Dry mode is available on those units, it just needs to be enabled in the MRCH1. But here's the catch - dry mode has no temperature control attached to it, so all the unit is going to do is keep running in low speed cooling (dry mode) until you take it out of dry mode because you're too cold. Honestly, it's one of the worst dehumidification modes that there is since there's no "overcool by XX° to dehumidify" setting. Also, if you have one of your units in dry mode and the other(s) in cool mode the coil on the one in dry mode will be so cold that it puts the system into a coil temperature protection mode and the areas that need cooling will suffer (Assuming these indoor units are on one outdoor unit. Disregard if they're all 1:1 units).

The shorter version is this: If you need dehumidification in one part of the house, get a dehumidifier for that part of the house. Dry mode isn't going to make you happy.

 

REPLY to #1 Post
This is the problem with any a/c that depends on overcooling to maintain <50%RH during evenings and rainy days.

Get a whole house dehumidifier like a Santa Fe ULtra, Broan, or Trane. These units have the option of fresh, filtered air ventilation when the home is occupied and not getting the recommended fresh air ventilation to purge indoor pollutants and renew oxygen while maintaining <50%RH throughout the home with small duct system to the important parts of your home.

This way you get all of important parts of healthy and comfortable home.

Keep us posted on the issues.

Regards Teddy Bear

 

Thank you both @flyersfan & @teddybear. Appreciate each of you taking the time to reply.
It sounds like the units are capable of being set to dry mode, but dry mode is not desirable, so I will stop trying to figure out how I can get someone to enable it.
I do have a ducted Santa Fe dehumidifier in the crawl space (I'm actually on the third unit in less than 3 years - they are not very durable). I keep the crawl at about 48% RH, which puts the balance of the house between 50-54% RH.

However, one part of the house also has an attic with open cell (vapor permeable) spray foam at the underside of the deck, which is common in Climate Zone 3a. However, humidity at the ridge gets over 60% some afternoons, which I'm trying to avoid. I had thought putting the mini split in the area below that attic into dry mode may lower the attic humidity. Based on the information in the replies, dry mode at one unit won't work in my setup because it is 3 indoor units: 1 outdoor.
I may look into having a small supply vent cut into the ductwork in that attic to deliver some conditioned (and dehumidified) air to bring down the humidity. Not really sure at what percentage RH I need to be concerned...

 

60% but at what temperature?

 

Are you getting some fresh air change in the home to purge whatever is killing those dehumidifier coils??? Bring in a dampered 6" duct for fresh air to the dehumidifier. It will purge the indoor pollutants in the home renew oxygen. Who nows, might even slow the corrosion on those evaporators.

We fewer coil problems is ventilated homes.

Thanks for the feed back.

Regards Teddy Bear

 

The house has two ERV's providing fresh air to the living area that run 24/7 when the house is occupied. Although the dehumidifier and the ERV are entirely separate systems, the return intake for the dehumidifier is about 10' away from the ERV fresh air supply.
No idea what is causing the issue with the dehumidifiers - they look pristine - no visible corrosion on the coils, but the coils start freezing. Santa Fe has replaced them...they did not say but on the second one when I gave them the serial number they stopped asking questions and immediately sent a new one - it's like having the serial number answered a question.

 

I am going to chime in here and see if I get spanked for what I am saying;

I have a 2 head Mitsubishi and have not experienced the issues what Teddy Bear and FlyersFan have said. Now I will admit that my house is not sealed up as well as yours, but I have not noticed any over cooling when using the Dry Mode.

Another option would be to run normal cooling mode where you can set a certain temperature and run the fan in the lowest speed possible.

Hope that helps.

 

Atta boy, Joe!

Regards Teddy Bear