Minisplits fan speeds

ChrisJ

Hi all,

I installed a 12K LG minisplit where I work and the book is pretty much useless.

I'm wondering if anyone can tell me how exactly the fan speeds inside interact with the evaporator temperature and thermostat setting.

For example, it has auto for fan which seems to suck. It ramps up and down a lot.
It then has 5 manual fan speeds.

Does it vary the evaporator temperature to meet the thermostat setting?
Does a lower fan speed result in a colder evaporator temperature or does the outdoor unit throttle back?

HVACNUT

The last six words said it. Without getting technical because I dont have the ability to get too deep, all those thermistors report back the the board which in turn control the speed of the fan in auto from the communication wiring, the outdoor fan speed, EEV's and pressures. All the multiple combinations between say four heads set for four different temperatures at four different fan speeds. All those thermistor inputs will regulate pressure and saturation temperature to hopefully meet all demand. If only one head is running, refrigerant is still flowing through other heads to keep pressures in check.
Mr. Ohm would be very happy.

pecmsg

Constant ramping up and down IF the charge is correct may be a sign of over sized head for the load.

The indoor, outdoor fans, compressor and EEV are all controlled by the computer from temperature thermistors. Always trying to match the heat load. Ill bet your seeing the refrigerant flow stopping for a few minuets before the fan ramps up.

ChrisJ

> @pecmsg said:
> Constant ramping up and down IF the charge is correct may be a sign of over sized head for the load.
>
> The indoor, outdoor fans, compressor and EEV are all controlled by the computer from temperature thermistors. Always trying to match the heat load. Ill bet your seeing the refrigerant flow stopping for a few minuets before the fan ramps up.


It's certainly oversized but it's an office where people are constantly coming and going. I'm assuming the charge is correct as I have more than the minimum lineset length and I one used what was in the unit.

GW

Seems odd, minis normally don’t do that. You’re sure the charge is good and a good vac was pulled?

ChrisJ

> @GW said:
> Seems odd, minis normally don’t do that. You’re sure the charge is good and a good vac was pulled?

Like I said, I didn't charge it. I don't know what LG put in it. It's got a port only on the low side and that apparently shuts off when you open the service valve.

I pulled a 200 micron vacuum and it stayed below 400 without the pump.


The system works very well, it's likely just oversized but I knew that before I bought it.

The head is also right by the door to the shop. Shop is hot.

@GW I can't believe you would even suggest the possibility that I didn't pull a good vacuum.

GW

Lol excuse me

ChrisJ

GW said:

Lol excuse me

Sorry, I was tired when I typed that, but I meant it in a humorous way.

I pulled a 7 hour vacuum on my own system down to 100 microns, stabilized at 120 only to have the manufacturer blame non-condensibles for their grossly oversized txv.

bulldoglax

The auto will keep the indoor unit within two degrees (adjustable )of the set point this the ramping up and down.

mikeg2015

We’ve had a LOT of trouble with leaks at the flared connections on Fujitsu that we sell. Going to switch to using and O ring in there. Was worse we found when we actually torqued them to factory specs.

If it’s low on charge, it could cause it to hunt or surge somewhat.

pecmsg

mikeg2015 said:

We’ve had a LOT of trouble with leaks at the flared connections on Fujitsu that we sell. Going to switch to using and O ring in there. Was worse we found when we actually torqued them to factory specs.

If it’s low on charge, it could cause it to hunt or surge somewhat.

Flairs have been used in refrigeration for longer then I can remember!

ChrisJ

Guys,

It's performance is excellent. It's not low on charge and I have no reason to suspect a leak. I didn't use a torque wrench.

95F out and unbelievably humid and it had no problem keeping the office 68 degrees with the fan on 3 out of 5.

I should've went a size smaller.

I originally was looking at doing a 9k but was concerned with how often doors are opened so I upped it to a 12.

It's ok, humidity control is still good and it runs nice and quiet so everyone is happy.