Roof mount exhaust fan vs wall mount on sides of food truck

Lee Weenies


No one who knows anything about exhaust systems would ever recommend the following:

"A while back I saw a suppler for twin electric (12v) auto fans abt $150 (???).   These could work in a wall mount with a transition air box to the hood piping; and a simple external louver.   "your kidding right" ?
 
BROWE...do yourself a favor talk directly with a manufacturer about their product. Have the following on hand: Your sq footage of the unit, fresh air intake sq ft available (windows/doors that will remain screened & open) and total BTU that is present. They do the math and calculate the proper exhaust fan you need it will be right and you will not be sorry.

 
NO I'M NOT!  ... 12 vote auto fans can be sized from abt 700 cfm to over 3000 cfm.  An advantage, is that these can be easily speed controlled from 60% to 100% air flow.   The Fans are low profile (3 to 4 inches) and used with a shutter (2 to 4 inches); and a combined length or thickness 8 to 12 inches from the face of the wall (exterior or interior).  No big long silver exhaust domes sticking out the back of the truck or the roof.   ...  A transition box to connect the piping is still needed.    .... This link can give CFM and size data of auto fans. Some can be bought on ebay and other websites.    http://www.flex-a-lite.com/auto/html/electric-fans.html      ... Note ... fans are available in 120 volt too ... look at WWGrainger website.     Check out Hoodmart, they have or build concession hoods.   Ask about low profile exhaust fans, as upblast fans is shown with the hoods.   8ft hood & fan $1700.   http://www.hoodmart.com/concession-trailer-hoods.aspx
 
Browe   ... as I suggested earlier, you do need to look at other food trucks and trailers.   ... You need to figure out how to build this the way you want & need; or get someone to design the system for you. 
 
So  ... Lee Weenies ... why don't you just stick to following the Plans & Specs given you by Engineers like a good Contractor should, and stop trying to give Engineering advice!

edwmax

Lee Weenies


No one who knows anything about exhaust systems would ever recommend the following:

"A while back I saw a suppler for twin electric (12v) auto fans abt $150 (???).   These could work in a wall mount with a transition air box to the hood piping; and a simple external louver.   "your kidding right" ?
 
BROWE...do yourself a favor talk directly with a manufacturer about their product. Have the following on hand: Your sq footage of the unit, fresh air intake sq ft available (windows/doors that will remain screened & open) and total BTU that is present. They do the math and calculate the proper exhaust fan you need it will be right and you will not be sorry.

NO I'M NOT!  ... 12 vote auto fans can be sized from abt 700 cfm to over 3000 cfm.  An advantage, is that these can be easily speed controlled from 60% to 100% air flow.   The Fans are low profile (3 to 4 inches) and used with a shutter (2 to 4 inches); and a combined length or thickness 8 to 12 inches from the face of the wall (exterior or interior).  No big long silver exhaust domes sticking out the back of the truck or the roof.   ...  A transition box to connect the piping is still needed.    .... This link can give CFM and size data of auto fans. Some can be bought on ebay and other websites.          ... Note ... fans are available in 120 volt too ... look at WWGrainger website.     Check out Hoodmart, they have or build concession hoods.   Ask about low profile exhaust fans, as upblast fans is shown with the hoods.   8ft hood & fan $1700.  

Browe   ... as I suggested earlier, you do need to look at other food trucks and trailers.   ... You need to figure out how to build this the way you want & need; or get someone to design the system for you. 

So  ... Lee Weenies ... why don't you just stick to following the Plans & Specs given you by Engineers like a good Contractor should, and stop trying to give Engineering advice!

edwmax...I've tried to look at other food trucks but we have very few.  The ones we have all have the typical exhaust fan as I'm assuming if no one around here has seen a movie truck or a west-coast built truck, they've never seen what I'm talking about.  I've talked to the health department and they have no requirement for either type.  I already know how I want it but have not been able to find what I need.  I tried contacting some of the west-coast truck makers but was unable to get them last week.  I'll try again on Monday.  I have a quote from Hoodmart but it is for 1700+ CFM.
 
My truck is going to be 20' long by 7'6 with an 8' ceiling.  There is an additional area over the driver's area that is 7'6 wide, 4' deep and probably 4' tall.

Can you describe what you are calling the 'west coast built' truck; or give a link of an example?   ...???....
 
This hood manufacture ( http://www.kitchenstainlesshoods.com/concession-trailer-hoods ) indicates the use of 75 CFM per foot of hood in concession trailer.    That is about 40% of the 200 cfm per ft used for commercial kitchen hoods and confirms my belief the concession trailer or truck is too small to require high volume exhaust hood fans.   ... Again a variable speed motor would be of an advantage.   At 75 cfm a 7 ft hood would have an air flow of 525 to 600 cfm.  
 
