Octopus Tracker

Griffindog

I’ve got the Meaco 20L low energy dehumidifier and haven’t used the tumble dryer since I got it. A load dries in a small room in 3 hours with the dehumidifier on constant or overnight if I set it to 50 (it goes on and off so isn’t running all the time). We keep the house warm and use about 18,000 kwh of gas each year and 2.800 kwh electricity. I try to do power heavy tasks on cheaper days but I don’t stress because tracker has built up a very healthy credit on my account this year.

masonic

Spies said:

masonic said:

Telegraph_Sam said:

My Meaco 20 L eco dehumidifier (type??) appears to show up well in the comparisons. The environmental room emperature is in the mid teens. These are currently retailing @ c. £250. Probably as good a solution as I'm going to get, but possibly not excluding some other if it was a matter of making a new outlay. Esp if compared with a new tumble drier.

It's a compressor type, and stated power consumption is up to 255 W "/h" (presumably typical usage in laundry mode, no data for standard operation, but expect this will be below 200 W). It gives extraction data for 30C @ 80%RH: 20 L/day and at 27C @ 60%RH: 12 L/day. This will be considerably lower when the temp is in the mid-teens. The below plot (general data, not your model specifically) gives an idea of the temperature dependence:

https://ionmax.com.au/blogs/resources/desiccant-or-compressor-dehumidifier

You could experiment and see how much water it produces from an empty tank at the start of your drying operation to the end, and divide by the number of hours it ran. If you have a plug-in energy meter you can even see exactly how much energy it used. Then you can work out the energy consumed per litre moisture removed, which is the best metric for efficiency.

masonic said:

Telegraph_Sam said:

My Meaco 20 L eco dehumidifier (type??) appears to show up well in the comparisons. The environmental room emperature is in the mid teens. These are currently retailing @ c. £250. Probably as good a solution as I'm going to get, but possibly not excluding some other if it was a matter of making a new outlay. Esp if compared with a new tumble drier.

It's a compressor type, and stated power consumption is up to 255 W "/h" (presumably typical usage in laundry mode, no data for standard operation, but expect this will be below 200 W). It gives extraction data for 30C @ 80%RH: 20 L/day and at 27C @ 60%RH: 12 L/day. This will be considerably lower when the temp is in the mid-teens. The below plot (general data, not your model specifically) gives an idea of the temperature dependence:

https://ionmax.com.au/blogs/resources/desiccant-or-compressor-dehumidifier

You could experiment and see how much water it produces from an empty tank at the start of your drying operation to the end, and divide by the number of hours it ran. If you have a plug-in energy meter you can even see exactly how much energy it used. Then you can work out the energy consumed per litre moisture removed, which is the best metric for efficiency.

Shall we also try to include the calculation of heat energy that's released when you condensate water? This is why compressor dehumidifiers are actually over 100% efficient as you get 2259 joules per gram of water condensed. 

That would be the same for both types per litre of water condensed (0.63 kWh of extra waste heat), as they both release latent heat through a phase change. However, that heat gain will be matched by an equal loss from evaporation of water from the wet clothes.

You will get a net gain only to the extent that the condensed water isn't replaced in the air through the reverse process.

In my example today when my desiccant dehumidifier pulled 2 litres of water off my drying clothes, the relative humidity fell from 60% to 40%, but only a small fraction of the water was originally in the air. The rest was just heat transfer from one object in the room to another.

Those of you with a gas supply would probably be better off using that for heating, but in my case any waste heat from electrical appliances is as good as me turning on a heater.

Telegraph_Sam

That illustrates the point: I have the Meaco on regularly in the evening as much for general comfort as for drying purposes (damp towels suspended above). I am aware vaguely of the humidity display but I believe this is not very accurate. It depends whether the condenser has cut in or not. There are so many variables as mentioned in this thread that you have to be a math whiz to distinguish wood from trees. Rather, it becomes an act of faith: Converting the humid to warmth in a low energy way "feels" right without quoting chapter + verse.

Telegraph_Sam

See mmmmikey's views and answer above

masonic

There's a separate discussion to be had about humidity, energy efficiency and comfort. I find that higher humidity makes the same temperature feel colder. I don't know if it is related to thermal conductivity of air or something else, but it is counter to what I'd assume (dry air leads to more rapid evaporation from skin and more of a cooling effect). Just me or is there something in that?

Spoonie_Turtle

masonic said:

There's a separate discussion to be had about humidity, energy efficiency and comfort. I find that higher humidity makes the same temperature feel colder. I don't know if it is related to thermal conductivity of air or something else, but it is counter to what I'd assume (dry air leads to more rapid evaporation from skin and more of a cooling effect). Just me or is there something in that?

