Dehumidifier Icing up

[Shox Dr]

I have an old but good Dehumidifier keeping my bikes and gear dry. The only problem is it doesn't have a heating element to de-ice the condensing coil.

Because the ambient temp can be low, it tends to freeze up. I've tried using heat trace without success.

I think it needs a stat so when the temp drops it at least stops running to allow the ice to melt?

Any ideas what I can do?

 

[tigler]

I've had a number of dehumidifiers over the years and the types without an auto de-ice function cannot be successfully used below 8-12 degrees, unless as you suggest, using a stat to turn them off below the critical temp. I remember one that I had wihtout de-ice froze up so solid that I had to take it into the house to defrost and it took about 6 hours !! The heat exchanger matrix was just a solid block of ice !!
Even the types with de-ice can freeze up in really cold conditions as many only have a fixed period de-ice function, when they really need full de-ice before reverting to dehumidifier function.
The one I have now was on offer at Boo and Queue but has de-ice and it's the best I've had apart from an inadequate water reservoir. However it has the facility to connect an external reservoir, which I've done.

 

[Shox Dr]

We have another in the house I bought last yr. Works a treat. I wanted to put that in the lockup and the old one in the house, HID was having none of that

As I'm typing this I've had a bit of a brain wave. I'm going to stick it on a timer, and see how it goes

 

[drivewasher]

This is a bit odd! I was under the impression that they had to defrost to melt the ice into water so it can be collected in a bucket or piped outside!
Thats how they work, Moist air is drawn over te evaporator thats cold so the moisture freezes (ice) the then moisture-less air is blown out and so this continues until the defrost cycle which is some sort of reversal of the sytem to melt thge ice that wa once water in the air.

Unless..... some of them just switch off, so if as said its cold the ice wont melt naturally

 

[tigler]

We have another in the house I bought last yr. Works a treat. I wanted to put that in the lockup and the old one in the house, HID was having none of that

As I'm typing this I've had a bit of a brain wave. I'm going to stick it on a timer, and see how it goes

I've tried that, without success in my case

Thats how they work, Moist air is drawn over te evaporator thats cold so the moisture freezes (ice) the then moisture-less air is blown out and so this continues until the defrost cycle which is some sort of reversal of the sytem to melt thge ice that wa once water in the air.

Unless..... some of them just switch off, so if as said its cold the ice wont melt naturally

Some don't have the defrost cycle that circulates hot refridgerant back through the heat exchanger, they just turn off the refridgerant flow and the fan blows ambient air over the matrix. That just doesn't work at low temps, the air isn't warm enough to defrost the matrix. Even some of the types with a defrost cycle don't defrost adequately between cycles and just accumulate ice. I used a borrowed commercial duty one once and it was brilliant, the defrost system was really powerful, just used too much juice for continuous domestic use, about 400 watts from memory !

 

[Shox Dr]

This is a bit odd! I was under the impression that they had to defrost to melt the ice into water so it can be collected in a bucket or piped outside!
Thats how they work, Moist air is drawn over te evaporator thats cold so the moisture freezes (ice) the then moisture-less air is blown out and so this continues until the defrost cycle which is some sort of reversal of the sytem to melt thge ice that wa once water in the air.

Unless..... some of them just switch off, so if as said its cold the ice wont melt naturally

No, The unit cools the coil, any vapour held in the air, condenses on the coil, and drips into the tank. The amount of vapour (moisture) removed is dictated by what setting you have it on.

A problem arises when the ambient temp is too low, combined with a low percentage of moisture in the air. The unit continues to run trying to reduce the moisture level, however because the ambient temp is so low the unit has to drop the temp to below this, causing it to freeze up. Because mine doesn't have the provision to detect this the unit freezes up.

That's how I understand it works

 

[breezer]

Could try the rocksalt in a bucket type.

Hang some rocksalt in cloth above a bucket. The salt pulls the moisture in, when it starts to get saturated the water drips out of the bag into the bucket.

 

[voipio]

I bought an Ebac Envirodry extra from BeenAndQueued to put in the garage many years ago and never looked back. I reckon it's paid for itself several times over for the tools, bikes, and other bits and bobs i've not had to replace through rusting. I covered over the holes in the eaves and under the garage door to reduce the rate at which fresh moist air could come in. This particular dehumidifier is of the type that turns off the compressor every so often but keeps the fan running to thaw out the condensing element. When the air is really cold, it's actual moisture content becomes quite low - saturated air at 0 degC only holds about one quarter of the water that it can hold at 20 degC so the dehumidifier has to work harder in cold weather to extract the same amount of moisture. It's better to put a bit of dry heat into the area every so often e.g. from a fan heater, particularly if there's been a run of cold weather and warmer weather is forecast. Large lumps of metal have a high thermal inertia so will warm up relatively slowly, and are more likely to attract condensation and become rusty.

 

[voipio]

Looks like there may be a "pre-loved" one in the Wirral for sale.

http://www.preloved.co.uk/fuseaction-adverts.showadvert/index-1032922110/b92c7c7b.html

 

[eil]

If you are sure you don't have a hot gas defrost system on it, wire up a timer just before the compressor and set it to run for 20 Min's and off for about 5 Min's, the fan needs to run all the time.

 

[Wedg1e]

I have a Bodgit & Quick £99-special dehumidifier that runs for about 350 days a year in my house, it means I never hang laundry out to dry! I accept that some of you have a female about the place for such tasks but mine lives twelve miles away and due to my job I have over the years inadvertently left portions of my wardrobe blowing in the wind and gone away for days at a time; the running costs of the dehumidifier are probably less than a full rekit even at Primani or Chavalan prices.
Anyway, it has an auto-defrost cycle, by what means I know not but I suspect it won't be complicated, it's only the workings of a fridge in a smaller box. I was under the impression that the heat generated by the compressor would be enough to keep the thing ice-free but I haven't run it with the covers off to see how bad it gets.

Edit: if I really need the place dehumidifying I just pop the 6.25kW aircon on - now THAT is an expensive hobby!

 

[graffian]

The Ebac ones I have had have all defrosted, I also had a Mitsubishi that did.
I have managed with non defrost ones for several years, It's a bit of a pain though, I defrosted them a few times a day with a heat gun, once you have the huge block of ice melting a bit you can break the ice up and take it off the coils; If your doing it every day you invariably melt the plastic drip tray a bit and end up with a dehumidifier that's a bit incontinent.
I seem to be lucky with the last/current Ebac, it's been fine for must be three years, apart from having to replace the fan.