Fujitsu Mini Split Outdoor Unit Fan Failure

Glidde8

Hi all. I have a Fijitsu MS installed on my first floor that I use for supplemental heat during the winter. The other day the indoor unit started flashing a code for an outdoor fan failure. I dug the outdoor unit out from the 4.5 feet of snow that was covering it and tried to reset it. No luck. When I press the reset button on the indoor unit the internal fan does respond, however still nothing from the outdoor unit. I plan on taking it apart this weekend. Anyone have any suggestions on what I should be looking for? I'm not all to familiar with mini split systems so any advise is greatly appreciated!

Abracadabra

no other flash codes?

i assume you've got power? breaker didn't trip?

JUGHNE

Was the outdoor fan blade locked up with snow/ice? Most of these MS shutdown at 5* or so outside temp. I believe they do a simple hot gas defrost cycle (AC mode with no fans running) and that melted ice has to get away from the coil bottom, is your unit elevated off the ground?
I have seen a Sanyo MS HP covered with snow, it formed it's own igloo of snow/ice and kept running. Probably not very efficiently but still put out warm air inside the building down to the 5* shutdown.

Glidde8

Abracadabra said:

no other flash codes?

i assume you've got power? breaker didn't trip?

Correct, no other flash codes. Breaker did not trip. Tried resetting the breaker just in case, no luck.

Jack

If the unit has been running in these conditions and the base of the condensing unit cannot get rid of the melt off in the defrost mode, you can build up an ice sheet in the bottom that can freeze the blades in place. I've seen those very efficient blades become very short as a result. Fujitsu has a neat "Mobil technicians app" if you get access to it. This is why you should elevate the condensing unit. The newer MS that will work down to -30 have base pan heaters.

SWEI

I've seen mention of minus 15°F in the literature, but minus 30°F? Wow.

Glidde8

Thanks Jack. That's honestly what I'm expecting to find when I take it apart. Everything just iced up. This winter has been crazy and I honestly did a horrible job of clearing the snow from the unit.

If it is a block of ice...should I just leave it be and kill the power to the unit, or should I try to remove the ice?

Harvey Ramer

Those heat pump operations in extreme cold or negative temps come at a substantial operating costs. Physics demands that it be so.

As said before units must be elevated to prevent ice buildup. Up here in the northeast, every suitcase style condenser should be installed with a fan guard. The fan guard should also be sealed along the top and on both sides to prevent water/rain from wrapping in on the fan shroud and freezing. This happens during cold rains while the unit is in heating mode. The ice will build up till it starts hitting the fan.

These are things I have encountered and addressed with daikin, however the recommendations hold true for other manufacturers as well.

JUGHNE

I would keep the circuit breaker on to maintain the crankcase heater. As for elevating the unit, in north central Nebraska a 8" cinder block has been enough height for MS, (most of the time).
If this was a conventional unit one could force a defrost cycle to get rid of frost/ice. But if your unit has a layer of ice in the bottom that the blade hits and does not have a base plate drain pan heater, then some external source of heat will have to melt it. The sun will come out again sometime . As far as chipping ice these things have fairly fragile tubing & fins. I have replaced expansion valves in commercial refrigeration where the owner used a torch to do a manual defrost on the coil including the TXV sensor bulbs.

Glidde8

JUGHNE said:

I would keep the circuit breaker on to maintain the crankcase heater. As for elevating the unit, in north central Nebraska a 8" cinder block has been enough height for MS, (most of the time).
If this was a conventional unit one could force a defrost cycle to get rid of frost/ice. But if your unit has a layer of ice in the bottom that the blade hits and does not have a base plate drain pan heater, then some external source of heat will have to melt it. The sun will come out again sometime . As far as chipping ice these things have fairly fragile tubing & fins. I have replaced expansion valves in commercial refrigeration where the owner used a torch to do a manual defrost on the coil including the TXV sensor bulbs.

