AC in a Kitchen and Exhaust Fan

[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.