The food trucks that you visited, what was the hood air flow like?    ... And, what were the owners' comments.

ED... look back at post #15....this is what he is talking about.
 
These use nothing more than  12v fans.

chef   .... thanks,      I did a search last night while on a dailup connection (Slooow)  and those were the style trucks I found but wasn't sure what made them 'west coast'.  ... Thanks for confirming those are 12 volt fans.   Awhile back somewhere, I saw another Concession manufacture indicate the use of 12 volt hood fans in concession trailers.     ... A very good reason for this is power back up if the supplied AC power goes out while working.  With a 12v hood and a few 12v lights, the vender can keep working as most of the cooking equipment is gas.   Also, another consideration is the anusl system; if the AC Fan stopped working (power outage), a sudden buildup of heat (melted heat link) can set off the fire suppression system making a big mess to be cleaned up and forcing the vender to stop work.
 
So question, the truck in post 15;   are the side wall 12v Fans pulling air through the hood?  Or, just venting the entire truck & the hood is a ventless type?      ... The sidewall vents are close together and look like they maybe connected to the back of the hood.
 
Also, I hope a vendor that uses a variable speed hood fan can tell us the speed setting and approx. cfm he normally uses.   I still think high volume exhaust fans (200 cfm/ft of hood) is to much for small trailers & trucks.

EDWMAX
       We have seen this time and time again...there is always someone out there who "seems" to know what he is talking about.  Giving advise on something you think you are sure about and know specifics are two different things.  I did not give  BROWE instructions  on what he needs for his system because manufacturers will do that and stand behind there product FOR FREE  all engineers know that . So your smart remark about me being a just being a contractor is not so smart. I went to college at Broward for engineering & architecture and soon realized I would have to work for a firm for endless amount of time to open my own company. So since 1984 I have been self employed...I am new to hot dogs however!

I've been an engineer since 1975. One learns to think outside of the box, to use standard equipment in non-standard ways.   .... The pictured 'Movie' truck above has 12 volts Fans in the side wall.   ... Not so 'Ridiculous' as you so indicate with the 'you got to kidding' remark.    ... So your attacking me was uncalled for; I wasn't directing any of my comment to you until then.
 
I didn't give Browe instructions as to what he needs; only suggestion of what could be done.   ... I think Browe is well qualified to determine what he needs.  ... Browe started this thread asking for advice and that was given by several posters.   Your attacks were uncalled for and not relevant to the thread.    ... You stated you were a Contractor   ... then follow the instructions given you by Engineers in plans & specs and don't give engineering advice (or judgement) when you don't understand the system.
 
Sorry for high jacking the thread, but a Mod should have hidden/deleted Lee Weenie's attach to begin with.

edwmax


chef   .... thanks,      I did a search last night while on a dailup connection (Slooow)  and those were the style trucks I found but wasn't sure what made them 'west coast'.  ... Thanks for confirming those are 12 volt fans.   Awhile back somewhere, I saw another Concession manufacture indicate the use of 12 volt hood fans in concession trailers.     ... A very good reason for this is power back up if the supplied AC power goes out while working.  With a 12v hood and a few 12v lights, the vender can keep working as most of the cooking equipment is gas.   Also, another consideration is the anusl system; if the AC Fan stopped working (power outage), a sudden buildup of heat (melted heat link) can set off the fire suppression system making a big mess to be cleaned up and forcing the vender to stop work.

So question, the truck in post 15;   are the side wall 12v Fans pulling air through the hood?  Or, just venting the entire truck & the hood is a ventless type?      ... The sidewall vents are close together and look like they maybe connected to the back of the hood.

Also, I hope a vendor that uses a variable speed hood fan can tell us the speed setting and approx. cfm he normally uses.   I still think high volume exhaust fans (200 cfm/ft of hood) is to much for small trailers & trucks.

Excellent points.  I am going to have a bank of batteries with an inverter and putting the hood and fan(s) on there is a great idea in case shore power fails or even the generator.  I would tend to agree those fans are pulling air through the back of the hood.
 
Are you really up in Cairo?

browe



Are you really up in Cairo?

 
Oh  ... I just noticed your location.   ... Yes ... how's the weather in Tally??  not much different, i suspect.
 
Low profile fans on the side wall would be easy; and through the roof fans too.   ... I'll have to make sketch later for the roof (if interested).   This would keep the side walls clean for graphics.

