Commercial kitchens have a lot of moving parts when it comes to what effects the a/c load. This can be a tricky business and rules of thumb are totally out the door. Here’s a few important things you need to be aware of when sizing the a/c for a kitchen:
- Ventilation air is usually the biggest factor – All the air the kitchen hood exhaust out of the building has to be replaced with cool, dehumidified, fresh air (ventilation air), and that can be a very expensive installation and operating cost if the hood is of a substantial size. Commercial Kitchen hoods are classified either exhaust-only or exhaust with make-up air. The exhaust-only hoods are cheaper to install, but require larger a/c units for the kitchen area in order to make-up 100% of the air that is being exhausted through the hood. Make-up air hoods cost more than exhaust-only hoods because of the additional hood supply air equipment, but elevate about 80% of the additional ventilation capacity needed in your kitchen a/c unit. If your replacing the kitchen hood along with the a/c, it’s worthwhile to have a professional engineer run a kitchen a/c load calc both ways for you (exhaust only vs. exhaust + make-up air) so that you can determine which option will be the most cost effective for your project.
- Kitchen Equipment layout – The type of equipment under the hood effects how much the hood needs to exhaust (which effects the a/c capacity). Griddles, fryers, stove tops can put out a lot of grease and smoke and require more aggressive exhaust. Kitchen equipment can put out a substantial amount of heat and moisture and should not be overlooked when sizing the a/c. Properly dehumidifying the kitchen area to prevent mold is just as important as cooling it. Knowing and properly estimating the moisture load from the kitchen equipment when sizing the a/c is important.
- Varying loads of equipment operation in kitchens – No reason to run the large kitchen a/c unit full capacity when there’s no activity going on in the kitchen. Multiple stage a/c units or variable speed units should be considered for kitchen a/c units. Kitchen a/c units typically have to handle a lot of fresh air, so conventional DX units don’t work well, (especial for kitchens with large exhaust only hoods). Consider using DX units designed of handling large amounts of fresh air, like a hot gas reheat a/c unit. These units are great way to battle varying kitchen a/c loads, but of course, they do come at a higher price.