, Germany, Oct. 13-15.
Publication date: 09/06/2004