Sorry for high jacking the thread, but a Mod should have hidden/deleted Lee Weenie's attach to begin with.
      Why because we don't agree?  Thats a reason to have someone else point removed? Primary reason for Forums is DISCUSSIONS. So you & I don't agree lets cry for a moderator
I believe your comment which started the wise cracks on being a contractor... twisted me its like your looking down your nose at others...Lots of people without college education are smarter than some engineers I know. 
Having a degree on the wall doesn't mean jack. I also have engineering background since 73 ...doesn't make me a brain surgeon and I don't go around flaunting it.
This is a hard fact:
              12 volt systems are weak and that was the point.  Electrically you are comparing a 12v drill to a 120v drill... Have you personally owned and experienced the 12volt fan system in a concession trailer?  If so tell us about it...tell us how it has held up over the years. Thats good info
     Great on a harddrive fan but that not what we are talking about. You can regulate 120v in single phase just as well as 12v so thats a wash. 12volts can not take the heat like a 120volt motor thats a fact... You just can not get the guts from a 12v motor consistently without issues. IMHO too many variables in a 12v system just to say "when the power goes out I can still operate" ....can you say generator?
  Sorry we don't agree..the forum is all yours!
       
 

Now you state your points ... That wasn't what you stated to begin with ... "your kidding, right"     ... You could have disagreed without being insulting.    
... So call up the owner of the $250K truck pictured in post #15 and tell him what the problems are using those five 12v fans and they can not stand up to the heat in the ventilation system.
.... ....

a agree.. those side vent fans have been used for years and years now without a problem. so in your ear YO !  ;-)

im going to jump in here and give my two cents......lol, imagine that...
 
12v automotive cooling fans.....draw air through a radiator that is full of 180-220 degree antifreeze, do it all day long 7 days a week
said fans pull anywhere up to around 1850cfm, most are in the 1200-1600cfm range
 
the hot air flow coming off of my griddle will be approx 200-250 degrees after making the 3 foot or so journey up into the hood, this includes being mixed with ambient air on the way..... well within the operating range of a quality fan
 
now im not saying go out and start installing radiator fans in your hoods, but just by simply sitting and thinking about it for a second, i can see that 12v fans are more then capable of doing the job......
 
as the engineers among us should be able to attest to...... if you can do the job with product A.... whats the point in over killing it with product B......
especially when product A gives you so much more freedom when it comes to running off the grid, and doing so quietly ?
 
to answer the question brought up about multiple fans, look at it like this, redundancy is a great thing sometimes :)
 
 

If I go with the roof-mounted exhaust fan, what is the difference between a downblast fan and an upblast fan?  I'm looking at pictures of other trucks and these have smaller fans that appear to be downblast...
 

This is a picture of the side mount fans that I would like:
 

Nice !!! I like the Tank boxes on this truck

BackAlleyBurger


12v automotive cooling fans.....draw air through a radiator that is full of 180-220 degree antifreeze, do it all day long 7 days a week said fans pull anywhere up to around 1850cfm, most are in the 1200-1600cfm range

the hot air flow coming off of my griddle will be approx 200-250 degrees after making the 3 foot or so journey up into the hood, this includes being mixed with ambient air on the way..... well within the operating range of a quality fan

now im not saying go out and start installing radiator fans in your hoods, but just by simply sitting and thinking about it for a second, i can see that 12v fans are more then capable of doing the job......

 

 
Ok I'm not saying your wrong in any way shape or form, but I had some questions that came to mind when I read your post. But first let me say when I built my trailer I used a ton of common sense. And thank god most (90%) worked out to be correct. But on that 10% I had to re do some parts that just didn't work out as expected. Here are my thoughts and questions....
 
You said "drawing air through a radiator that is full of 180-220 degree antifreeze"
I'd have to know does antifreeze, change anything? I don't know if it effects the cooling process or not. And I'm not sure who I'd go ask locally to even find out. Just curious.
 
You also said "hot air flow coming off of my griddle will be approx 200-250 degrees after making the 3 foot or so journey up into the hood".
 
So your only going to use a flat iron griddle  and you don't have any other heat source? They all add up with a cumulative total that brings the interior air temp up dramatically. The entire country has been suffering through an August type heat wave for the last month, and the interior of my trailer has been running around 100 degrees, and some days as high as 115. I have a roof vent exhaust fan the changes the air in the trailer every two minutes. But when your bringing in air that is 95 degrees and mixing it with air coming off my panini grill at 500 degrees, and add on the steam tables (2) and both rib drawers you have increased the total heat a bunch. How much I don't know but even with the high volume turn over in outside air to inside air the interior temp sucks. LOL
 
I really like the side air vents and want to go that direction with my build but that said we need an experts knowledge/advice, and how many fans vs how powerful they need be to really do the job.
 
