Author Topic: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)  (Read 662 times)

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Offline Kipa

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Hi all.  Great forum.  I've learned a lot by reading through the threads here.  One question I can't find much on is how to make a decision on whether I need to get a fan or not.  Weather station is for the Seattle area.  Temperatures are mild compared to most of you, although it will be in full sun 100% of the time.  It seems to be a failure-prone part, and I could save myself $ and maint. hassle by skipping it, if accuracy won't take too much of a hit.  Any opinions?

Kipa

Offline CW2274

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #1 on: July 13, 2018, 05:53:38 PM »
One question I can't find much on is how to make a decision on whether I need to get a fan or not. 
Kipa
Howdy. Need too? No. However if you want greater accuracy during light or no wind conditions, a fan is a must. Davis themselves quote as much as a 4F difference between aspirated and passive in calm wind.

Offline Old Tele man

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #2 on: July 13, 2018, 07:36:30 PM »
Hi all.  Great forum.  I've learned a lot by reading through the threads here.  One question I can't find much on is how to make a decision on whether I need to get a fan or not.  Weather station is for the Seattle area.  Temperatures are mild compared to most of you, although it will be in full sun 100% of the time.  It seems to be a failure-prone part, and I could save myself $ and maint. hassle by skipping it, if accuracy won't take too much of a hit.  Any opinions?

Kipa
If where you're at (PNW = Pacific Northwest?) it gets HOT or has LOTs of sunshine, then a FARS is recommended to mitigate "solar heating."
« Last Edit: July 25, 2018, 09:08:17 AM by Old Tele man »
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Offline galfert

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #3 on: July 13, 2018, 09:38:54 PM »
Since you are in Seattle the number of hot sunny with no wind days are probably few. Your call how accurate you want it to be those 3 days of the year when there is no wind in Seattle and it is hot and sunny.

Now if you get the one without FARS and you mount the ISS on the roof then you are asking for trouble. Shouldn't be on the roof even with a FARS but if that was your only mounting option then you need the FARS.

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Offline CW2274

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #4 on: July 13, 2018, 10:08:38 PM »
Now if you get the one without FARS and you mount the ISS on the roof then you are asking for trouble. Shouldn't be on the roof even with a FARS but if that was your only mounting option then you need the FARS.
Not sure where the roof came into play, but you're right about it being a bad siting place, in most cases. However, be certain of one thing, FARS will do nothing to correct a bad siting, roof or otherwise. All a FARS will do is show the error of the siting faster and more accurately. 

Offline dport

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #5 on: July 13, 2018, 10:30:06 PM »
Hi all.  Great forum.  I've learned a lot by reading through the threads here.  One question I can't find much on is how to make a decision on whether I need to get a fan or not.  Weather station is for the Seattle area.  Temperatures are mild compared to most of you, although it will be in full sun 100% of the time.  It seems to be a failure-prone part, and I could save myself $ and maint. hassle by skipping it, if accuracy won't take too much of a hit.  Any opinions?

Kipa

I used to live in Seattle.  You know as well as I do that June through early September you have sunny and long days.  That said, think about your micro climate.  Are you on the sound in west Seattle? Lakefront? Then it might be windy enough where FARS would have little impact.  If not, and you're landlocked in beacon hill then you might need it. 

I would think more about wind flow than temperatures.

Offline CW2274

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #6 on: July 13, 2018, 10:35:15 PM »
Hi all.  Great forum.  I've learned a lot by reading through the threads here.  One question I can't find much on is how to make a decision on whether I need to get a fan or not.  Weather station is for the Seattle area.  Temperatures are mild compared to most of you, although it will be in full sun 100% of the time.  It seems to be a failure-prone part, and I could save myself $ and maint. hassle by skipping it, if accuracy won't take too much of a hit.  Any opinions?

Kipa
I would think more about wind flow than temperatures.
=D>

Offline SnowHiker

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #7 on: July 14, 2018, 12:44:26 AM »
Also keep in mind that when the fan does fail your readings will be less accurate than a passive shield.  Though as I remember one member here who considers a FARS almost an absolute necessity didn't seem to notice for some time when one of his FARS failed.  Now there's discussion on another thread about how the New Improved Temp/Hum sensor may need to be replaced up to a couple of times a year when used in humid environments with FARS.  Even without FARS the replacement rate appears not to be acceptable, as I understand it, but FARS is suspected to greatly aggravate the problem.

So FARS will increase cost and maintenance and, depending on your situation and view, either marginally or greatly increase the accuracy of your station, assuming you you replace the FARS components before they fail and the sensor when it starts to drift out of spec, otherwise you may be worse off with the FARS.

