thx Kas. Ok, you talked me into making the MUA for safety reasons. we decided to go with option #2, we will get the capital Capital Maestro Series MCT365GS,
a under cabinet rangehood (either NXR PH3651, $649 or the broan E64E36ss with the Broan 335 1200 cfm motor, $1200). My question is that the NXR is 18" H, my cooktop to cabinet is 34", that leaves 34-18=16" between the cooktop and the bottom of the rangehood. Would that be too close for fire hazard?

Thirty to thirty-six inches above the cooktop for the hood base should provide sufficient distance for good visibility and safe head clearance. (My Wolf hood clearance is about 34 inches.) Design your cabinets accordingly. It appears that your existing cabinet was intended to provide no space for an adequate hood. I suppose that with downdraft quasi-ventilation it wasn't needed.

Even without head clearance and visibility requirements, I think sixteen inches starts to intrude into clearance for larger pots. In any case, I would replace the cabinet above with a shorter one, or, as in some popular layouts, none at all.

Fire hazard requirements for stoves generally relate to combustibles. With a metal hood there might not be any combustibles, but plastic or electronic parts could suffer greatly.

The hood front to back dimension should be sufficient that the front of the hood aperture overlaps the front edge of the hot part of your wok on the central burner by at least ten degrees angle to vertical at the hood height to capture most of the hot cooking plume. This should also be achieved for likely pans on the other front burners, although their effluent might be more modest, depending on what is cooked at what temperature.

kas

Thx, kas. I guess 10" Broan hood shell w external blower would be the most economical way to go?

I can't answer economical, but an external blower will move a significant part of the total noise generation away from the cook. It will also allow, if space is available, installation of an in-line Fantech silencer (muffler) to greatly reduce blower blade tip turbulence noise transmitted back to the hood through the ducting.

kas

Also, what do you mean by ten-inch hood shell? Is this the bottom to top dimension?

And if by hood shell you mean hood insert, then the wood cabinet overlay will most certainly have to be at a height that conforms to the combustible safe separation requirements of the stove manufacturer.

Thx Kas. I meant the Broan E64E36ss undercabinet range hood that's 10" h, 22" deep, 36" wide w the 1200 cfm Brian 335 blower. This will give me 24" clearance from cooktop to hood) so I don't have to get rid of the small cabinets above/ new crown molding on both sides/ re tile if had chose the 18" H, 24" deep, 1000cfm NXR hood from Costco. Do you think the Broan combo is a better choice in both cfm and noise? I would not be able to install a silencer since it would go thru the cabinet, ceiling, left turn to outside wall. Total less than 10ft.

I see that Broan is calling their hood a shell given that using an internal blower is optional.

Choosing a path that is economical in overall construction cost is generally better (all else being equal).

I have no idea what their relative noise levels are.

I have experience with various Broan/NuTone fans and blowers and can say that most of them have been operational for over 25 years without failure.

I probably have a fan curve for the 335. You may be able to find a copy on their web site. I don't know anything about availability of NXR fan curves.

I notice with a quick look that Broan is able to provide some integration with the MUA system that they sell. This may be a plus also, economy-wise.

You might mock up a hood shape out of cardboard or draw a side view of the hood in place to determine whether sight lines are adequate and head bumps unlikely.

kas

I have a Universal Tradewind hood and blower (4 years old now,) that is very powerful and I love it. We cook Indian food so I need the power. No problems and cheaper than Modernaire.