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