Giving a shout out to the forum expert on ventilation, @kaseki. He/she should be able to answer your question.

I will offer, that it’s better to plan for more CFMs, and not need them, than finding out that what you’ve got is not enough at times.

Thanks @kaseki interesting. Attached is the schematic from my Thermador hood (Model no. VCIN 48JP/01), for wiring up a remote blower. It is discontinue and I can't find a downloadable manual for the hood.

I'm looking to purchase a Best (IBL11) 1100 cfm inline blower which will be installed directly above the hood in the attic. Attached below is a photo of the schematic from a Best WP28M series hood which would be compatible with the Best IBL11 blower.

Fantech was very helpful to deal with but wasn't able to confirm if they would be compatible, They said I would need to confirm that the Thermador hood could work with a variable speed motor oppose to a multiple speed motor? Fantech said all their blowers work on a variable speed. Thermador said the blower needed to be multiple speed and quickly answered only Thermador blowers are compatible with Thermador hoods.

Are you using one or two fantech silencers, in your setup? I was debating between one or two LD 10 silencers, the exhaust will travel straight up from the kitchen through a master bedroom closet up to the attic. I often work nights so I'm concerned about noise.

Figure 19 shows a typical triac control for induction motors, capable of variable ("infinite") control. This is consistent with what Best told you. The previous connection drawing confirms that the Thermador expects to control a three-speed motor (motor wound for three speeds).

To use a Fantech motor, for example, one would have to gut the Thermador hood of its control switch and associated wiring, and install a typical motor control (ones for wall use look like rotary light dimmers, but are constructed so that off to on yields full power, and further CW rotation reduces power). This aids motor starting. One could also put the control on a nearby wall and the hood control could stay, just not be connected to anything. Fantech may supply suitable controls for separate mounting (NuTone used to). Adapting such a control into a hood such that the control shaft could replace the supplied control shaft and the shaft end could take the same knob seems to be a stretch in the luck department.

I have two roof blowers. One is connected to my hood via a 10-inch Fantech silencer, the other is connected to a couple of ceiling registers (with filters) via an 8-inch Fantech silencer.

With respect to my hood and its blower, the full power operation noise from my 1500 (rated) CFM Wolf blower (made by Broan) is highly attenuated. Blade tip turbulence noise is defeated by the silencer, and some motor rumble and vibration are attenuated by automotive damping material wrapped around the ducting. Most noise is baffle turbulence noise in the form of hiss, and one can talk at a normal level when cooking under this hood. Wok noise is louder.

The other blower is by NuTone, and I haven't found my information about its parameters. It is a down-blast type unit. Noise is slight in the kitchen -- more of a wind noise. I still need to measure its actual flow rate to guess at its blower rating. In lieu of baffles, it uses 3M Filtrite 1-inch pleated furnace filters to catch any grease that reaches the ceiling over the oven stack. As usual with attempts to capture opening-the-oven effluent, it is marginal.

Curious what you decided with this inline blower and possible silencer. Debating on range hoods for our 48" range.

So reading through the faq for the best blower it specified it had to be installed horizontally and since I had a straight vertical line up I didn’t want to have to add two 90 degree bends on the duct work. As this would have added a ton of noise.

I ended up purchasing a fantech fkd10xl blower, it is real powerful. And I purchased one ld10 silencer. I haven’t completely enclosed the duct work yet but it doesn’t seem to bad right now for noise. I’m surrounding all the duct work with insulation as well to reduce the noise.

The thermador hood was not compatible with the fantech blower and I wish I would have done more research before purchasing it. I would stay away from thermador, the hood was a pain to put up, very counterintuitive and they wherent helpful when calling their customer service. So what I did instead was run the wire for the blower down to a variable speed switch on my backsplash, had to order a switch from USA to get one that was white with high enough amps and it has been delayed due to covid. In meantime I just have it on a normal switch and I crack a window when I turn it on to avoid any back draft

@DougKotulak . You will need a make-up air (MUA) system for that blower, even if there is no code enforcement in your area. Depending on the type of combustion appliance you are avoiding back-drafting, the MUA system may be complex or simple. We will need more information to be helpful for that subject. In the meantime, please review MUA-related threads here.