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Dehumidifier Scheduling for 2.7m Fibreglass Observatory

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#1 Paul J

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Posted 14 September 2022 - 04:53 PM

Hi there I recently installed an EcoAir DD1 Mk5 dehumidifier in my Pulsar Observatory. Looking for recommendations for scheduling. I currently have the unit scheduled on between 05:00 and 09:00. I’m thinking that in addition to this I should probably have the unit running during the evening as well. Or… perhaps there are more optimal schedules?

I live in central Scotland.

Kind Regards

Paul.

#2 sharkmelley

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Posted 14 September 2022 - 05:02 PM

Does it allow you to set a target humidity level?  If so, set your required target level and leave it running 24/7.


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#3 R Botero

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Posted 15 September 2022 - 03:39 AM

Paul

 

I'm in south London and humidity is pretty high year round also (check the weather station link in my signature). 

I have my dehumidifier set to come on between 6AM and 9AM every day.  I have an RoR not a dome though.  I know that after all night imaging sessions, in autumn for example when it is particularly humid, everything is dripping wet in the early morning.  However, with the above schedule, I have never had any issues with my optics (four scopes inside the RoR), or any of the electronics (two scopes imaging with all sorts of cables and connections running through to them).  The timber has also held up well and I can see no signs of rot (observatory installed in 2014).   Make sure your dehumidifier has a way of letting the water it collects out through a pipe to the outside or similar (most do).  They collect A LOT of water.

 

Roberto



#4 ScottS

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Posted 15 September 2022 - 10:35 AM

Just a quick questions, dehumidifiers are mostly like A/C units except: 1) they are optimized to take moisture out of the air and 2) they don't use a coolant system to cool the air.  But, both units exhaust hot air correct? Are you having the hot air venting to the outside of your observatory or is it staying inside effectively increase the temperature inside your observatory?  I may have all this wrong. 

 

Clear Skies! 


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#5 archer1960

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Posted 15 September 2022 - 11:02 AM

Just a quick questions, dehumidifiers are mostly like A/C units except: 1) they are optimized to take moisture out of the air and 2) they don't use a coolant system to cool the air.  But, both units exhaust hot air correct? Are you having the hot air venting to the outside of your observatory or is it staying inside effectively increase the temperature inside your observatory?  I may have all this wrong. 

 

Clear Skies! 

If you vent the hot air outside, without also having an external intake for the cooling air, you end up pulling the humid ambient air into the dome to replace the exhaust.



#6 R Botero

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Posted 15 September 2022 - 12:04 PM

Just a quick questions, dehumidifiers are mostly like A/C units except: 1) they are optimized to take moisture out of the air and 2) they don't use a coolant system to cool the air.  But, both units exhaust hot air correct? Are you having the hot air venting to the outside of your observatory or is it staying inside effectively increase the temperature inside your observatory?  I may have all this wrong. 

 

Clear Skies! 

See the discussion here for example: https://www.cloudyni...prevent-fungus/  My dehumidifier is a simple rotating wheel with what I assume is desiccant inside, drawing moisture from the ambient air.  It does push warm air out into the space it is placed in, raising the dew point.  That's why I only run it in the morning after the night session, not before or during.  The only exhaust outside of my RoR is for water.   An A/C unit works differently in that it creates a temperature differential and has to exhaust hot air to the outside.

 

Roberto


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#7 Paul J

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Posted 15 September 2022 - 12:33 PM

Does it allow you to set a target humidity level? If so, set your required target level and leave it running 24/7.



#8 Paul J

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Posted 15 September 2022 - 12:38 PM

The unit strives to bring the RH down to between 50 and 60%, leaving the unit running is certainly one approach, however in these days of rising energy costs it’s perhaps not ideal. Having said this, once we get into the colder temps of winter it’s possible that this may be required.

