By the way, it probably needs a major repair. It completely stopped working today.

I pressed the buttons to turn it on today and the fan and lights came on for 1 second and then shut off.

Of course, I verified that a circuit didn’t get tripped by plugging something else into the same outlet and verifying that the power outlet was still live.

The physical buttons on the right end for delay off and the light have also been not popping all the way out and I have been living with that annoyance for years, but now I can’t use it at all.

Since I swapped out my gas range for induction, I wonder if I even really need a dedicated range hood anymore. Maybe now is the time to just switch to an OTR microwave.

I had a Zephyr Typhoon. Yes, it was noisy. And wasn't very effective either because there is no capture area. Replaced with a Vent A Hood that has onboard blowers but is much quieter. Also more effective.

Induction mostly cuts down on the heat from cooking. You still have odors and grease laden vapors so you still need an exhaust, IMO.

Yes, I would still need some kind of exhaust when cooking, but maybe with induction, the exhaust built into some OTR microwaves may be enough.

Any*** baffle or mesh filter hood can be gutted of its blower(s) and a remote blower installed. The catch is that the control interface of the remote blower may not be compatible with the control interface built into the hood for the OEM hood blower. There are some threads here about particular cases. Usually, one has to change the control, or add a wall control and ignore whatever blower control is on the hood.

Whether a remote blower is modestly quieter or much quieter depends on whether there is room in the duct path for a silencer. The alternative for a silencer is a larger slower blower reducing blade tip turbulence. Duct turbulence noise and hood filter turbulence noise will always be present.

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*The VaH "magic lung" hoods, wherein squirrel-cage fans act as the fire stop, have to be excluded unless some means of adding baffle or mesh filters is adopted. This would probably not be cost-effective unless there were other expense ramifications. Commercial suppliers of baffle filters for custom/bespoke hoods exist. Keeping the old VaH hood would require temporary hood removal and some welding of adapter surfaces. The result would not be UL/CE approved.

**The Typhon in the video above is even more difficult to adapt, as it has a somewhat tenuous capture area and fans performing the fire stop function. I would replace it for deviating too far from the general hood design principles that we have argued for here for more than a decade.

I don’t want to put a lot of labor expense into duct modifications for solving this issue.

Is Venta A Hood the only recommendation to replace an under cabinet Typhoon?

The main things I don’t like about my older model Typhoon is the amount of noise it makes when not at the lowest fan speed and the fact the the control buttons have a bad design or are just poor quality. When it was delivered new out of the box, buttons were broken and the installer didn’t mention it until after it was already mounted. It was fixed under warranty, then the new buttons broke a few years later and fixed again under warranty. Now, the buttons are sticking again and the whole unit completely dead, but I assume it’s now out of warranty.

Zephyr seems to have solved the button issue on this model by switching to capacitive touch.

The video above now says the newer model is also ultra quiet and near silent,

Did Zephyr make a major change to make the newer version of the Typhoon quiet or are they lying?

Since I had this hood installed before 2012, there were no MUA requirements at the time.

I think getting new ducting for MUA would cost thousands. So, I will have to either just pay to repair the existing hood or else downgrade to a 400 CFM hood or just go back to an OTR microwave.

The home came with an OTR microwave from the builder. So, the ducting was designed with that in mind.

Is Venta A Hood the only recommendation to replace an under cabinet Typhoon?

No, I only mentioned it as being more quiet and more effective than the Typhoon. The reason I went with it is because I found a 42" unit second hand (new but never installed) for about 1/3 the price of a new one. It is a decent hood, definitely an improvement over the Typhoon.

If I replace the Typhoon rather than repairing it, I will need to get a 400 CFM model to avoid the extra several thousand dollars in renovations required to retrofit MUA which is extremely unlikely to be warranted using induction cooking.

Are the 400 CFM Vent A Hoods noisier at max speeds than a high CFM model running at a fan speed that delivers equivalent air flow? Do they have smaller motors and fans or do they just max out at lower speeds?

