Should a kitchen using gas fired appliances have a negative or positive air pressure?
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Should a kitchen using gas fired appliances have a negative or positive air pressure?
All the one's I've seen have a negative air flow.
This is the start of a good thread. First thing that comes to mind, are the vents from the gas-fired appliances. If the A/C creates a negative pressure, what happens within the mixing ventilation, such as the water heater vent? Do we pull after-burnt residue from the vent, back into the room?
I agree with a negative pressure in the kitchen, but what if the kitchen were enclosed.... maybe a catering kitchen with no other air to ventilate?
Is it possible that a positive pressure would be wiser to achieve? Pushing the CO out?
Is it possible that a negative pressure would defeat a gravity damper exhaust and circulate CO, etc through the kitchen before achieving exhaust?
What effect does a negative pressure have on the air/gas mixture for efficient burning?
I think there are kitchens with gas burning appliances which require diametrically opposite answers to this question.... simply because there are diametrically opposite kitchens in this world.
Perhaps they could just use electric and not have to worry about it?
Hot water heaters are supposed to have a source of make up air. I assume this means they should not be located near the kitchen?
Any room, whether it is a kitchen or not needs a balanced flow of air to be properly ventilated. However, there are many variations of this rule. Both positive and negative, and the designer should consider which one is the most appropriate for the application.
In a kitchen it is normally best to design for a negative pressure so that the cooking odours do not egress from the space but are discharged to atmosphere by the canopy extract fan. A balance of 75% make up air to 100% extract is quite normal, the remaining 25% input air being drawn from the surrounding areas.
Obviously, where the kitchen contains gas burning appliances then careful consideration MUST be given to the supply of combustion air without the risk of affecting the flame characturistics. If the kitchen is a sealed room then UK regulations dictate that separate static vents are required or if the room is below ground then powered input combustion air is required with an interlock between the fan and gas valve.
Certain situations need a positive pressure air supply to prevent dirt and undesirables from entering the space with the excess pressure/volume escaping through the building fabric or relief valves. Some examples are clean rooms, Pharmacy prep rooms and offices where the return air is drawn from the corridors.
A competant designer will consider all these points and more before advising the customer.
Also, some cooking areas do have a positive pressure air supply so that the cooking odours or smells are meant to leak out - a good example is the bakery section of the local supermarket. The smell of bread baking drifting across the shop floor makes the customers head a bee line straight to the bread counter for a fresh baked loaf!
The answer to your question is not quite so straight forward.
Frank
Any room, whether it is a kitchen or not needs a balanced flow of air to be properly ventilated. However, there are many variations of this rule. Both positive and negative, and the designer should consider which one is the most appropriate for the application.
In a kitchen it is normally best to design for a negative pressure so that the cooking odours do not egress from the space but are discharged to atmosphere by the canopy extract fan. A balance of 75% make up air to 100% extract is quite normal, the remaining 25% input air being drawn from the surrounding areas.
Obviously, where the kitchen contains gas burning appliances then careful consideration MUST be given to the supply of combustion air without the risk of affecting the flame characturistics. If the kitchen is a sealed room then UK regulations dictate that separate static vents are required or if the room is below ground then powered input combustion air is required with an interlock between the fan and gas valve.
Certain situations need a positive pressure air supply to prevent dirt and undesirables from entering the space with the excess pressure/volume escaping through the building fabric or relief valves. Some examples are clean rooms, Pharmacy prep rooms and offices where the return air is drawn from the corridors.
A competant designer will consider all these points and more before advising the customer.
Also, some cooking areas do have a positive pressure air supply so that the cooking odours or smells are meant to leak out - a good example is the bakery section of the local supermarket. The smell of bread baking drifting across the shop floor makes the customers head a bee line straight to the bread counter for a fresh baked loaf!
The answer to your question is not quite so straight forward.
Frank
Thanks Frank!! Excellent response,I am in Canada with similar gas codes,the space has a direct fired make up air ( no heat exchanger)The customer complained of a negative air pressure in the hotel lobby, drawing in cold air from outside. I suspect this is due to the kitchen being beside the lobby and running a negative air pressure,I just wanted some response before I stick my neck out.
I agree with everything that you said, Frank. I've seen both. One kitchen that comes to mind is in a local fraternal club. It get's used quite heavily, and has almost no makeup air for it's exhaust.Quote:
Originally posted by frank
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Also, some cooking areas do have a positive pressure air supply so that the cooking odours or smells are meant to leak out - a good example is the bakery section of the local supermarket. The smell of bread baking drifting across the shop floor makes the customers head a bee line straight to the bread counter for a fresh baked loaf!
The answer to your question is not quite so straight forward.
Frank
When the chef lights up the hood, the swinging doors open about 60% inward, bringing air in from the bar area. It's particularly neat to see the effect that this little design "issue" has ontheir prehistoric 15 ton Trane heatpump! (The return on that thing is grossly undersized, has been for years, so somebody cut a hole in the side of the unit at the return!
It gets very cold in that building in the winter...
Now, about that quote up there, I have a supermarket customer that went so far as to install a bathroom exhaust fan right over their bread oven, and duct the baking odor to the entry foyer of the store!
The owner claims that he's experienced a thirty percent increase in sales since doing this. :rolleyes: Subliminal advertising at it's sneakiest!:D
Hey Guy's,
Surely in kitchen type environments you would have proper extract(fan assist) via hoods etc and appropiate(slight positive pressure) makeup air. Kitchens couldn't afford to have dust, grime etc from the outside spicing up the food!!
Mind you I don't like to look into many kitchens where I am cause I'd stop eating in them.
The key to this scenario is DIRECT-FIRED make up air ( no heat exchanger )... therefore you have to exhaust all of the products of combustion coming in with the supply air.And then some = negative pressure
Originally, you said:Quote:
Originally posted by acman
The key to this scenario is DIRECT-FIRED make up air ( no heat exchanger )... therefore you have to exhaust all of the products of combustion coming in with the supply air.And then some = negative pressure
Quote:
Positive or negative?
Should a kitchen using gas fired appliances have a negative or positive air pressure?
This change makes a blatant, obvious self answering statement.
The answer now, of course, is, of course.
:D
Most kitchens around here are designed to be negative with relation to the seating areas but equal to or positive with relation to atmosphere.
Many of the newer restaurants here are designed so all of the air exhausted through the kitchen exhaust systems is replaced through the dining/seating area's rooftop HVAC units. The HVAC units are sized for the additional heating and cooling loads imposed by the ventilation requirements. Generally the rooftop heating section is indirect fired with stainless steel heat exchangers.