AC in a Kitchen and Exhaust Fan

[hvacsteve82]

I have this ice cream stand...very small but they have a 5' grill with a 6' hood. They have exhaust air with makeup air, but the makeup air blows out the front. The customer just cannot understand that they installed the wrong hood in their kitchen. Does anyone have any info they can e-mail me about hoods, air conditioing, and makeup air?

All ref equip is water cooled. Problem is when it gets 95 out and they have the exhaust going alone or if they have the exhaust hood going with the makup air blowing out the front. I told them they should have it blowing inside.

Any help explaining this to a thick customer is appreciated.

[Dad]

Although I don't understand your problem you describe I do know that it makes no difference if the makeup blows out the front or back.

What's going on? Is it blowing out the grill burners or pilot?

[Carnak]

Sounds like the OP is talking about wanting a short circuit hood, POS in my opinion

I like the ones that blow down the back Lusk

[Mstrav]

the air out side the hood is not a problem, you could have a compensating hood or standard hanging plenums or even registers in the ceiling outside the hood and they all work some slightly better.

your problem is the supply air is hot, which is the same as the outside temperature. sounds like you have a supply fan with no cooling in it. In many climates instead of a supply fan, we use a evap (swamp) cooler to temper the air to make it more barable for the kitchen staff.

is the water off to it by chance?

matt

[Dad]

I've read this over and over.... Steve doesn't say there is a problem just that the hood blows out the front which is no big deal.

What is the actual problem?

The customer doesn't have to worry about the hood construction.

[Mstrav]

All ref equip is water cooled. Problem is when it gets 95 out and they have the exhaust going alone or if they have the exhaust hood going with the makup air blowing out the front. I told them they should have it blowing inside.

Any help explaining this to a thick customer is appreciated.




1) the make-up on the outside of the hood is fine, otherwise i have a lot of hoods to tear out.

2) whenever the hood is on they must run the make-up air otherwise they will suck out the a/c air / and or create a negative which will cause other problems since that hood is moving around 2000 cfm.

3) the all the hoods I do have a control panel to turn make-up on with the exhaust. only thing that is seperate is the pumps if there is an evap. customers in restaurants are dumb and will leave the hood off and just start cooking, next thing you know, via the chimney effect the fussible link melts, fire supresion tanks dump and the health department has you shut down.

again, focus on the ice cream problem, they even have 6" inches of hood overhang, sound good to me.

matt

[hvaccolo]

I think the problem may be that they have 5' grill in the first place. If it's an ice cream stand, what is a 5' grill doing there?:D

[Mstrav]

5' grill 6' hood, thats perfect, I see lots of people that think 6' means 6' of equipment.


remember, if you are on a call to fix the tayler frozen bev dispensor, you shouldnt be worried about the new hood unless you know what you are looking at. could backfire on you, your company or the other company could get a call about something you dont know anything about.

matt

[hvacsteve82]

I realized my post was vague. These long days are catching up with me.

The customer I have has air conditioning in the kitchen. On the 95+ days the place will not stay cool. Last time I was here 100 degree air was blowing INTO the place from the frontal discharge make up air from the hood. I told the customer it should discharge the makeup air into the hood, not outside the hood. I got some information from greenheck and some other sites showing how those hoods are not designed for our climate.

When they use the system on 80 degree or less days the place is fine. The makeup air blows right at a return in the kitchen. The return is 9 feet away from the hood.

The customer is starting to get very annoyed at me and they do not understand they have an incorrectly designed hood for this application when they want a conditioned kitchen.

[Dad]

My next question would be this and I believe it was brought up above too.

Air balance and heat load.

I understand small kitchen, that's OK

I understand grill heat and outside ambient air @ 95* +

Is there enough b-t-u to cool their b-u-t-t?

You may have already worked with this but did you or can you slow down the exhaust and the make up air speed? Is there an OAD on the AC unit or can you install one.

Reason... exhaust system running too fast pulls out a lot of AC air. You compensate with make up... 95* make up.... that seems to be your real problem, right?

Suggest, if you haven't already, turn off the make up air. Slow down the exhaust. Open up the OAD if you have one. Start the make up air and adjust it's speed to give the building a slightly positive air balance.

Not being there makes it tough so all I can suggest is a WAG (wild ass guess)

The front blast from the make up can be diverted up or redirected. Matters not where the air blows as long as it "makes up" the exhausted air.

You probably have already worked on all of this and I know I am not answering your real question. "Where can you find literature showing you are correct in what you are telling your customer". Unfortunately I, like some others here, don't think you are correct by telling them the hood is wrong and are steering you to balance the building pressure by reducing exhaust and make up speed and give your ac a chance to catch up.

[Carnak]

steve, are you talking about prefering a hood where the make up air is supplied inside of the hood?

or one where the air blows down from the make up plenum on the front of the hood as opposed to out the face of the plenum into the kitchen?

