I recently had a ecox model EDCM018H16B installed in my garage which I am converting into a brewhouse and I am very disappointed to both be seeing high humididty (high 60's to low 70s) and erratic cooling. The installer keeps insisting that it's working fine, but my crappy window A/C that's all rusted out yet somehow still working will suck all the moisture out of the garage and cool it down quickly. This massive 18000 Btu/h unit can't even get close. It will cool...that's for sure, down to 58 degrees in the middle of a sweltering afternoon but the humidity stays way way up! I can feel it and it's both frustrating and baffling. Meanwhile the wall unit will go down to 45% in no time at all. What can I do?

Air seal better - leakage is where the humidity comes from (unless you have something internal creating it). If there aren't any adjustments available on the AC, then you may need to add a standalone dehumidifier.

Of course dehumidification doesn't depend on cooling BTUs alone, but rather the temp of the coils, which sets the dewpoint of the exiting air. Set by the ratio of cooling BTUs and airflow cfm. SEER will increase with cfm/BTU, but dehumidifcation will suffer.

Still, I would expect this all to be built into the controller for a mini....perhaps it has a bad humidity sensor. If its new, make a warranty claim.

The wall unit is exchanging air, the mini is conditioning existing air.

I assume brewhouse equals higher humidity?

Thanks for the replies everyone.

FBBP The "brewhouse" isn't really in need of higher humidity and since I'm making mead rather than beer (no boiling) it's really about keeping things cool and at 50% humidity. It's not like I want a ridiculously low percentage or anything. 50 to 55% is more than enough. I am very concerned about that statement however...which makes sense... there is no exchange of air... I will be fit to be tied since I have made clear to my installer that the lowering of humidity (the main enemy of everything here in Miami) is half the reason we all have A/C. So I've just spent 2000 bucks on crap I don't need.

jonr...if leakage is the issue, then how is it that the crappy wall unit is slamming down the humidity, yet the mini split is causing HIGHER humidity indoors than out? Testing the other day 55% outsde...65% inside.

woodgeek68... That's the answer I'm hoping is on the mark! I can't get a straight answer (or any answer for that matter) from this manufacturer so I hope there's just some issue with a sensor.

Thanks again to all you guys for taking the time to answer... I have no clue about these things and your input helps.

Air leakage is almost certainly a big part of the issue- garages are notoriously leaky.

Crummy non-modulating window/wall units have a much heavier latent-to-sensible cooling ratio than modulating mini-splits, and it's no surprise that it would dehumidify the place faster than it would cool it down.

I'm not familiar with the ECOX units and the 1-pager online doesn't really say much about it (http://www.ecoxline.com/web/media/catalogos/catalog_21035.pdf), but if working properly it should be doing at least SOME latent cooling, and you'd be able to see how much condensate it's producing. Many;/most mini-splits have a "dehumidify" mode which runs the blower at min-speed and modulates the compressor to keep the coil about 35F or so for fast & efficient dehumidification, but without a users manual don't know if this one does. If the air temp is 58F indoors it may be tough to pull much humidity out, but when it's 75F indoors or higher it should be pulling quite a bit, even in normal cooling mode.

The % relative humidity is RELATIVE- relative to the temperature. If it's 55% RH @ 78F outdoors, cooling that air to 70F without dehumidifying would result in an RH of 64%, and reducing it's temp to 58F would result in wet fog indoors. The RH number without the associated temperature is a meaningless number. With the RH & temp you can infer the wet-bulb temp or the dew point temp, either of which is an absolute measure of the humidity in that air. (Lower wet bulb or lower dew point means drier.) Play around with this online psycrhometric calculator a bit to get the feel of it:

http://www.sugartech.co.za/psychro/

(click on the IP button if you want to use Fahrenheit instead of Celcius degrees.)

Or download the image of a pychrometric chart and google how to use it.

…or use our psychrometrics software:

http://www.borstengineeringconstruction.com/Psychrometrics_Calculator.html

Read the detailed directions if you have any questions about using it.

Do the energy use standards account for latent heat removal and also require a certain dehumidification capability? This may be a case of ratings distorting reasonable behavior.

An AC unit or dehumidifier may fix the symptoms, but air leakage is the cause.

The whole SEER test is something of an inside joke for a number of reasons, but is still a pretty good apples-to-apples comparison for non-modulating 1 & 2 stage systems.

The very high part-load sensible cooling efficiency of modulating efficiencies results in worse latent cooling efficiency when oversized than oversized single speed systems. If the sensible cooling load in this garage is way below the rated 1.5 tons the oversizing issue could be contributing to the problem.

But either way, if he air-seals the building (including air & moisture-sealing the slab), it would be astounding if it wouldn't keep up with the latent load, given there is very little internal latent source if there is no open boiling of the wort, etc. But garage doors are notoriously leaky and hard to seal well.