Dehumidifiers - suggestions?

[Ian Jackson]

Does anyone have any suggestions about which is a good dehumidifier to buy (up to about £160)?

[js.b1]

Compressor provide little heating (just a bit from phase change), about 180=

-270 Watts. Pretty reliable, usual failure is the fan motor. Good for 2-3yr= s (at least re money risk).

Dessicant provide much more heating (dessicant disc must be heated), about =

750-810W (they tend to under report). Not that reliable, usual failure is t= he heater, which can run =A370. Good for 1-2yrs (at least re money risk).

Best dehumidifier is a split-aircon heat pump :-) because you get 3 devices= in one re air-con for summer, heat pump for winter & dehumidifier.

Best quality dehumidifier is the Mitsubishi unit at =A3279 (non LCD display= ) and =A3300-309 (LCD display) made in Japan. They are VERY expensive, but = the humidity sensor is reliable, whole thing turns on only when needed, qua= lity build, photocatalytic filter AND anti-mildew (auto-dry) function DO wo= rk so the air blown out does not make you sneeze etc. Power is 240-270W, ca= n't recall.

The downside is #1 the air blast washes walls of heat and creates draughts,= #2 even the Mitsubishi is not silent and a light sleeper would not like it= s presence.

Also, to truly strip moisture off windows you need to go down to about 40% = humidity which is a bit impractical because your throat will be like a scot= tish hillside in winter. Specifically thinking of Ebac whose quality is a b= it iffy. The Mitsubishi goes down to 50%, but that is still very good and w= ill minimise condensation which will strip off the minute the sun hits it (= well within 30-120mins).

Takes 3 wks for a dehumidifier to stabilise the house, until then you may b= e emptying 7pts every day out of the Mitsubishi set to 60% (wet year). Ther= eafter it is less, and energy consumption falls.

I've had them all, the current Mitsubishi with Mildew Guard & Photocatalyti= c filter avoids the problem of "instant cold" breathing the air output. Tha= t for me is something ALL the other dessicant & compressor dehumidifiers su= ffered from. Worth the extra =A3150 over a cheap B&Q? Well it depends on th= e usage/need, it is a LOT of money (same price is a quite usable washing ma= chine!). I bought one for a relative and am very very glad I did.

[Dan]

got my Ruby Dry a couple of weeks ago, works a treat and noise levels really low. Power consumption is probably a bit higher than compressor models but in my case a small price for nigh on silent running.

More expensive than your budget but I needed something that actually worked (water running down walls!)

For silent running get a dessicant type, for cheap it's a compressor type. They all do they're job as described.

[Dan]

[meow2222]

80-270 Watts. Pretty reliable, usual failure is the fan motor. Good for 2-3= yrs (at least re money risk).

t 750-810W (they tend to under report). Not that reliable, usual failure is= the heater, which can run =A370. Good for 1-2yrs (at least re money risk).

Seems you had bad luck with those two.

NT

[js.b1]

Perhaps, the quality is variable. Heater element is however a key failure mode, I recall quite a few reviews = found same - but how many did not fail. As always reviews do not highlight = that important point.

For cost, you could have TWO dessicant dehumidifiers in a house for the pri= ce of 1 Mitsubishi. Which highlights a problem - sometimes a dehumidifier o= n each floor level can be quite useful, because doors shut present an inevi= table limit on their reach. You could probably manage THREE generic =A399 c= ompressor units for the price of one Mitsubishi, which could cover kitchen,= upstairs and perhaps shed with a 120-240W tube heater.

For a cold garage, a compressor dehumidifier can struggle re temps - the ex= tra heat from a dessicant dehumidifier can offset the cold temperatures. Co= mes down to how limited the air changes are.

[Robin]

I'm also in the market for a dehumidifier but I'm struggling to find useful data on comparative effiiciency - i.e. not the absolute power consumption as above but the litres/kWh. Where efficiency ratios are available they seem to be at temperatures which for typical UK use flatter compressors (e.g. 27 Celsius for heat pumps if I'm reading BS EN

810:1997 right). I note too that some manufacturers quote figures using the wet bulb temperature rather than the dry. Do you know if anyone has compared them in winter conditions in the UK (which, in this bit of the housing stock at least, is a damn sight less than the high 20s during the day let alone overnight)?

[js.b1]

I have not - might exist for some HVAC systems.

In the first 2-3 weeks compressor will surprise, dessicant will shock, in t= he amount of energy used. However thereafter they DO drop. The wall washing= is very noticeable, disturbing the boundary layer on hall walls for exampl= e is quite significant - and at the eaves, a traditionally high energy loss= area on many houses. So dessicant may be less negative re warm air compens= ation - albeit from an expensive peak day rate electrical source.

Noise is a big factor, and even the Mitsubishi compressor unit is NOT silen= t. It IS quieter if you put the louvres to straight up rather than "swing" =

- but would certainly interfere with light sleepers. It is a pure white noi= se, there is no other noise in there. The compressor DOES thump on startup = so may benefit from some isolation on certain upstairs timber floor structu= res. The aluminium fin spacing is insanely tight on the Mitsubishi (one rea= son for the pure whitenoise), some cheap ones can be quite frugal in the fi= ns which is a cheap cost saving.

[metric_trade]

I'm very happy with:

's my second one. I gave the first one to somebody else and they said they liked it.

It got high scores in a review by 'Which'.

[metric_trade]

From the Which review:

***************************** use a special climate-controlled test room measuring 2.0x2.1x2.4m. This = means we can find out how the dehumidifiers work at normal room temperature= (21=B0C) and in a chillier space (10=B0C). *****************************

[Robin]

Thanks. But I had been to Which? and AFAICS they reviewed only compressor-driven dehumidifiers:

I really wanted to see them compared with desiccant models. -- Robin reply to address is (meant to be) valid

[Robin]

OK thanks. It does seem that hard figures mainly come with kit for commerciual use where they need the tick for enhanced capital allowances.

I'm shocked by pretty much everything I've read about the efficiency of these beasties. Eg charts in Appendix D in

show how the efficiency of several "Energy Star" compressor models decline from the "normal" temperature down to 15 degrees C. Given how cold this Victorian hovel can get overnight I've had to re-think the idea of leaving one on a timer downstairs overnight.

[dennis]

Don't forget any energy put into a dehumidifier will come out as heat to warm the room a bit. They also recover the latent heat from condensing the water so you gain more heat. If the rooms draught free it will quickly shut off as the humidity drops and the stat cuts out.