[Carnak]

swamp cooler on the make up as already suggested could make them happy

[Carnak]

you mentioned Greenheck steve, I think they are a good resource

http://www.greenheck.com/products/kitchen/DemoKitchen.php

http://www.greenheck.com/pdf/kitchen/KVSAppl&DesignSeptember2005.pdf

http://www.greenheck.com/products/kitchen/

[Mstrav]

re-read my posts above, you need an evap cooler instead of supply fan, we can talk circles all day, bottom line is if its on an evap cooler,on the hot days it will not be a problem. an air balance or "hood cert" will adjust supply vs exhaust.

As far as a return being to close to the hot air, we never put returns in a kitchen, and if we do it goes towards the perimeter or away from the equipment as much as possible, even by the managers office if possible, not sure if this is a walk up stand or restaurant.

there is nothing wrong with tha hanging plenums outside the hood or air curtain or whatever they have. you could put a scoop on it but if balanced right wont matter. the kitchen needs to have a switch that can turn the pump on and off in the cooler, when its cool outside, fan only works fine

matt

[Carnak]

I would have a commercial kitchen on its own system. You therefore draw return from it.

No returns from a kitchen is a residential strategy

If the hot air goes towards the return of a system serving a commercial kitchen then I say good, it is giving the AC a chance to deal with some of make up air heat before it all mixes into the kitchen

A swamp cooler will make a big difference on the make up air of a new york kitchen

[Mstrav]

No returns from a kitchen is a residential strategy



sorry but not sure where you heard this, in some places it is in fact code for no returns in kitchens from outside zones (such as dinning areas), you could spread smoke! my background is 95% commercial and very large custom homes. I have several hundred restaurants and prob 150 hoods that I have personally installed.

matt

[Carnak]

matt, don't put the kitchen on the same system as the dining room. Keep the kitchen negative with respect to the dining room.

No returns from a kitchen is a residential strategy as you have it on the same system as the rest of the house.

[hvacsteve82]

The whole place is open except for the bathroom.

There is the Kitchen, Area where the windows are to serve the people ordering ice cream (2 windows), and then that area is open to the dining area.

Everything is pretty much wide open except for a knee wall and a bathroom.

Commercial heat load was calculated and thats where I suggested water cooled equipment and exhaust hood. Unfortunately we didn't do the hood or ref. equipment, just the H & AC. Now in the winter time this make up air is going to blow in 20 degree air from outside.

I didn't calculate cfm for hood or makeup air or any of that because it should be the responsibility of the guy that designed the kitchen equipement.

[Mstrav]

evap for pre-cooling make -up air

rezner or equal for the peheating the air in the winter, the cooler is the fan for both modes

bottom line is they should have had it engineered or speced so this could have been addresed

yes dedicated system for kitchen, which is standard practice where I come from, but since this is an open floor with no kitchen or pass through window with a wall, the returns should not have been by the heat source cook area, piss poor design on a/c end as well, you could spread smoke!!! return away from kitchen supplys dont matter, and make-up is only in volume to the e.fan for the hood, not to temper the kitchen to keep from pulling a negative. you could have added extra tonnage to the a/c and use a/c as make-up, but that is expensive and the volume needed could possibly not fit in this small restaurant

so add a evap and reznor and move the returns you will be fine,

matt

[hvacsteve82]

There are 4 returns throught the area. 9 feet away from the hood is such a big deal on that? Even if I moved it to the other room, the whole area will still heat up due to the amount of air being pushed into the building. Smoke will spread no matter what with this floor plan being open throughout. This is an 825 sq ft area as well. Not big rooms or area.

[Mstrav]

if designed correct there is no smoke, slight neg on hood exhaust!!!

poor design

matt

[markwolf]

You may not have put the hood in but if you don't balance it you are going to be the bad guy.
You will never convince the owner that you didn't undersize the equipment until it works on a hot day.
You are coming into this as the bad guy.Stop pointing the finger,air balance the hood & make the customer happyIMO.
That is unless of course you really did undersize the equipment.
It is new you could address the issue with the hood contractor & get them to come out to readjust the hood if you are not comfortable doing so.

[core]

Steve, sounds like your talking about a combo make-up air and exhaust hood where the make-up air blows out from the front of the exhaust hood.

That’s the cheapest one you can get and not very good , there is a lot of spillage with those hoods.

Bottom line in our area you need to condition/ temper the make-up air.