You may want a FARS if you see the need to have highly accurate readings for important scientific studies that you're doing as a professional meteorologist or something.  If you just want to know what the weather is like in your backyard, you may not need one.

Personally, I see siting as far more important, as CW2274 has said.  I think probably relatively few home weather stations are properly sited, and I think it would be better to stress the need for that over FARS.

Offline Kipa

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #8 on: July 15, 2018, 08:20:58 PM »
Very helpful, thank you. We live near the sound and it's almost always breezy here.

Thanks everyone else as well - good info to think about.

Kipa


I used to live in Seattle.  You know as well as I do that June through early September you have sunny and long days.  That said, think about your micro climate.  Are you on the sound in west Seattle? Lakefront? Then it might be windy enough where FARS would have little impact.  If not, and you're landlocked in beacon hill then you might need it. 

I would think more about wind flow than temperatures.

Offline dsscheibe

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #9 on: July 25, 2018, 02:57:52 AM »
I live in Phoenix and have the solar shield with a solar powered fan,  I think the fan has now died, it was making noise and has stopped.. I have not noticed any significant heating problem, mine runs lower than several around Phoenix. It sits in full sun on the south side of my house.
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Offline galfert

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #10 on: July 25, 2018, 06:44:16 AM »
I live in Phoenix and have the solar shield with a solar powered fan,  I think the fan has now died, it was making noise and has stopped.. I have not noticed any significant heating problem, mine runs lower than several around Phoenix. It sits in full sun on the south side of my house.


How long did you fan last before it died? Like till you started hearing the noise? Years hopefully.
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Offline Old Tele man

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #11 on: July 25, 2018, 08:58:19 AM »
I live in Phoenix and have the solar shield with a solar powered fan,  I think the fan has now died, it was making noise and has stopped.. I have not noticed any significant heating problem, mine runs lower than several around Phoenix. It sits in full sun on the south side of my house.


How long did you fan last before it died? Like till you started hearing the noise? Years hopefully.
Down here in Tucson, my original VP2 FARS fan lasted three years, but subsequent replacements only seem to last about one year, usually failing during hottest summer day.
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Offline Aardvark

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #12 on: July 25, 2018, 09:03:49 AM »
NEED THE FAN?   No.
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Offline SnowHiker

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #13 on: July 25, 2018, 12:12:11 PM »
I live in Phoenix and have the solar shield with a solar powered fan,  I think the fan has now died, it was making noise and has stopped.. I have not noticed any significant heating problem, mine runs lower than several around Phoenix. It sits in full sun on the south side of my house.
Hmmm, I'm not sure where I got the idea that the FARS shield with a dead fan was worse than a passive shield, it seems I had heard that somewhere.  Thinking about it, I'm not sure why it would be as long as the air flow is at least as good as the passive without the fan running.

Still, for the sake of consistency, I would rather have a station that is either passive 100% of the time, or fan aspirated 100% of the time.

Offline redlynr

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #14 on: July 25, 2018, 05:55:35 PM »
my 6153 24-hour aspiration should arrive tomorrow.  I’ve already read the manual and there are three choices:

use 2 batteries for 24 hour aspiration and low daytime aspiration.  Or 1 battery for increased daytime aspiration, and nighttime will last as long as it can. Or zero batteries for maximum daytime aspiration and zero nighttime.

I’m thinking of using 1 battery since I don’t expect much solar radiation in the wee hours of the morning.

Offline CW2274

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #15 on: July 25, 2018, 06:15:17 PM »
I live in Phoenix and have the solar shield with a solar powered fan,  I think the fan has now died, it was making noise and has stopped.. I have not noticed any significant heating problem, mine runs lower than several around Phoenix. It sits in full sun on the south side of my house.
Hmmm, I'm not sure where I got the idea that the FARS shield with a dead fan was worse than a passive shield, it seems I had heard that somewhere. 
In the case of a 24hr VP2, this is indeed correct. The radiation shield is specifically designed to be aspirated as the sensor chamber is completely shielded from outside air except for the inlet at the bottom and the outlet up top. It will work, marginally, but you'd need a pretty stiff breeze.
« Last Edit: July 25, 2018, 07:00:50 PM by CW2274 »

Offline SnowHiker

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Re: Buying new Davis Pro2 Plus - do I need the fan (6163 vs 6162)
« Reply #16 on: July 25, 2018, 09:43:56 PM »

In the case of a 24hr VP2, this is indeed correct. The radiation shield is specifically designed to be aspirated as the sensor chamber is completely shielded from outside air except for the inlet at the bottom and the outlet up top. It will work, marginally, but you'd need a pretty stiff breeze.
Thanks for the verification.

 

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