You can use either an inline axial blower such as Fantech makes or a centrifugal roof blower such as Wolf/Broan and Abakka make. (Smaller commercial up-blast blowers are also an option for roof mounting, particularly where deep snow accumulates.) There are a few advantages to this route: First, by moving the blower away from the hood that sound source is downstream past where one (given enough space) can install a silencer, such as Fantech makes, in the duct.

Second, the roof blowers are larger and can run at lower blade tip speeds, thereby also reducing sound level.

Third, duct turbulence noise downstream from the silencer will also be attenuated by the silencer.

You may be able to go this route by adding blower and silencer components and subtracting the blower from your existing hood, if you otherwise like its aesthetics and baffle efficiency.

I don''t have a Fantech inline blower, but have a Wolf/Broan 1500 CFM rated roof blower with a Fantech silencer in the 10-inch duct path. There is some slight rumble from the blower, possibly unbalance vibration reacting against the roof structure and carried down the duct. (The size of the silencer limits it to only attenuating high frequencies.) Otherwise, all the sound in the kitchen is turbulence noise (hiss) from the baffle edges in the hood. These are not practical to attenuate.

One can converse under this hood without raising one's voice above normal talking level (this is slightly higher than a TV level appropriate to a quiet room). Wok sizzle is close in loudness to the baffle hiss. The hood is the largest Wolf Pro Island hood with approximately 10 square feet of hood aperture, and I estimate that at full blower power and fairly free MUA around 90 CFM/square foot of hood aperture is being pulled through the baffles -- a value I recommend for most residential applications.

Note that this desired flow rate is only possible if the blower is sufficiently higher zero-static-pressure rated that all the pressure losses from cooktop to roof and thence back to cooktop via the various MUA paths allow the blower's actual flow rate to equal the desired flow rate.

kas

Thanks Kaseki. I just went into the attic to look and, unfortunately there's only about 3' of duct run between the attic floor and the exit through the roof, which includes a small jog around a joist, so an in-line and silencer won't work and probably not a silencer at all. We do have MUA. Given no silencer, a roof-mount is probably preferable, but the exit point is just above our deck and I'm curious about exterior noise. Any insight with your Wolf?

Unfortunately, we can't just take the blower out of the current Zephyr unit and reuse it, as it has six blower settings, and one of the things I (now) want is the ability to dial up and down. The dealer suggested a Wolf insert, which comes with a number of inline and remote blower options. I was hoping a Fantech-and-other-brand-insert might be cheaper, lessening the pain of this do-over if we decide to go that route, but it may just be easier to do all Wolf at this point in the remodel exhaustion.

Your posts here have been really helpful when planning all of this initially; huge thanks for your input over the months and years. As have others, I sure wish there were more consistent and easily comparable ways to discuss the noise component, as the Zephyr literature and dealer assurances haven't panned out.

My Wolf blower points down a separate roof slope than that which slopes to the deck, so it isn't particularly noticeable. It mostly makes a whirring noise when I listen for it in the back yard. My attic vent fans make similar sounds.

A question I wish I had the answer to is whether the Abakka blower is significantly quieter than its nearest Wolf/Broan counterpart. (Note that while I'm aware that the fan curves for Wolf blowers are those of counterpart Broan blowers, I don't know whether the specification given Broan by Wolf is different than that to which Broan builds them for their own use.)

Depending on your tolerance for financial pain, you could build a chimney chase on the roof which contained either (a) the silencer (could be partly in the attic) and an inline blower (would need some type of suitable cap) or (b) the silencer (partly in the attic) with an upblast blower on top, or (c) a sloped-top chase with a conventional Wolf or Abakka blower on top with the silencer partly in the chase.

For upblast examples, see the "teen" pages of:

http://www.greenheck.com/media/pdf/catalogs/SeriesC_catalog.pdf

This is a pretty extensive catalog with a lot of background information I hope myself to get time to review. I haven't bought any goodies from Greenheck, so I don't know their pricing, but I expect a smaller unit would be competitive with its alternatives.

kas

naïve question: I was informed by several range hood manufacturers that one cannot mix blowers and range hoods from different manufactures. They claimed that it would

(1) void the warranty and

(2) damage one or other of the components.

It's been a while, so I don't recall the reason that they gave for (2). One of the manufacturers was Best. I do not recall the other.

Is there some truth to this or were the range hood manufacturers just trying to lock me into their product with respect to blowers?

(1) Nothing would surprise me about the limitations included in warranties; they aren't written to provide any more customer benefit than is needed to support sales.

(2) Possible actions causing damage (that I can think of):

• Trying to force a blower assembly into a hood space it wasn't designed to fit
• Connecting an incompatible blower motor with a hood's included blower control.

Otherwise, lock-in is a likely manufacturer goal, as is also not having to support customers who have problems when they try mix-n-match. For entertainment, review a warranty to see how many sentences provide benefit to the customer, and how many limit the liability of the company.

In the case of in-line or roof or wall mounted blowers, no incompatible shape forcing is involved. If the hood has a typical continuous motor control (diac/triac, some more sophisticated control chip with SCR) module, it should work with any single-phase induction motor that is not more powerful than the one it was designed to work with. If, like the OP, there is an intent to change the control anyway, then there can be no issue with compatibility.

All then that is left with a blowerless hood to warrant would be weld durability, (in the rare case of actually specifying the stainless steel it was claimed to be made of) resistance to corrosion, and maybe a lamp control circuit under one-year warranty. It would be laughable if a claim of warranty exclusion was asserted for a lamp control because the interior blower was removed.

In general, I would suggest that if one is in the middle of a renovation, with all the issues that arise in design and then in execution, from lumber quality to spousal tolerance, it may be more efficient to go with a manufacturer's combination. Otherwise, given understanding by the customer or his sub-contractor of the principles involved, there should be no problem with using a different blower manufacturer than hood manufacturer when the blower is external to the hood.

In general 2, I would suggest for those that can afford it that purchase from a hood manufacturer that one can determine from Internet comments stands behind their product is a good idea. This forum has some threads on lack of response or poor response from some brands' manufacturers. I don't expect there are many for Wolf, or ModernAire, inter alia.

kas