Hi there to all at RE!!!

My first posting, and in need an experianced word, with trying to troubleshoot a knocking freezer 3ph compressor on start up.

Over the summer a freezer door was left open which caused damage to a ball shut off valve and compressor, semi hemitically sealed. When inspecting the system, in running the system the TLV was hissing into the evaporator so I shut the system down and changed the compressor, filter dryer and valve.

On pressure testing I found that the condensor was leaking so I repaired the leak. The system held pressure. I vaced down the system and charged with the correct amount of 404a.

Switching the system on the compressor ran smoothly on the first startup pulling the temp down efficiently. On its second pulldown there was a lound knock on start up. This happened on the next two startups. Slightly worried I have powered down the system and pumped out the refrigerant.

Can anyone help in pointing me in the right direction with the problem of the compressor on startup. I noticed frost forming around the suction pipe into the compressor.

The system is a basic walkin freezer comprising of the following:-

Telemacanique compressor 3Ph.
filter dryer
TLV
accumulator

and all the other goodies.

Hope you can help.

AC.