When I listened to the Zephyr and Vent a Hood in person I found that the Vent a Hood was much quieter (tested a 36" below cabinet range hood with two fans). I chose Vent a Hood because it was quieter to the Zephyr equivalent (not that it or any range hood is 'quiet'). I have problems with my hearing and the Vent a Hood sound frequency was also less annoying. The sales guy said the newer Vent a Hoods are easier to clean. I have no idea if this is true but it's worth comparing the newer ones in terms of how they clean up to what you have. Good luck.

Hi Melanie - Update: I received a push button assembly and a capacitor parts from Zephyr. We consulted our electrician (who happened to be on site doing unrelated work), he told us that our existing push button assembly is working fine so that part was not needed. He did install the new capacitor and said that by the sound the unit was making he could tell that electricity is feeding the unit adequately so that's not the issue either. He carefully lifted one of the two grids on the side of the blower and noticed that the blower wheel (sorry for not knowing the proper technical terms) was stuck in place, kind of gummed up, which is probably due to some grease accumulation over the years. He manually prodded the wheel to make it spin freely. He did this to both sides of the blower and the unit started working again. However, we still have the unpleasant screeching noises but have regained use of the hood. We decided to use it sparingly as long as it extracts odors, steam etc until we can replace it (or find someone who restores these types of motors.....not sure how cost effective that route would be though....). Thank you for your question and I hope you find a satisfactory solution!

@J Y Yes. We installed the two blowers in the Tempest II and have had it for over a year now. It was the best decision ever and the range hood is one of our favorite purchases during the kitchen renovation. It is not loud when you use it on speed 3 which is the speed we use all the time when cooking. We can still have a conversation in the kitchen at that speed without having to yell at each other. It has 6 speed settings and we only have to use speed 4 when we fry steak occasionally. The two blowers make such a huge difference in sucking up all the cooking smell. Can’t smell someone is cooking as normally the smell would travel up to the rooms upstairs. Very happy with Zephyr’s customer service as well as I called in a couple times prior to making my decision on a range hood and they had been very helpful in answering my questions. Let me know in case you have other questions.

A few comments: 1. Pipe diameter can be used to find the VOLUME or CAPACITY of the pipe. Saying a 6" exhaust duct, assuming round here, is half the size of an 8" is not correct. It has half the VOLUME of an 8". Remember grand school geometry pi x r-squared give the area of a circle. So the inference in saying the 6" is half the size really is referring to it's 2d AREA. 6" round exhaust hood has an AREA of 3x3x3.14159 = 28.2743 square inches of area 8" round exhaust hood has an AREA of 4x4x3.14159 = 50.2654 square inches of area. 10" round exhaust hood has an AREA of 5x5x3.14159 = 78.5397 square inches of area. When talking about exhaust venting for a grease carrying duct (which is what kitchen hoods are) ASHRE says a MINIMUM velocity of 500FPM should be used. This is also the most efficient velocity. Faster velocities are less efficient, require larger motors and do not capture grease as well, but are acceptable up to about 2000FPM. Lower velocities allow grease to condense and can cause fires, reduced capture and poor performance. So lets see what the velocities are for the 6" and 8" range hoods (We have to convert the are of the pipe from above from square inches to square ft): 700 CFM 6" - 700 / (28.2643/144) = 3566 FPM 8" - 700 / (50.2654/144) = 2005 FPM 10" - 700 x (78.5397/144) = 1283 FPM 12" - 700 x ( 113.0972/144) = 891 FPM 14" - 700 x (153.9379/144) = 654 FPM 16" - 700 x (201.0617/144) = 501 FPM So as we see above the CORRECT duct size should be 16" for a 700 CFM blower to achieve the ASHRE recommended 500FPM minimum velocity for a grease carrying exhaust duct. This would also be assuming the duct run is very short and has minimal to no friction losses due to it's short length and no bends. If the run is LONG or has a lot of bends then there will frictional loss in the pipe. These losses are fairly well defined based on pipe size and length and can be found online with simple searches. If the exhaust pipe is not round then the math for area is simple, but the frictional loss calculations become more complex. There are charts to get a rough estimate. When running the fan at LESS than it's maximum speed then we need to figure out the correct duct size to achieve 500 FPM. Keep in mind that this will mean that we will have a higher FPM through the same size duct when running at a higher speed. To do this calculation we need to know what the total static pressure the hood fan is capable of achieving. For Zephyr models they list the total static pressure as 1.25 w.g. at the specific hoods maximum listed CFM. Static pressure is the resistance to air movement. This could be from restrictions in the exhaust pipe, lack of available air to put in the pipe, etc. This is where make up air (MUA) comes into the picture. Some new homes are built with a vapor barrier (tyvek or plastic sheet) that "seals" the house so well that air does not leak in around windows, cracks, etc. If an exhaust fan is running it is removing air from the building. When this happens the air pressure inside the building goes down. The exhaust fan has to work harder to continue to move more air. Once the pressure goes beyond the design static pressure for the fan the air flow slows down. In commercial building a MUA unit will have a fan and a way to heat or cool the air. This unit is controlled by a static pressure sensor that meaures the pressure difference between the outiside and incide the building. When the pressure drops inside the building the MUA fan speed increases to supply more air and equalize the pressure. In a home the MUA could be opening a kitchen window. When the exhaust hood/fan is on the make up air will be drawn in through the window. Or a system, like what a commercial building uses, can be installed. NOW all that explained we want to know what the correct duct size should be for a Zephyr hood that has multiple speeds. I will use the Typhoon model. It has a CFM range of 250-850. Duct Size (FPM) CFM 6" 8" 10" 12" 14" 16" 250 1273 716 458 318 233 179 850 4329 2005 1558 1082 795 608 So what did we learn from the above chart? For this particular hood we should have at LEAST an 8" duct, but I would argue that a 10" duct should be the minimum. The max working static pressure of most Zephyr hood is about 1.25" w.g. That works about to about 1500FPM in duct before the fan runs out of oomph to push more. Add in bends or other restrictions and 10-12" would make the most sense. Now if you you are venting directly out the back through the wall and there is no real ductwork, then all of these numbers can go out the window as there is not realy duct to worry about.