Commercial Kitchen Hood Makeup Air

[ME27272727]

In cold climates, I've always been specifying makeup be tempered (heating only). The IMC requires tempering, or the ability of the HVAC system to be able to handle the additional load of raw makeup air. However, I've seen others moving towards no conditioning of makeup air when using compensating hoods (makeup delivered to perforated MUA plenum outside of cooking surface). Since all of this air will be immediately exhausted, I don't see it having much effect on the kitchen heating system, and seems to be a major energy waste. I'm unsure if the radiant and convective heat of cooking surfaces is enough to overcome the blast of cold makeup air. Thoughts?

 

[EnergyProfessional]

I'd start by finding out what flowrate is needed and what typical cooking scenario is (burner size and how many used etc.). Add climate zone and what tolerance the cooks would have.

Based on the information provided, you could be in Florida with a 800 cfm stove that uses all 4 burners or in Alaska with a 4,000 cfm stove where an old fray lady fries a single egg.

 

[ME27272727]

Cold climates (zero degree design day). I suppose a "typical" restaraunt kitchen containing a heavy-duty hood with ranges, kettles, deep dryers, with aproximately 7,500 CFM exhaust and 80% makeup at the hood.

 

[EnergyProfessional]

For lack of other information, I'd do an energy balance and determine the average temperature based on the heat output of some of the smaller burners that can be counted on being used most the time. Maybe guess how much of that make-up air short-circuits into the exhaust.
Most of those hoods still use a small % room air. So if you exhaust 4,000 cfm, that cold air may only be 3,000 cfm and the rest room air. That room air needs to be made-up separately.

That won't tell much about comfort at a specific location (where the cook is), but would be a start to know how cold the air actually could be. Also estimate if the kitchen in general is hot, that would help. That hood manufacturer may have data on how the cold air distributes and washes over the cook's head. So what flows where will be important.

There will be sensible and latent heat from the fire, and the cooked food. But for comfort feeling, this may not matter as much since cold air and steam still will feel warm. But this is just a guess.

 

[chicopee]

Instead of looking at heating make up air, there is another concept of ventilation over cooking appliances without worrying about heat loss and heat gain. About twenty year ago I was making a survey of a golf club in Connecticut and as I walked through the kitchen work was progressing in installing a push pull ventilation system. While probably more expansive than a regular ventilation system over cooking facilities the push pull ventilation system was installed to minimize heat loss during the winter and heat gain during the summer.

 

[Drazen]

What you call compensating hood usually don't have all the makeup delivered at the hood, but the large portion of it, which makes a saving and sense of using it.

There is no issue of cold draft as this concept uses syphonic effect to accelerate exhaust effectiveness. Yet you do need some level of preheat in extremely cold climates because of possible icing/freezing/outside condensation.

 

[nuuvox000]

You'll need to get with the manufacturer of the compensating hood to make sure they can meet the flowrate you require.
IMC requires indoor, occupied spaces to be heated to at least 68 °F and it also requires makeup air for commercial equipment to not be more than 10 °F different than room temperature so I think you'd need to heat the air to a minimum of 58 °F.

 

[AdrienneGC]

I design for hot climates, so don't have too much to add to what has already been discussed other than this: maximize ventilation air to the dining area to supplement the make-up air. In this way, the amount of air being treated and then immediately exhausted can be reduced, and instead, the air that is being exhausted has been previously "used" by the customers before being exhausted. And not to hijack your thread, but I have a handy ASHRAE calculator on my webpage for sizing exhaust hood CFM: Commercial Kitchen Exhaust Hood Calculator

Adrienne Gould-Choquette, P.E.

http://www.adicotengineering.com