Commercial Kitchen Ventilation Inquiry

[DavidDeBord]

I'm gonna guess there is one branch for each 3 panel section. I've seen similar in restaurants but they have all been conditioned. I'm under the impression, the air does NOT require, by local code, conditioning, if it is dumped under the hood. That air is being dumped into the kitchen, and would be conditioned if it were in Chicago.

[VTP99]

I'm gonna guess there is one branch for each 3 panel section. I've seen similar in restaurants but they have all been conditioned. I'm under the impression, the air does NOT require, by local code, conditioning, if it is dumped under the hood. That air is being dumped into the kitchen, and would be conditioned if it were in Chicago.

👍

[SandShark]

I've seen a lot of hoods but I have never seen one that looks like that. How is the air supplied into that ? Multiple ducts from the top ?

By roof mounted, ducted, filtered, belt driven squirrel-cage blowers inside a sheet metal box.

[VTP99]

By roof mounted, ducted, filtered, belt driven squirrel-cage blowers inside a sheet metal box.

I was referring to how's it tied into the top of the hood. Middle, ends, both ?
The best setup I've seen is the make up down the back wall exiting low behind the equipment.

[VTP99]

Picture is sideways but you'll get the idea. The bottom of that duct is open with a screen over it.

[SandShark]

From the MUA unit on the roof, a square sheet metal duct runs down to the hood where it “manifolds”, for lack of a better description, to each section of the hood where you see the perforated panels. For the hoods in question, there are 3 perforated panel sections in each hood.

[VTP99]

Will they approve a DX coil to provide the cooling ?

[SandShark]

Will they approve a DX coil to provide the cooling ?

If the current situation doesn’t get resolved, I’m going to push for those two MUA units to be replaced with MUA units with integrated DX cooling. Of course, I would suggest an outside contractor be brought in first to ensure it’s feasible to do so.

[SandShark]

Here are what the exhaust hoods look like. You can see how the face of the hood is at an angle where the make-up air exhausts. This angle is what causes the air to move away from the hood and blow on the staff when they're prepping and serving food.

[VTP99]

I'm gonna guess there is one branch for each 3 panel section. I've seen similar in restaurants but they have all been conditioned. I'm under the impression, the air does NOT require, by local code, conditioning, if it is dumped under the hood. That air is being dumped into the kitchen, and would be conditioned if it were in Chicago.

This ^^^^
That style hood surely required conditioned make-up.
Is there a manufacturer plate on those hoods ?

[WAYNE3298]

The tables close to the hoods are food prep tables. The entire kitchen needs balanced not just the hoods. Until you know where the air is going and how much is supplied and exhausted you are not likely to solve your problems. With belt driven fans the total airflow is adjustable but it needs measured first. At this point for all you know the airflows could have been adjusted and are all out of whack.
s was stated previously most hood make-up air is not conditioned except in cold climates most is heated.

[shellkamp]

This ^^^^
That style hood surely required conditioned make-up.
Is there a manufacturer plate on those hoods ?

I think that style would be OK (or at least more tolerable) if they don't try to supply all of the makeup air from the hood and used fresh air intakes from the air conditioners to supply as much as possible.

But as you mentioned before - the behind the equipment makeup air design is the best and least costly to operate : you just lose valuable kitchen space by doing that. :Grin:

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[VTP99]

The tables close to the hoods are food prep tables. The entire kitchen needs balanced not just the hoods. Until you know where the air is going and how much is supplied and exhausted you are not likely to solve your problems. With belt driven fans the total airflow is adjustable but it needs measured first. At this point for all you know the airflows could have been adjusted and are all out of whack.
s was stated previously most hood make-up air is not conditioned except in cold climates most is heated.

I agree there should be a air flow check first. Who knows if the make-up is twice that of the exhaust. Also I'm in a lot of commercial kitchens and here in Cleveland I can think of very few that have expensive conditioned. Now the national chain restaurants almost always but not your average owner/operator.
Here's a Red Lobster. Guess how much that cost versus a sheet metal box with a blower wheel and motor.

