Portable dehumidifier/heat pumps

[yorkie_chris]

Ey up.

I think we could do with a dehumidifier. The room I'm putting all my dive kit in has a slight damp problem anyway and a chill feel to it.

There are quite a few kicking about on eBay for <£100, the spec on a lot of them seems to indicate they can act as heat pumps. I presume this is just by being air conditioning in reverse and they expel the cold air out of the window. But this doesn't seem thermodynamically sound to me.

Has anyone used one for heat? Are they at all effective?

[johnnyrod]

A dehumidifier is indeed a frdieg set, cool the air so the water condenses, catch it in a tank, pour it away. Like a domestic fridge, they are one unit so the heat is moved from front to back (and you add to that the power used by the compressor and any fan). I guess if there is a duct of some sort then you could vent the hot air outside, but if that were the case really you should just open a window, it's free.

[yorkie_chris]

I live in Yorkshire, what would I possibly need air-con for.

A heat pump is air-con in reverse... brings heat inside and "compresses" it to raise the temperature. It means you get more heat inside the house than you use in electricity.

I've never encountered a dehumidifier being used as a heat pump but the Electrical Contractors Association blurb states;

" recover both sensible and latent heat released during dehumidification and use it to heat the air as it leaves the product.....for other useful purposes such as heating water"

So I can see what the point is.

I would have been sceptical. I've done a few ground source heat pump installations at various barn conversions, they are not very cost effective or efficient.
But, I've just finished a development of new 2/3/4 bed houses at Little Ribston near Wetherby and they were provided with heating/hot water by Daikin air source heat pumps. Very efficient, grant qualifying and you have the magic word "green"


So, I can see the point and I can see how it works. It may be worth contacting your local authority/building control/sustainable energy geezer and requesting any guidelines they have re. grants and specified equipment. You never know.

I'm totally confused by the responses. But, I've used a base spec Ebac dehumidifier for a few years in my house over the winters and it works well and the house feels drier and warmer.

[yorkie_chris]

Originally Posted by Small Clanger

I've never encountered a dehumidifier being used as a heat pump but the Electrical Contractors Association blurb states;

" recover both sensible and latent heat released during dehumidification and use it to heat the air as it leaves the product.....for other useful purposes such as heating water"

So I can see what the point is.

Don't think these I am looking at dehumidify and heat at the same time.

Reason being the cold coils are in use to extract heat from the cold reservoir (outside) when in heat pump mode so can't remove water from inside at the same time.


However I did do a fair bit of thermodynamics at uni, and can't see why you would say air source is better than ground source, surely in winter the bigger dT would reduce the coefficient of performance of an airsource pump massively.

Got one. Not much use as a heat pump. Nice idea tho.

Thing to consider is they cost a fortune to run. Can you open a window.?

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[yorkie_chris]

Yeah but when it gets to december or so and I've got a room full of soggy dive kit opening a window is going to waste heat too surely?

Yep mine borrowed and old. Takes a long time to dry a damp cellar. Do.nt know what you would need for dive kit

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[maviczap]

We've got a dehumidifier and for absorbing the water vapour from your dive kit, its probably ideal?

I know with our BA kit, we need to prevent moisture build up in the fittings & lines, as its not good to be breathing it.

We use our dehumidifier same as Aidan does, little EBAC one. If its a closed room, it'll work must better and faster