Rosahl dehumidifiers.

[JollyJohn]

I struggle with keeping the humidity down in my curing chamber, never have the opposite problem, so started to look around for a reasonably sized, reasonably priced dehumidifier. Don’t want to mess about with having to replace sachets, or “recharge” devices, so has to be controllable , using my DHC100, and just need emptying as necessary. The choice seems very limited, 30-50 quid gets you a small, cheap and nasty job that will probably last a year if you’re lucky, according to buyers ratings.

Whilst looking around on ‘tinternet, I came across these devices:

http://www.rosahl.co.uk/

They seem to be the ideal solution. They don’t take up any space, don’t need emptying, no moving parts, life span of ten years (after which, they deteriorate by only a few % per year), low voltage supply (3v), and extremely low running cost. Looks very easy to install, and the only thing I would have to provide, is a stabilised 3v supply, no prob.

I’ve been in touch with them, asking for prices and suppliers, received the following reply:

“Hello Mr Barker
These products are available from Westside International who are based in the UK. www.westside-int.com
The unit price for MDL3 is 105.00Euro, and for MDL5 185.00Euro. Shipment is generally from stock but prices do not include delivery and local taxes, clearance charges and so on. However, for individual units we would normally air-post at the prices shown.
We are currently looking at making the products available on eBay if this would help.”

The MDL3 will be fine in a cabinet up to half a cubic meter, I’ve just measured mine, and it’s only 0.15 of a cubic meter (0.48W x 0.43D x 0.75H), so should be plenty big enough. It would be ok in a larger cabinet at a later date. At 105 euros it initially sounds expensive, but it’s no more than the cost of a couple of the cheapo dehumidifiers.

Before I buy and try one, can anyone point out any glaring mistake in my thinking?

John.

[manfran]

what with the no emptying and general efficiency, I'm not entirely certain as to how it works. I think if we just put it down to magic, then I'm prepared to accept it!

The only thing I would mention (and I probably havent read the website very carefully), but is it just a question of it being on or off?
If so, unless you hook it up to a timeswitch or some kind of humidity sensor switch, are you in danger of just heading towards really low humidity. Whereas for drying, you do actually want some decent level of humidity.

I'm sure you've thought of this, but thought I'd mention it anyway!

[onewheeler]

The devices don't appear from the specs to have a large water extraction capability, they're designed for nominally sealed cabinets. Reading between the lines the MDL3 might only be taking out a gramme or so per day (it takes half days to extract the moisture from a 50 l enclosure which would, at 90% humidity / 15 C, contain very roughly half a gramme of water). If you're drying a few kilos of sausage this means that the device would need a lot of assistance from the water extraction of the refrigeration unit.

Unless I've done the sums wrong!

Interesting though...

Martin/

[Yannis]

Very interesting indeed !!

However I agree with Martin that these models are not capable to remove humidity from a chamber loaded with meat as can be seen at performance chart.



If I understand correctly for mounting this unit you should open a big hole to the chamber so dehumidifying side is inside and moisture discharging side is outside http://www.rosahl.co.uk/rosahl/how-does-rosahl-work/

I had the same problem and I connected dehumidifying output to refrigerator in parallel with cooling output. When RH (or Temperature) is high then refrigerator is turned on to condense moisture. If this causes temperature to drop below threshold then heater turns on to compensate. Since you have a humidity controller you could give it a try paying attention to avoid short circuit in paralleling the two outputs and maybe using a delay on break timer to protect compressor.

[onewheeler]

Although much less sophisticated than Yannis's kit, I also control humidity by adding some heat to kick the refrigerator into cooling, which will take moisture out.

The heat comes from a short length of trace heating tape. Ideally (i.e. when I get around to it) it would be nice to adjust the heat output to something like 10, 20 or 30 watts to suit the prevailing ambient temperatures. When it's fairly mild (as it is now - ambient is around the temperature I'm controlling to) there's too much heat going in (25 W), so the 'fridge operates too frequently and the RH is too low.

Cheers!

[JollyJohn]

Hmmm...extraction rate does seem to be the problem.

[saucisson]

Can this be used for home environment to reduce humidity?
Thanks for your question, Unfortunately ROSAHL is not suitable for the application you have in mind as its moisture extraction rate is too low.
It is designed to protect equipment in closed cabinets.

So it's great for keeping dry things like gun powder from getting damp ? but not for what we would want?