And to those of you thinking oh heck I'll have air conditioning and stay cool....(lmao)....  forget it. There is no rooftop air unit going to really cool a mobile kitchen in a midwest summer with all the heat sources and the outside air at 90 or higher. Bottom line is drink lots of water and sweat your ass off all day.
 
But back to the side vents and using electric fans as described go for it, as long as you have great filters and keep them very clean so your fan doesn't load up with grease, and start a fire or cause your Ansul System to go off, I'm hoping they work out.
 
Jack
 
 
 
 
 

those louvers are like attic louvers, $15-20 at home depot, one 12" radiator fan, and a marine battery hooked up to a solar trickle charger or battery isolator to keep the charge and you are set.  used hood = $500 installation = $400, exhaust fan with battery and charger = $150  Total $1050  Savings $1500  you can even buy the fans and vent at your local electrical supply house. 

@ DR- well, ya got me on that one, i was guilty of just visioning the griddle centered under the hood, but yes, there will be at least one deep fryer, and probably a charbroiler at some point.... will have to do some more google laps, lol
 
my smoker (HD willing) will be vented separately through a static side vent 
 
i did find small exhaust fans UL rated for 300 degrees intake air in the 10"-12" size range, i forgot to bookmark the page, so im looking for them again, they were not easy to find, they were industrial ventilation fans, and look exactly like what you see the "builders" using....IIRC they were between 600 and 1200 cfm 2 speed fans.....
so that means 2 of these would give you the ability to run at 600/1200/1800/2400 cfm depending on switch settings..... i think given reasonable air restriction levels something along this set up would fit the bill for just about any smaller truck/trailer....
 
whats kicking butt is the radiant heat coming off the equipment.... a different animal then the convection heat that is going up the exhaust vent.....
your right, if you are turning the air over every 30 seconds, or once a minute, you are as cool as your going to be, outside of aiming an ac vent somehow directly at you

Antifreeze or water, it doesn't matter; but just indicates the set operating temperature of the radiator.   But the airflow temp wouldn't be less when at operating temp.    ... The auto radiator fan is built to work in a harsh environment.  The motor is sealed against oil & gasoline contamination & fire danger.   A good question to a manufacture is what the maximum design working temperature of the fan???   I think much higher than the 200 deg operating temp. of most auto radiators.
 
Now the vent hood:   Many years ago while working on a kitchen remodel, it was indicated the hood temperature could be as high as 400 deg.  The discussion at that time was the possibility of installing a heat pump water heater to capture the waste heat (heat -BTUs - bought & paid for) and exhaust cool air at kitchen work locations.     ... You can't cool a kitchen, but can blow (vent) cool air at cook's work station.   ....
 
Question ... Dr BBQ  ... and anyone else  ... Can you put a thermometer in your hood and check the Temp  for a few days?      ... I think with the high volume of air flow used in concession trucks/trailers the exhaust temp would be 200 to 350 range.
 
Idea for those building Concession Trucks or trailers:    The possibility to install copper coils in the hood to heat your hot water.  This would save cost of gas or the high amp draw of the Electric heater and have stored hot water as needed.

browe


If I go with the roof-mounted exhaust fan, what is the difference between a downblast fan and an upblast fan?  I'm looking at pictures of other trucks and these have smaller fans that appear to be downblast...

 
Upblast fans have the outer bowl to make air blow upward.  These are usually stand much higher above the roof.   The bowl helps to catch condensate and drains to a collection system.  ...
 
The downblast fan are the ones with mushroom style caps and shorter.   These blow the air against the roof or wall where condensation could be a problem.   A separate roof pan should be installed to collect condensate and drain off the roof.

edwmax

browe


If I go with the roof-mounted exhaust fan, what is the difference between a downblast fan and an upblast fan?  I'm looking at pictures of other trucks and these have smaller fans that appear to be downblast...

Upblast fans have the outer bowl to make air blow upward.  These are usually stand much higher above the roof.   The bowl helps to catch condensate and drains to a collection system.  ...

The downblast fan are the ones with mushroom style caps and shorter.   These blow the air against the roof or wall where condensation could be a problem.   A separate roof pan should be installed to collect condensate and drain off the roof.

 
With the shorter profile, I'd be more likely to go with this style than the upblast.  Given the short distance between the hood and fan, is there any reason to not go with the downblast?  I found a lot of pictures of trucks that have the downblast. This truck has one...

 
And this is the hood under the fan...

