Display case freezing up?

[Wester399]

I work at a deli for now trying to get my foot into the door at a refrigeration company but for now i got a display case that the evaporator is frosting up rather quickly. Im pretty sure the defrost timer is shot but it freezes up almost daily and we have to shut it off 2 hrs a day then it will come back down to temperature. I checked the sight glass too and it looks like we are low on freon but makes no sense seeing that it runs really cold until the coils frost up. Any suggestions im 90% sure its the defrost timer or heater thats shot.

[markettech]

I work at a deli for now trying to get my foot into the door at a refrigeration company but for now i got a display case that the evaporator is frosting up rather quickly. Im pretty sure the defrost timer is shot but it freezes up almost daily and we have to shut it off 2 hrs a day then it will come back down to temperature. I checked the sight glass too and it looks like we are low on freon but makes no sense seeing that it runs really cold until the coils frost up. Any suggestions im 90% sure its the defrost timer or heater thats shot.

Is this a freezer or cooler display case? Do you happen to have the brand name/model number?

Did you check power to the defrost timer motor? What model timer is it.....and what did you get for a voltage reading?

Does the time clock advance?

Did you take a voltage reading across the normally open and normally closed contacts in the timer.....while in refrigeration as well as defrost? If so, what did you come up with?

What was the voltage/amp draw reading on the defrost heaters? Was that reading within the nameplate specs?

I wouldn't get my heart set on swapping out a defrost timer just yet if I were you.

[mustangpaul]

check your thermastat verify it's working correctly it could be stuck in a closed position keeping the compressor running constantly resulting in icing up. An iced up coil will usually show a bubbly sightglass. If that checks out ok then check that timer. Provide model# so we know what type of case you got.

[ZeroTolerance]

Not hard to tell if a defrost timer or electric defrost is not working. First make sure all the mechanics of the system are operating properly. A defrost Timer can be the culprit of a freezing up coil

[skpkey9]

Very easy to tell if timer is at fault, as Markettech said, " is it advancing" turn dial to a line and wait a few minutes and that will tell you if its operational second while turning dial, if tight ( Hard to turn ) replace timer, if not set it to defrost and check amperage to make certain all heaters are operating as normal...

Also agree that there may be other issues as well....

Refrigerant should be topped off and leak found and corrected...

[VTP99]

If your checking the site glass when the coil is frozen it will most likely show low. One of the biggest reasons systems get overcharged.