#9 Paul J

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Posted 15 September 2022 - 12:38 PM

Paul

I'm in south London and humidity is pretty high year round also (check the weather station link in my signature).
I have my dehumidifier set to come on between 6AM and 9AM every day. I have an RoR not a dome though. I know that after all night imaging sessions, in autumn for example when it is particularly humid, everything is dripping wet in the early morning. However, with the above schedule, I have never had any issues with my optics (four scopes inside the RoR), or any of the electronics (two scopes imaging with all sorts of cables and connections running through to them). The timber has also held up well and I can see no signs of rot (observatory installed in 2014). Make sure your dehumidifier has a way of letting the water it collects out through a pipe to the outside or similar (most do). They collect A LOT of water.

Roberto



#10 Paul J

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Posted 15 September 2022 - 12:43 PM

Hi Roberto thanks for your feedback. The DD1 has a continuous drainage capability. The unit drains via a gland in the obsy wall to the outside.
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#11 Paul J

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Posted 15 September 2022 - 12:44 PM

See the discussion here for example: https://www.cloudyni...prevent-fungus/ My dehumidifier is a simple rotating wheel with what I assume is desiccant inside, drawing moisture from the ambient air. It does push warm air out into the space it is placed in, raising the dew point. That's why I only run it in the morning after the night session, not before or during. The only exhaust outside of my RoR is for water. An A/C unit works differently in that it creates a temperature differential and has to exhaust hot air to the outside.

Roberto



#12 Paul J

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Posted 15 September 2022 - 12:53 PM

The EcoAir DD1 is a dessicant type dehumidifier. The amount of warm air generated by the process is relatively minor compared to the volume of cooler air in the observatory. At most as Roberto states the warm air generated may assist in keeping the ambient temperature of the observatory slightly above the dew point. If the observatory were a sealed enclosure then cumulative temp increase might be an issue, however this is not the case with the Pulsar observatory design which incorporates more than adequate ventilation.

Edited by Paul J, 15 September 2022 - 12:56 PM.

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#13 Ihtegla Sar

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Posted 15 September 2022 - 01:02 PM

The EcoAir DD1 is a dessicant type dehumidifier. The amount of warm air generated by the process is relatively minor compared to the volume of cooler air in the observatory. At most as Roberto states the warm air generated may assist in keeping the ambient temperature of the observatory slightly above the dew point. If the observatory were a sealed enclosure then cumulative temp increase might be an issue, however this is not the case with the Pulsar observatory design which incorporates more than adequate ventilation.

I have a small dessicant dehumidifier in my observatory (8' exploradome on a 10 by 10' wood building) and I leave it running 24/7 set to keep the humidity at or below 55 RH. I am in the pacific northwest of the US, so a somewhat similar climate as Scotland.

If I had it set to only run certain hours of the day the RH would go above 60 the rest of the day. I keep humidity below RH 60 24/7 to prevent mold from growing. Given the value of the equipment I have stored, I am not concerned about the power bill. Dessicant dehumidifiers don't use much power as compares to AC.

Edited by Ihtegla Sar, 16 September 2022 - 11:19 AM.


#14 speedster

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Posted 15 September 2022 - 11:57 PM

Compressor dehumidifiers can remove a good deal more water per watt consumed but get less effective as the temp decreases.  At about 10C they are spending a lot of time defrosting and at about 5C they quit working.  If you have cold temps, dessicant is the only way to go.  There are inexpensive controls that sense temp and humidity and calculate dew point temp and operate a fan or relay based on an offset setting from dew point temp.



#15 Ihtegla Sar

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Posted 16 September 2022 - 12:07 AM

That's why I went with a dessicant dehumidifier. Where I live, temps drop to 5 C or lower at night nine months out of the year and even in the summer frequently drop to 10 C.

Edit: My dessicant dehumidifier came with built in controls to automatically shut off when RH is below a set level. I keep it at 55 to keep RH below 60 to prevent fungus. Dessicant dehumidifiers blow out slightly warmer than ambient air. I have the oscillating fan pointed in the direction of the scope to get good air circulation around it. We get a lot of wet rainy days and I have a valuable scope set up just waiting for clear skies. This setup gives me peace of mind that mold won't be able to grow on it. I turn off the dehumidifier when the scope is in use.

Edited by Ihtegla Sar, 16 September 2022 - 11:27 AM.



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