mitsubishi vrf puryp300yhma

[regcooldude]

has anybody else experienced outdoor coils frosting up really bad during cold snap and not fully being able to defrost ??

[Roundflow]

Can be a common problem if one of the following is relevant.

Over diversified in heating (above 100%).
Short of refrigerant.
Under sized.

[Oilfilter]

Yep short of gas for sure try adding refrigerant and monitor discharge temperature 407c below 100 degs C in heating mode @ 100 %

[regcooldude]

it's r410a not 407c

[Thermatech]

I have been working on a number of sites with these units over the last few weeks with this very cold weather.
Defosting not an issue for any that I have seen.

Have commissioned an awfull lot of this model over the last couple of years.
Not one report of defrosting problems & you can be sure if there were any problems the installing contractors would be straight on the phone.

If the outdoor unit terminates defrost before coil is fully clear then suspect defrost terminating pipe temp sensor providing incorrect data to the outdoor circuit board.
System SOG is also a prime suspect.
Make sure the outdoor dips are set correctly for the defrost options.
The defost time can be 50 or 90 mins
The start temp can be -5 or -8
the termination temp can be +7 or +12.

[robin r33 gtr]

What do you mean by freezing up ? I see condensers go white with frost but clear up on defrost. If it was solid ice I would be concerned.

[regcooldude]

freezing up, thick ice all around coil, accumulator frozen up too.

[marc5180]

Take the refrigerant out and check the charge, you will probably find it to be low.