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ELA DD822 Rotary Desiccant Dehumidifier

Psychobilly

By Psychobilly
in Member Equipment Reviews

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Psychobilly

Psychobilly

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Having had a near miss with the scopes in the Observatory which meant I had to strip and clean the optics in the CPC800 and Megrez72 I decide it was time to look at getting a dehumidifier for the observatory...

A thread was running about Dehumidifiers for Observatories and I took the advice there and spoke to Roger at Dry-It-Out to see what he would recommend...

For outdoor year round use you really need a Rotary Desiccant Type these are more expensive than the basic Refrigerant based units but work down to 0C ...

So I purchased the ELA DD822

ELA DD822 Dehumidifier & Laundry Drier | Laundry Driers | Dehumidifiers

Anyway ...

The unit is installed in the obs with the permanent drain hose run out through an angled hole in the obs wall and base...

I also decided that I would invest in a stand alone Temperature/Humidity/Dew point data logger (Lascar EL-USB-2) to check the performance of the unit and give me data that I could integrate with the data from the weather station that I also run at home...

To keep the house finances square I also added an energy meter to monitor the electricity used in the Observatory...

I ran the unit at full capacity for 24 hours to pull the humidity down it started at 90% and after 24 hours it was down to 22% (not logged but according to the temp/humidity display i have in there)

I then set the Humidistat to 40% RH with the fan on low which cost 46p for 24 hours running...

Here is the logged result

Graigola%20Observatory%2040%20RH%20Test.jpg

and here's the plotted data from the Weather Station...

Graigola%20Observatory%2040%20RH%20Test%20Outdoor.jpg

So it looks like the humidifier is also keeping the observatory temp about 6-8C higher than ambient whilst its running ..

I am now running it at 50% RH for 24 hours before setting it to the 60% RH level recommended by Roger at Dry-it-Out...

I am so pleased with the unit I have bought another for use in the House and Garage Workshop as required...

I will add pics etc over the weekend and also add data for the 50% and 60% 24 hour runs when it becomes available...

Billy....

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Helen

Helen

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I've been away for a few days and have just been out to empty the tank in mine. I need to get the drill out... It certainly feels drier out there though, so like you, Peter, I think money well spent!

Helen

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  • 2 weeks later...
Psychobilly

Psychobilly

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Just a few more graphs....

The first one shows how quickly the RH rose in the obs following a Power outage - I forgot to reset the RCCD feeding the Obs...

ELA%20DD-822%2060RH%20LOW%20MAINS%20TRIP.jpg

And the second one how its been "controlled" over whats been a rather dismal few days...

ELA%20DD-822%2060RH%20LOW.jpg

and finally the Outdoor RH Temp and dewpoint...

Outdoor%20RH%20temp%20Dewpoint.jpg

Billy...

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opticalpath

opticalpath

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That data logger is impressive - very informative. It shows just how effective these units are at stabilising the humidity. I feel a lot happier now leaving all that expensive gear in the shed.

To keep just an approximate check on things, I got a cheap max-min thermometer/ hygrometer, widely available, such as from here:

Digital THERMOMETER HYGROMETER MIN/MAX Humidity meter on eBay (end time 26-Jan-11 19:08:39 GMT)

The slight heating is due to the warm air that is passed over the desiccant disk to regenerate it. Not sure if it's heating all the time, though; possibly not when it has reached target humidity and the fan is just operating in 'air-sampling' mode.

Like others, I soon got fed up emptying the tank and drilled the hole the other day!

Adrian

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  • 2 years later...
opticalpath

opticalpath

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Nice graphs, though looks like you got no observing time in over this week!

 

Just a query - I follow the idea that the dessicant is heated to remove water, but does it have a finite life and require replacement?

Don't think it ever needs replacing. AFAIK, the only maintenance required is to clean the filter panel occasionally.

<< The important thing is to power them down using the button on the unit rather than at the mains.. this keeps the disc rotating as it and the oven cool down...>>

 

Ah, so that's the reason you shouldn't switch it on and off on a timer ...... I wondered why that was warned against. Presumably that would risk damaging the disk

 

Adrian

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Psychobilly

Psychobilly

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The only things to watch when they are used in the obs over the winter is that if temperature drops around or below  freezing that you check that the small bore  drain hose doesn't freeze up.

If it does the water will back fill into the tank in the unit and the unit will stop working when the tank is full... I used to use a thermostatic greenhouse "frost" heater  set at abou 4 degrees in the obs at the same time as the de-humidifier...

You wouldn't want the tank freezing and cracking...

Peter...

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opticalpath

opticalpath

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The only things to watch when they are used in the obs over the winter is that if temperature drops around or below  freezing that you check that the small bore  drain hose doesn't freeze up.

 

If it does the water will back fill into the tank in the unit and the unit will stop working when the tank is full... I used to use a thermostatic greenhouse "frost" heater  set at abou 4 degrees in the obs at the same time as the de-humidifier...

 

You wouldn't want the tank freezing and cracking...

 

Peter...

Hmm, good point .... never thought of that. Maybe some lagging on the indoor section of the hose? The outside section after it exits the shed is tricky though.

Adrian

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opticalpath

opticalpath

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I had my drain  freeze up once... 

 

Maybe install a larger diameter pipe with decent fall through the wall of the obs  for the external drain and keep the smaller stuff inside the obs...

 

Peter...

Yep, makes sense. The outlet from the dehumidifier is quite low and already I can see some standing water in the hose where it dips a bit. Time to raise the unit on to a low platform to get a better fall.

Good tip - thanks.

Adrian

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Helen

Helen

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I've put mine on what my little niece calls a 'stepper-upper' to increase the fall for the pipe which goes through the obs wall.  It is important to avoid kinks (although if it does get blocked at least there's a cut off when the tray gets full.

Helen

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