[maninblack]

I work for a company that does cooking equipment and HVAC service for many restaurants. Recently I went to a one day seminar put on by Captive Aire, and it really opened my eyes to the problems encountered in commercial kitchens. I would recommend calling Captive Aire to get some expert advise. In the seminar they illustrated the problems with most types of makeup air delivery. The best type is the perforated kind that blows down in front of hood. Velocities are very critical and as someone mentioned slowing down exhaust and MAU will lower the heat load for the HVAC units in the kitchen. You do not want the untempered air entering the space that you are trying to cool. Most of the makeup air in a properly designed and set up system will be exhausted through the hood. The "short circuit" style hood that you referred to is also an obsolete design.http://www.captiveaire.com/engineering.asp

[Mstrav]

you are just suporting our info here!

Captive air is the brand I install the most of, good lead time and good prices, their web site is great for putting specs together for control panels and getting cut sheets

matt

[superfittertech]

a swamp cooler in new york will not work, just as it won't work in minnesota. there is too much humidity in the air. the issue is correct balancing & making sure the building a/c is large enough to handle the load. as far as winter time goes, yeah, you can add a duct heater with a stainless steel heat exchanger or you can remove the supply fan & install a direct fired make up air unit. you can add a/c to the make up air if needed. here in mn. a non tempered make up air system is illegal. was any permits pulled when they put this system in? if it was all of this should have been caught & corrected by the original installer.

[stoutner]

Just as ManinBlack said...Short Circuit hoods do not work. Thet are a poor design and you don't see them installed very often anymore. Is the hood that you are talking about a "face discharge" hood? In otherwords, is it blowing the make up ait out away from the hood? If it is, you can change it to a down discharge by buying a new make up air plenum and installing the duct to the new plenum. About 80-90% of the down discharge make up air is captured by the exhaust canopy if it is installed and working properly.

Make up air is not air conditioning....unless it is conditioned. Also, that grill is radiating heat. Radiant heat will not be captured by any hood. Captive Air make air-conditioned make up air units.

go to www.captiveair.com

[maddfridge]

My next question would be this and I believe it was brought up above too.

Air balance and heat load.

I understand small kitchen, that's OK

I understand grill heat and outside ambient air @ 95* +

Is there enough b-t-u to cool their b-u-t-t?

You may have already worked with this but did you or can you slow down the exhaust and the make up air speed? Is there an OAD on the AC unit or can you install one.

Reason... exhaust system running too fast pulls out a lot of AC air. You compensate with make up... 95* make up.... that seems to be your real problem, right?

Suggest, if you haven't already, turn off the make up air. Slow down the exhaust. Open up the OAD if you have one. Start the make up air and adjust it's speed to give the building a slightly positive air balance.

Not being there makes it tough so all I can suggest is a WAG (wild ass guess)

The front blast from the make up can be diverted up or redirected. Matters not where the air blows as long as it "makes up" the exhausted air.

You probably have already worked on all of this and I know I am not answering your real question. "Where can you find literature showing you are correct in what you are telling your customer". Unfortunately I, like some others here, don't think you are correct by telling them the hood is wrong and are steering you to balance the building pressure by reducing exhaust and make up speed and give your ac a chance to catch up.



be carefull reducing the make up air could cause the combustion air if this is not just an ice cream stall any other kit in there

just a thought

[Dad]

Good point... yellow/floating flames are only trouble due to lack of secondary air.

Keeping a slightly positive air balance should elevate any combustion air issue.

[johnnyb]

common problem. yse you have to condition make up air most of the time unless you can control the path of the make up air and get all of it to go out the exhaust without crossing the conditioned space. the path of the air flow is as important as the air balance.

[andrewd33]

try reznor make up air unit with a dx cooling coil in it and condition the make up air. but make sure your air is in balance.

[fxb80]

A gas-fired make up air unit with DX, plus an air balance, sounds like the 100% sure way to fix this problem. But, if the customer resists, or can't afford that option:
Don't condition the kitchen directly with the new HVAC system. To do this, disable the kitchen return or relocate it to the dining area if necessary to maintain total HVAC system airflow. Disable HVAC supply grills in the kitchen. This might require adding more outlets in the dining area, or increasing sizes of existing outlets. Configure the HVAC unit to run the blower continuously whenever the cooking hood is running. Set the outside air hood to 20% open or the economizer to a 20% minimum position. This will be a source of conditioned make up air and will produce a positive pressure in the dining room. The MUA should be adjusted to introduce less air than the exhaust is removing. The resulting negative pressure will pull conditioned air from the dining area into the kitchen. I understand that this might create some negative pressure in the kitchen, relative to outside, but it might be unavoidable if this "quick fix" is to have an effect on the dining area. Next, would it be possible to cover the make up grills with a fabricated plenum that would redirect the air down? The plenum would need to be full length (6') and have perforated metal for the outlet. Velocity is critical, downward flow can tend to induce smoke out of the hood. Or, it might be possible to just cover the grills with a perforated box, perhaps with splash plates directly in front of the grills, that would reduce velocity to a point that the supply air doesn't mix with room air.
Please smile when you call me Shadetree.