Heated Makeup Air

[Teppy]

I'm helping to start a restaurant in Pittsburgh, and one code requirement is baffling me: The makeup air for the hood is required to be heated.

 

I understand the reason for makeup air itself, but why heat air that will be ejected through the roof a second later? This adds $4000 or so to the cost of the hood, and $13-$52 per hour that the unit operates (1M-4M BTU/hr, which is just a guess - we need to have an approved engineer tell us the size of the makeup air heater we need.)

 

I've asked this question of two different companies that sell the makeup air heaters, of several local chefs, and of several hood installers, and everyone's answer is the same: "I don't know, but the code requires it, so there's no use arguing about it." I even read the code itself, and it's true that heated makeup air is required, but there's no explanation of why.

 

Guesses have included "for the comfort of the chefs" (Pittsburgh is cold in the winter), that cold air tends to fall (the makeup air should go up the hood), that the temperature differential could cause grease to condense faster and create a fire hazard by sticking to the ductwork, and that some cold makeup air might escape into the dining room.

 

Perhaps I'll invent a sink whistle and lobby to have that written into the code.

[pastrygirl]

I don't know, but heated makeup air was my complete and utter nightmare when we moved the restaurant to a new space a few years ago.  It took months of complaining and threatening to quit, with multiple visits from multiple HVAC guys before a switch was installed to be able to turn the heat off.  The makeup air blew down in front of the hot line, but did not immediately get sucked back up the hood.  Instead, we had a heated kitchen.  Yes, the heat was sometimes on 24/7, in addition to ovens, flattops, and a wood grill during service.  Fucking stifling, way beyond comfortable.  I was the pastry chef, went in to work around 6 or 7 am so I could get things done - roll buttery doughs, temper chocolate, etc - before the cooks came in and fired things up.  If the heat was on all night it would be upper 70's even at 6am on a winter morning.  The day it was snowing outside and the kitchen was 77F, I truly almost walked out.  A PASTRY NIGHTMARE!!!  But the way the air blew directly down, if the heat was off the cooks would freeze and the hot food would get cold (unless it was summer), so I had to let them turn the heat on during prep, even though the back half of the kitchen not under the hood was plenty warm.  Yeah... poor circulation/ventilation despite the shiny new hood.

 

So I urge you to make sure you have the options to turn the hood itself off and to turn the heat off and blow outside-temp air instead.  And consider where this heat is blowing and whether it actually will go right back up the hood or heat the kitchen.  And if you have a pastry chef who you don't want to see suicidal, make sure you have a cool spot somewhere in the kitchen!  There is no reason to heat the kitchen overnight!  OK, maybe PA winters are way harsher and there is a reason, but still, make sure you have options!

Edited November 20, 2014 by pastrygirl (log)

[dcarch]

No. Ask a HVAC contractor, or an engineer about a heat exchanger.

 

dcarch

Edited November 20, 2014 by dcarch (log)

[MSRadell]

The heat exchanger would take the heat out of the air your exhausting to warn the incoming air! It certainly helps energy efficiency.

[ElainaA]

I'm turning this over to my  husband who is an HVAC contractor

Elaina

 

I hope you have an experienced engineer who actually knows how these products work.  PastryGirl is right - you need to make sure you get a remote control panel so you can select discharge air temperature to meet kitchen conditions.  I prefer the packaged systems from CaptiveAire or equal because their guys really know the work.  It gets cold in Pittsburgh and you'll really want heated makeup air on a cold night.  If you have cold air sweeping over the grille, nothing cooks right and your technique will be disrupted and everything will suck.  And if you turn it off, your building HVAC system won't handle the infiltration and your diners will feel it and that sucks too.  If it doesn't feel right, get a certified balancing contractor to make sure that your makeup air is 80% of exhaust. That 20% deficit should be blowing past you as you cook.  If the code lets you have a 2 speed exhaust (most don't), be sure you can match the makeup.  Just my 2 cents and good luck!

 

Barney

Edited November 21, 2014 by ElainaA (log)

[pyrguy]

Depending on the adopted code there is an exception IF the kitchen HVAC system is designed to handle the outside air temperature.

[Tri2Cook]

We have a 2-speed exhaust and a thermostat controlled makeup heater at work. When the exhaust is on low, the air makeup stays off. On high it kicks in and we can control the temp via the thermostat. But this in Ontario, Canada... I don't have any idea if it would fly anywhere else. I know that heater is essential and sometimes bordering on insufficient when it's 30 or 40 below zero.