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15 or 20 tons

How do you figure out a load estimate for a pizza poular. There are 4 ovens /hood/a new 2200cfm exhaust fan / a new 1800cfm gas fired make-up air unit.The make -up air is dumped in thru 5  2x2  4way ceiling registers.So, on any HOT day that air is 80* 90* 100*f and in desperate need  of being cooled. I for one, do not want my pizza guy sweating  on my slice The existing 5t rooftop is a little small now,I think.The building is 25'x20'x20' w/ a hung cieling @10' /no insulation above ceiling tiles. One good thing is the roof is painted SILVER. But I think the roof is  really painted SILVER to torture us roof dwellers.This place might be a wind tunnel w/ all of this air moving about .This is on Long Island N.Y.


  • meplumber
    meplumber Member Posts: 678
    Try this.

    Do your heat gain on the building as normal.  Try and get your hands on the current ASHRAE handbook.  In it are allowance numbers for commercial kitchen stuff.  Also, if you know which manufacturer's equipment that you want to use, give the rep a call, they will be glad to help you figure it out.  They have always helped me with the equipment sizing. 

    That is how I do it.  Seems to work, but hey I am in coastal Maine and it doesn't get that hot up here. 

    Good Luck. 
  • Techman
    Techman Member Posts: 2,144
    edited March 2011
    Good Idea.

    I downloaded a BUNCH of stuff ,funny,  there's an OPTIONAL DX coil available, funny that's not my part of the job, funny, no one mentioned  this to anyone at any time  during the job ,funny ,I was ignored when I tried to explain this during the renovation,funny ,that's not my part of the job,funny,that one refrigerator  w/ 2 evaps { NEVER HAD ANY PROBLEMS !  I SWEAR!!!!!!!!!!!!!!!!!!!!!!!!!!!} with  one woking fine ,the other evap had an 8" fan blade 10 was needed, cw rotation blade ccw was needed, motor was 230vac 115 vac was needed, funny , was the expression on the owners face when I handed him my invoices, that was funny!
  • meplumber
    meplumber Member Posts: 678
    Don't you just love those jobs.

    They want a Cadillac for the price of a Yugo.

    Good Luck.
  • don_9
    don_9 Member Posts: 395
    Makeup air unit

    The makeup air unit handle the heat and cool for the hood,so i would do as suggested by other to the load on the building...lights,people,fresh air,peak load and always keep in mind for the most part the fresh air requirement is usally what increases the load on those type buildings.

    Assuming the makeup air unit is one that heats and cools the air.
  • Brad White
    Brad White Member Posts: 2,393

    the equipment underneath a proper canopy hood (ovens, fryers, etc.) will emit about 10% of their heat as output to the space. In other words, the hood should take 90 percent of that away. The ASHRAE tables cover this in more detail and include considerations for radiant output which is not easily addressed by air movement.

    I agree with the advice to size the base comfort unit (as opposed to the makeup air unit), for the load as you see it, the proverbial "box in space". This would (were I designing it), allow sufficient outside air for the dining population plus some to counter infiltration. (ASHRAE 62.1 would cover this, if not your state building code, likely similar). This bonus of outside air helps offset migration of cooking odors from the kitchen to the dining area. Push from clean to less clean, as it were.

    Your make-up air unit may have certain conditioning criteria per your local code. Here in MA we have to "temper" the air to within 10 degrees of space temperature. Now, to cool air to 70F to maintain 80F in a kitchen is not going to dehumidify a bit. It will serve to add humidity to the space.

    If going to a hood, directly, that may be OK, but to foist this on Anthony and Dmitri will not get you cheeburger.

    The ability to get below space dewpoint is critical as you stated.

    For dispersing large volumes of air in a smaller space, consider perforated plate diffusers. By breaking up the airstream via perforated plates, the mixing is increased by induction and exit velocities are reduced within a foot of the face. Easy and cheap.

    Your biggest challenge is refrigeration control and humidity control over a wide range of load demands. One device we specify is the Rawal APR valve. This is a form of a "quench valve" which takes liquid denied to the evaporator and hot gas denied to the condenser, to pass vapor back to the compressor, based on suction temperature. This allows a 5 ton unit as one example, to modulate down to about 1.5 tons without cycling off. Imagine gaining variable refrigerant capacity from on-off units. Follow the instructions but do check them out. I have zero stake in the matter. Just suggesting.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • clammy
    clammy Member Posts: 2,668
    Speed controllers ,exhaust hoods and make up air

    Tech man do they have speed controllers on the exhaust hoods ? I have used them in the past they are great for reducing the amount of exhaust and balancing exhaust to make up and ridding kithens of negative pressure issuse which end up blowing your cooling right out the door .Usually when i have been invoulded in these types of jobs we install a seperate unit just for the kithen area .We have also suggested that a drop soffit or apron be installed dropping the apron usually including the oven area and counter area.This usally keeps the heat load from really drifting into  the dining area.I do not think i would use any type of mini split due to the grease and flour they end up clogging the coils  and drainage quickly.Use a unit with a economizer and 2 stage cooling and if you an order it with a 2 inch filter rack it is all we uses always .Good luck it seems i have wasted more time in pizza joints that wanted cooling in the kitchen /oven counter areas and after all was said and done they did nothing except blow a hole in the wall and add the biggest through the wall unit money could buy .Did it work No did they save alot of money  on the install yeah where they still hot Yeap and yes they still complained.Please remenber that running that cooling is going to cost a pretty penny cause  when the first electric bill comes the thermostat ends up getting turned way up or off and like everything at a pizza palor maintance is  of course the first prority . I think i would leave the 5 ton unit and add a small 6 ton 2 stage unit, Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
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