DIY HVAC system over pressure device

I know its been a little while on this thread. I think my last readings are more realistic, and at 150 pa, set point I’ve not yet tripped it with any vent activity.

Sounds reasonable?

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So I knows its not summer anymore but I figured I would see if I could help you some incase your are still having problems. There could be a couple of things causing your problem. 1 The big one is your HVAC is to small. I’ve never seen a HVAC company put in to small of a unit they always round up when figuring out the size needed but it could happen. 2 Someone has added on to your house without upgrading the HVAC system. This happens all the time. 3 You have major leaks in the HVAC. Those darn mice will eat a hole an anything. Now that those are out of the way. 4 Did you install the probs correctly. I tried looking through the thread and did not see anyone say what the proper installation direction is. It will make a huge difference if installed wrong. The prob is suppose to point into the air flow not with it. If you have a horizontal unit and the air flows from the right (filter side) to the left (out to the registers) then the probs should point to the right when installed. 5 When was the last time the A coil was cleaned. If you bought your house used the A coil is probably nasty. Most people don’t change out the filter every month or 3 like they should (set an alarm you will thank yourself down the road). If it is dirty this will cause a great reduction in air flow. If your system flow is filter, fan, A coil, then registers your fan is going to be nasty also so make sure you pull it and clean it to. Make sure you center the fan in the housing. If it is off to one side it will not be as efficient depending on how big the housing is. To clean the A coil in this setup you have to pull the small triangle piece of sheet metal on the A coil behind all the copper tubes because the inside will be the dirty area. Bend the sheet metal not the tubes to get it out. It will make a mess when you are cleaning it just be warned. I just bought my house and both the A coil and fan had a lot of build up on them from the filters not being change properly. I could tell a big difference after cleaning them. 6 Someone has turned down the fan speed on the HVAC. Most HVAC fans have multi speeds but only 1 or 2 speeds are used. If you have more then 2 wires coming from your fan it probably has multi speeds. The default is normally high speed but someone could of changed it. If you do not see anything on the drawing on the door that tells you what color wire means what speed you will have to pull the motor to read the label on it. You are technically not suppose to hear the air coming out of the registers. If you do you have back pressure. If you can hear almost like a whistling then you have to much back pressure no matter what the gauge reads. After testing my system I actually was able to turn my fan speed way down and not hurt the system and it actually runs better and uses way less electric to cool the house (working on a way to control the fan speed with ST). 7 Open the door to the room. A room with a closed door will run hotter or colder then the rest of the house. You are trying to pump air into a room but the air in the room has no where to go. You can also give each room a return so it can “breath” properly. The return does not have to be tied into the HVAC system. You just have to give the room a way to circulate the air with to door closed. The comin practice is to install a return in the wall to the hallway. If your registers are in the floor then the return in the room will be in the wall by the ceiling. In between 2 studs cut a hole in the wall by the CEILING and put a register cover over it. In the hallway by the FLOOR cut a hole between the same 2 studs and install a register cover. You don’t need one that can close. They will look similar to your filter cover but just no filter. Now here is the math part. The returns you install need to be 1.5 times bigger then ALL the registers in the room. Or you will hear and feel the air coming through and out the walls. I hope this helps you.

Hi @jh0 Could you please share your Radon monitor solution.

I bought this pressure switch and connected it in to the air line that runs from the PVC pipe with radon fan to the u-tube. Then I wired the pressure switch to the auxiliary input on this door switch.

The hardest part was getting the right size hose and tee to connect the air lines. You’ll have to measure the hose your system uses and match to that.

I’ve been happy with the results. Over the winter my fan froze and I knew about it right away!

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Hi @jh0 Can you share some pictures?

Here you go!

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Hi @jh0, I got the pressure switch P233A-4-PAC but I am still looking for the “tee” could you help again.

It will depend on the size tubing your u-tube uses now. I bought this tee in 5/32"x1/4" size and this tubing to connect the tee to the pressure switch. It didn’t fit perfectly, but I was able to make it work.

Try to accurately measure the outer diameter of the tubing you currently have to get the right size tee.

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I see other wires going to the Z-Wave sensor. Are you powering it that way?