[VTP99]

I think that style would be OK (or at least more tolerable) if they don't try to supply all of the makeup air from the hood and used fresh air intakes from the air conditioners to supply as much as possible.

But as you mentioned before - the behind the equipment makeup air design is the best and least costly to operate : you just lose valuable kitchen space by doing that. :Grin:

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This may be his only option if the powers that be are tight on budget.

[shellkamp]

This may be his only option if the powers that be are tight on budget.

Feels fine in their office!

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[VTP99]

Feels fine in their office!

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The truth has been told !

[WAYNE3298]

An example of the things that happen iI got a frantic call from an owner whose restaurant was full of smoke and customers were leaving. He said I don't care what you charge as long as you fix it now. When I checked his exhaust fan the belt was so loose it barely turned the fan. I tightened the belt and the fan motor overamped. Turns out a day or two before an electrician replaced the fan motor and not knowing how to adjust the fan sheave he loosened the belt until the belt slipped enough to not overload the motor. The belt wore and as the fan slowed down the entire building filled with smoke. The fix was as simple as adjusting the sheave, turning off the MAU and opening the front doors until the building cleared. Those things happen and don't expect someone to tell you they did anything or what was done. You need the equipment to find those problems.

[VTP99]

I like the ones where the motor was changed but the rotation was not checked.
How about cycling on the overload because it was left on 220 when the supply was 110 ?
Manufacturers wire them this way for the unknowing.

[WAYNE3298]

I got called back to a water plant where an entire 3 phase panel had been changed and a whole series of exhaust fans were running backwards. The design engineer called me and ask if I would meet him at the plant. He knew me and knew I wouldn't have left it like that. When we got there sure enough a lot of fans were running backwards. When I told the operators I didn't leave it that way the response was a likely story. I ask if any electrical work had been done since I did the balance they told me the panel had been changed. I had them switch two of the 3-phase wires on the panel and all was good.
Balancers can tell by the sound when a fan is running backwards and our rotation check is conformation. The fans make too much noise, draw too many amps and deliver around 60% of the design airflow.

[SandShark]

I'm not an air balancer and I don't play one on TV. What I do know is this kitchen and serving line area were built to the designer's specifications and the systems were balanced on start-up in 1999. Since then, who knows who did what to the exhaust fans and MUA units? I got here in 2011. The guy that introduced me to this kitchen and the other kitchens in the school district was the lead HVAC "technician" and jack-of-all-trades for the maintenance department. When he retired a couple years ago, he had 35 years with this school district. I put quotes around technician for a reason. Before me, the Nutrition Department depended on the Maintenance Department and this "technician" to maintain, service and repair the kitchen equipment. The Director of Nutrition Services told me after I got hired that the reason she created the position was because she could never depend on the maintenance department to take care of the kitchens. It didn't take long for me to understand why she needed a permanent technician to attend to the kitchens. The first thing they gave me, besides a work truck, was a stack of about 50 open work orders going back more than a year. I knew I had my hands full!

As I became familiar with the kitchens and the equipment, I realized that many of the "repairs" that were made to the equipment were made by people who...well, let's just say their heart wasn't in it. This ventilation system is something I have been putting off for years because of what I found when I initially evaluated the system. There were motor starters that had been disabled, with some having no overloads installed, worn out belts, burnt up motors, dry bearings, brittle and cracked wiring and many other disasters waiting to happen. Without any help, it became a bit overwhelming when I realized I was over my head with the system. Everything I know about the system is either from hands-on or reading technical publications, and I still feel overwhelmed. Ignorance won't get you very far in this trade, so I knew I needed some guidance. Coming here, I knew I could find the information I needed to head in the proper direction. I appreciate all the positive feedback and knowledge you all have given. I'll keep you posted when or if things get moved along.