I can’t find documentation for an MRCH2 controller on Mitsubishi’s site. Did your system come with a handheld remote? If so, that will get you down lower. What is the model of your indoor unit?

By the way, I keep my house at 58-60 degrees with my Mitsubishi.

 

Found it. You have the MHK2 controller. Go into the setup menu and find function code 181. You can set it all the way down to 50 degrees.

 

Thanks for posting that! I’ll keep it squirreled away in my OneNote for the future. I do run into those stats every now and then [emoji106]

 

Cooling minimum temperature is set by the equipment, not the MHK2. If it's connected to a ducted model or a 4 way ceiling cassette the lowest cooling temperature setpoint is 67° and there is no way to change it. What's the model of the indoor unit?

 

Ah so you think all he did was set thermostat min/max temp limits but that in no way can override the equipment’s programmed min and max? That would totally make sense!

So let’s say you go in the stat and change min to 50, set stat to cool to 50…the unit just runs down to 67 and shuts off? Kinda dealing with that now on a Multi V (long story but kinda similar).

 

Thread moved to AOP, this is the homeowner section.

 

And thus, a warranty claim was born.

 

And thus, a warranty claim was born.

I wouldnt post your serial number, some of us work for mitsubishi.

 

SVZ-KP24NA

 

It seems the installer changed the PIN from its default. I also tried the most common PINs, but no joy. I guess I might have to call them.

 

The default PIN is the date code on the back plus 1234 (unless the date code on the sticker is wrong). Or press Menu go to screen lock>full lock>select and it'll show the PIN. (All this is in the manual so it's not really DIY)

 

What if I just put the thermostat outside in 90 degree temperatures? Like will the unit keep cooling as long as the thermostat reads above 67?

 

SVZ models have a minimum cooling setpoint of 67° and there is no way to change that. Some people have tried installing a conventional thermostat to override this, but the return air sensor in the unit will still shut the unit down when it hits 67° no matter what the thermostat is calling for so don't waste your money going that route. If you have a need for cooling below 67° you have the wrong piece of equipment for the job.

 

Well that's something I wish had been explained before having this unit installed. I have some hope though, as the return air register is in the hallway, so I can for the most part stop the conditioned air from getting to it.

 

Where are you going to get unconditioned air from?
If you try and get it from outside, the space will actually get hotter.

If you try to block it, it will shutdown due to no airflow.

Its literally trying to prevent you from killing it.

 

I just meant most of the cooled air will stay in the rooms if I don't leave the doors open. Obviously the rooms aren't air tight, but the return air would largely be drawn from the hallway the return air register is in. I wouldn't block return airflow, just try to contain as much conditioned air as I can from getting to it so the return air sensor doesn't trip at 67°.

 

No. It never occurred to me that was something I would need to specify. I don't even want it set to 59°, but 62° or 63° would be far more acceptable floor than 67°.

 

Standard indoor temperatures are around 75°f. Around 70°f or lower you start risking condensing water in the walls and causing mold on humid days. Personally I am cold at 75°f if the humidity is 40% or lower. Most of the time when someone thinks they need it that cold there is a humidity problem.

 

Well since I've never lived in a low humidity region, I guess I'll never know if 75° can be comfortable at 40% humidity. The only time the humidity gets that low here is when it gets bellow freezing.

 

When I lived in Oklahoma it would get up into the 110°s, even low 120°s, and we could get the inside of the house into the low 60°s with single zone systems, and I knew people who could keep their house a chilly 55° with multi-zoned systems. In 43 years, the highest low temperature setting I've ever seen was 62, which is why I never thought to ask what it would be for this system.

 

I always just assume people are going to run their units between 70 and 75. So if they run it colder they need to tell me.

I’m with r600 that I’m betting you have a humidity issue. I have my unit set for 75 and 50% humidity and it is comfortable

How old is the house?

Have you ever tested the humidity?

Where is the house located


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This unit came with a humidity reading, and I have no reason currently to doubt it is reading true, but I've never had any sort of testing done. Comparing what the thermostat is reading and my phone's sensors, it's either 37% or 44.1% humidity as I type this. The house is about 120 years old, but the area of the house with the new HVAC system has been remodeled with new insulation and windows in the last 5 years. The bottom floor has oil heat and window unit ACs for now. I'm in Central New England, right near a bunch of water, but on the east side of a mountain ridge, so the rain drops on the mountains and then we usually only get the humidity that didn't coalesce into rain. This valley's best chance of rain is when the front comes up the coast from the south so that it feeds into the valley, but then those are really humid storm fronts, so they don't usually bring any relief. I guess I'll have to wait until we get into the heat of the summer and see if I have to buy a separate dehumidifier for a room or two.

Edit: Just wanted to be clear those are humidity readings from inside.

 

Or it might be a good time for you to exit a conversation you obviously don't want to partake in in good faith. Different people have different comfort levels. It doesn't mean they have something wrong with them. You don't have to come visit me in my 65 degree home, so if you don't have something constructive, and pertinent to my original question, to say, see yourself out.

