Need a small desiccant drum dehumidifier for my workshop

[Gazz292]

My workshop is a wooden shed, 6 meters long by 2.5 meters wide, 2.3 meters tall, split into 2 sections (2.5 and 3.5 meters) with a sliding door and 15mm ply partition wall.
It's insulated on all sides, floor and ceiling with 50mm EPS (polystyrene slabs)

Door and window are upvc double glazed jobbies, it's totally water tight and i have 6 hit and miss type vents, these i can close off in winter, which i have done but left them cracked open a tiny bit... wondering if i should have these open, or totally close them and tape them up?

I have a frost heater in each part of the shed, the small side has a 60 watt tubular heater, and the main side has a 120 watt one... which the person who pays the electric bill is moaning about because they think frost heaters should be 30 watts max, they are thermostatic and i have the thermostat set on min, so they only come on in the night.

The logging thermometer in there shows that the min temp inside so far has been 3 degrees C, whilst outside has been minus 4 so the frost heaters are doing their job, there's a 2KW fan heater to bring the temp up when i go in there.

It seems that it just wants to sit at ~75% humidity tho, i'm near the coast in the Scarborough area, so it's wet here a lot, today is the first day it hasn't been drizzling for well over 2 weeks.


i have a compressor type dehumidifier, but that's useless at these temps, the coils just freeze up, then it pee's water everywhere when they defrost.

So i think i need a desiccant drum type dehumidifier, and ideally one i can pipe the drain outside on so it's fit and forget.
They all seem to boast that they are good for a 4 bedroom house and all that, and thus pull 100+ watts all the time.

Searching for shed or even caravan dehumidifiers seem to show those plastic boxes with a handful of desiccant granules in them.

I've figured i'll have to pay £100+ for one, but i really want a small one that i can either wall mount or sit under a bench, and be sized for a small area.

Do they exist?
Or is it usual chinese style marketing, and one for a 4 bed house really means it'll just about work for a small shed.

[awemawson]

The desicant types I've come across are all based on Silica Gel and to re-genrerate the silica gel needs  cooking at about 120 C for a few hours so can't be drained outside.

See this thread of mine from a few years back - but airline only not the whole workshop !

http://www.madmodder.net/index.php/topic,11936.0.html

[howsitwork?]

I use an EBAC  one. it’s like a fridge in reverse so the coils freeze up , then thaw to remove the water  into a bucket or it’s built in collector. It works well AND actually warms the shop a bit in the heating phase of the cycle .

[tom osselton]

I use a DryStream 

[PekkaNF]

I use a DryStream

Is't that a bit expensive kit to keep workshop interior slightly less humid?

[tom osselton]

This is so the waranty is covered. Apparently the pellets are not good enough.

 

[Gazz292]

I went for an 'EcoAir DD1' desiccant wheel type dehumidifier,  £150 off amazon.

shed / workshop was sitting at ~79% humidity, i put it in on it's high setting and the humidistat about half way round the dial, and a day later humidity was at about 59%, emptied it's tank 3 times that day.

I then turned it to it's low setting, humidistat wound slightly farther round,  and over the next 2 to 3 days it got the humidity to 50% in there...
read with multiple humidity meters at opposite ends of the workshop... one is a logging thermostat and humidity meter that reads outside and inside temps... hence i know how cold it gets in and out of the workshop over night... inside no lower than 3 degrees C before the dehumidifier due to the 2 tubular frost heaters in use,
 
Now the humidity is under control, the dehumidifier just sits there coming on when it gets upto about 55, and bringing it back down to 50 fairly fast, and the catch tank takes about 2 weeks to fill now.

As the dehumidifier has a heater in it to dry the desiccant wheel and release the moisture it's absorbed, the air blowing from it is warm (a lot warmer than from the refrigerant type i had before) so that adds to the interior temp a little, and now it averages 5 degrees C inside over night when the dehumidifier is running, how much the tubular heaters come on now i don't know, but it's been averaging -4 outside lately.


It pulls about 250 watts when running, that is a sharp increase over the ~ 40 watts for my old refrigerant based dehumidifier, but that one was no use as it's heat exchanger coils just froze up all the time in this cold weather, it got so bad at one point the metal case was bulged outwards from the ice build up!  and when i shut it off to let it defrost, it pee'd most of that melting ice water all over the floor.

[awemawson]

Come and try it in my foundry  building where the humidity has sat at 98% for about a week 

(Mind you nothing stands a chance there as there is a LOT of ventilation to outside and we are on the brink of flooding again