Davis 24hr fars the differance replacing the batteries makes

[The PIT]

I have noticed before that when the fan stops spinning it can make a big difference in recorded temperature.

Today early on I changed the batteries I noticed there was a big difference between the actual temperature (Stephenson Screen) and what the sensor was saying. Both units are side by side.

I swapped the batteries in the shade you guess from the time when I changed them over.

[reef]

I run mine 24/7 with a 12v DC fan powered from the mains for this very reason. 

The Davis 24hrs FARS shield is exceptional but does not perform well when the fan isn't running. In that situation it shows a big temperature lag and actually performs worse than the non-aspirated shield.

[DaveL]

That's one of the things that put me off getting a 24h FARS so I opted for a DFARS in the end, which retains open slats all around it and performs quite well when the fan is off. In certain conditions, I suspect that it performs better with the fan off, though I can't prove it - but the throughput of air seems to be quite low when it's running so that may be an issue.

[The PIT]

Sometimes I wonder if it's just worth putting the sensors in the Stephenson screen.

[The PIT]

19 hours ago, reef said:

I run mine 24/7 with a 12v DC fan powered from the mains for this very reason. 

The Davis 24hrs FARS shield is exceptional but does not perform well when the fan isn't running. In that situation it shows a big temperature lag and actually performs worse than the non-aspirated shield.

What fan do you use?

[reef]

It's a drum fan from a Xerox photocopier. It sits right in with a couple of cable ties. I run it at 9v as it produces enough flow at that voltage and it will prolong its life. It's been going 24/7 for 4 years so its reliable too.

[The PIT]

Is this the fan

Xerox Drum Cooling Fan Phaser 8560 AD0912US-A71GL 127E16010 for sale online

WWW.EBAY.COM

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Find many great new & used options and get the best deals for Xerox Drum Cooling Fan Phaser 8560 AD0912US-A71GL 127E16010 at the best online prices at...

 

[reef]

That's the type of fan yes, but you'll want the version that blows in the other direction as the fan housing then sits nicely in the ISS chamber and the flat side seals the gaps.

127E16890 - Xerox 8570 Drum Cooling Fan Item Inc.

WWW.ITEMINCONLINE.COM

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127E16890 - Xerox 8570 Drum Cooling Fan

It will then connect nicely with  scotch lock connectors to a 2 wire cable and 12v DC adaptor.

[The PIT]

Mmmm interesting. What I'm going to do is mount the batteries outside the fars so it's simple task of unscrewing the cover and then swapping them out.

[reef]

A picture of the fan sitting in the ISS. A few cable ties and it fits nicely. The yellow cable can be snipped as its for RPM monitoring:

[4wd]

On 20/01/2020 at 00:59, DaveL said:

That's one of the things that put me off getting a 24h FARS so I opted for a DFARS in the end, which retains open slats all around it and performs quite well when the fan is off. In certain conditions, I suspect that it performs better with the fan off, though I can't prove it - but the throughput of air seems to be quite low when it's running so that may be an issue.

I did get that set-up for mine but the fan seemed to seize up after a couple of years, they aren't cheap so don't intend replacing - the fan itself isn't too bad but no telling if something else hasn't stopped too.