Domestic dehumidifiers - are customers being deceived?

[Psychro]

Domestic dehumidifiers are now available from most DIY stores or by shopping on the web, but are manufacturers deliberately misleading customers?

Most manufacturers of mass produced refrigeration “heat pump” type dehumidifiers state the drying capacity is at 30°C, 80%RH. This equates to a humidity ratio of 22.0 g/kg (26.5°Cdp). At these extreme levels, refrigeration dehumidifiers work at their best, but unless the dehumidifier is being used in a tropical climate the actual capacity will be a lot less.

At 30°C, 80%RH a domestic unit will typically extract 15 litres/day, but in Europe, at a more realistic condition of say 20°C, 60%RH (12°Cdp) that same unit is likely to extract only 5 litres/day (or just 1/3rd of that indicated on the box). One major UK manufacturer shows maximum performance at 32°C, 90%RH (27.5 g/kg, >30°Cdp). This humidity ratio is more appropriate to Calcutta (ASHRAE), one of the most humid places on the planet!
:confused:
So my question is: “Should manufacturers conform to a common sensible standard, by which the capacity shown on the box is applicable to a temperature & relative humidity more appropriate to the geographical region?”

I am presently discussing this subject with Trading Standards in UK, so your comments will be much appreciated.

Thanks in advance
Psychro

[chillin out]

Thats quite a good point you have.

It's a bit like quoting power output for solar panels sold in the UK using sun measurements taken from the middle of a desert.
Very misleading.

Chillin:) :)

[Psychro]

It's hard to believe that with the recent onset of political "global warming" the regulations set by the same governments seem so lax when it comes to proving energy saving methods.

Since my last post, I came across this, which I believe is from Hong Kong (2007). If they are aware of the problems, how come our government appointed Cretins aren't?

Some dehumidifier manufacturers have exaggerated their products' performance capacity, the Consumer Council says. Five of 10 models tested have been found to operate at up to 15% below the levels claimed.

The models claim to be able to dehumidify up to 24 litres of moisture a day. Eight based their rating at conditions of 30 degrees Celsius and 80% humidity. The other two based their rating at 32 degrees Celsius and the same humidity. The capacity measured ranged from 13.83 litres to 23.38.

The council said this approach does not accurately reflect the indoor environment when the dehumidifier is operating with the windows closed. It recommended that a more realistic measurement of dehumidifying capacity be adopted as laid down in the US Association of Home Appliance Manufacturers standard, which sets the test conditions at 26.7 degrees Celsius and 60% humidity.

When tested against this American standard, the actual capacity ranged from to 5.61 litres to 13.24. The council urged the industry to consider adopting the test conditions of regional or national standards, which reflect more accurate dehumidifier performance.

The council also found substantial variation in the energy efficiency of the devices.

[US Iceman]

Here is a link to a similar standard for pool dehumidifiers that may be of interest.

http://www.ari.org/standardscert/standards/910-99.htm

Differing equipment performance statements are similar to what we call "weights & measures" here in the US. These are a qualification program to ensure the customer receives what he thought he purchased.

Overstating the performance of a device should result in some penalty to the manufacturer. Even if they provided a range of values for varying conditions this might be acceptable, if the performance was "qualified" as true.

Anything less than this should be considered preying on the general public.

[Ravi]

I couldn't quite understand the question. When the dehumidifier can work in a worst case scenario, it works for a better condition. At 20C and 60%RH you have humidity ratio of about 8.73gms/kg of dry air and you need not reduce as much moisture as you do at the worst conditions.

What you should check is the drop in moisture across the dehumidifier.

...or I am terribly missing something.

[Psychro]

I couldn't quite understand the question. When the dehumidifier can work in a worst case scenario, it works for a better condition. At 20C and 60%RH you have humidity ratio of about 8.73gms/kg of dry air and you need not reduce as much moisture as you do at the worst conditions.

What you should check is the drop in moisture across the dehumidifier.

...or I am terribly missing something.

Hi Ravi. I think you have missed the point.

In Europe we don't experience the extreme conditions that you get in India. In European climates a refrigeration dehumidifier will extract a lot less moisture than that shown so therefore the moisture extraction rates should be stated at a more realistic level.

It's like a car manufacturer claiming a fuel consumption of 80 miles per gallon .....and in small print .... "only applies when travelling downhill with a 100 mph wind up ya backside"!!! :mad:

Regards
Psychro

[Abby Normal]

On this side of the Atlantic, the residential and commercial grade mechanical dehumidifiers seem to be rated in the 'pints per day' of water they can remove based on entering air at 80F ( 26.7C) and 60% RH.

Some manufacturers will list 'pints per day' removed based on other entering conditions, but this is the commercial grade equipment or the high end residential equipment.

[Abby Normal]

I see that pyschro already mentioned the 80F 60% RH used in NA.

Spot cooler manufacturers like to rate their equipment based on some pretty hot conditions. Movincool used to rate their units based on about a 90F dry bulb entering, not many IT guys like it that hot