I had a situation crop up last week. A resturant opened and closed the day it opened . It took a few days to unwrap the problem. The gas company hooked up service and inspected it. They recomended venting fresh air to furnace. No notice to me , but I would have required it . The heat and air guy installed new forced fans to the commercial vent hood . [two 1500 cfm] The fresh air fans were not touched or inspected until the problem was called to my attention and the state inspector last Tuesday. The kitchen got over 100 degrees and the store front reached 85 degrees. The customers left unhappy over the heat and the assistent manager quit and walked out. The owner at that time shut it down. He called the health department and they were not interrested. hmmm. They then called the state board of health and here came the State inspector. He called me and we met at the store site. I backed his lead mostly at that meeting. He wasnt interrested either as it was all prexisting. hmm . The next morning he called me mad. I met him once again by my self. My findings as to date ;
I found that the fresh air was nearly non existent . How ? I turned the switch on the the vent hood fans and went to the floor drains to be knocked over by sewer gas after holding my hand over the fresh air vents to the hoods.
I plan on requiring venting fresh air but the no one knows exactly how to do it yet . I will also require venting on the furnace for fresh air.
Any thoughts ?
Tim Mooney
Replies
Do the FD fans have inlet-side duct to the outside, or do they intend to draw air from the room? If you feel (and smell) air coming out of the floor drains, sounds like they are the path of least resistnce for make-up air...and there should be some resistance there!
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
Ed, the hood is made with an exaust and an inlet . Both are powered . The exaust fans were replaced with out knowing what size was ran before for some reason. They were replaced with two 1500 cfms. The inside fresh air comes in just out side the unit on the front. One switch powers four fans at once . The fresh air comming in the old fans representing fresh air are nearly "dead" in my opinion. Thus the root of the problem ;
Sewer gas is being brought from the floor drains. Thus also every where else the exaust air can find . The air conditioning is being robbed of its cold air in the same process.
Tim Mooney
Tim, I posted at the same time as your post. I see you already understand how they operate. But there should be a data plate with the design info on the hood to show the perameters and everything should have been replaced same/same. Should I say. Also both inlet and outlets have filters. They need to be checked to be sure there are no blockages. DanT
Thanks Dan .
Im going to also have a working meeting with the tradesman already mentioned. I have concerns about the size of the fans he has installed. Im thinking maybe he went much bigger ????????????????????????????? We will see Tuesday according to his shedule. He admits the incomming air may be blocked in some way , but a service company did maintenence on it, for what thats worth. I may be missing some of the story because I havent heard from them ? How would the system be checked for negative pressure as was suggested in another post without engineering???????????
Thanks,
Tim Mooney
Non- scientific and accuracy depends on your eyes. . . water level, one end outside and one end inside, note the inside elevation of the water and then turn on the fans. The water WILL rise because you won't get absolutely zero -pressure. The amount of rise is the level of -pressure. I don't know what should be specced. I imagine it is a few milimeters.
A barometer should also work as they are designed to register a slight change in absolute pressure and all that matters is the difference with the fans off and on.
You will want a slight differential from dining room to kitchen to keep odors in the kitchen.
SamT
Tim,
Slight negative is not bad, even considered advantagous by some. If you are pulling sewer gas past the traps it is a serious amount. As said earlier the make up air and exhaust air must match or be engineered to allow for any other exhaust fans in the space. Also if the HVAC system is designed with a certain amount of make up air this needs to be factored in too.
If the intent was to increase the exhaust air the question in my mind first is why? If it was because too much heat was building up in the space (normally this is the reason) then your owner probably took the cheap way out and had the fans replaced assuming that it would help. In reality the need was increased A/C due to increased heat loads from more/larger cooking requirements or equipment.
All that being said a kitchen space is an engineered area. Exhaust and intake must be balanced, or at least close or this is what happens. Usually the original system is engineered and then when suttle changes screw up the balance someone starts making changes without realizing what can come next. And this is a text book case of just that.
