Mini split vs dehumidifier

[jmarkwolf]

I've decided I have to do something about mitigating the humidity in my 28ft x 30ft detached shop/garage.

In southeast Michigan, the summer heat/humidity frequently reaches 90/90 and is just too uncomfortable to work in. The shop is roughly 750 sq ft, with 10ft ceilings, with R14 "everywhere", and an insulated big door facing west.

I'm also concerned about my machine tools in the humidity.

I'm torn between getting a big dehumidifier or a DIY mini split. I know that a dehumidifier exhausts some heat into the room, but maybe it's a wash with the reduced humidity. Conversely, the mini split is roughly 4-5 times the cost of a dehumidifier.

Can anyone advise of first hand experience with both dehumidifier and mini splits in the same space?

Also, are mini splits always heat and cool? Already have a ceiling mounted heater. Don't want to pay for a heater again.

And yes, I have searched this forum and the web before posting this queary.

 

[theoldwizard1]

Also, are mini splits always heat and cool? Already have a ceiling mounted heater.

You can buy an A/C only mini-split. The savings is not huge (basically that add a reversing valve and some check valves).

Heat pumps, especially the mini-split heat pumps, are the most efficient form of heat in the 35F-60F ambient temperature range. Probably better than natural gas. Remember a heat pump does not "make" heat, it just moves it from one place to another.

 

[yeldogt]

The dehumidifier will produce a lot of heat -- I need them in the shoulder season at my weekend place by the river.

AC takes care of the problem when it's warm.

Get the minisplit

 

[Full Throttle]

2 ton mini split is what you want

 

[LS6 Tommy]

X2 on the minisplit. I stopped using my dehumidifer after I installed a minisplit in my basement. I leave the minisplit on "Dry" all summer and I really don't see an apprciable increase in energy use over not running the dehumidifier. I see a decrease in energy use over running the dehumidifier.

Tommy

 

[aunsafe2015]

X2 on the minisplit. I stopped using my dehumidifer after I installed a minisplit in my basement. I leave the minisplit on "Dry" all summer and I really don't see an apprciable increase in energy use over not running the dehumidifier. I see a decrease in energy use over running the dehumidifier.

Tommy

What brand mini split do you have that dry mode doesn't result in overcooling?

 

[LS6 Tommy]

What brand mini split do you have that dry mode doesn't result in overcooling?

Fujitsu Halcyon. I've never seen any minisplit with "Dry" mode that overcooled. Dehumidification only removes latent heat.

Tommy

 

[u3b3rg33k]

I'm torn between getting a big dehumidifier or a DIY mini split. I know that a dehumidifier exhausts some heat into the room, but maybe it's a wash with the reduced humidity. The mini split is roughly 4-5 times the cost of a dehumidifier.

Can anyone advise of first hand experience with both dehumidifier and mini splits in the same space?

Also, are mini splits always heat and cool? Already have a ceiling mounted heater. Don't want to pay for a heater again.

a dehumidifier doesn't release "some" heat into the room, it releases ALL its heat into the room. that's the 600W+ of plug power, plus the latent heat released by condensing the water (if it's humid, that's up to 3x the plug draw, so it's basically running a space heater).

I would not search out a cool only minisplit for the purpose of saving money. you'll more than make up the difference in finding a good installer who won't overcharge.

what kind of ceiling mounted heater do you have now? if gas, I understand your argument - just don't run the minisplit in heat/auto if you don't want to.
if it's electric, the minisplit will likely cost 1/4 the $ to run as the electric heater.

 

[aunsafe2015]

Fujitsu Halcyon. I've never seen any minisplit with "Dry" mode that overcooled. Dehumidification only removes latent heat.

Tommy

Reports of Mitsubishi dry mode are almost universally that it overcools. My understanding is that they are not acting as pure dehumidifiers. They are still split systems that are producing some sensible cooling even in dry mode, from everything I've read (and from my own experience with my Mitsubishi which cooled down into the 60s in the middle of Summer in dry mode).

 

[outdoorspace]

I have a 2 ton mini split in my 24x40x16. It's dry mode definitely cools things down, but not by a lot. Maybe 5 deg or so? It hasn't been a problem.

 

[LS6 Tommy]

That's interesting. Mine doesn't get below whatever setpiont I set it to.

Tommy

 

[outdoorspace]

Mine is a Midea SEER 20 inverter heat pump unit. I know the fan slows way down in dry mode, but there is still some air flowing through it, and the evap is just above freezing to condense the most water. Because the condenser is outside (unlike a dehumidifier) it doesn't heat the air back up. I guess it could switch back and forth from dry to heating but it doesn't do that. Mine seems to prioritize drying over the temperature setting, it certainly goes below the setpoint.

