Multi Deck Hussmann & other cases Sweating

[anasmilbes]

Hey guys, this is my first post so il try to include as much info as I can or available to me.

I've been working with a Super Market Chain for about a year now, I'm the only in house Tech servicing 9 stores in the Southern California area. So far I've managed it, for the most part. Lately, I've been getting a lot of complaints that self-service or Multi-deck meat cases are sweating(on the inside of the case, mostly top panel) and usually I'd see this happen during defrost. But cases are not in defrost and continue to sweat. Conditions are as follows;
Outside temp and humidity, 61, 88%
Store temp and humidity, 68, 65%
Case set point, 32degress, 2 degree differential
Defrost times, 10am, 3pm, 10pm, 3am, 40minutes each.

Cases are either Hussmann or Arneg, don't have model numbers yet. Will try to add ASAP. Although humidity is high, I've noticed this also happened this past summer, when conditions were dry. So now, I'm stuck scratching my head. I only have about a year and couple months experience in mostly commercial. I've done residential calls for co-workers and corporate employees. So most of my experience has been commercial. For this case we use a Danfoss controller and case temps, defrost ect. Are controlled by this controller. This is the only store with a Danfoss system. Other stores are using Emerson Einstein 2 RX.

That's all the info I have and thought of, if any extra info is needed just let me know. I'm doing maintenance work all day today at one of the stores, so il try to reply In a timely manner.

Thanks for the help

[R123]

This should be posted in the Refrigeration and Ice Making forum. Hopefully one of the moderators will move it for you.

[anasmilbes]

Sorry, I figured Tech to Tech was the place to post this. How do I move it?

[jpsmith1cm]

Is your airflow correct for the cases? Low airflow will cause low surface temperatures and condensation.

Also, forget about measuring %RH. DEWPOINT is what we need to know and to control to get condensation problems under control.

[Capz]

I am not sure the design of your cases, is the sweating occurring on or near the evaporator covers? I'd make sure the temp swings are in line as not to freezing the evaps and than having the evaps thaw some before the next refrig cycle? This along with JP's mention of the evap fans.

[jpsmith1cm]

I went ahead and merged the two threads for you.

[Phase Loss]

I'd check case airflow with a velometer.

If you don't have one...

At the very least, I'd make sure all case fans are running, coils are clean, & honeycombs are clean.

[anasmilbes]

Some cases are brand new. Other a year or 2 old. I havent check airflow. Where can I get specs on air flow for specified case? How to I measure? Average readings or just one spot?

Thanks a lot for the help guys!

[neumonic]

A velometer is a great tool for measuring airflow. You just put the device in the discharge air and should give you a reading in FPM. If you get the model numbers of the cases in question you can usually find the specs on the airflow that is required . You can then compare your readings with the specs. May or may not give you an answer.

[jpsmith1cm]

Some cases are brand new. Other a year or 2 old. I havent check airflow. Where can I get specs on air flow for specified case? How to I measure? Average readings or just one spot?

Thanks a lot for the help guys!

I had a case that, by the time I got to is was NOT brand new, but the problem that I finally resolved was there since brand new.

The case airflow was 3 times factory spec.

Factory installed wrong motors and nobody caught it. I broke silicone seals when I pulled those motors out and replaced them.

DO NOT assume that they are correct.

[anasmilbes]

Okay. Now if I cannot find specs on a case becasue its too old or something, is there a rule of thumb or no?

[mspanky]

Your indoor humidity is way too high. Take care of that and your case problems will clear up.

[Phase Loss]

It's true, 65% Humidity is high.

Most refrigerated cases in a supermarket are designed to operate at a maximum 55% RH and 75*F.

There is a direct relation to case performance and store air conditions.

Running a drier store air will reduce the latent load on the display cases by reducing the amount of moisture entering the cases.

Reducing the amount of moisture entering the case also reduces the amount of condensation & frost formation inside the case.

You are experiencing your problems on your meat cases. The meat cases are typically the lowest temperature case out of the medium temp open air cases.

Typically running a 18* SST or lower, the higher level of store humidity entering the case will increase frost formation on the meat case evaporators, reducing case airflow, allowing even more humid air to enter the case, where it then condenses on internal surfaces.

Dew point is important as it pertains to the temperature at which moisture in the air will condense on a surface. Surely the interior surfaces of your case will be below the store air dew point. Dew point comes into play mostly with your frozen door cases & their anti-sweat heaters. You need to make sure the external surfaces of the frozen cases are above store air dew point to prevent condensation on the external surfaces of the cases, mainly doors & their frames.

[anasmilbes]

Sorry guys. Ive been caught up past couple days. But wow, very useful info has been posted since I last checked. So il try and test your recommendations. Your input is highly appreciated.

Thanks everyone