Anyway I would first find out why anyone changed anything. Next check what changes have been made. Then you can determine how to get back to a balanced system. In a negative pressure building the doors that normally swing to the outside will pull themselves shut, sometimes rapidly. You will also find the A/C system has a hard time getting rid of the condensation from the coil pans as air will be pulled in through those traps two. Great location an situation for legionaires disease. Also any gas appliance vents such as water heaters etc will have air being pulled in those vents and the carbon monoxide too.
Easy to check though. Lit cigarette or cigar is one of my favorites or a smoke tester for fire alarms. Fire up the systems and see if smoke is sucked in or out of these areas. If it is coming in start shutting off items to find whats causing it. Its not hard. If the exhaust is pulling it out then you simply have to have air coming in to feed the exhaust to balance the building. And with a hood system out going and incoming should be about the same. I would look at make up air first. A lot of times the make up air hasn't worked in awhile, which may have caused the issues in the first place. So the answer is to increas out go not realizing that they simply lacked make up air so the system would work in the first place. Probabley a bad make up air motor or the filters have never been checked. DanT
Write it up so that the fresh air to the shall be X square inches no further than X feet from the furnace intake. And the fresh air to the kitchen shall be such that the negative pressure shall be no more that Xmm of water or whatever.
The negative pressure must be less than the 'vacuum' generated by the rising flue gasses. Better if the furnace room is sealed from the kitchen.
Let the engineer spec the dims for the ducts/openings.
SamT
I hadnt thought of reccomending an engineer.
H&A guy says its not in his books for the hood , so whose department is it to tell him ?
I plan on calling the state inspector Monday morning for his imput.
I like the engineer idea though because it just leaves me to inspecting and not designing which is not my job, nor the installers. Great point. Thanks.
Tim Mooney
Tim - in addition to calling for an engineered solution, you should require actual performance testing and verification of the system.
44110.6 in reply to 44110.4
Tim - in addition to calling for an engineered solution, you should require actual performance testing and verification of the system.
Would you care to go into detail?
Thanks for responding .
Tim Mooney
I plan on shutting the store officially down until work is done so it will not reopen , but I dont really think thats a concern. On an off note I dont understand why the health department wasnt interrested in it. This seems to me Im doing their job on this one and the gas company.
In other words , I have the authority to act but I think the utility comany should have required a vent before energizing gas service, and the health inspector should have shut it down before I got there .
Tim Mooney
Edited 6/6/2004 2:26 pm ET by Tim Mooney
I 'm amazed by the scenario you are describing. I've started specializing in resturaunts over the last year & can not for the life of me imagine this happening in my area (Columbus Ohio & area). Was there not an architect, or plan review? What about inspections during the process? Inquiring minds want to know. Definitely an engineer is the way to go on this one.
Thanks for the back up on the engineer.
Nope , this store is over 30 years old and had the exaust fans replaced.
Tim Mooney
rob,
I worked in the hotel industry for 7 years in Columbus and I can tell you without a doubt this happens in Columbus too. It is not a matter of poor initial design but poor practices during maintenance, repair and replacement. I found a hotel in Columbus that had all of the make up air dampers in the P-tac units screwed shut so it would heat better in the winter. As soon as summer came with the A/C on and the bathroom exhaust all running it had negative pressure so bad it was pulling the water off the A/C coils into the duct work and dripping on the floor. They never knew they had a problem they just wanted me to figure out why the HVAC system leaked out of the ductwork. When I walked in the door and it slammed behind me I knew almost immediately what the basic problem was. Simple fix, figured it out in an hour. DanT
Dan , a nice peice of writing you did on this one .
As I read your posts , something came to my mind ;
The store has been vaccant for a long time and even then Im wondering about the use of the floor drains.
I now suspect the water in the traps of the floor drains has dried up! The path of least resistence rules with filtered and non filtered air. I will fill the drains with water to eliminate the thought. You made me think it when you said , "pulling air past water in the traps. LOL, who said there was water in them????????
Ive noted every ones comments but there is a list from you.
This problem is not my strong point that is certain. I belong in new construction , but my job requires a lot wider range .
Thanks ,
Tim Mooney
Tim,
I am glad it is of some value. I take so much information from this site and its participants and rarely get to offer much. Nice to be able to.
