make up air to cold

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GerryB

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Location
woodbridge, ct. USA
A small take out chicken place is complaining it is to cold and wants to shut off the make up air. Any suggestions I can give them? I am thinking you can't just shut it off. Could it not be balanced right?
 
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Make-up air could be balanced air in the kitchen hood system or it could be fresh air intake under ASHRAE for the HVAC system. Which are they talking about?

In either case I suggest they have someone take a look at it first for compliance purposes. It's possible somebody went overboard or made a mistake.

The HVAC may have a manual or motorized damper which can be adjusted.

If the kitchen hood is balanced, I would not mess with it. That air balance is intended to prevent excess accumulation of grease laden vapors.

Maybe they should call a HVAC contractor. It is a HVAC issue.
 
They shouldn't shut off the make up air. The Makeup air may need to be heated.

IMC 2012
508.1.1 Makeup air temperature.
The temperature differential between makeup air and the air in the conditioned space shall not exceed 10°F (6°C) except where the added heating and cooling loads of the makeup air do not exceed the capacity of the HVAC system.
 
Where does makeup air enter the space in relation to the hood? If pulling it across the entire building it is going to take a lot of heat with it when pulled out the hood. Inject that air near the hood and this effect is not as severe.

Next is the make up air conditioned? If so is the conditioning component working?

Turning off the makeup air makes the hood pull negative air pressure on the building. Assuming the makeup air provided a reasonably balanced pressure when running. It will try to pull makeup air in every opening available, which can cause backdrafting of gas appliances if there are any still using draft type ventilation, can even blow out pilot lights if they use a standing pilot, also can make opening exterior doors difficult with the negative pressure. If you ever entered a place with poor balance on such a system and has negative pressure, pulling the door open those first couple inches is hard to do, once you break the vacuum, it pulls easily.
 
kwired said:
If you ever entered a place with poor balance on such a system and has negative pressure, pulling the door open those first couple inches is hard to do, once you break the vacuum, it pulls easily.
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almost every Chipotle I've entered has this problem.

To GerryB,
I recently worked at a bar and grill that had the makeup air unit removed. They wanted me to use the electrical circuit for something else, i told them I'm not touching that circuit, and you need to have your makeup air unit put back in.

And that's how i left it. If it's not right, however that may be, it's an HVAC/fire suppression issue, both requiring certification.
 
I posed this question to the head of our mechanical department. After a short chuckle, he said that he has encountered this situation many times in the past. In simplest terms, removing or disabling the make up air system is a dumb idea, one that will have exactly the opposite of the desired effect. The kitchen vent hood is designed to remove air (and the smells of cooking) from the stove top and surrounding area. The make up air system brings outside air to that same area, where it is needed. If the make up air system is turned off, then a low pressure area is created, and air will be sucked in from the outside via any and all available paths. This includes any leaks in the building envelop. It also includes the door to the restaurant. So when a new customer enters, they first of all have to fight the low pressure on the inside of the door, just to get the door open. When the door does open, the cold outside air will be drawn into the room, causing the customers already inside to get a blast of cold air. In addition, the rapid influx of outside air will cause flies and other bugs to be drawn into the space.
 
Not a good idea to disable. Without make up air, the ventilation system will become ineffective. I'm guessing they either need a higher BTU makeup air unit ($$$) otherwise if the system doesn't have one, a commercial air exchanger. Basically an air-to-air radiator that would preheat the intake air for the RTU with the exhaust air going out. Would make the system much more efficient on cold days.
CommExchanger-2_000.gif
 
Unfortunately it is much easier to install an air to air heat exchanger on a purely ventilation system for a tight building than for an exhaust hood for a kitchen. The heat exchanger takes up space and the cold surfaces of the heat exchanger will be excellent grease traps, as well as requiring fire rating.
If all you have is makeup air coming in with no link to the exhaust air there is nothing to preheat the incoming air.
 
Somebody needs to check to see if that system is balanced. Maybe one is turning slower, etc.
They should be calling an HVAC guy, not the EC. It's not an electrical issue.
 
Typically the way I seen it done is the Make up air unit has an interlocking relay or air proving switch that turns the exhaust contactor on.
The make up air unit senses the air temp from the outside and heats as necessary.
Sometimes they blow the air in too hard and it feels like cold air.



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We are talking about two different things here.

One is fresh air for an HVAC system. That's where you pre-condition the air. But that's not what OP is dealing with.

The other is the restaurant kitchen hood system where it's a straight pipe from above. Code requires balanced air. Most people if they could would have the make-up air about 95% of the exhaust air to keep the heat from the kitchen from going to other rooms in the building, and to make it more comfortable (and productive) for the kitchen staff.

OP needs to tell his customer to get a HVAC contractor to find out what's going on with those fans. One may be slowed down; it happens. If it were properly balanced, he would not be getting so much cold air in there. As long as there is line voltage to each fan, this is not an electrical issue.
 
One consequence of shutting off the make-up air supply is that the hood will then pull a negative air pressure in the building if it can't find another adequate source. With even just a few inches of vacuum, outward opening doors can get stuck closed, and people panic. Happened to me once, they called the fire dept., who smashed the doors. Very expensive mistake.
 
charlie b said:
I posed this question to the head of our mechanical department. After a short chuckle, he said that he has encountered this situation many times in the past. In simplest terms, removing or disabling the make up air system is a dumb idea, one that will have exactly the opposite of the desired effect. The kitchen vent hood is designed to remove air (and the smells of cooking) from the stove top and surrounding area. The make up air system brings outside air to that same area, where it is needed. If the make up air system is turned off, then a low pressure area is created, and air will be sucked in from the outside via any and all available paths. This includes any leaks in the building envelop. It also includes the door to the restaurant. So when a new customer enters, they first of all have to fight the low pressure on the inside of the door, just to get the door open. When the door does open, the cold outside air will be drawn into the room, causing the customers already inside to get a blast of cold air. In addition, the rapid influx of outside air will cause flies and other bugs to be drawn into the space.
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If the flies and other bugs are active it isn't really cold air being drawn in, unless you live somewhere that rarely sees below freezing temperatures.

High temps today and tomorrow here not expected to be much above 10F with -25 wind chill temps, I don't expect to be having much insect problems;)
 
Jraef said:
One consequence of shutting off the make-up air supply is that the hood will then pull a negative air pressure in the building if it can't find another adequate source. With even just a few inches of vacuum, outward opening doors can get stuck closed, and people panic. Happened to me once, they called the fire dept., who smashed the doors. Very expensive mistake.
Click to expand...
Went out to dinner Sat night, my wife had a little trouble pushing the door on the way out. Thought of this post:).
I have a lot of info to pass on to my customer. This is a new hood, only about 10 feet long for the grill and the pressure cooker. (They fry the chicken in the pressure cooker, really good).
The make up air comes in at the bottom rear. The previous tenant was a Chinese take out with no hood system at all. The romex we pulled out of the drop ceiling was dark brown covered with grease.
They probably don't have the heat turned on or high enough either to save money.
I will tell them also to contact the installers as this is a brand new system.
Thanks for all replies.
 
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