 

Ill agree anything much below 70°F is unrealistic. If you want 60°F hire a commercial refrigeration contractor.

You might want to play nice with the people trying to help you.

For FREE I'll add!

 

Hey guys, I love it cold. I totally get the OP’s desires. Our bedroom is in the 50’s in the Winter, and my Mitsubishi keeps it around 62 in the Summer. I’m out working in the heat all day. I want it damn cold when I get home.

 

I appreciate your help. Thank you.

 

Some of the people were not even trying to help me, much like yourself. I didn't come here for medical advice, or musings on what other people think is a comfortable temperature. Such "help" is unwelcome, and unhelpful, no matter the price. Try being professional and sticking to the question, or just don't reply. The first couple of people who replied did a wonderful job of explaining how my system works so that I now understand it better, pretty much everyone else, including you, have just been a peanut gallery.

 

An air conditioner removes the heat from the air. Below 68° there is not enough heat in the air thus damage can be done to the equipment.
Perhaps a P series unit allows a lower temp? I don’t know but others will.


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I mean, technically, there's a whole lot of heat between 68 Fahrenheit and 0 Kelvin, but I get what you are saying. There's not much I can do about it now except use my little AC on wheels if it gets unbearable. Maybe if/when I decide to put AC into first floor I might upgrade the unit, but then that'll be a whole different system since it would be used to force the air in from the floor via the basement, and the current system brings the air to the second floor ceiling from the attic. These old houses are beautiful, and the timber they used is great (2x12s actually being 2 inches by 12 inches!), but they don't easily allow for installing modern conveniences.

 

So one of the difficulties with cooling lower than 67° is that the evaporator for needs to be 30° to 35° cooler than the return air. So 67° retire puts you right around 32° and any lower and it's going to try to start making ice.
The reason people can often get away with it is that their systems are so oversized that they don't run very long during peak load so even though they are running the evaporator at freezing temperatures they have time between cycles to thaw.
Here's the dilemma if it's not running long enough it's not going to dehumidify very well and if the humidity is higher you are going to feel hot and you're going to turn it down. So many times people think they have to have the house really cool when in reality if their system was sized and adjusted correctly so it could control humidity and they had a whole house dehumidifier if necessary for good humidity control they would not be able to handle it so cold because the lower humidity would keep them comfortable at a higher temperature.

Also I apologize for mentioning going to a doctor. I didn't mean to offend you. I just know there are medical conditions that can affect your comfort levels and untreated they can cause far worse issues in the long run so I figured it was something to think about.

 

Thank you for the detailed explanation of how the system works, and for the apology. I too work in a field (gunsmithing) that has people ask for things that seem outlandish to me, but it is not my job to give personal opinions of how they should instead set their guns up to my preferences. I will gladly share my personal opinion when asked for it, but otherwise I keep my professional expertise limited to the laws of metallurgy, physics, and federal and state regulations as to what can and cannot be customized on a gun. So I understand the urge to tell someone their ideas are unadvised. And I do have teams of doctors dealing with the plethora of health issues I have from hard driving in both military and civilian life, but my preference for the cold is one thing they have never linked to any of my issues. In Oklahoma I remember people still wearing jackets when the temperatures were in the 70's, but here people start wearing shorts in the 50's, and further north I've seen people do that in the 40's. I think a lot of it comes down to acclimation, as when I was in Korea they keep their apartments in the low 80's during the winter and shed off their layers when they came inside, while New Englanders would consider that a waste of heat and just wear more cloths while indoors.

 

Is it possible that another thermostat might be able to allow you to go lower in temperature? I am not familiar the the Mitsubishi system you have, but I would think there is a solution to be found here.

I work on and install Fujitsu systems and on their ducted type systems wiyj a wall mount controller, you can set the temperature sensor in the controller or the indoor unit (which I think is the attic in your case). See if you can change where there temperature is sensed and see if that helps.

This is a fairly new install, you might want to call the installing contractor and see if he has any solutions.

 

Is it possible that another thermostat might be able to allow you to go lower in temperature? I am not familiar the the Mitsubishi system you have, but I would think there is a solution to be found here.

By default the unit senses temperature at the return, but it can be changed to the wall thermostat with function settings. On the residential stuff there really is no way around the 67° setpoint even using a conventional thermostat interface, because the return air thermistor is always in play. Once it hits 67° in cooling the unit shuts down.

 

The recommended indoor temp for cooling is 78*. Why in the world would you try to kill that unit running it so low?

But you're in luck, if the refrigerant lines get too cold because there's not enough heat in the home to absorb, the compressor will start frost protection and begin running limp modes up to 5 stages. So you wont be able to kill it but it will stop you from getting the ridiculously low indoor temps your trying to achieve.

One of the many reasons Mitsubishi's dont die easy! Be grateful you bought good equipment! The only thing that is gonna save you from yourself.

 

Thanks for supplying no useful information. Like, you know you don't have to comment on someone's post, right?