Topic: Dumb question but I'm going to ask it anyway

[NoQuitters]

The wife decided to redo one of the bedrooms in the house. Just so happens that it is the one where the computer and console for the weather station are. Nothing major, new paint, new rug on the floor, new curtains. Ever since then she insists on keeping the door closed to keep the cat out of the room. To make a long story short, ever since the redo my pressure readings have been off by about +3. Only other thing that changed was adding the Boltek lightning detector.

I find it hard to believe that either of the changes would cause such a thing but you never know. Just having the door closed shouldn't change the pressure readings. Any chance the Boltek is in some way causing an issue? I'm at a loss to explain it.

[PSJohn]

Several years ago, I experienced a similar effect. I had an OS WMR-968 in a small 20x 20 foot room. I also kept the door closed due to cats! My baro readings were more erratic than high. The thing that I determined it was was the central A/C! With the door closed the room was more "sealed". I could see the baro increase slightly as the air turned on and the door closed.

I do not see this at all with my VP. But it is also now in a larger room!

Hope that gives you some ideas!

[Mark / Ohio]

I would agree with PS John's thought.  Might keep a window cracked for a few days and see what happens.  

I've wondered about the HVAC having an effect on the readings.  The door is closed about half the time and I never noticed any changes in the baro from night to day.  But our home has a small return vent in each room opposite of the heat / cool vent.

[ocala]

John, I'm doubting you but I just find it hard to believe that that an AC vent could increase the pressure in a room enough that it could measured. Being that it's an inside door I'm sure there isn't any weather stripping on the bottom to completely seal the room. Any pressure would escape underneath the door.  At least I think the way it should work.

[ncpilot]

my pressure readings have been off by about +3.

What does +3 mean? Is that mm, or tenths of an inch?

I've had doors that were open by a few inches, close by themselves when the HVAC came on, and if you have carpeting, while certainly not a perfect seal, it can form a pretty good barrier on the bottom of the door. With no return vent in a room, it does get pressurized a bit...

[Clammer]

Hi!

Most HVAC guys want at least 1" space between the door and the floor, if there is no return provided!  Depending on the size of the room, size of the vent and the airpresure fron the fan, there can be an appreciable pressure build up in the room.  Add the new carpet and pad, he could end up with a very small crack under the door.  If they added strip between carpets, More space is gone!  If the room is close to the air-handler, the pressure will be higher and if the other rooms have the same problem, it all adds up!

Best,

Clammer

[ncpilot]

Yeah, I hate when my ears pop every time the AC comes on...

 
 

[PSJohn]

John, I'm doubting you but I just find it hard to believe that that an AC vent could increase the pressure in a room enough that it could measured. Being that it's an inside door I'm sure there isn't any weather stripping on the bottom to completely seal the room. Any pressure would escape underneath the door.  At least I think the way it should work.

In my case there is a 1" space between the door and carpet (my carpet is thick resulting in narrowing that to 1/2") you can definietly feel the air under that door with the A/C on and door closed!

Times when I had a head cold and were in the room you could feel the pressure change in your ears when the air kicked on!

[NoQuitters]

What does +3 mean? Is that mm, or tenths of an inch?

+3 millibars, at least according to cwop.
http://weather.gladstonefamily.net/site/C3658

I have a manual barometer and it is dead on with my VP2.
For what it's worth, there is about an inch gap at the bottom of the door (all hardwood floors). There is also a return vent in the room.

[Clammer]

Well, there goes that theory!!!
Clammer