Mini Split A/C & Heat Pump FAQs

Diagnostic questions & answers set #2

Split System Refrigerant Charge or Leak FAQs

Is Low Freon in Mitsubishi Ductless System - normal?

My Mitsubishi ductless system is low on refrigerant and was installed in 2011

Do I need to have a costly leak check or should I just have freon replaced, it is at 40%.

Is it normal to have freon level go down after 6 years? - On 2017-06-16 by Mike

Reply by (mod)

@Mike

Freon is not a consumable substance in A/C or heat pump systems. If your level of freon drops then there is a leak that needs to be found and fixed.

 

Which refrigerant lines are hot and cold on a Pioneer mini split?

I have a pioneer mini split unit and one line is hot and the other is cold. - On 2015-12-15 by Michael G.

Reply by (mod) Suction line is cold, high pressure refrigerant is warm or hot

Michael

In normal A/C and heat pump operation one line is warm to hot - depending on where along its length you check its temperature - and the other cool to cold.

The suction line or low pressure line is cold and the high pressure line or refrigerant line can be hot - depending as I say on where it's touched.

But keep in mind that unlike a "cooling only" air conditioner, in a heat pump when it changes from cooling to heating mode, the direction of refrigerant flow (liquid and gas) is reversed, so "which line is hot" and "which refrigernant line is cold" depends on whether your system is in heat or cool mode.

Here are signs of a sudden refrigerant loss

I had a mini split installed in November, I found that after installation (week later) there was a small bit of oil on the small line set connection point. I called the tech back and he found a leak so they tightened the fitting and checked for leaks again, all seemed to be ok.

A couple weeks later the unit was frozen (i thawed it by turing it into ac mode and watched the unit steam... it got pretty hot) and after talking to the manufacturer they said is was low on refrigerant, so I had the same tech come out and recharge the system because he never recharged after the leak.

He pulled the fluid out and recharged it with the amount noted on the unit. We don't really use this unit in when its really cold outside only when the temperature is around the 32f mark.

The unit froze when it was around -3c to -5c. Previously to the unit freezing it seemed to work ok, the unit would go into a defrost mode then start heating again right away.... At least i think it was going into the defrost mode.

Now during these winter months in heating mode the unit runs anywhere from 30-60min (daytime) to 15min (evening) then defrost light comes on. The indoor unit stops blowing air, the outdoor fan shuts down, and nothing happens.

The temperature on the line sets outdoor start decreasing and the defrost cycle doesn't kick on.

An hour later you can hear a woosh noise outside and then a hum that gets louder, and the whole outdoor unit defrosts. Then the outdoor fan kicks on and the defrost light on the indoor unit goes off and the unit starts heating again for another 15min or so. The process repeats.

I'm not sure what is happening and why there is such a delay for the defrost cycle to come on

I'm concerned that the unit was ok to begin with, and having the tech pull fluid and recharge may have been a bad idea, or maybe they didn't purge all the air from the system when they initially installed the line set, or me turning the unit to ac to defrost ice buildup damaged a component. Any help or advice would be appreciated.

When they recharged the system it was -5c outside pressure was 440psi- 460 ish high side pressure was suppose to be at 550psi. When unit is in heating mode the hotter line is 37c and the cooler line is 15c, until the unit goes into defrost.
Thanks for your time

I should also add that during its operation last night, the defrost light went off and the indoor unit was heating for 10 seconds then the unit went into defrost mode again.

A wooshing noise came from the inside unit and it sounded like a crackling noise then the defrost light went off and the unit began heating again. It was like the indoor unit was going into defrost mode.
Thanks again. On 2018-01-09 by Sean A.

Reply by (mod) -

Sean

Good going - if you see a small oil leak at a refrigerant line fitting, indeed that's often a clue indicating a refrigerant leak.

Frosting can occur at abnormal levels if the refrigerant charge is low.

Beyond that I can but guess that there may be a control relay or board that's not working as it should.

Many Refrigerant Leaks at Carrier Mini Split 40MVQ Installation

I have had hell from day 1 with a Carrier Mini-split 40MVQ. Installer has come out many times for freon leaks, made us pay for them to re-do THEIR installed outside valves. Finally, after 3 years (and multiple freon additions), they finally performed a leak test and found the evaporator coils on the inside unit were leaking pretty badly.