I fear that there is a misunderstanding about make-up air by the OP. The hood flow and the MUA flow (including house leakage) are always equal. What happens without deliberate MUA is that the hood blower, by its nature, adjusts flow to balance its performance against the pressure loss from cooktop to outside to cooktop. In doing so, it lowers the house pressure relative to the external (outside) pressure. This can cause back-drafting of combustion appliances depending on whether there are any and how they are operated. Back-drafting brings carbon monoxide into the house.

The 400 CFM rule is at best an attempt to balance competing economic issues against safety issues and depends on a certain level of house leakage, something modern construction tries to avoid. Whether using a blower that is rated only for 400 CFM will actually be safe is a question that requires a lot more information to answer than we have, possibly more than the OP has.

Back-draft susceptibility is summarized below. Note that this back-draft susceptibility data was provided by another forum member a few years ago as an image. (I haven't found the source of this, but it is believable.)

*****

Mechanical-Draft Appliances

Heating systems with fan-powered exhaust systems can withstand higher negative pressures than natural-draft appliances. Some types of fan-powered systems are much better than others, however. In order of effectiveness, the choices are:

« Sealed-combustion. Also called “direct vent,” these appliances draw all combustion and dilution air from outside. These can typically tolerate negative pressures in the range from 25 to 50 Pa.

* Power-vented. These draw their makeup air from indoors and are also called fan-assisted, forced-draft, or mechanical-draft. These can typically tolerate up to 15 to 20 Pa of negative pressure.

* Induced-draft. These have a small fan added for energy performance, not to overcome house depressurization. These can typically tolerate 5 to 15 Pa of negative pressure.

By comparison, an atmospherically vented furnace can back-draft with as little as 5 Pa of negative pressure, and a gas water heater will have spillage at 2 or 3 Pa. Fireplaces can start having problems at about 3 Pa. Canadian codes limit negative pressures in homes with atmospherically vented equipment to 5 Pa. U.S. codes do not currently address the issue (in a plainly spelled out "prescriptive" number).

1 pascal = 0.00402 inches, water column

1 atmosphere = 407 inches, w.c.

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tl;dr: MUA renovation expense may or may not be needed for safety even with a 400 CFM rated blower.

Where is the carbon monoxide going to come from?

I have an induction range with electric oven.

The gas furnace is in the attic.

The gas water heater is installed outside.

There is a gas fireplace, but it’s not in use

There is a gas dryer in the house, but I can simply not dry clothes at the same time cooking something requiring the exhaust fan to be running.

I can also crack open a window when using the exhaust fan. Even in summer or winter, the few extra dollars a month in utilities to account for lost heating an air conditioning due to the window being open during cooking certain foods would never compare to the multiple or tens of thousands of dollars it would cost to retrofit MUA into an existing home.

Even replacing the gas dryer and gas furnace with electric heat pump versions when the time comes to replace them would still cost much less, especially if you only count the difference between replacng aging gas appliances with all electric heat pump appliances vs new gas appliances..

Ah! Note my "may or may not" phrasing. Also note that code compliance is directed toward what someone may or may not do that is adverse to safety; in other words worst case.

I actually do want to get rid of all the natural gas in the house over time. The electric rates here are low in winter and not that high even in summer except during peak weekday hours. The induction range was the first step towards going all electric.

The furnace is at an age where it would be normal to replace it. Likely going to be replaced with an electric heat pump. Even if a heat pump was cost prohibitive, I could still get a direct vent gas furnace replacement. Maybe the existing gas furnace is already direct vent unless that was not commonly installed by home builders 20 years ago.

I also plan to replace the gas dryer with electric heat pump or combo washer dryer.

I haven’t turned on the gas fireplace in years.

Are MUA codes a consideration in an all electric home?

I think that is a question for your authority having jurisdiction. It may vary with municipality. In such cases I would argue that passive MUA would be fine and just put in a hole feeding a damper, filter, and heater. And the reason for MUA at all in such cases is (a) better hood performance, and (b) less dust and moisture pulled through wall cracks.