We used to put a little vegtable oil in little used traps so the water would not evaporate. The oil sat on the top of the water and sealed of the evaporation process. DanT
Dan there is no dobt it still goes on. For some reason I missed the fact this was only new moteors. For some reason I thought it was a build out. If you haven't been working with the building department here for a while you are in for a suprise. they have really tightened up & I have to say even a proffesional bunch. They may be tough but they are also fair. I don't have them enforcing their own codes (ie: it dosen't exist on paper any where but I want you to do this) like in some of the other municipalities around here.
rob,
I also worked for an engineering firm there. It is no M Engineering, used to be M-E. I was a field rep, the guy that was in the middle between design and contractors. I never had problems or concerns with Columbus' building department. Their plan approval got behind sometimes but code enforcement was fair. Hated Hilliard, Dublin and Whitehall though. Like their own country. DanT
Dan I know the firm. I am currently building a pizza shop in one of the 2 you mentioned. I prefer dictatorship over country but that's just me.
rob,
In 92 or so I was we were doing community library renovations on some of the Columbus City Library satelite locations. Limited budget but meant to improve or ad libraries to the smaller border communities. As you know it used to be, I suppose still is, that if the cost of a renovation exceeded 50% of value you must bring the building to current code. So in some cases it was important to stay below this threshold as the Library board was simply trying to reach as many readers as possible.
In one of the communities we named earlier the inspector, after plan review, during construction phase well after demo deems it is now necessary to either spray all the roof trusses with fire proofing, or replace them with steel. Long story short we explained that this would drive the cost over the limit and cost the library board more than the building would be worth, plus a severe time over run in which his own neighbor hoods would be without library services. Don't care. Look, here are some solutions such as ducted returns etc that would be far less expensive and still within NFPA guidlines. Don't care. How about a little gift for you and the missus. Don't care. Want it the way I want it. I left the company and that job still hadn't resumed. Sad and stupid. DanT
This seems to me Im doing their job on this one Seems to me you're doing a lot of people's jobs. I'm a little surprised that you don't just red tag the kitchen and tell the owner to call you for a final when he solves the problem. That's what archys and engineers and mfgr reps and qualified subs are for. Then on the other hand it's nice to see a building official who tries to help rather than just get in the way.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
"This seems to me Im doing their job on this one Seems to me you're doing a lot of people's jobs. I'm a little surprised that you don't just red tag the kitchen and tell the owner to call you for a final when he solves the problem. That's what archys and engineers and mfgr reps and qualified subs are for. Then on the other hand it's nice to see a building official who tries to help rather than just get in the way."
Well thanks , but I guess I better respond to it ;
The Mayor is my boss with influence from 6 city council members. All those positions are elected positions by the "people". Im there to serve the public as a code inforcement officer. If I red tag it or close it with out the owner having knowledge of recourse then that said owner will probably be unhappy. If that same person feels that Im in their court trying my best to help then we will get past it hopefully with good feelings. Im there to help and try to establish a good repore while doing what I need to do as far as enforcing the codes. How that is done reflects on how valuable I am to the city. Its the same as running a business with happy customers. A good rep still will not sacrifice doing it up to snuff . Im still going to get what I want in the end .
Tim Mooney
Tim,
Commercial building maintenance is my one of my previous proffessions. Probably my most knowledgable area. Most true kitchen hoods are designed with an outer sleeve and an inner sleeve. Return air is brought in in between the two layers and the air is pulled around the edge of the inner layer and up into the hood and out through the exaust fans. They are supposed to be engineered so the rates are the same thus there is no negative building pressure.
If this is a true store bought hood system then it is probably a matter of no one hooking up the return air system side. If it is a home built deal simply adding supply air from say outdoors will only force the kitchen to have an HVAC system large enough to make up all the too hot, or too cold air being pulled in from the outside. Some can be made up through the HVAC system but almost never enough to supply the amount of air it takes to truly exhaust a kitchen so the tempatures stay habitable and the restraunt area can't smell the food being cooked. Both are issues in the food service business. An engineering firm is a good place for info but these hood systems come as a package an also there should be some requirement for fire suppression as well as protected lighting. Hope this helps. DanT