I told them that I suspected that from the beginning because every time they charged with freon, we could smell it inside the house!

Now, they are claiming that Carrier no longer carries this unit or the parts for it. It's been 4 weeks now and supposedly we are waiting for Carrier to respond to them! I know we're getting the run around. The unit is out of warranty but they should be responsible for misdiagnosing the problem.

We've already paid 61% of the original cost of the unit for new valves and freon charges!

So, my question...if there is no way they can repair this unit, how difficult is it to buy a different mini-split, either from Carrier or a different company, and install it?

IOW, will piping, wall opening size, etc need to be modified or do most mini-splits use a standard installation for these things? Can I buy a replacement and pop it in? On 2016-04-12 by Kelly

Reply by (mod) -

Kelly,

Sorry for so much aggravation, indeed often the service tech is under pressure to fill and bill rather than spend their time and your money on finding the leak.

I prefer to find the leak for many reasons.

I don't think you'd smell freon - it's odorless. Still a corroded coil is not repairable.

Possibly Carrier or your supplier can give you a price on a replacement of the cooling half of your system, but if the original equipment is old enough to be using an old refrigerant now obsolete (R22) I'd replace the system.

Split System / Ductless A/C or Heat Pump Odor Complaints

Fujitsu Halcyon I.A.Q. smells like it's on fire

When I turn on my Fujitsu Halcyon I.A.Q. unit to cool down out of the blue and quickly it emits a very strong chemical burning smell, as if something is on fire inside the unit.

Has anyone come across this before?

We had to turn the unit off and leave it off. On 2016-07-20 by Pam Grant

Reply by (mod) chemical burning smell from Fujitsu Halcyon I.A.Q. unit

Pam

Watch out: TURN OFF ELECTRICAL POWER to the system and KEEP IT OFF (as you've done).

It sounds as if there is a failing control; there is a risk of an electrical fire.

Then you can call your service technician for repair.

Split System A/C Odor Complaint

When our split unit air conditioners are on, the fan runs continuously even when the compressor turns itself off.

When the compressor turns off (but the fan is still running), the room begins to feel very humid and it has a horrible, musty smell.

All of our units have had the same issue since day 1.

There's not an option to have the fan shut off when the compressor stops.

Is this smell and humidity normal? Is there anything I can do about it? It bothers me immensely. Thanks! - On 2017-06-12 by Not so pleased

Reply by (mod) Compressor unit fan runs continuously, Fix an odor complaint

Not

Some systems have a "fan-on" control switch on the remote or right on the bottom of the indoor air blower unit itself. Check that those are not set to ON or MAN.

When the A/C is OFF and the fan is running you are continuing to circulate and filter the air, but that should not be the cause of an odor;

Take a further look at the air conditioner wall mounted indoor unit to see if it looks moldy - Then see SPLIT SYSTEM AC MOLD CONTAMINATION REMOVAL at https://inspectapedia.com/aircond/Air_Conditioner_Mold_Removal.php

It is normal for indoor humidity to creep up in hot humid weather when the A/C is "off" - the fan won't be the cause.

Some split systems like our office Sanyo unit have a "dehumidification" mode that is specifically designed to reduce indoor humidity without making it too chilly indoors.

What underlies this problem is this : if an air conditioner is over-sized (too much BTUh cooling capacity) for the space it is conditioning, it will drop the indoor temperature too quickly - before dehumidification has been sufficient.

That's because the system needs to run longer -not just the fan but the cooling system - to remove high levels of indoor humidity.

About the odor complaint, I'd start by having a service tech inspect the indoor wall-mount air handler or blower unit for mold or other dirt and contamination, and of course then to clean the system if necessary.

Also check, clean, and sanitize the removable air filters.

Keep me posted.

 

Split System Heat Pump / Air Conditioner Not Cooling or Not Heating

Lennox heat pump Mod:12hpb with a CB30M air handler runs constantly, doesn't cool

I have a Lennox heat pump Mod:12hpb with a CB30M air handler. The unit runs constantly but little to no cooling .

Defrost reversing valve seams to shift from A/C to Heat mode, checked the temp at the Liquid and Vapor lines & Liquid line is 84*F and the Vapor line is 81* F ambient temp 94*F.

