Observatory Dehumidifier

[MarkS]

Does anyone use a dehumidifier in their observatory?

I bought a good one in Screwfix yesterday and it works very effectively - filling its 4 litre bucket overnight (I haven't fitted the permanent drain hose option yet).  It gives a digital readout of the humidity level, which hasn't gone below 70% yet, when it was 93% outside. It has already made a big difference because the glass door of the beer fridge is no longer dewed up and dripping on the floor.

However, the problem is that with my roll off roof design, there is plenty of ventilation and draughts coming through, especially with the wind, so the air will never become dry. I'd like to achieve around 55%.  It also means the dehumidifier is constantly working very hard which consumes electricity and shortens its life. 

So I'm thinking of making some flaps that hinge down from the roof and seal against the inside wall to prevent those draughts.

Any other thoughts?

Mark

[MarkH]

Mark if it's any help at work we use a dehumidifier, we originally used the bucket but found it much more efficient to use a hose and dispose of the water remotely on a continuous basis.

[mickw]

I'm guessing you would only need drop down flap at the front because the sides already overhang, it should flip up as the roof rolls back if you radius the angle iron at end and drop down under it's own weight.
The flap may also stop wind getting under the roof - which is a good thing.

You've also got the gap around the pier which will let the coldest dampest air in.  Some expanding foam should do the trick, the normal high expansion stuff should do the trick (bigger/more bubbles) without causing a vibration path between floor and pier.

Unfortunately the minute you open the roof, all the damp air gets in but at least you will help to dry it out between sessions.

What model A/C did you get ?

[MarkS]

What model A/C did you get ?

This one:
http://www.screwfix.com/p/16ltr-dehumidifier/49718

I've covered some of the more obvious gaps and this has already made a big difference - it's now getting down to 55% relative humidity and switching off.  The gap between floor and pier I taped over - a temporary solution but effective.

Mark

[Carole]

I use the Dry it Out dehumidifier, the chap that sells them is an imager himself and gives a really good follow up service.  Some dehumidifiers are not supposed to be used under 5 degrees (like the first one I bought), and this one does.  I have it on continuous drainage most of the winter and it does an excellent job. 

Carole

[MarkS]

Some dehumidifiers are not supposed to be used under 5 degrees

The instructions for mine says not to use under 5C.  In such cases I might heat the air.

Mark

[mickw]

I'm guessing you would only need drop down flap at the front because the sides already overhang, it should flip up as the roof rolls back if you radius the angle iron at end and drop down under it's own weight

.

Oops, I was thinking of flaps on the outside

Aircons do actually put out a small amount of heat - not a lot

[MarkS]

Carole, what type of dehmidifier is yours? Is it the dessicant type or the compressor type?  Mine is a compressor and it's becoming quickly apparent that it is not very effective once the temperature drops below 8C or so.

Now I have read a bit more about them, it would appear that the dessicant type is far more effective at low temperatures and is therefore better for outbuildings.  Even though they have a higher power rating e.g. 600W instead of 250W it is claimed they can actually save money in cooler temperatures by being on a lot less. 

Mark

[Carole]

It's this one Mark, the dark one on the left which seems to be reduced at the moment:
It's dessicant.

http://www.dry-it-out.com/dehumidifiers/observatories

[RobertM]

Do you plan to use it all the time or when needed (however that is interpreted) or on a timer ?  I had heard continuous running can be quite expensive (as in several times the purchase price per year).

Robert