Evaporator freezing up

[chillben]

Hi All. I am new to this forum. I have been out of the A/C business for about 8 years.So I may not be up to date with the industry .
My question concerns my daughters Floral walk in cooler ref system. (6'x 6' ) She just had the system serviced a month ago by a local service company in Denver . I am here in Texas and she called me about the evap unit freezing up-- in the first few turns of the evap unit. She has to shutdown and do a defrost.
The unit was cleaned and and filled with 414a instead of R22. There is good airflow thru the evaporator. What would the pressures be ?.From my experience that indicates that the unit may be low on *****. I understand that 414a is a sub for R22. I don't have any experience with this type of cooler. Are there any special circumstances that concern this type of system. I have a supply of R22.
Any advice would be greatly appreciated.

I will probably will be going up there in 2 weeks and will take my tools and check it out.

ChillBen

[old gas bottle]

hi matey, i woiuld check its full of gas,[clear sight glass], then start looking at the defrost and t/stat,with flowers there is a high water content and they need plenty of defrosts,the other thing is r22 and derivatives give quite a fierce evaporating temperature that can burn the stock and dry it up,i allways use R134A with a small TD accross the evap, good luck. by the way,check door seals etc.