I can not determine if the defrost reversing valve is leaking and would be the culprit.The Defrost Control Board Led's both are on constant red. I Am a 36 yrs veteran in A/C-H, Commercial refrigeration & electrical business and am retired now.

Could use much needed assistance ASAP. w r i t e me-r a y m on dflo ry @ g m ai l,c o m wife dealing with cancer 10 yrs.
Thank You very much. - On 2017-05-22 by Rajun Kajun

Reply by (mod) - check first for a refrigerant leak then for a bad reversing valve on heat pump

Rajun

I agree that a reversing valve that's not working properly or is cycling could cause loss of cooling, but it seems more likely that your system has a refrigerant leak.

See the diagnostic and repair suggestions at

LOST COOLING CAPACITY- the air conditioning system seems to be "running" but not enough cool air, or no cool air at all is being delivered to the occupied space.

LG Mini Split System Heat Pump Heat Mode Not Working

I have a LG mini split 1200 BTU unit that won't provide enough heat.

It was working great on cooling past summer but now winter has arrived it's set to heat

We can get heat but a very low flow of air even when remote is set high

It seems that we can set remote at any high Temps but always only works until 17C then shuts off

I cleaned filters and check compresser and seems all OK.

Could this be a bad control board or hoping it's a simple fix - On 2016-12-17 by Greg

Aura 18HF/MO Wall Unit Stopped Blowing Warm Air

Greetings. Senville Aura 18HF/MO installed in July 2014. Dual head. Worked fine until one of the heads quit blowing hot air, really does not blow at all.

The other head is still functioning fine. When I turn on the malfunctioning head, the fan in the outside unit turns, after approximately 5-10 minutes the outside unit will make a whosing sound like air brakes, but deeper.

Any suggestions before I call for service? Thanks On 2016-12-03 by Richard Robinson Senville

Heat not working on mini split in heat mode

I have a mini split system heat pump and when I switch to heat the condenser comes on and the air handler it won't come on - On 2015-12-18 by andres

Reply by (mod) - What to check first if the Mini Split Heat Pump Stops Providing Heat in "heat mode"

When a split system heat pump heat-mode isn't working we check

First: the outdoor temperature, against the unit's operating specifications, so that we know if it should be providing heat from the heat pump or if the outdoor temperature is so low that the system will have switched to backup heat.

Second: if it's too cold outside for the heat pump to provide heat, then the service tech will check the operation of your backup heat system.

On a split system heat pump backup heat, if provided, will usually be electric, so don't forget to check the breakers in your electrical panel before calling a repair technician.

And depending on your heat pump's capacity, your backup heat may be a completely separate system such as electric heating baseboards.

 

Directair heat pump MSAEB-12HRFN1-MT0W won't run, displays -- error message

hi, I have a Directair heat pump MSAEB-12HRFN1-MT0W, 20 SEER, 12k Btu/H. one of the indoor units is acting strange, the system is only 3 months old,

The problem is when I power up the head unit it comes on and after a few moments it shuts off and displays -- in the temp indication window.

Is there something I can do or do I have to contact the installer. can you explain what is happening please. On 2016-11-11 by jeanpierre

Reply by (mod)

I would call the installer or service company, IF the "Unit does not start" troubleshooting steps in table below don't work for you.

The manual for your Directair heat pump is at

• DIRECT AIR HEAT PUMP IO MANUAL [PDF] User's Manual for the Direct Air Inverter Split-Type Heat Pump

Or contact the company directly at Direct Air - Contact Powrmatic, a Canadian Company, Tel: (800) 667-7697 Email: info@powrmatic.ca Web: https://powrmatic.ca/

Mishubishi Split-System Heat Pump Model PKA-A12HA4 cools but won't work in Heat Mode

I have a Mishubishi Split-System Heat Pump Model PKA-A12HA4 (air handler) Model PUY-A12NHA4 (Condensing unit) .

In the summer time the AC working great. Now i switch to Heat Mode. But only cold air coming out. Please help On 2015-11-21 by Tom N

Reply by (mod) - diagnose Mishubishi Split-System Heat Pump Model PKA-A12HA4 (air handler) Model PUY-A12NHA4 (Condensing unit)

Tom:

If it's quite cold out then your system may be switched to backup-heat and it'd be the backup heat that's not working.

