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High Humidity inside observatory and condensation (nexdome)

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#1 markm75c

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Posted 14 October 2019 - 10:07 AM

I'm plagued with high humidity and condensation every evening and morning in the dome.  Bay walls are moist, counterweight is wet in the AM if i dont cover tightly.

So far the fix on the counterweight at least does seem to be running a fan medium aimed at the pier (10" pvc filled with concrete).  But the levels in the dome are still peaking at 90%.  I've sealed off the floor areas and cracks on the walls on the outside mainly for prevention of moisture.

 

I have a toolbox storing things like an asi294mc and eyepieces, i havent measured the drawer humidity yet, but i'd have to assume that its the same as the rest of the area.

 

So at this point it feels like my options are use the fan and find some way to lower drawer humidity, or go the route of a dehumidifier (what happens to the exit tube in sub freezing temps), like this unit: https://www.amazon.c...0?ie=UTF8&psc=1  (the top of it only has about 1/2" clearance under my bay table though).  I might just try to get this solution working (and verify it really does work in the nexdome)

 

My small ceramic (750/1000 watt) heater does lower things pretty quickly, but would be too expensive and would create an imbalance in temps for spontaneous viewing sessions.

 

It was mentioned that the DD122FW Classic is another good choice/shorter and works in low temps, however that doesnt seem to be sold in the USA.

One person in the nexdome group seemed to say that they used 1/2" foam padding on all walls/ceiling and it worked, however, i tried just 6 2x2 squares "hung" not glued though, to the wall and no change was observed.

 

Thanks in advance for any suggestions



#2 TOMDEY

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Posted 14 October 2019 - 11:08 AM

Your building either needs to breathe or you will just have to run both a heater and dehumidifier, because the dehumidifier will ice up if it gets too cold in there.    Tom



#3 markm75c

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Posted 14 October 2019 - 11:23 AM

Your building either needs to breathe or you will just have to run both a heater and dehumidifier, because the dehumidifier will ice up if it gets too cold in there.    Tom

Yeah this is true, but i think some run them at lower temps, as there isnt much humidity when it gets supercold, but some also run the heater to keep things above a certain point, but that could get real expensive depending on what the heat source is.

 

Someone said that this worked well in a 7 foot dome, but at only 25 oz in 24 hours, unsure:

https://www.eva-dry....IVD6PuCVEHgwJxM



#4 Couder

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Posted 14 October 2019 - 11:30 AM

We live in the Missouri Ozarks on a slope in a valley, it gets plenty moist here. I had the same problem in the observatory, and in the machine and woodworking shops. I put ceiling fans in all 3 places. They don't cost much to run, I leave them on 24/7. This stopped the rust film from developing on everything. Doesn't change the temperature either.



#5 markm75c

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Posted 14 October 2019 - 11:48 AM

We live in the Missouri Ozarks on a slope in a valley, it gets plenty moist here. I had the same problem in the observatory, and in the machine and woodworking shops. I put ceiling fans in all 3 places. They don't cost much to run, I leave them on 24/7. This stopped the rust film from developing on everything. Doesn't change the temperature either.

The fan i tested did stop the moisture on the pier, but not in bays and probably not in the tool chest where all the equipment is (humidity levels still peak at 93%).



#6 John Fitzgerald

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Posted 14 October 2019 - 11:53 AM

Yeah this is true, but i think some run them at lower temps, as there isnt much humidity when it gets supercold, but some also run the heater to keep things above a certain point, but that could get real expensive depending on what the heat source is.

 

Someone said that this worked well in a 7 foot dome, but at only 25 oz in 24 hours, unsure:

https://www.eva-dry....IVD6PuCVEHgwJxM

Your floor is wet.  New treated wood is wet.  It needs to have a dry floor placed over that, even if you have to give up height.  That's one of the main causes of your moisture problem, IMO.  Also, your new concrete pier is still giving off moisture.


Edited by John Fitzgerald, 14 October 2019 - 11:53 AM.


#7 markm75c

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Posted 14 October 2019 - 12:11 PM

Your floor is wet.  New treated wood is wet.  It needs to have a dry floor placed over that, even if you have to give up height.  That's one of the main causes of your moisture problem, IMO.  Also, your new concrete pier is still giving off moisture.