Except when it's warmer (e.g. in spring and summer) and higher humidity makes us feel hotter.

I have friends from Goa and Nigeria who lament the humid heat of England, and friends from Poland who lament the damp cold here.  Definitely something in the humidity affecting how a temperature feels, but I don't know what exactly.

Telegraph_Sam

masonic said:

There's a separate discussion to be had about humidity, energy efficiency and comfort. I find that higher humidity makes the same temperature feel colder. I don't know if it is related to thermal conductivity of air or something else, but it is counter to what I'd assume (dry air leads to more rapid evaporation from skin and more of a cooling effect). Just me or is there something in that?

I agree with your physical feelings but not with your assumptions!

masonic

Spoonie_Turtle said:

masonic said:

There's a separate discussion to be had about humidity, energy efficiency and comfort. I find that higher humidity makes the same temperature feel colder. I don't know if it is related to thermal conductivity of air or something else, but it is counter to what I'd assume (dry air leads to more rapid evaporation from skin and more of a cooling effect). Just me or is there something in that?

Except when it's warmer (e.g. in spring and summer) and higher humidity makes us feel hotter.

Indeed. I guess I was applying that logic to the cold, but clearly there are different factors at play.

This has turned out to be an unexpected means through which I've tolerated lower temperatures indoors so far this winter.

Spies

masonic said:

Spies said:

masonic said:

Telegraph_Sam said:

My Meaco 20 L eco dehumidifier (type??) appears to show up well in the comparisons. The environmental room emperature is in the mid teens. These are currently retailing @ c. £250. Probably as good a solution as I'm going to get, but possibly not excluding some other if it was a matter of making a new outlay. Esp if compared with a new tumble drier.

It's a compressor type, and stated power consumption is up to 255 W "/h" (presumably typical usage in laundry mode, no data for standard operation, but expect this will be below 200 W). It gives extraction data for 30C @ 80%RH: 20 L/day and at 27C @ 60%RH: 12 L/day. This will be considerably lower when the temp is in the mid-teens. The below plot (general data, not your model specifically) gives an idea of the temperature dependence:

https://ionmax.com.au/blogs/resources/desiccant-or-compressor-dehumidifier

You could experiment and see how much water it produces from an empty tank at the start of your drying operation to the end, and divide by the number of hours it ran. If you have a plug-in energy meter you can even see exactly how much energy it used. Then you can work out the energy consumed per litre moisture removed, which is the best metric for efficiency.

masonic said:

Telegraph_Sam said:

My Meaco 20 L eco dehumidifier (type??) appears to show up well in the comparisons. The environmental room emperature is in the mid teens. These are currently retailing @ c. £250. Probably as good a solution as I'm going to get, but possibly not excluding some other if it was a matter of making a new outlay. Esp if compared with a new tumble drier.

It's a compressor type, and stated power consumption is up to 255 W "/h" (presumably typical usage in laundry mode, no data for standard operation, but expect this will be below 200 W). It gives extraction data for 30C @ 80%RH: 20 L/day and at 27C @ 60%RH: 12 L/day. This will be considerably lower when the temp is in the mid-teens. The below plot (general data, not your model specifically) gives an idea of the temperature dependence:

https://ionmax.com.au/blogs/resources/desiccant-or-compressor-dehumidifier

You could experiment and see how much water it produces from an empty tank at the start of your drying operation to the end, and divide by the number of hours it ran. If you have a plug-in energy meter you can even see exactly how much energy it used. Then you can work out the energy consumed per litre moisture removed, which is the best metric for efficiency.

Shall we also try to include the calculation of heat energy that's released when you condensate water? This is why compressor dehumidifiers are actually over 100% efficient as you get 2259 joules per gram of water condensed. 

That would be the same for both types per litre of water condensed (0.63 kWh of extra waste heat), as they both release latent heat through a phase change. However, that heat gain will be matched by an equal loss from evaporation of water from the wet clothes.

You will get a net gain only to the extent that the condensed water isn't replaced in the air through the reverse process.

In my example today when my desiccant dehumidifier pulled 2 litres of water off my drying clothes, the relative humidity fell from 60% to 40%, but only a small fraction of the water was originally in the air. The rest was just heat transfer from one object in the room to another.

Those of you with a gas supply would probably be better off using that for heating, but in my case any waste heat from electrical appliances is as good as me turning on a heater.

I personally don't use a dehumidifier to dry clothes, I have a heat pump tumble dryer for that, I typically run the dehumifider to get RH under 60% as we live in a very damp climate (although lately it's been more like 50% RH without even using the dehumidifier). 

Telegraph_Sam

Humidity variations from a mean accentuate perceived temperature differences up or down?