Otherwise, presuming the thermostat is correctly set, I suspect a bad temperature sensor or control board.

Klimaire dual zone mini split heat pump works in heating but not in cooling mode

I purchased a new Klimaire dual zone mini split Heat and air unit.

It worked great for a month but now the one inside unit quit cooling. It heats fine but does not cool. The other inside unit still works great. Any Ideas? On 2017-10-09 by John -

Reply by (mod) -

If the unit is a heat pump that works in heating mode but not in cooling mode I suspect that a control or reversing valve is not working. Call your installer; on a brand new unit you'd hope repairs would be under warranty.

Unless like my Wappingers Falls plumber, the job was guaranteed only "until my truck reaches the end of your driveway"

Split System HVAC Installation FAQs

OK to install indoor half of a split system AC on an interior wall

I have a Mrcool 36k btu DIY pre-charged unit that I'm currently in the process of installing. The room I'm installing it in isn't on an exterior wall unfortunately.

I want to install it through the indoor wall, then run the refrigerant lines up vertically about a 1.5' to the ceiling, then strait across the ceiling, then out of the exterior wall, and down to the outdoor unit. Is it ok to run the refrigerant lines upwards like this? I have the condensate drain separate and angled with a downward flow. On 2016-06-15 by Matt

Reply by (mod)

You can certainly install a split system indoor half on an interior wall, we've done that; the refrigerant line has to be appropriately routed and you might need to increase the charge according to added volume for the piping length.

Refrigerant lines can run in any direction; However some components like some TEVs must of course be in an "upright" position as the manufacturer may specify.

Watch those flexible condensate drains - I've found sags and as a result clogs and subsequent blockages if the lines are not run with care, sloped and supported. We want standard drain slope of 1/8 to 1/4 " per foot.

 

Installing a Split Sytem on an old CoOp Building: Can I have the condensate drain pipe connect to the bathroom drains? Will it hurt the roof?

I have a top floor 2 room apartment in an old cooperative building where the rules currently require window units.

I want to install a mini-split system with the compressor on the roof, refrigerant lines and power line running up/down through the roof along the inside of the exterior building wall to my bathroom, and serving two air handlers, one on either side of the bathroom, in the bedroom and living room.

Can I have the condensate drain pipe connect to the bathroom drains?

Can the refrigerant line/power be safely installed without damaging the integrity of the roof?

How would you advise the Board of my building to respond to my request for rule waivers? On 2017-08-03 by Davis -

Reply by (mod) - do not connect condensate drains directly to a plumbing drain

No Davis, you cannot pipe a condensate drain directly to a plumbing drain.

Such a connection is unsafe because of both bacterial hazards and the chance of drawing sewer gases (explosive) into the building.

See CONDENSATE DRAINS, CODES for details

And yes, a competent installer can run electrical and refrigerant lines to your split system without compromising the structural or waterproof integrity of the roof, though the particular details depend of course on the building condition, roof material, access, etc.

Split System Temperature & Time Control FAQs

How to Set the LG Split System to turn on and off at specific times

Our LG split ductless has a timer on and off program so I set it up to come on at a certain time and also to turn off at a certain time.I have it in the heat mode by the way.

Anyway it doesnt come on at the selected time. Otherwise it works fine.I am wondering if I should have programmed it with the remote pointed at the wall unit? On 2015-11-17 by Tim -

Reply by (mod) - LG split ductless timer programming

Tim, the brains are usually in the remote in this case.

Check the position of the slide switches inside the remote cover.

One may need to be set to AUTO.

The IO manual for your unit will explain how to use the timer feature on the remote control if that is available.

How to set the Frigidaire split system A/C to maintain a specific room temperature

I have a Frigidaire split type air conditioner. I want to be able to set high/low temps so that the unit will turn off/on automatically and maintain a certain temp range.

It seems like there is no option for this, that I have to manually switch it on and just let it run until I manually switch it off. This doesn't appear to be very energy efficient, especially at night. I've read the instruction manual and can't seem to figure this out. Any advice? On 2015-07-13 by Melanie O

Reply by (mod) Frigidaire split type air conditioner doesn't respond to remote

Melanie

The remote control typically has a cover you can open to set programmable themostatic controls for the split system AC unit. Just remember to leave the remote where the wall unit can "see" it.