I control it through an automation system to keep the humidity around 60%. It runs in dry mode 2-3 hrs a day during humid weather. When I built the shop I sealed it the best I could. Insulation is R19 walls R25 ceiling.

I have conventional dehumidifiers in my other garage and house. If I had to guess I'd say the mini split is a fair amount more efficient than a typical dehumidifier.

 

[yeldogt]

Reports of Mitsubishi dry mode are almost universally that it overcools. My understanding is that they are not acting as pure dehumidifiers. They are still split systems that are producing some sensible cooling even in dry mode, from everything I've read (and from my own experience with my Mitsubishi which cooled down into the 60s in the middle of Summer in dry mode).

It's all a question of the set point and the humidity level. On a cool wet day it's going to drop the temp ..some systems have an "overcool" set point.

Also - not all mini-splits have the same min run ability -- especially the multi-heads. Old habits die hard -- people are installing oversized mini-splits -- it's all in the minimums.

A commercial type dehumidifier will remove a lot of water per KW --- in some climates and humidity levels a dehumidifier is still needed.

 

[Kaizen]

I have both in the house. 12k mr cool on the second floor and a nice dehumidifier in the basement. Both spaces about 650.
The dehumidifier jacks up the heat. Last summer the cellar was 20 degrees hotter then usual.
Mr cool dry mode is incredible. The drain looks like you left the water running. Great for days that are sticky but not hot. Ac is added benefit. Would guess it’s half as much to run.


Sent from my iPhone using Tapatalk

 

[aunsafe2015]

It's all a question of the set point and the humidity level. On a cool wet day it's going to drop the temp ..some systems have an "overcool" set point.



Also - not all mini-splits have the same min run ability -- especially the multi-heads. Old habits die hard -- people are installing oversized mini-splits -- it's all in the minimums.



A commercial type dehumidifier will remove a lot of water per KW --- in some climates and humidity levels a dehumidifier is still needed.

My Mitsubishi does not even allow me to set a setpoint in dry mode. And it's the latest FH09 model.

 

[Showkey]

a dehumidifier doesn't release "some" heat into the room, it releases ALL its heat into the room. that's the 600W+ of plug power, plus the latent heat released by condensing the water (if it's humid, that's up to 3x the plug draw, so it's basically running a space heater).

Dehumidifier are energy hogs.....no question.
Don’t have an opinion on dehumidifier vs mini split ..........but........general conversation:

The dehumidifier does “add heat” and it “adds cold” in general lay terms, as the condenser and evaporator are in the same box. Seems to me in use there’s little temperature change in the area of dehumidifier operation.

 

[TRWham]

Fujitsu Halcyon. I've never seen any minisplit with "Dry" mode that overcooled. Dehumidification only removes latent heat.

Tommy

Reports of Mitsubishi dry mode are almost universally that it overcools. My understanding is that they are not acting as pure dehumidifiers. They are still split systems that are producing some sensible cooling even in dry mode, from everything I've read (and from my own experience with my Mitsubishi which cooled down into the 60s in the middle of Summer in dry mode).

You cannot achieve latent cooling without first doing enough sensible cooling to drop the air down to the dewpoint. You can reduce the airflow and cool a small amount of airflow to a very low temp to dehumidify, which is what I imagine most units do when in dry mode.

 

[LS6 Tommy]

You cannot achieve latent cooling without first doing enough sensible cooling to drop the air down to the dewpoint. You can reduce the airflow and cool a small amount of airflow to a very low temp to dehumidify, which is what I imagine most units do when in dry mode.

You're right. That's exactly how my Fujitsu runs in "Dry" mode. The evaporator blower is almost unnoticable. I'm getting old and not thinking my heat transfer processes through properly.

Tommy

 

[Yankeefarmer]

Our Fujitsu Halcyon system manual notes that in dry mode, the temperature set point must be low enough for the system to run, in order to achieve the drying. It sounds like this is how they avoid overcooling, vs. the Mitsubishi system that doesn’t have a temperature set point in dry mode.

 

[u3b3rg33k]

I've been sealing and insulating my garage, and particularly with parking snowy/slushy cars indoors in it in the winter, I tried a regular dehumidifier. it's worthless at 40F. runs for days and produces maybe a cup of water.
I picked up a desiccant wheel dehumidifier, and that thing works great! it's only rated for 20 pints but even with that set at 40% it still cycles on/off so it's more than adequate.