I just heard from Ventilation Direct and they are saying the downblast fans are not rated for kitchen ventilation applications.  I'm a little confused given quotes from some of the fan companies.

edwmax


Question ... Dr BBQ  ... and anyone else  ... Can you put a thermometer in your hood and check the Temp  for a few days?      ... I think with the high volume of air flow used in concession trucks/trailers the exhaust temp would be 200 to 350 range.

Idea for those building Concession Trucks or trailers:    The possibility to install copper coils in the hood to heat your hot water.  This would save cost of gas or the high amp draw of the Electric heater and have stored hot water as needed.

 
I can do that no problem (check temp) but on the heat recovery to heat water.....my local fire department would want proof from 20 experts that it was a safe move and had been done before. And as soon as you offered them proof they would read the reports and do their best to destroy it because they wouldn't understand it. LOL But that said the only problem I could see with it would be cleaning the vent hood. The more you have (pipes electrical etc) in that area the more grease it will collect and less efficient it will become. But it is an interesting idea.
 
Jack

well, i think thats an awesomely crazy idea!
as far as cleaning issues, couldnt you just double wall the hood, with the copper running inside the void, then its just like a regular hood as far as cleaning goes...
 
and yes, i too am interested in a few days worth of temp reading inside the hood, as well as temps of the output air if thats possible

browe

With the shorter profile, I'd be more likely to go with this style than the upblast.  Given the short distance between the hood and fan, is there any reason to not go with the downblast?  I found a lot of pictures of trucks that have the downblast. This truck has one...

As long as the fan will move the rated CFM, it should not make a difference.   I have seen a number of restaurants use these fans.    They are used in many locations where height and visibility is a problem.   
The exhaust air blowing down on the cold roof will cause condensation of water & grease.   You need a collector pan to drain the water & grease off the roof; and the pan will need regular cleaning to insure the drain is open.    ... Many restaurants don't do the cleaning and have a slick mess on the roof and grease running down the building side.
 
I was trying to make a sketch of elbow blowing to the side, but it would still need about 14 to 16 inches of height.    ... I don't much for low height except the pop-open roof rain cover like shown in the first pic and the fan blowing up.   ... So how the cover be opened & closed with out trouble???
 
In the picture above:  ... an exhaust vent from the end of the hood to back wall of the truck (next to the door) would have been a good place and would not add to the width of the truck. Oh, use a elbow to blow the smoke & air up.

Dr of BBQ

edwmax


Question ... Dr BBQ  ... and anyone else  ... Can you put a thermometer in your hood and check the Temp  for a few days?      ... I think with the high volume of air flow used in concession trucks/trailers the exhaust temp would be 200 to 350 range.

Idea for those building Concession Trucks or trailers:    The possibility to install copper coils in the hood to heat your hot water.  This would save cost of gas or the high amp draw of the Electric heater and have stored hot water as needed.

I can do that no problem (check temp) but on the heat recovery to heat water.....my local fire department would want proof from 20 experts that it was a safe move and had been done before. And as soon as you offered them proof they would read the reports and do their best to destroy it because they wouldn't understand it. LOL But that said the only problem I could see with it would be cleaning the vent hood. The more you have (pipes electrical etc) in that area the more grease it will collect and less efficient it will become. But it is an interesting idea.

Jack

 
I don't think it would be hard to find reports on 'heat recovery' equipment used in restaurant hood systems.   This is a modern concept of the 'old' copper pipe warped around the stove pipe of a wood cook stove.     There are radiators (heat exchangers) available for this application, but I was thinking in the DIY mode of a few loops of copper pipe attached to the back wall of the hood in the air plenum above the filters.
 
Cleaning the truck, floor, and hood;   ... I keep picturing washing it out with a power sprayer once a month and let the water run out the door.  

BackAlleyBurger


my smoker (HD willing) will be vented separately through a static side vent 

 
If your going to use an electric smoker inside your truck (cook shack ) or what ever brand you'll NEED a special vent that will evacuate (suck) the smoke out of the smoker before you open the door. They are like a small vacuum cleaner that sucks all the air out and pushes it outside the truck. I was looking at a used cook shack smoker in a building here in Springfield (chain restaurant) and the sales manager for cook shack lives here in town. So I called him about the unit. He told me it was in great working order but the owners had not installed any sort of smoke evacuation system in the building and when they opened the door to pull the meat it left a hell of a mess. So anyway I went to look at it and he was right the walls and ceiling had big grease runs all over the place it was a mess. I can't believe our local HD didn't shut them down before they went bankrupt.
Jack

aahhhh :) 
i love this place, and all its people..... i see exactly what your saying, and no, i dont think i would have thought of that until after the first use, lol good call !