Mitsubishi ductless split with a short line set

[Newtech72]

I recently installed a Mitsubishi MUH-09TW. This unit was not being used in one location and moved to another building. Prior to be moved there were no issues.

In the new location I mounted the condensing unit on brackets and ran the lines straight out through the wall. The lineset turned out being only about 3' long. I've read the specs on this unit and it doesn't mention anything about removing charge for a short lineset (total charge 2 lb 3 oz).

The unit's small (liquid?) line is frosting up from the king valve to a couple of coils in the evaporator. Supply air today was 71 degrees, outside temp is 82 dewpoint 72.

It doesn't seem to be cooling properly but short of reclaiming and recharging I'm not sure which direction to go.

[Tony3696]

Is sounds like it's metering at the king valve? Possible restriction? Low charge? If you do end up doing a recovery, I would blow the condenser out with nitrogen. I went to a call after one of our techs that only weighed in 1.5 lbs, it needed 3 (2 head unit), the tag said 1.5 lbs per head unit. The shortest lineset that I have charged was about 6' and it purred like a kitten with the factory charge. Let us know what you come up with.

[monkeyspanners]

Weigh in a fresh charge, but adjust it for the short pipe run, usually there is a minimum pipe run of about 10ft but check with Mitsi tech dept. Then see how it runs.

[Newtech72]

Turned out it was a bad 4 way valve.

[chuckcrj]

A bad 4 way valve will not cause frosting.....

[hvacvegas]

A bad 4 way valve will not cause frosting.....

Your not suggesting the mitsu/fujitsu tech support have ever diagnosed a wrong part, are you?

Lineset is to short.

There is a reason that you can't buy a lineset shorter than 15'.

[chuckcrj]

Your not suggesting the mitsu/fujitsu tech support have ever diagnosed a wrong part, are you?

Lineset is to short.

There is a reason that you can't buy a lineset shorter than 15'.

They can only work with the info they're given. I work on them all the time, and rarely have to call tech support anymore.

Please explain how a lineset that is too short would cause freezing?

Fujitsu has a 9 ft minimum line length. Mitsubishi does not publish a minimum length. It is only for noise concerns that you want a minimum line length, they work just fine with a 3 ft line set.

[B1978]

I think its a charge or restriction issue.

[VanIsleRefrig]

Fujitsu has a 9 ft minimum line length.

what fuji's are you working on? just curious

The ones we install if it is a single the first has to be 16' and and if a dual head the second must be 33' with a minimum of 49' total and max of 150'

[BURL-REF]

Fujitsu requires 9 feet for cooling units and 16 feet for heat pumps