What makes a conduction retherm system better than a convection retherm system?
Convection has several other strikes against it.
First, convection uses significantly more energy than conduction systems. For example, a typical 50-minute retherm cycle with a 20-shelf ISECO Vitalis Evo cart uses about 3 kilowatt hours; a comparable convection cart uses more than twice that. All the extra heat wasted by convection goes into the environment (i.e. the hospital / long-term care facility), which then has to be air-conditioned out, wasting even more energy. Estimate annual savings for using conduction vs. convection is over $500 per cart per year (assuming three meals per day).
Another problem with convection is noise. They make alot of it, because of the fans used to circulate hot air through the cart. Since conduction carts (like ISECO’s Vitalis Evo) have no fans to circulate hot air, they are much quieter.
Since convection carts have hot air fans, they break and must be repaired. In comparison, thermal conduction heating requires no fans to circulate hot air, and therefore are significantly more reliable.
A third strike against convection is lack of flexibility. Flexibility for conduction carts come in two areas:
1. Number of trays and size of the "hot side": ISECO’s Vitalis Evo conduction retherm system only uses the energy it needs. If a tray requires a smaller heating area, the cart uses less energy to heat it. If a tray requires no heating (or is absent), then no energy is used (or wasted) heating that tray. In comparison, the energy consumption for convection systems is fixed.
2. Convection retherm carts must carry their own refrigeration equipment (either internally or in attached "stands") in order to keep the "cold side" cold. ISECO’s Vitalis Evo carts have additional options, including:
– no internal cooling: the carts can be rethermed in a cold room, with folding doors that expose the "cold side" to the cold room, while keeping the "hot side" mostly insulated from the cold. Convection carts cannot do this because of the large amount of excess heat that they generate.
– CarboFresh: this patented system from Air Liquide (exclusively licensed to ISECO) injects liquid CO2 into a vented compartment inside the cart. The CO2 expands and forms CO2 "snow", or dry ice. The dry ice can keep a Vitalis cart cold for up to 6 hours without using any electricity. An ISECO Navis cold transport cart can "keep its cool" for up to 18 hours. This is ideal for transporting meals from central cook-chill facilities to distributed buildings, obviating the need for refrigerated trucks or cold rooms.
The final strike against convection is safety. With convection, the trays get so hot that they cannot be touched with bare hands; gloves are required to handle the trays. No such risk exists with thermal conduction; the edge of the trays get warm, but not hot enough to burn.
Convection systems tend to dry foods during the retherm process, whereas the À la Cart conduction system gently heats menu items through the bottom of the plate to maintain the foods’ natural moisture. This is especially important if the menu includes pureed items, low moisture vegetables or delicate entrees such as fish and egg dishes.
