View Full Version : Looking for an experienced hood person that can...
05-31-2012, 11:35 PM
I am a sales and design consultant and my family owns a restaurant. I do most of the hvac maintenance on the a/c and ice machines. We have a refer guy that does refer because I will only clean condensers and do minor repairs on that stuff. However there has been a significant problem with kitchen MUA in the past months that was more recognizable in the winter, but still is an issue. I am at the point where I think it is better to bring someone that specializes in this in to evaluate the system we have and see if it is out of balance and bring system up to par. Where I work we don't service or install this equipment. Currently there is a Captive Aire hood with 2 upblast exhaust fans (3ph) not sure of hp and 2 MUAS (untempered) .50 hp each single phase 240/208. (Short circuit inlet configuration) The supply air volume seems to have diminished, the draft at the door is more pronounced. I had the damper on the RTU (10 tons) set at 25% in the winter and we were still getting a big draft. I have since reduced that since the door in the kithen is open all summer and we were getting to humid with the rain in the past few weeks. The only maintenance I have done on them is change belts, a hood cleaning company has cleaned the hoods per fire code every 6 mos. I am also interested in examining if the VFDs on these units with a modulating control would make a signifcant savings. We burn a lot of electric in the summer. We leave the fans on 24 /7 until october. The control is one line voltage switch that throws 2 separate contactors on to bring on all four machines simultanously. We are located in Northern NJ. If anyone out there that is good and reliable can help, please advise. Thanks
hvac wiz 79
06-01-2012, 12:39 AM
Melink is the only company I know of. I'm uncertain if they work on non national account stuff & don't know pricing but they do a great job. Can't hurt to look into them.
06-01-2012, 01:56 AM
We own a restaurant and on our hood the mua goes through a stainless grate down the front that is full of holes. About every 6-9 months I take it down and spray it off with water as the dust stops it up.
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06-01-2012, 07:49 AM
What door are you leaving open? Door from kitchen to dining room or door to outside.
Is the RTU part of supply air to kitchen?
Is kitchen smoky?
Balancing the exhaust makeup air is done through belt tightness in a small way, or sheave change for larger changes. There shoCould be beltuld also be positive pressure from Dining into kitchen and from dining and kitchen to outside. Leaving an outside door open, from either dining or kitchen defeats design for proper air flow and increases energy useage.
I have found and solved air flow/exhaust issues in many restaurants.
Have there been any repairs to RTU's. New belts? New IDF. If it worked in the past something has changed or has been changed.
06-01-2012, 10:41 PM
I replaced the RTU in December. I don't think the kitchen exhaust / mua was ever set up properly. In the winter with the exhaust and the muas running the building was always in a negative pressure, Open the doors a big cold draft comes in. In the summer with the outside door open with screen the effect on the restaurant bar is not as bad because the pressure is being relieved from the open door. I had the 10 ton RTU set at 25% oa in the winter to try to reduce the draft, still draft but not as bad. We reduced the OA now due to humidity. We are not getting hardly any air to the supply grilles on one of the MUA units. I was always told the kitchen should be in a slight negative pressure to prevent cooking fumes from "spilling" into dining area. The slight negative pressure is made up from the OA damper on the RTU HVAC unit. Now if the doors are closed the buiding is way too negative!
06-03-2012, 10:55 PM
You want positive pressure from Kitchen and dining to outside, and from dining to kitchen. You certainly don't want high humidity/high temp air coming in from outside. I would need much info to further diagnose your problem.
06-04-2012, 12:11 AM
Are the MUA units Captive Aire as well ?
06-04-2012, 02:59 AM
you need to make sure the kitchen is negative pressure and dining is the same amount of positive pressure to have your system balanced (overall a little bit positive pressure is recommended).
You definitely need to check your MUA. Your kitchen is too negative if there is a heavy draft.
Winter is probably worst because you need less cfm to heat than cool, so your dining unit isn't making up the air exhausted in the kitchen.
Is there a fire damper somewhere with a fusible link that may have melted/failed.
06-14-2012, 07:04 PM
Whoever set up your hoods may have made the typical mistake of over sizing the exhausts to cover there ass. You need some one to come in and do the calculations of what you really need and then what you actually have. Then adjustments can be made. 24/7 hoods can benefit from vfd's if they are used to ramp down during off peak usage. I love investigating issues like this.:grin2:
You definitely have a balance problem.........................:gah:
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