Returning with a Wet Car

[Howard Wright]

Hi All

Interesting discussion.

How well sealed does the storage have to be for a dehumidifier to work?  Probably a "how long is a piece of string" type question.  

My double garage has an "up and over" door with about 1" gap across the bottom and daylight visible around the edges.  Is it worth trying a dehumidifier or am I just trying to stop it raining in Wales?

Cheers

Howard

[Bruce Nicholls]

Hi All

Interesting discussion.

How well sealed does the storage have to be for a dehumidifier to work?  Probably a "how long is a piece of string" type question.  

My double garage has an "up and over" door with about 1" gap across the bottom and daylight visible around the edges.  Is it worth trying a dehumidifier or am I just trying to stop it raining in Wales?

Cheers

Howard

I would go to Screwfix, toolstation or similar and buy some brush type draught excluder strips. Put them round the door openings and you should be fine.

[Peter Naulls]

Peter,
Twenty plus years ago I sold, amongst other things, dehums for a living. The company I worked for sold mostly refrigerant based dehums, but from time to time an application for desiccant units would arise. We sold to domestic, industrial and process applications and had a very good hire trade to the construction industry and flood restoration applications. A study and trial we carried out at the Rover factory in Oxford, was to prevent raw steel stock rusting in the former KD warehouse, it was a success but the big saving was in turning the heating off (which was unacceptable to the warehouse staff). This can be achieved if the humidity is kept below 45%. In cold conditions the amount of water vapour in the atmosphere at a given humidity is less than at the same humidity % when warm. The result is that a dehum will produce much less water at lower temperatures, which can result in queries about whether the unit is actually working.
It was a given at the the time that desiccant dehums worked better at lower temperatures than refrigerant units. I suggest that either your unit is working, but not producing much water or it is not and needs attention. To read the humidity accurately a hygrometer is required, we used a paper drum type to keep a weekly reading, but I suspect today a digital version will be available and probably cheaper.
The neat thing about dehums is that they produce more energy in heat than they use in driving the device, a net gain, so in a cold garage they are a very useful tool, but you do need a pretty air tight building to take full advantage of the effect.
You probably knew all this anyway, but I thought it might help. It reminded me of an occasion when in a new office building, the contractor requested hire dehums so that the building could be dried rapidly to meet the contract completion date. After two weeks despite an overkill of machines, the humidity level in the building had not reduced. I toured the building with the contract manager, who had pulled out all the workers until he could get in to do the final fit. I asked how the 25 litre catch tanks were maintained, he said they had a labourer on site ensuring the security lights stayed on and the machines were emptied. We found him and asked how often he dealt with the tanks, "Oh well sir, every evening they are full so I go round and empty them", "Where do you put the water?" "I just chuck it on the floor, its soon gone"?☘ ??

Very interesting thank you Jack. My machine had a theormostat to prevent it running if there was danger of frost and would simply switch the power off below 10 degrees. It was returned for recalibration to Germany but returned just the same. I intended to pull it apart once the warranty expired to see if the stat was adjustable - but within a couple of weeks the circulation fan had failed so I called it a day! Not typical of German engineering I know, but then maybe it was made elsewhere.

Peter.

[Oxford Jack]

Bruce,
Water vapour in the atmosphere is similar to barometric pressure, unless separated from the general air mass, it will behave much as the remainder of the air mass, mixing freely. In other words it must be prevented from mixing otherwise it will be the same humidity. The gaps around your door would be like having a bath with gaps between the sides and bottom, although in this case humid air will leak into your 'drier' garage. First seal the gaps and then lower the water vapour level, otherwise as you say Wales will become dry, much like it used to on a Sunday.
Despite this disadvantage, dehumidification is a much better and far less costly way to conserve materials, such as those found in the average prewar car. I commend it to the reader. I sold  refrigerant dehums to the Aston Martin Club museum, housed in a wooden barn, which was made as airtight as possible. It significantly reduced the humidity level and slowed the decline in condition of steel, aluminium and leather.