Airflow messing with range flames

[fixbear]

First check the static pressure of the kitchen. It should be near nuetral.  But slightly on the negative side to prevent smells from entering the dining area.  Now check the incoming vent grills. If the fins are angled, try turning the grills around to have the flow on the cook instead of the stove. Your in Florida, so it’s not like they will freeze in the winter.  If the grills are a straight down, you may have to add baffles to redirect the flow forward of the stove. Or replace the grills with ones that have a minor angle. Or shim the grills.  Airflow should never hit the top deck of the range.  Did the line get placed where the designer intended, or somewhat forward for service room?

 

If the static pressure increases when the fans are on, you may have to change the belt pulley ratio on the make up fan only. Or install a vari-drive if your codes allow it.  At commissioning of the hood system, the installer was supposed to balance the system and test for static pressure.  Problem is that a lot of hood installers don’t even know.  And the designer doesn’t always have all the factors of the installation. Like a offset that adds resistance. Or a installers change to make it fit. Or a substitute blower because the spec one is not made or available anymore. 

 

They make battery food smokers today so that you can see the air flow. Over the years I have used cigarette smoke, a piece of crape paper fastened to a stick, and Chinese incense sticks.  But  incense and cig’s both drop ash. Some cooks already have the little portable smokers today.  It’s important to be able to see the air flow to determine what is really happening. You’ll need 2 people. one to watch at the end of the cook line while the other moves the smoke source in and out and down the line. High and low.    It’s really hard to see it if you are in the front.of the line. 

[olivero]

Okay, The building I work in has gone through the whole test and balance drill with various contractors, I’ve also had Captiveaire out here before to check it out and see if everything in regards to the exhaust system was in order, he told me it was.

 

I am curious as to how the positive/negative air flow would affect this, from what I understand, the make up air where it sits on the outside of the hood, right above where the chefs would be, and all of the exhaust pulling directly on the opposite side, the concept I understood is that its supposed to create a “wall” of air or otherwise roll into the hood and block smoke, fumes, smells, etc. from escaping the hood area.

 

The airlflow seems distorted when you look at the flame, its not like its constantly being dragged in one direction but more so kind of beaten around. Right where this unit is, is smack center of the 2 hoods so the partition of the 2 hoods is directly above the unit, so in all reality, the range is half in one hood and half in another. They both exhaust from the same fan on the roof and from what I know, both get the same air from the make up air fans.

 

How is the make up air supposed to do its thing? Be a wall of air or push into the hood or what? Maybe I’ll call Captiveaire back out and see if they have any bright ideas. 

[fixbear]

Are your incoming air vents in the bottom or face of the hood.  I am familiar with Captivair. hoods. They use a double wall front.  There is supposed to be a flow baffle inside the back behind the grease filters when they marry 2 hoods.  I’ve also seen a blank grease filter spacer in the center. to make the flow more toward the ends. If your using a filter cleaning agency that just comes in a swaps out the filters they may have lost it.

[olivero]

CaptiveAire – Supply Plenums 

 

That’s what I got, without the fancy lights and A/C feature, that probably didn’t exist when these were put in.

 

They are on the bottom I guess, I don’t remember seeing one of those spacers and I’ve been servicing this kitchen since it started getting used.

 

The cleaning company we use cleans the filters in the kitchen, they don’t swap them. I also give them a list of where each filter goes and one of our staff supervise them.

[fixbear]

I am curious as to how the positive/negative air flow would affect this, from what I understand, the make up air where it sits on the outside of the hood, right above where the chefs would be, and all of the exhaust pulling directly on the opposite side, the concept I understood is that its supposed to create a “wall” of air or otherwise roll into the hood and block smoke, fumes, smells, etc. from escaping the hood area.

Ok, The range is supposed to have it’s own regulator on the supply pipe. If not, kitchen pressure can vary several inches of water.  The gas main senses outside air for it’s pressure regulation. Most main pressures run about 7 inches WC.The range regulator will probably be set at 5″WC. Now if you raise the kitchen static pressure 4 inches, The range will only see about 3.5 to 4 inches.relative.  Let alone the pressure drop across the regulator.  Which will of course throw’s the burner mix off.  On the low static, it’s not as drastic, but venting and O2 levels are the problem, but more forgiving. Also, barometric pressure effects the outside regulator pressure. Like when a super low comes in at say 930 milli bar.(hurricane) It does effect all combustion. That’s about 2.7 inch WC drop outside.

[fixbear]

Wall line or center line?

 

Do your own static test and smoke will tell you if there is high flow zones.

 

Do you actually see the front of the burner flames start to push to the sides?

[olivero]

The range does have its own supply regulator, I measure at the manifold right before it splits to the burners and the highest I could  get it to was 4.2″ and that regulator was maxed out.

 

Interesting didn’t know storms and barometric pressure had a play in this.

 

I am going to measure the line pressure and then see what it’s at. So many things were done by guesswork in this kitchen it seems, people just assumed things were this way and that way and so did what they thought was right. 3.5″ is the MOST common setting for manifold across my equipment so I am not surprised it was set to that.

 

The regulator just for that range can do 3-6″ W.C so I can only imagine there is not enough pressure going to the regulator making it so it can’t supply the 5″ I need. 

 

Now I am trying to solve a mystery of 2 griddles where one heats much slower than the other one, 5-6 burners and they all heat slower than the other griddle.

 

Gotta love this stuff.

[olivero]

Not sure what you mean by wall line or center line? 

 

They used to be pushed around a bit if you just turned them on without any pots or pans on them, now that it’s at 4.2″ W.C I don’t see much movement anymore until near the top of the flame.

[fixbear]

Hey, some years ago I was brought in to a restaurant that was about to open, but the Town would not approve the Co due to the gas line.  The owner had cobbed together both galvanized and black iron to feed his new line. Had installed a hot top, 8 bay steam table, range with broiler, a 72 inch double range, a 60 inch grill, and 4 fryers. And through the wall a double deck pizza oven. Oh yea, forgot the 120 gallon hot water tank, 165,ooo BTU furnace,  and dishwasher. All on a 1 1/4″ line. Original biz. was a bar/tavern.  First inspection I notice the mixed pipe and added up the BTU load. Needed to have 2 1/2 inch line. Checked the service, Feed from main  3/4″. to small as well as small  meter.. Then after install of all the needed material, CO build-up. He had added a exhaust fan but never provided more incoming. Hot water heater and furnace sucking right back to the kitchen. Making everybody sick. I always tested building static after that one. One day job he told me.  Try a month plus.  Ran for 6 months and went under. Back to a bar. We are just to far from the sea to have a successful fish restaurant.  Let alone in a rural area.

[fixbear]

Some modern kitchens today use a double line. One on each side of the hood with the hood down the center line. A wall line is just that, equipment on a wall and hood over it.

 

Is your hood system still under warranty?