My son has a ductless mini-split air conditioner/heater combo. It operates at 220 volts. He says that on the lowest setting the fan still has too much volume. I believe there are three settings. Is there a way to electrically slow the fan ? Since the unit is wired for 220 volts I don’t think it wise to try it at 110 volts.
Normally not possible. You might get icing of the evaporator if you slowed the airflow down.
Almost certainly it would not function at 120, definitely not the motor, and the electronics is probably depending on that 220v input, even though it is stepped down.
If the only issue is air flow, what about putting a deflector so it goes up to the ceiling. If the issue is noise that would be tougher.
Greg
Thanks Greg, I thought as much. I just think he ordered too large of a unit four the space he has.
Undoubtedly as Greg alluded to if you were able to slow down the evaporator fan, more likely than not the reduced airflow would cause the evaporator coil to frost up if not freeze solid. This is a common anomaly generally realized from poor maintenance i.e., reduced air flow of a dirty or clogged air filter and or evaporator coil or in some circumstance realized of an inadequate refrigerant charge…
Michael
Well thanks guys! You may just have solved a problem I’m having with a dehumidifier that freezes up the top of the coils. Everything I read on line said it was low on refrigerant and was a candidate for replacement (Non serviceable), but it will be worth a look behind the coils to see if they are plugged up. It still woks if I run it on the 2hrs on / 2hrs off cycle giving it time to thaw, but that’s not efficient enough to get me much below 70% Rel. Humidity in the basement.
Jon
You could also try raising the unit up off the basement floor closer to the rafters as perhaps the ambient temp of the basement is too cool. Could certainly be restricted air flow on the coil or as stated low refrigerant.
First sorry to Don for hijacking this thread. I believe you got your answer.
Thanks Roos - The unit was located at bench height when I first noticed problems this season. The temp hasn’t gone below 70 in quite a few weeks, so I don’t think it’s too cold, even on the floor. Probably is the refrigerant as these cheap units (LG) only seem to last 4 or 5 years. The one it replaced was 30 years old and still working, just didn’t have all the fancy setting options.
But just in case, I’ll open it up as much as I can and give it a good cleaning with the air compressor this weekend.
Daktah John,
Check to make sure the air intake filter is clean.
Mine appeared clean until I rubbed it a little and I got bunches of lint like stuff just like in a laundry drier filter!
Daktah John said:
But just in case, I’ll open it up as much as I can and give it a good cleaning with the air compressor this weekend.
Pics or it didn’t happen!
Daktah John said:
First sorry to Don for hijacking this thread. I believe you got your answer.
It’s Dan !
John is old!
They just don’t build them like they used to.
David Russell said:
Daktah John said:
First sorry to Don for hijacking this thread. I believe you got your answer.
It’s Dan !
John is old!
Thanks Dave
Yes, and needing new glasses. Sorry Dan!
Clean your coils as well as change the filters. There are liquid pump bottles that don’t require scrubbing. Be very careful of the fins on the coils, too easy to flatten, real hard to lift…
$6,000 for a replacement AC/heater2 weeks ago… but it sure is odd adjusting to 1 degree sensitivity. The old unit had a range of 5-10 degrees. The new one claims a 1 degree activation.
John
Back to my original question; There may be some confusion about the type of air-conditioning unit we are working with. We have a mini split system where the condenser sits outdoors and the fan or blower unit is mounted on an interior wall.
As mentioned the system runs on 220 volts. The power goes to the condenser first, then is fed to the blower. In the blower there is a circuit board powered by 11 VDC. Power for the blower motor ties into this board where there seems to be what looks like relay switches. The way I figure it works is that depending on what speed you have the blower set on, these relays control the voltage to the blower motor.
It was mentioned that the coils might freeze if the fan were slowed. I don’t see how this would happen as the condenser has it’s own fan and as said sits remotely from the indoor unit. I don’t want to slow the condenser fan.
In the attached photos you will see the circuit board, fan motor and step down transformer that powers the circuit board. The company sent my son these pieces for him to “experiment” with. You will notice a black wire and a white wire that run from the circuit board to the motor, along with a green and yellow wire. These seem to be the main power for the motor, with the others controlling speed, my assumption.
Firstly, why couldn’t I place a step down transformer on the black and white wires and step the voltage down at that pout. This way, no matter what the brains are telling the motor to do, it can only get the maximum voltage allowed by the transformer.
The bottom line is that there are three speeds that the blower has. The lowest speed does the job of cooling the room more than adequately. If the lowest speed could be made to be the highest speed, how can this be done in a method other than the one I described?
