Fantech 9800000 RSK-4 Backdraft Damper, 4" Duct

I live in a typical NYC apartment building. The typical thing about buildings like these are.... Generally terrible and cursed things everywhere. Including the mechanicals. Like many many NYC buildings, the exhaust-only ventilation system is not working correctly, and sometimes backdrafts. The building does not understand this, and nobody cares. In addition to being unpleasant with the smells, it can also be an infectious disease hazard (all airborne diseases, like the flu, COVID, and similar, can travel through ventilation systems). Eventually I got tired of trying to do the right thing (them fixing it CORRECTLY) and looked for a weakly-sprung backdraft damper to do the job. There aren't many useful square ones, the good ones are all round. Anything with a strong spring will fail to open under the poor static pressure when the ventilation system is operating semi-correctly. This fit the bill. It's almost too weak to close correctly, but if installed with the right tilt, it works fine. I had to use like 4 pounds of duct putty, but I stuck a round damper in a square hole!

Very well made, it impressed the guy installing the vent hood and ductwork. He had done an installation in the same floor model home 3 doors away, and had to remove the cheap damper supplied by the homeowner, as it was noisy and started spinning around when air flowed. The Fantech mounting system prevents it from spinning, and the rubber gasket makes the operation silent. It opens easily, even on the low (110 CFM) position of my Elica vent hood. The fit and finish is very good. It dropped right into the 7" to 5" reducer, as both were perfectly round. Note: The cheap duct parts tend to easily get out-of-round, are harder to assemble, and make noise. Buy good stuff, including this Fantech backdraft damper.

Well constructed. No complaints. I think negative reviews from some reflect misunderstanding of how these work. Complaints have been that the spring is not strong enough to shut the damper when the positive air pressure is removed. In fact, the spring is rather light, but it needs to be. First, make sure you install this correctly with the axis oriented vertically (NOT horizontally as shown in the product photo). The vertical axis allows the flaps to work freely with minimal effect of gravity. Second, don't bind the hinge with tape. There's plenty of room for tape to form a good seal around the collar without impeding the hinge. Finally, keep in mind that the spring only needs to return the flaps a small part of the way. While the spring can and may force the flaps closed, it's really the backdraft itself that will force them closed. The spring needs to be light enough to allow your fan to draw the flaps open easily.

Quality! Worked great in a horizontal 6 inch duct in series with a Broan model 512M wall exhaust fan that used to let a lot of cold air in from the outside. I used metallic duct tape on install to make it secure as my ducting was not flared correctly on the side where I had to cut my duct shorter and crimp it with pliers in order to make the damper fit. If you are a little handy no problem. Closes fully when fan is off and opens fully when fan is on. Fan is 70 CFM.

I just added this to my Panasonic 140 CFM exhaust fan and it works better than expected, with very cold temps well below zero I needed to add a better air damper than the factory one, this made all the difference in the world, I have no noticeable cold air flowing back into the house with the fan off. Two very lightly spring loaded flaps only open when air pressure from the fan pushes on them, back flow pushes the flap in the other direction against a rubber seal making a leak free seal. The stronger the back flow pressure is the better the seal. I don't get that cool breeze when I walk past my Bathroom ceiling fan on a windy day anymore or any day for that matter. Last week it was -10F below zero with high winds, I got my step ladder out so I could get my hand up near the side of my fan where the vent pipe connects, I felt nothing. I'm very pleased with this damper, if you're installing a bathroom vent spend a little more and add this, it not not prevents air back flow but also keeps rodents from going past the one way valve.

This is a well-designed and made product at a great price. There may be others but I can't imagine them to be any better for 4" exhaust venting needs. Mine went in a 4" by 4" by 6" Y to stop backdraft to each of the outgoing 4" runs since my only option was to vent everything thru a 6" roof vent. They are spring loaded to shut/seal well on a rubber gasket and but open easily with a puff of your breath; good to test them before install.

Ordered this one after reading all of the reviews for this brand and for the competitors, because of the comments about the robust metal construction. That part is true, it's just too bad the rest of the construction is inherently flawed. The design of the functional components is poor, being loosely designed and assembled. The flaps fall against standard round foam rod used for caulking gaps in construction. The butterfly flaps are on a rod that is simply bent to keep it from falling out, and both have a large amount of travel in the finished construction -- not in the way you want travel. When delivered, one side of the flaps showed a large (1/8") gap. This is inherent, since the profiles of the foam seal is round, the radius falls away from the travel of the flap. It's an inherently low quality design. I't's possible when you get one that it works, however, it's equally possible that it won't, because the manufacturer clearly has no quality control.

Yes, obviously I can see how this damper is constructed in the pictures before I bought it. I read one of the reviews talking about a solution since it won't do a downdraft, without the flaps simply staying open due to gravity. Since I'm doing a horizontal vent I didn't pay much attention to it. But this is something I feel is an important consideration for other potential buyers of this damper; WILL YOU BE ABLE TO GET TO THIS AFTER IT'S INSTALLED? I'm finishing a ceiling. This is for a bathroom exhaust. It will be in the ceiling near the wall where it meets an elbow and vent. The spring for the two flaps? It is almost as thin as a hair! You can easily blow the flaps open with even a normal breath. Others mentioned this as praise for the flaps opening easily... but here's where my design question comes in for the manufacturer. You could have easily opening, and positive closing... while losing that spring and the split-hinged flaps. If the flaps fall open under gravity anyway, then why not keep it one piece, with two vertical wires ("bars", like the current one down the center that the split-flaps are hinged on)... so the single piece flapper is perfectly centered in the vent... then simply have two holes at the top that the two wires are bent through (just like the current design)... and then the whole flapper would open with even less resistance, and close by gravity. (optionally, you could angle this within the damper, so that even if the damper is at a slightly downward angle the flap would still close very securely)... you'd save production costs with a simpler design... plus eliminate that hair-fine spring and the hinged split-flapper. You could accomplish this angled, securely self-closing flap within the current cylinder with the foam rubber seal at an angle. Sure, the outer cylinder is totally bomb-proof... so yes, thank you for that... but the mechanism... the reason we're buying this... is all built on extremely delicate parts. Why? I can't help wondering how many years this will last and/or if the hinged assembly will need any cleaning or maintenance when I can no longer get to it? That's why 3-stars... "it's okay"... yes, the outer cylinder is ridiculously well-constructed and solid... but on inspection, I'm surprised just how delicate the important bits are... the hinged flaps, and especially the tiny spring.

La pequeña manivela si abre la tapa pero no tiene fuerza suficiente para cerrarla tiene que ser manualmente Y llego un poco golpeado Tal vez no es un producto para algo específico

I had this fixed in my kitchen chimney duct. Helps to prevent back draft, very strong wind outside, sea facing. Exact fit for 4" aluminium duct

Nice damper, a bit hard to fit with a flexible aluminium foil tube, but works great. I like hearing it clamp shut when my dryer stops.

Not installed yet but product is well built and appears it will perform well with our 400cfm range hood.

Good quality Backdraft damper.