Tjernlund PS1503 Pressure Activation Switch for Duct Fans in Central Heating and Air Conditioning Systems

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.

Great product. There are a few key reviews that you have to pay attention to for the installation to go right. First, the review by Jimmy Adams is great, and well worth its rank as the most helpful review. When he reviewed the switch in 2013 he noted 4 terminals on the switch. My version (purchased in 2015) simplified the wiring to only two terminals - normally open and common. The wiring instructions that accompany the product are still worthless. Follow Jimmy's advice for wiring and you won't go wrong.I would have been better served to have read GoDark's review on location of the pressure sensor one more time before attempting installation. On my first attempt, I mounted the sensor to the return side. This won't work. The sensor won't trip and close the circuit in a negative air environment. It has to be placed on a supply side duct where air is being forced OUT. This is the only way the sensor will work. The closer to the air handler the better.I can't say enough about Tjernlund's customer service. I called their phone number and talked to a live Midwesterner (I believe his name was Steve) and he walked me through the troubleshooting when I had mounted the sensor in the wrong location. It's hard to find that kind of customer service these days. I purchased this pressure sensor as well as Tjernlund's M-6 inline duct fan. I highly recommend the company. Great products and great customer service.

Install went well. Good instructionsTied to duct fan.If fan speed too high, switch shuts it off due to inadequate air pressure.Tubing aimed per instructions.

This is the perfect solution for DYI UV installation to only use UV when the HVAC is operating. Awesome 👍

It turns out this is a positive pressure switch. Problem is when it turns the downstream booster fan on for the clothes dryer it is now operating in a negative pressure so it immediately shuts off. You then have a one second or less cycle where it starts and then stops the auxiliary fan. This means the auxiliary fan is always trying to start and never allowed to come to power. The motor is running on its start windings exclusively creating heat and a fire hazard as well. The switch cannot be installed on the positive side of the auxiliary fan either as this would mean once the switch turned the fan on it would be on forever, never being in a negative pressure. Any competent engineer could have forseen this on such a passive pressure switch. I am left to the conclusion that this item is marketed as an intentional rip off. The Tjernlund customer service people just stopped replying when presented with these facts.

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

Used it on the supply side of my furnace duct, the pressure switch makes contact about 3 seconds after the furnace fan comes on, I use it to turn on a UV light. Please make sure to install it in the correct orientation as it will not work if you install it upside down.

work perfectly and easy connection

Good quality pressure switch. The instructions that come in the box are very handy for setting your coffee cup on. They are poorly written and do not explain how to wire the switch in. I used it with a T-6 booster fan. My heart felt thanks go out to the person who provided the wire diagrams in the reviews. Very odd that the manufacture could not provide them in the box.

Get product did just what I needed it to do.