Workshop Dehumidifier Recommendation

[aesmith]

Hi,

I'm thinking about getting a mobile dehumidifier for the workshop. Based on past experience something like the Calorex DH35 would be about the capacity that I'd need. http://www.calorex.com/building-dryers/DH35.htm

Plus points for Calorex include the fact that they document performance under realistic conditions (claims at 30 deg and 90% are pretty meaningless when you're choosing something for an unheated building). The unit's available with hot gas defrost, and I know their units are reasonably reliable and easy to fix if they need it. Disadvantage is that I have a feeling they're a bit old fashioned. The defrost timer for example is out of the ark and expensive if it fails. Another disadvantage is that they don't switch off at really low temperatures where there's a danger of the condensate freezing. That means it can't be left running if we're away during the winter.

Any recommendations from the forum for alternatives? Or anyone have any current experience of Calorex? My comments are all based on a 10 year old machine and they may well have become more up to date.

Thanks,

Tony S

 

[TrimTheKing]

I had one of these bad boys in my old workshop and it was great, even in the middle of winter. Outputs warm air so gets the temp up a bit in winter.

HTH

 

[aesmith]

Thanks, that's interesting. One of the specialist retailers was recommending the "X-Dry" from the same manufacturer - similar spec but I think slightly more powerful and noisier.

As usual, specifications are a nightmare to decode, and seem to be designed to confuse. For example citing the temperature rise on one machine vs another is meaningless unless they also quote the relevant airflows!

These desiccant models look like they may be a step forward from the older machines I've used, and are nowhere near as expensive as I expected.

 

[SVB]

I have a desecant model in my garage and it is excellent.

It is only a domestic model but has been running for the last 5 years without a problem.

Bought from these people who were really knowledgable and helpful:

http://www.meaco.com/products.asp?cat=9

The only thing to keep in mind is that the desecant models do consume 2 or 3 times the running power of a similar spec traditional unit. The manuf. will claim this additional power consumption is off-set by reduced heating requirements which is probably true if you are in the shop 7 days / week but not so relavent if the odd couple of days a month is all you can grab.

Best of luck
Simon.

 

[aesmith]

The only thing to keep in mind is that the desecant models do consume 2 or 3 times the running power of a similar spec traditional unit. The manuf. will claim this additional power consumption is off-set by reduced heating requirements which is probably true if you are in the shop 7 days / week but not so relavent if the odd couple of days a month is all you can grab.

I've been checking the specifications, and that seems to be the case although it doesn't help that the desiccant models don't seem to have such thorough documentation. For example at 60% and 10 deg

Calorex DH30 will consume 550W, collect 11l/day and put 1.2KW of heat into the building.

X-Dry - consume around 600W, collect 6l/day. Total heat output is unspecified but if you assume its equal to the electrical power plus the latent heat from the condensate, then I guess at around 950W.

So running costs look expensive, but I mustn't forget that these bigger compressor machines are pretty expensive to buy.

 

[ivan]

I have had an Ebac in the 2 car atached garage for over 10 years, no problems. It was actually branded Wickes, and was the Ebac base model from their earlier range. In humid weather (a lot of it in Devon) it fills up a gallon container in about 2 days, and keeps the unheated garage at around 55%-60% humidity. No rust at all since put in use. Only drawback, common to most small dehumidifiers, the humidistat is temperature sensitive and needs adjustment a few times a year as temperatures gradually rise/fall summer/winter(check RH 55-60% with dial gauge now and then). Rusting point is usually said to be ~70% RH, keep under this to protect.

WE liked the Ebac so much we got another larger model for indoors, as wife discoverd mouldy clothes in wardrobes - apparently you risk this if indoor RH is 70% or more. This has proved excellent over 8 years too. Removes about 1 gallon/day when warm and RH is 70% outside, keeps internal at 55-60% (and windows condensation free in winter)

This type of "refrigerator" dehumidifier removes moisture by condensing and freezing it on cold coils (like those in your fridge icebox). It relies on the air temperature beig sufficiently above freezing to melt the ice so it drips into the storage reservoir when in the "melt" phase. (the machine alernately freezes out moisture and then melts it into storage) If it is too cold, the ice does not melt, and the whole machine will freeze solid (there goes experience, I left one "on" in an unoccupied, unheated house in winter) Will probqably work down to about 7 degC, check with mfr. Posh models with a built in heater for melting if cold, are available, but of course cost more!

 

[aesmith]

I've used Ebac, and they seem to be decent pieces of kit. The early one we had was prone to ice-up at moderate temperatures and high RH - the fixed-interval defrost didn't completely clear the ice off the evaporator. Ebac were very decent and swapped it for a newer model with more sophisticated "brains". They could easily have tried to wriggle out by claiming it was domestic model and not suitable for that sort of use.

Its a shame they don't seem to make any suitable higher capacity models.

Regarding very low temp, our Ebac switches off at low temperatures, below about 3 deg or so. The old Calorex doesn't so if the temperature's below freezing so the condensate can't drain away then it gets a bit messy. That's a problem as I can't leave it running unattended if we're away in the winter.

 

[devonwoody]

Sounds interesting.

I have a double garage, but the roof is corrugated asbestos which obviously has ventilation leaks at overlaps. Single concrete block walls, no insulation anywhere. Insulation not an option, beyond my capabilities now,

Would it be any good me having a dehumidifier in my setup?

What would be the running costs per day. (Around 50cu mtrs volume of garage)

 

[aesmith]

A dehumidifier could be the right solution for you, but you need to make the building as draft proof as possible. From experience with a corrugated roof you will need to check the eaves and the ridge, as many forms of construction leave these unsealed - for example if the ridge piece is a flat sheet lying on top of the corrugations.

A dehumidifier doesn't require insulation, as it does not depend on a temperature difference between inside and out.

 

[devonwoody]

Thanks aesmith.
Perhaps there is enough sawdust at corrugated joins to stop drafts, ends and sides are draftproof.
Next problem is sawdust getting in the dehumidifier, its only a thin latex membrane on my Ebac.

 

[aesmith]

I've found that that sawdust is carried off by the condensation as it drips off the heat exchanger.

Edit - That's assuming a heat-pump machine, goodness knows what'll happen with a desiccant one.