separate make-up air unit required?

[syarn]

newark DE 2500 sf fast food salad restaurant. 2009 IMC.

existing restaurant being renovated to a new restaurant.

the design shows one existing air handling unit supply air 4000 cfm.

the existing return main duct 2650 cfm.

the engineer claims there was no outside air duct connected to the existing system....

the engineer adds a new outside air duct connected to existing return duct side of main system at 1350 cfm to satisfy make-up air for new exhaust fans aka the make-up air is coming from the main system (not separate).

the kitchen adds a new oven exhaust hood 880 cfm.

the serving area adds a new toaster exhaust hood 450 cfm.

the 2 bathrooms add new exhaust fans 75 cfm each.

the air balance schedule shows a (-130) cfm [1350-880-450-75-75].

is a separate make-up fan unit 1330 cfm required?

if the existing system DOES have an existing outside air duct connected would that condition than trigger need for an additional make-up fan unit?

 

[Gregg Harris]

It appears that he only satisfied the return air shortage for the 4000 cfm system. There needs to be makeup for the exhaust units that where installed.

 

[klarenbeek]

If 1350 cfm of outside air is truly being brought in through the existing HVAC unit, a separate makeup air unit is not required. The 1350 cfm can serve the dual purpose of satisfying makeup air requirements and airflow requirements of the HVAC system. The HVAC unit would have to be interlocked to run whenever either of the hoods are running and the system designed so that it brings in that 1350 cfm at a minimum whenever the hoods are running--balance report required.

Have the designer get approval from the manufacturer to bring in that amount of outside air in through the unit. Most manufacturers don't want more than about 25% outside air through the unit, at least in our area, or the mixed air temp. will be too low causing condensation problems inside the unit.