Illini, sorry I can't help on your conversion question, but we really like the Zephyr we have, we use it over a 36" BS with 6 burners on it. We normally use it on the 2-3 settings and we can still have a conversation then, unless my head is right under the hood, then it can make it hard for me to hear, but I think that is also due to age!! We kick it up to 5 or 6 on occasion, but not to often, it has done a great job, only one time has the max (6) setting not been enough and that was when I did a steak in a cast iron pan but I had put in to much butter and oil and the smoke just came off of that pan/steak like mad. It is the only time in a just over a year that I have set off the smoke alarm in the new kitchen. But all that smoke cleared out in about 10 minutes after I kept it cranked on 6. It was more my fault for using to much oil. Would I like more CFMs, yea, but for how we cook 95% of the time the 715 is more than enough for us. Heck like I said we mostly use it on 2-3 for normal everyday cooking and it is just fine. Hitting up the wine trail a lot Illini? :) lol Phil

I have a 42" Zephyr Napoli island hood over a 36" BlueStar rangetop, both of which were installed in our newly remodeled kitchen about 2 months ago. The Zephyr hood arrived with one of the lights out. The dealer we purchased it from called Zephyr, who called the local warranty repair service and sent a new light harness from the West Coast to the repair service here on the East Coast. The repair service made an appointment and came out and repaired the light issue. The whole process took a week or so. Fast forward to this July 13th. When I turned on the hood that morning, it came on in "burst" mode, which I nearly never use. It should've come on in the lowest speed, which is the speed I had last used. I turned it down a couple of notches and suddenly the motor started making noises as if it had a length of coat hanger wire wrapped around it. So I repeated the process for getting service. I called the dealer, who called Zephyr in California, who created a work order with Hadco locally for the repair. Zephyr couldn't be reached on the weekend so the service request went in on Monday. After more than a week of radio silence from Zephyr and Hadco, I got a contact number from the dealer and called Zephyr myself only to learn they had shipped parts and that Hadco would call me when the parts arrived. Remember, nobody had contacted me yet or checked the product to know what the problem actually is. I got the UPS tracking # from Zephyr and saw that the parts were delivered to Hadco today. I called them to set up an appointment and it will be another week before they can come out. By then, 2-1/2 weeks will have gone by. I'm sure they will fix it and it will be fine until the next time something happens. Zephyr products get great reviews so maybe I just got a lemon, but is this a portent of things to come? A brand new vent hood (especially one that cost well over $2000), shouldn't be having these issues. BTW, the installation was done professionally by an installer recommended by the dealer. The other thing is the lack of communication from Zephyr and when I called them, they were very unconcerned that I was having this problem with my NEW hood. I can't recommend Zephyr to anyone, and especially not anyone east of the Mississippi. It takes too long to get anything done and they don't have a customer service mindset. This post was edited by vlunceford on Tue, Jul 23, 13 at 19:32

There are a few sources of noise in a hood ventilation system (and potentially also in a powered make-up air system). The dominant noise when a silencer isn't or can't be used is fan blade tip turbulence noise. Second will be either baffle turbulence noise (more like a hiss), or its counterpart if mesh filtering is used, or duct turbulence noise. Baffle noise domination assumes that the duct is damped on the outside and the air velocity in the duct is not too high. Otherwise duct turbulence noise may dominate baffle noise, and the duct may also rattle passing on blower unbalance vibration noises. External blower noise is usually lower with a long duct than with a short duct, but one should not expect a really big reduction in noise just because the blower is outside instead of in the hood (for equal volumetric flow rate). (The exception would be a commercial external blower, configured deliberately so that the fan is oversized and the belt drive sheaf ratio is set for a slower tip speed.) For residential operation, where room for a silencer is available, an external roof blower and inline silencer is the quieter approach, leaving baffle hiss below normal speaking levels at full power. That is my configuration. Part of the duct turbulence noise will also be removed -- that from the duct between the silencer and the external blower. Fantech silencers are larger than the ducts, e.g., 14 inches in diameter for a 10-inch duct. http://www.fantech.net/products/fans--accessories/accessories-ventilation/silencers/ld/ld-10-silencer/ They have the general appearance of a motorcycle muffler scaled to a dragline excavator engine. The silencers are also somewhat longish, so if the duct was going to go up into an attic and straight to the roof at the roof edge, it would be necessary to use an angle duct after entering the attic to extend the duct length in the attic to accommodate the silencer, thence use another angle to bring the duct to the roof. Avoid horizontal ducting if possible. Try to make the ducting accessible if possible.

MUA may be introduced to the kitchen in any way that doesn't cause cross-draft disruption of the rising expanding cooking plume, but not in any way that "short circuits" the ventilation by flowing into the hood in place of the plume. A diffuser in the ceiling next to the hood might violate both aspects unless the diffuser blades were oriented to force the air away from the hood along the ceiling such that the air current would follow the ceiling, wall, and floor, ultimately approaching the hood from below. There is no limit to how far away the MUA is introduced so long as there is a path to the kitchen air volume. Devious paths may require consideration of their pressure losses when analyzing the MUA performance. As for hood overlap, the principle that is being addressed is that the cooking plume (with gas jet plume where applicable) rises and expands from a hot cooking surface (and from around it when gas cooking). The plume velocity profile (and effluent per unit time profile) is mountain shaped, but the larger part is contained roughly within a 20-degree cone. (Plume shapes vary with temperature and cooking surface.) The cone half angle, then, is 10 degrees. So long as the hood collecting aperture is at least 10 degrees outside every effluent emitting point on whatever pans you use, you should obtain decent capture, barring cross drafts. Note that at 36 inches above the pans, 10 degrees is an offset of 6.45 inches. This is as I said from the pan bases (pan edges for gas flames) and not from the edge of the cooking appliance. Where this doesn't apply is at a back wall where present, and at the sides if cabinets or side skirts direct the plume upward. The hood effective aperture also grows slightly with air flow into the hood, but this is likely (at the recommended 90 ft/min) to be only a couple of inches added effective capture area. The exact behavior depends on the velocity profile of the plume vs. the velocity profile of the hood intake at the edge. (Figure 6 page 30.4 of the 2003 ASHRAE HVAC Applications Handbook provides an illustration of how quickly the hood air velocity drops past the edge.) kas