Yikes..yeah not bringing a torch anywhere near it. The unit is elevated off the ground...only about 4 inches though. No match for the 4.5 feet of snow we have got in Eastern Mass.

I'm going to make sure that it is actually iced up. If it is, I will clear our a good area around it and let mother nature take care of the melting the ice.

Thanks everyone for the quick feedback. I'll let you know what it looks like when I take a look on Saturday.

Techman

You might want to think about all of the snow in the windings of the outdoor motor and those very expensive circuit boards. Shutting off the power might not be a bad idea, BUT you CANNOT start up the compressor for 2 days after power is restored.

Bob Bona_4

Had aFit RLS2 with fan failure/code a few weeks ago. Was stuck from ice blowback at one point. Shut off breaker to unit for 15 minutes, reconnect. This reset the code.

JUGHNE

Yes, whatever you do with power be sure to get the compressor warmed before turning on. The outdoor fan motors I have seen on MS HP are totally enclosed (but not water proof) and the boards are under the top cover. The elevation is to ensure that the water from defrost drains away from the HP. Just so that there are no connecting icicles between the unit and the ground. Mini splits are really good until they are not. We had severe weather this June and power surges knocked out one outdoor Fij unit, ended up changing out all 3 boards and OD fan motor. It is recommended that you change motor if main board failed, or bad motor may waste new board. There seems like that should be a better design of board that a bad motor would not destroy it.
Here I raise conventional HP up 16" on a stand and if there are connecting icicles then there is a defrost timer problem maybe.
So here in NE where we usually have winter I can see my brown lawn and it was 32* today.

Techman

I agree that the outdoor fan motor is NOT waterproof, hence my concern about motor getting water into it from the 4.5' of wind whipped driven snow getting into everything,everywhere . The outdoor unit is required to be a given height ABOVE the normal snow height and that is not 8-12" off the ground. My one boss installed dozens and dozens of packaged RTU HP about 12" above the roofs. Guess where we were when it snowed?At least on his in warranty customers, but out of warranty customers were on their own or they were charged for our snow shovel expertise. When I was 1st hired by him I mentioned the height requirement for HP's and I was laughed at, AND then he told me that he would teach me EVERYTHING I would need to know about HP's. AND THEN he told me to cancel my 1 week Carrier HP Class( in Syracuse, N.Y.) that I signed up for prior to being employed his company.Boy -o-boy was he upset when I came back from Carrier , and showed my fellow workers the 2 -5" thick binders of Carrier HP info. He went so far as to tell me (in his office) that I was to "NEVER" bring those binders into his business again. We didn't last to long together,for sure!

JUGHNE

That "normal snow height" phrase again. That is always a guess anywhere in the country and then the wind does whatever it wants. With any heat pump installed here there is usually full capacity auxiliary back up heat. To convince people it is best to not use the heat pump for certain weather conditions can be challenging. First the word "Emergency Heat" scares some people. Second to try to explain that you are not going to look at their HP when it is 10* and they will not pay much more KWH money if they just switch to EMG HEAT. If T-stat allows I lock out HP at maybe 20* to save the machine wear & tear.

Jack

The technology is really fantastic in this equip today. They have great heating capability at low temps. As noted here the units have to be given a break though to be able to operate at those low conditions. Pushing them to hard when they are all iced up is kinda asking for it. I've found them to be really durable. Last year I set a new pole and ran a new underground electrical service to the house. Over a period of time I had some weirdness in the house electrically.i had my electrician come out and we found that PG&E had screwed up the service drop to the new pole. My MS we freaking out, as was I. They put in a new service and I was very pleased when all three units ran properly. I know that the mS sales are enormous in the frozen north, but there are limits to what you can expect out of them. As much as I like them my primary heat remains my Rinnai Energysaver. Gas fired warm air at floor level is pretty good and they make a great combination.

The Electric utilities are reclaiming the heating market with the rebates being offered, but for comfort in extreme climate tic conditions, gas is still hard to beat.