Do it yourself mini split heat / AC

[OldSparks]

By 'froze up' do you mean the inside coils getting covered with frost/ice during AC use, or do you mean the outside coils getting covered with frost/ice during heat pump use, or something else?

As mentioned above I am in the process of a DIY minisplit install, and am curious about the failure you experienced.

-Jon

The inside coils in all cases. The shop unit was above my electronics test bench and the office unit above my desk and computers. Needless to say, the resulting water damage made me less than a happy camper, so I finally had them taken out. This was at a municipal potable water plant in California, and all the problems occurred at night when nobody was there to catch it before damage resulted.

 

[petersonra]

I have given serious thought to having a mini split installed in my bedroom. The only place I really need air conditioning. Eventually my central air unit will fail and rather than replace it I might just get a mini split for the bedroom.

 

[junkhound]

The inside coils in all cases. The shop unit was above my electronics test bench and the office unit above my desk and computers. Needless to say, the resulting water damage made me less than a happy camper, so I finally had them taken out. This was at a municipal potable water plant in California, and all the problems occurred at night when nobody was there to catch it before damage resulted.

Recently installed a 'hacked' Daikin AC for use as a cooler with the inside temp of 34F. Main hack was adding 22 kohm across the room temp thermistor to enable temps below the 60F setting minimum (with resistor, uniti thinks 35F is 75 F, etc). Initially also added a 50K ohm resistor across the thermistor on the evaporator coil. Coil froze up. Removed that resistor so 'as designed' evap coil thermistor, and coil does NOT ice even with 33 F cooler temp. Was impressed with the design of that unit. (Daikin FTX/S)
Be sure you buy a minisplit with the evap coil fitted with thermistor and frost control circuits (e.g Daikin, think Klimeair also, dont know about others) and you will have no inside coil freezing.

In heat pump operation, you will ALWAYs get the outside coils to ice over when outside temp below freezing and humidity over 0%. Defrost circuits are used to defrost outside coils on heat pumps.

 

[Frank DuVal]

The inside coils in all cases. The shop unit was above my electronics test bench and the office unit above my desk and computers. Needless to say, the resulting water damage made me less than a happy camper,

1. freezing coils is a sign of low refrigerant from leaks of improper installation
2. any water in the evaporator unit should have drained through the hose to a proper place, even when the coils defrosted.

I'm going with improper installation since probably the same person installed both units.

All the units I have installed are working great. Sure, that's less than 20 units, but...

Vacuum pump, micron gauge, and the adapter from 1/4" flare (used on the R12, R22, etc. systems) to the R410 fitting threads.

 

[mtnelect]

In California the HERS requirements for duct leakages are getting harder to comply. That's why I changed to ductless and the waist of energy running ducts in the attic.

In doing service calls on ductless these are the most common problems found:
1. The flair fittings leaking
2. Getting the power cables switched on multi units.

 

[Todd0x1]

In California the HERS requirements for duct leakages are getting harder to comply.

I've been seeing on new multifamily construction central hvac with the ducting all running in bulkheads so the ducts are all inside conditioned space.

 

[GoldDigger]

1. freezing coils is a sign of low refrigerant from leaks of improper installation
2. any water in the evaporator unit should have drained through the hose to a proper place, even when the coils defrosted.

I'm going with improper installation since probably the same person installed both units.

All the units I have installed are working great. Sure, that's less than 20 units, but...

Vacuum pump, micron gauge, and the adapter from 1/4" flare (used on the R12, R22, etc. systems) to the R410 fitting threads.

Two comments:
1. Sometimes moss or slime mold or other organic growth will plug the evaporator area drain if not cleaned periodically.
2. If the freezing is really extensive it might go all the way to the drain, with the coil melting before the drain. (More of a problem with self-defrosting refrigerators than A/Cs.

 

[ggunn]

1. freezing coils is a sign of low refrigerant from leaks of improper installation

It can also be a sign of dirty evaporator coils.
It can also be a sign of trying to cool a volume of air too large for the unit.

 

[kwired]

It can also be a sign of dirty evaporator coils.
It can also be a sign of trying to cool a volume of air too large for the unit.

Or not enough air flowing over the coil for various reasons. Plugged air filter, not enough return inlets/too small of duct, etc. Though some those things shouldn't apply to certain mini split indoor fan coils.