Author Topic: Placing Anemometer on Roof - Good or Bad Idea?  (Read 4456 times)

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Offline DellNec

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Placing Anemometer on Roof - Good or Bad Idea?
« on: May 10, 2011, 04:03:02 AM »
The first photo shows where my CURRENT anemometer is placed. It is a LaCrosse (bad idea) and I will be returning it back to Costco because it is NOT an accurate weather station. I have since bought a Davis VP2.  :grin: Getting back to the location, in the photo you can see that the trees can cause inaccurate readings:



Here is where I want to place the VP2 anemometer. It is on the roof of a 2 story home. So it will be around 30-40 feet from the ground. I was going to use a rigid PVC pipe and attach that to one of the roof vents that are visible in the photo:



My questions are as follows:

1 - How much wind load/resistance will their be with the anemometer attached to a round PVC pipe, sitting on top of a roof?

2 - Running the 40 foot cable from the anemometer down to where the other sensors will be, does the cable need to be tucked under the tiles, exposed, or run through conduit? How exposed can it be? Especially with the intense UV light in Phx, AZ and sitting on a hot roof.

3 - Or should I just mount the anemometer back at the same wood post location I had the LaCrosse anemometer in picture #1?

« Last Edit: May 10, 2011, 04:06:21 AM by DellNec »

Offline miraculon

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Re: Placing Anemometer on Roof - Good or Bad Idea?
« Reply #1 on: May 10, 2011, 05:55:04 AM »
1 - How much wind load/resistance will their be with the anemometer attached to a round PVC pipe, sitting on top of a roof?

This sounds completely scary to me. I helped install a VP2 at work and the rain gauge panel, radiation shield and solar panel look to me like there is quite a bit of surface area. If you get high winds, I would be very concerned about the stress on the PVC pipe. You will lose more than just the Davis if the pipe cracks off. I wouldn't trust that.

Also, years ago I tied a guy wire for my weather station to a vent stack. (Not the station itself)

The force of the guy wire shifted the "boot" around the stack and made a leak. Fortunately it was into my garage where it didn't cause any problem other than unexpected drips on my car. This was with a cast iron stack pipe.

I think that you would be setting yourself up for a lot of problems with this approach.


2 - Running the 40 foot cable from the anemometer down to where the other sensors will be, does the cable need to be tucked under the tiles, exposed, or run through conduit? How exposed can it be? Especially with the intense UV light in Phx, AZ and sitting on a hot roof.

I don't know what the UV rating of the Davis wiring is, but I know that UV can have brutal effects on plastic and vinyl. I lived in Mexico for three years (Chihuahua City) and I know first hand about how intense the sun is. (I currently live in not-so-sunny Michigan). I would try to protect it from the sun. Conduit may be overkill, but may be a good option. Otherwise tucking it out of direct sunlight where ever possible sounds like a good plan.

3 - Or should I just mount the anemometer back at the same wood post location I had the LaCrosse anemometer in picture #1?

I would do this before I mounted it to the vent stack.




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Offline d_l

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Re: Placing Anemometer on Roof - Good or Bad Idea?
« Reply #2 on: May 10, 2011, 10:43:00 AM »
2 - Running the 40 foot cable from the anemometer down to where the other sensors will be, does the cable need to be tucked under the tiles, exposed, or run through conduit? How exposed can it be? Especially with the intense UV light in Phx, AZ and sitting on a hot roof.

In addition to the eventual UV deterioration of the plastic, any looseness in the wire run will allow winds to flex the copper strands within and over time break them.  I would guess that the electrical continuity of the wire could even be broken by flexing before the plastic insulation has been fully deteriorated from the sun if the wire isn't wind-flex protected.
--Dave--

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People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  www.tceweather.com

Offline richb

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Re: Placing Anemometer on Roof - Good or Bad Idea?
« Reply #3 on: May 10, 2011, 12:41:12 PM »
Congradulations on your VP2 purchase. I too live in Phoenix and put up with LaCrosse stations for several years until I finally got a clue and now have a VP2. I might suggest locating the anemometer at it's current location only on a taller pole. I mounted mine on an antenna mast at the peak of my single story roof, but I have asphalt shingles making it easier to access for maintenance. Also, I decided to add an anemometer transmitter to eliminate as much exposed cable as possible. It's more $ but hey, you know how hobbys are! This AZ sun is brutal in the summer. If you do use the 40' cable (you can also add an extention to the cable), you might want to run it inside the pole. I definately prefer locating the ISS closer to the ground where you would have easy access to the sensors.

Offline Bunty

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Re: Placing Anemometer on Roof - Good or Bad Idea?
« Reply #4 on: May 10, 2011, 12:41:39 PM »
Avoid the 40 ft. cable by going with solar-wireless.  But solar will cost $175 to $195, depending on where you get it.

Also the 2nd home page using modified AltDashboard 6.81 at http://stillwaterweather.com/wx/2ndhome.php

Offline DellNec

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Re: Placing Anemometer on Roof - Good or Bad Idea?
« Reply #5 on: May 10, 2011, 03:14:00 PM »
THANKS to all who responded!

Just to clarify, the anemometer would be the ONLY thing attached to the PVC pole, nothing else. The rest of the weather station sensors would be located closer to ground level.

I am now leaning towards going back to the original spot (wood post) but mounting the anemometer a little higher. I haven't completely abandoned the roof idea, I still need to think about it.

« Last Edit: May 10, 2011, 03:15:53 PM by DellNec »

Offline neondesert

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Re: Placing Anemometer on Roof - Good or Bad Idea?
« Reply #6 on: May 11, 2011, 12:00:08 PM »
DellNec,

I would NOT use the PVC pole for mounting.  I live in Las Vegas, NV and have the same type of roof
with the same PVC poles and they will not be able to take the stress of the anemometer and pole assembly.

As far as the cable goes, if you are able to protect it from the sun then go for it.  Otherwise I would not
worry too much about that.  My anemometer as well as other cables have been exposed to 300+ days of
desert sun/wind for years and I haven't had any issues.  Regular cable ties and unprotected white PVC pipe, well that
will go brittle on you real fast.  ;)
Larry
"But it's a DRY Heat!"


Offline DellNec

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Re: Placing Anemometer on Roof - Good or Bad Idea?
« Reply #7 on: May 13, 2011, 05:46:36 PM »
I think I will go back to the original location and mount it where my LaCrosse was. I will try and mount it a little higher. The roof is too much work and can become a lightening rod invite.

I might not get full wind speed due to some of the trees but if I needed full wind speed, I can check the airport weather station which is just 3 miles down the road. They monitor that stuff.

 

anything