Bypass temperature setting limits on a Mitsubishi Split System

I have a Mitsubishi mini-split I am using to keep a large storage room above freezing. My goal is to heat the room to 40 degrees when the outside temperature falls below that. I do not need cooling in the summer.

The wireless thermostat will not prevent setting the heat lower than 61 degrees. There is no physical reason for this limit because all it means to set the unit to a lower heating temperature is that the unit would come on less often.

Does anyone know how to bypass this artificial limit or to add a separate thermostat that will turn the unit on and off to maintain 40 degrees? - On 2017-10-26 by Rob -

Reply by (mod) -

Rob,

I would consider installing the Wireless Remote Controller and Reciever Kit - MHK1 - but you will have some trouble finding just where to connect the control cables at your mini split to hook up the unit's receiver.

Basically you have to remove the cover, open your wall-mounted Mitsubishi mini-split, access the circuit board that controls the unit, and connect the new thermostat's receiver cable to the CN105 connector port on the control board's upper left corner. You should see the connector ID marked on the printed circuit board.

Clean Energy Wonk has an article on doing this at
https://cleanenergywonk [DOT] com/2013/04/16/adding-a-programmable-thermostat-to-mitsubishi-mr-slim-heat-pumps/

Or you might give Mitsubishi a call to ask them for other specific suggestions.

See MITSUBISHI HVAC including Split Systems at MITSUBISHI HVAC

A/C Won't Turn On and LED Display Blinks Between "RUN" and "TIMER"

Why the air cond wouldn't work because the wall-mounted AC LED'S keep blinking from RUN to TIMER. (Sept 5, 2012) Pearl

Reply:

Perl, check your remote control settings; if the remote has been accidentally set to put the A/C in timer mode, it may not be turning on and off manually.

Or someone stepped only partly through the Timer function on the remote control.

If all else fails, take the batteries out of your remote control and wait a minute, then re-insert them to default back to its basic program.

Question: Split system wall unit won't respond to the remote control

We own a BnB and one of our units is not working. The wall unit is lit and showing set to a/c with thermostat set on 80.

The remote shows 74 and a/c. When you point the remote at the unit, it does not respond. Purchased new batteries - no change.

The two are apparently not "reading" each other. I am sold out this weekend with guests, and I don't know what to try next! I flipped breakers on and off,

I changed batteries in the remote twice. Normall there is a "beep" when the remote speaks to the unit, but there is nothing at this time. Suggestions would help - my HVAC tech is out of town on vacation! (May 9, 2014) Rebecca said:

Reply:

Rebecca, if the A/C unit is working when you control it directly from the thermostat but not from the remote unit, then clearly it's a problem with the remote-TT communication.

Try powering off both units and then back on.

Split System A/C or Heat Pump Dehumidification FAQs

Mitsubishi Mxz3B30NA Outdoor Unit with 3 Msz-Geo9NA Indoor Unit - Sizing vs dehumifification

In June 2014, I installed a Mitsubishi Mxz3B30NA Outdoor Unit with 3 Msz-Geo9NA Indoor Unit.

Installed in Bedrooms that are about 12 X 12 ea. Mitsubishi said that with Hyper system this would work. fine.

They would only give enough cooling for 0 to 400 sq ft. what every was needed for the room. They encouraged me to put this size in.

Now the room will cool and take the humidity down some. Then the humidity will go as high as 80%.

Plus this unit has a dry mode that's supposed to take humidity down instead it will increase. What do I do now ? On 2015-07-10 by Eddie

Reply by (mod)

I would first check the air flow temperatures to see what actually happens with cooling; then same with indoor relative humidity at the unit and in the room center;

I'd check the cool-down time. If the room cools off too fast then in general an AC system won't dehumidify.

For AC systems that have a dehumidification mode you're basically trying to remove humidity without continuing to cool down the room - I'd make the same measurements with the equipment in that mode.

Then I'd go to the manufacturer with that data.

Keep in mind that advice about HVAC sizing, to be accurate, needs to consider more than room size; we add consideration of the building heat gain rate and we also look for sources of moisture beyond normal, such as leaks or wet crawl areas.

See

• HUMIDITY CONTROL & TARGETS INDOORS
• HUMIDITY CONTROL INDOORS