Liquid line frosting on a mini split heat pump

[jrock52766]

Sry i dont have much to work with at this point but i am looking for a little help before i go back out to this house. Was already dark when i got there so i wasnt going to tear the unit down at night.

System is a one year old mini split heatpump and is frosting from the liquid line king valve toward the evap coil. It is a 410-A system. Board on the condenser was flashing an overheat code for the compressor. Condensor discharge air was equal to ambient outdoor temp. I have no experience with mini splits but went to put my guages on it and only the suction side king valve had a service port which i found odd considering it is a 410-a system.

Main thing i would like to know is, would a stuck reversing valve cause this problem?

According to the home owner the system cooled great all last summer and the heatpump did fine over the winter but has not cooled well this entire spring. thx in advance for any help.

[beenthere]

Look for leak.

R410A ductless only have a suction port fitting.
And its not 1/4"

[jrock52766]

thx for reply..on a side note...isnt it weird to only have a suction side service port on a 410-a system when you charge 410-a systems by means of subcooling which is checked at the liquid line service port?

At least that is how i was taught to charge them at a 410-a class at the carrier plant in memphis,tn.

[beenthere]

R410A isn't charged by SC if the system uses a piston, which some manufacturers do.
Your class may have been a brand specific one.

Since that insn't a liquid line that you see, it makes sense not to have a port on it.

[jrock52766]

http://www.mrslim.com/UploadedFiles/Resource/MSeries_OB450A.pdf

According to page 6 of the tech manual the liquid line is the 1/4" line and that was the line that was freezing up. that pdf has a trouble shooting section ill try to read before i pass out

[sr20detb13]

I'm in the middle of my first ductless mini split install, so i took some temps in test mode and in full cool. temps seemed alright but I did noticed that after the system was just running the fan on the evaporator the liquid line was sweating, and about 50 something degrees. but once the compressor kicked on the suction got cold 45 deg. and liquid went from sweating to roughly room temp. R410 is pretty new, even my dad with 10 12 years experience says its wrong but its running fine.

I'm working on a 3 1/4 ton sanyo and it has service on suction and liquid.

[jrock52766]

guess you see why im scratching my head. this is a mitsubishi 15k btu.

I know its low on refridgerant but i was leary of just putting some in since i was seeing a frosted liquid line. :-/ Hopefully i can get it straightened out tomorrow. Thanks for the help!

[sysrq2000]

From the mini-splits I've dealt with thus far, its not truly a 'liquid' line as someone else stated in another thread. If the unit you are working on is similar to my experience, the metering device is at the outdoor unit. The manufacturer specifically stated both lines must be insulated for this reason. This could be different in your case, since they are differing brands.

[beenthere]

It carries liquid. It is not a liquid line.
A liquid line is before the metering device.

[jrock52766]

From the mini-splits I've dealt with thus far, its not truly a 'liquid' line as someone else stated in another thread. If the unit you are working on is similar to my experience, the metering device is at the outdoor unit. The manufacturer specifically stated both lines must be insulated for this reason. This could be different in your case, since they are differing brands.

AHHH!!! i see, that helps a lot and explains why beenthere is saying it is not a liquid line. I didnt know the metering device was in the outdoor unit. That really clears things up. thx a ton guys.

[sr20detb13]

yea i found this out last night... the line is sitting with freon in it, with not enough insulation and its just getting cold..

[Gunslinger]

Mini splits are precison charged. You need to recover and weigh in the correct charge. You also need to calculate the line length and add the appropriate amount of r3efrigerant if over the normal length.

[sr20detb13]

this sanyo is pre charged with 7.9lbs and is good for 10-100 feet line set. just needed to leak check, vac lines, and test run. And runs awesome.

[cmajerus]

Mini splits are precison charged. You need to recover and weigh in the correct charge. You also need to calculate the line length and add the appropriate amount of r3efrigerant if over the normal length.

right. The fujitsu's and mitsubishis and I am sure other inverter type systems very rarely need an additional charge added, and when they do it is ounces. they have receivers to hold the extra charge for short linesets.

The best way recharge is to recover evacuate, weighin charge. Check the indoor coil 1st for airflow issues.


I should add if you get the chance to go to a fujitsu class go, doesn't matter how busy you are, make the time. Very informative class, good thing is they are very similar to the mr. slim inverters, so you get a good idea how they all work just from one class, if you find a mitsu. class instead I am sure you will learn about the same amount of info.

[jpsmith1cm]

williamsa7728

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