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Your cart is empty.The Tjernlund Duct Airstat senses positive pressure in a forced air heating and/or cooling system. The single pole, single throw, snap-acting switch is activated by a diaphragm with integral pressure probe inserted directly into the duct or plenum. The Duct Airstat can be used to initiate such auxiliary devices as: Duct Boosters, Electronic Air Cleaners, Electrical Duct Heaters, and Humidifiers. The electrical contacts of the switch are closed upon sensing positive air pressure generated by the blower.
JAH
Reviewed in the United States on January 21, 2025
Have now purchased two of these and they both work the same. I am using as a pressure switch to to turn on a duct boost fan. With a meter, regardless of orientation the switch will not close under vacuum....unless I flip upside down and use the normally closed circuit. Then it (both of them, thought the first was a defect) works perfectly.
farasdf123
Reviewed in the United States on January 12, 2025
Worked as advertised for 6 months" then remained stuck in on position. Stopped to turn accessory fan off as furnace turned off.
Nelson
Reviewed in Canada on September 27, 2024
I was sceptical but it does work. Took a few seconds for the pressure to build up but it did come on.
John V.
Reviewed in the United States on September 12, 2024
Works great. Installation instructions are confusing, just mount vertical, top and bottom doesn't matter, just be vertical.
Ashley
Reviewed in the United States on August 19, 2024
This HVAC pressure switch works flawlessly! Needed two in-line duct booster fans and this switch works perfectly to operate both!
Steven H
Reviewed in Canada on August 15, 2024
I had to place the switch directly on the plenum because anywhere else wouldn’t activate it. Beyond that it was simple to install and understand
murray downie
Reviewed in Canada on February 27, 2024
I bought this to control a duct booster fan. I followed the instructions and installed it in the main plenum close to the furnace. It didn't work so I repositioned it a little further from the furnace and again it wouldn't work. In desperation, I moved it to the end of the plenum with similar results. I was removing it while the furnace was running and had it part way out when it started to work, pushed it back in and it stopped. So its currently hanging out of the hole in the duct and working perfectly.
Michael Foley
Reviewed in the United States on October 13, 2024
I used this for my installed duct fan to only run the fan when the furnace fan starts. Can be wired with extension cords. Works well so far.
Purchaser
Reviewed in the United States on September 2, 2023
I needed something that would allow my HVAC UV duct light to turn on and off when the furnace/AC fan kicked on.This unit fit the bill perfectly. I was hesitant for a very long time but the UV Light was on constantly whereas the furnace/AC was only running about 20% of the time so I was just shortening the lifespan of the UV Light.It installed within minutes, looks good and works like a champ. Now when the unit detects air pressure in the vent it activates the outlet which the light is plugged in and now the light goes on and off as needed, saving both electricity and life of the UV Light.HIGHLY RECOMMENDED !!!!!
Mr. Smarty Pants
Reviewed in the United States on June 8, 2023
Update after 3m of use: works as it should. This summer was hot and my installation of the booster fan with this switch paid for itself triple. I saved a lot of energy cost because now the master bedroom gets colder much faster. Great solution - install it and you wont regret it!Original review: As many owners of two story houses with cathedral ceilings I have a problem with air pressure in my master bedroom hvac registers. Put simply - the air pressure is almost non-existing, the length of ducts is extremely long and my brand new furnace has not enough juice to push air from basement 3 stories up. Solution? A booster fan! Thoses with smart guts are expensive. So, I opted for a basic fan and separate pressure switch - this thing. It works perfectly. I did not drill 1/2” hole as manual suggests, instead, I drilled a tiny 1/4 hole under duct and inserted plastic 90° angle sensor (comes with switch) into it. Wiring is relatively easy - you just need to cut hot wire and connect each end to two separate contacts, ground and neutral pass the switch without cutting them (ground is screwed in). I connected the switch to in-line 6” booster fan and it now turns when furnace kicks on, and turns off when furnace turns off. Switch is installed into main duct, while the in-line booster fan is about 5’ down the duct, in a branch 6” duct. I was worrying that the pressure that fan creates will be enough to trip the switch but my worries were baseless. Even on maximum speed this 240cfm fan allows the switch to turn off when the furnace is off. I cannot be happier with how everything worked out.
Rocky Liu
Reviewed in Canada on October 12, 2021
work perfectly and easy connection
Customer
Reviewed in Canada on October 23, 2020
It works very on my fan. But Do not know the durability and reliability. Will see how well it goes within one year. And two year, and much more.
Spydo Staxxe
Reviewed in the United States on February 12, 2018
I looked at mounting this switch on the air handler, but there wasn't a really good spot to drill and mount it since the fan is at the far end. So I mounted it on the side of the plenum. But you can't just stick screws into a fiberboard plenum and expect it to stay put. So I devised a mounting plate which is a piece of steel stock, where I added a 1in bend on top.I set the stock on the outside of the box with the bend resting on top, and marked where the 2 holes were drilled on the outside so I knew how . I drilled the plenum at the marks (actually pushed a punch thru).Then I made a slice on top of the plenum as shown, and pushed the plate down through the slice until the 1in bend was sitting on top. I then made the port opening send mounted the switch. Then I pushed the metal screws through the plenum, and fished around until they were over the holes. Then I tightened them gently so not to crush the fiberboard.Then I taped the top 1in bend to secure it and prevent leaks. Diagram A shows the location of the switch, and the cut. Diagram B shows the metal stock.This is of course all unnecessary if you have access to the inside of the plenum, when you can add a mount plate and nuts with no trickery.After day 1, I'm very impressed. My UV purifier and my booster fans all are working perfectly. I have 3 zones- the loft, the living room, and the bedroom. At any one time only one zone would normally be on since we usually occupy the same room. But more than one CAN be on. I expect this to produce a savings, since cooling is now biased to the occupied zone. So I can set the thermostat to say 74, but if I'm in the bedroom, most of the airflow will be in there. So the bedroom may get to say 70, before the loft (where the thermostat is) reaches 74. Which is perfect because we're not keeping unoccupied rooms as cool as occupied rooms.My longterm goal once sensors get better, is to set these up as "scenes" oh my home hub, and let it decide which fans need to be on. But unlike lighting, cooling is a much longer-term proposal- I don't want to redirect cooling to the bedroom just because I walk in there to get a pair of glasses. The control switches ARE ZWAVE, so for now, I may just estimate occupancy by time of day. After 11, its a good bed BR is occupied and the other rooms are not.This switch was a vital missing component from the whole A/C control system. I had to know when it was running. Its a little *once-removed* from a *true* test which might be inductive sensors on the fan wires for example, but I'm pretty confident this switch will serve the purpose well.
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