I guess the eva foam flooring isnt sealing off the wood as much as it should.

 

That would certainly explain a lot of it.



#8 John Fitzgerald

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Posted 14 October 2019 - 12:32 PM

I have to state fact here.  To be mean or condescending is not my intent at all.   

 

Your observatory was placed directly on a flat deck that is larger than the building.  That is never a good plan. 

 

The ultimate cure for your problem is to raise the dome a bit and put in a raised floor that is very slightly smaller than the outside of the dome.  I would cut some 1.5 inch thick treated wood from 2x6 or 2x8 or so lumber, and form a ring along the outside for the dome to sit on, just barely inside the perimeter, then build a (treated) grid for a floor, and make a 3/4 inch treated plywood floor on top of the grid.  Before you put that floor down, rip out some of the caulk between the deck boards along the edges inside to allow for drainage.  This plan would would entail raising the dome 1.5 inches above the existing deck, and making the floor only 3/4 inch higher than it now is in relation to the dome.  To keep the pier the same height as it is now, in relation to the floor, you would need to somehow raise it 2-1/4 inches with a spacer on top.

 

It's wood moisture, ground moisture, and moisture still coming out of the pier as it cures that is causing the problem.  The ground moisture and wood moisture problems will never go away as things are right now.  The moisture from rains,  and especially, snow, will continue to wick inside through the grain of those deck boards.



#9 TOMDEY

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Posted 14 October 2019 - 12:33 PM

The advantage to plain vanilla internal fans is that they DO put some heat into the enclosure... exactly equal to the power consumption of the fan! If it's drawing 50 watts, then it is also putting 50 watts of heat into the interior. This applies only to fans that are completely inside... not exhaust or positive pressure fans! Depending on the insulating properties of the building, you may not notice that the temperature has stabilized at a degree or two above ~what it would have been~, but that is usually enough to keep the interior above the dew point!  And the building does need to ~breathe~ just a bit. Hermetically sealed is not good, unless you have a complete climate-control system running constantly.  Tom



#10 TOMDEY

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Posted 14 October 2019 - 12:42 PM

I guess the eva foam flooring isnt sealing off the wood as much as it should.

 

That would certainly explain a lot of it.

Related observation --- some carpeting acts as a giant moisture sink --- hundreds/thousands of square feet of wick (affinity to H2O). Once that adsorbs many liters of water from the air... changing conditions can waft that back into the air and onto all your stuff. The telltale sign of such problem is... for the first few weeks or months... everything is fine... Then (as the initially bone dry carpet saturates) it blesses the interior with all that water it has adsorbed for so long... and a funny smell greets you each time you go in. It's the musty mudroom syndrome.   Tom


Edited by TOMDEY, 14 October 2019 - 12:45 PM.


#11 markm75c

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Posted 14 October 2019 - 12:53 PM

Related observation --- some carpeting acts as a giant moisture sink --- hundreds/thousands of square feet of wick (affinity to H2O). Once that adsorbs many liters of water from the air... changing conditions can waft that back into the air and onto all your stuff. The telltale sign of such problem is... for the first few weeks or months... everything is fine... Then (as the initially bone dry carpet saturates) it blesses the interior with all that water it has adsorbed for so long... and a funny smell greets you each time you go in. It's the musty mudroom syndrome.   Tom

I guess ill find out on that, maybe later even up doing the raised dome idea.

 

The lid of the dome is not sealed, plenty of air flow there, you can feel it on the colder nights.

 

In terms of the foam, technically they are supposed to be waterproof and not absorb water, but flow under if any gets in (tested with a some on one panel, seems to be the case), but i guess ill notice it if it gets musty later.

 

ill probably try the eva 2400 unit for now, just see if i can get the actual levels under 65%, ill just send the tube down through the floor inside the bay (small hole).

 

I may still keep the fan for further pushing of the air.

 

This unit is smaller than the first one i linked, it would be my secondary test unit: 

https://www.amazon.c...0?ie=UTF8&psc=1

 

Then yes there could be the issue of needing to heat things to prevent freezing, or maybe not.




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