Dan,
Your questions abound across multiple trades. Yes you could use a properly sized transformer to lower the voltage to the fan motor. This is essentially what is occurring with the fan motor in play now. Three speeds are available by stacking the motor coils in two distinct series connections or not as depicted by the schematic of said motor.
I work with electric motors, pumps, fans, compressors, boilers, water chillers, refrigeration systems and more. Specifically I own a small company that specializes in the sales/service/construction of commercial/industrial laundry and dry cleaning facilities. Initially I worked in the HVAC/Refrigeration industry that grew into the multifaceted specialized industry I have been involved in for the last 30 years.
Typically air conditioning evaporator coils are designed to operate at peak efficiency between 350 and 450 CFM per ton of cooing capacity. Most equipment’s default fan speeds are set in cooling mode at 400 CFM/ton. Lowering the fan speed will result in providing a reduced heat load entering the evaporator coil. Subsequent resultant behavior decreases suction pressure and the vaporization rate of the entrained refrigerant. Eventually low suction pressure drives refrigerant flowing through the evaporator coil to below freezing temperatures.
RH or relative humidity plays a role herein too, decreased airflow over the colder coil removes more water vapor (humidity) which in turn causes the colder than normal coil to sweat or condense the aforementioned airborne water vapor more profusely than normal causing it to frost and eventually freeze.
An asynchronous induction motor, like your air-conditioners fan motor, will not run properly with reduced voltage. The power/watts required is a function of the load not of the motor. If voltage is reduced, amperage will increase to maintain rated wattage or horsepower. Increased amperage results in excessive heat which can cause a motor to burn out prematurely. I’ve dealt with this vary issue many a time, a 10% under voltage rating can cause an electric to motor to operate at 125% of its normal operating temperature.
The outdoor condenser fan is only utilized to remove heat; cool air is drawn through the condensing coil, this cause’s hot high pressure refrigerant vapor (derived from compression cycle) to be cooled and condensed into a sub-cooled high pressure liquid which feeds a metering device, the metering device causes a pressure drop at the inlet of the evaporator coil, a COLD fog laden with liquid refrigerant is sprayed into the evaporator coil, as warm air passes over the cold evaporator coil, heat is adsorbed and travels on to the compressor under suction as a cool low pressure vapor.
All that said, give it a try. Restrict the airflow somewhat and observe the evaporator coil. Restricting the air flow will decrease the fan motor current draw. I’d suggest you could learn enough to decide if you want to go further with your adventure. Is the fan motor located within the units airstream, this would be great for cooling but bad in heat-pump mode?
Michael
Thanks Michael. So I must not be understanding the “Freeze” problem. I thought that the coils in the condenser would freeze if the condenser fan was slowed. But I didn’t think that there would be any issues on the indoor unit with those coils. Also, I hadn’t thought about overheating the motor.
Since the unit in question is not returnable, his best bet would be to try and sell it and get a smaller unit. Sometimes a father’s advice is worth listening to.
It’s the indoor unit that gets cold… too cold and with moisture = ice.
That’s what I was talking about… the outdoor unit gets hot, so no possibility it will freeze.
Restrict air flow on the indoor unit and you might ice up. Induction motors do not work on voltage alone like brushed DC motors.
I think that sentence above is a concentration of what Michael (and I) have been saying.
By the way, I remember old car systems where the fan cut out and I got a block of ice that subsequently melted and pooled up water in the passenger footwell. Early systems did not have a lot of sensors.
Greg
Greg, I must have had a memory lapse. I’ve been in the construction industry for well over forty years and should have instantly known that the outdoor unit dissipates the heat sent to it by the indoor unit.
As I say to some of the younger guys in my trade, I have forgotten more about this business than you guys will ever hope to know 
Okay now that we are all on the same page with indoor evaporators and or air handlers with same. Allow me to muddy the water again; modern HVAC equipment and other types of commercial/industrial equipment often utilize what is commonly referenced or known as a HEAT PUMP circuit.
A heat pump is essentially a refrigeration circuit designed to operate in reverse or in simple terms by reversing the refrigerant flow… So in heating or heat pump mode, the evaporator and condenser switch roles or reverse, hot indoors and cold outdoors. Kinda like reverse technology, albeit there is more to it than that.
Dan, them young bucks are from another world, what happened ever to common sense, honor and respect for yer elders! For some mundane reason they have little to no interest in old guys sharing their wealth of knowledge garnered by years of experience. I enjoy “learning” my guys how to diagnose/repair machines and or equipment, problem is most of em don’t seem to have much or any interest in understanding how things work. Instant gratification reaped of changing out parts seems to be held in higher esteem than figuring out the how, why and when things work properly or not.
Michael