What do YOU do?

[K_Neil]

There has to be oil sightglass somewhere. What's happening in there when the comp runs ?
calm 3/4 full ok
foaming top level visible double check
full sightglass is not good either
a few more answers will help too
Freezer suction lines only have to be at 25* F and they'll make ice easily with no liquid.
less humidity would lower the frost too
make sure U stick to your guns when U make a call

[jpsmith1cm]

I would like a reply stating the following:

1) you have supermarket rack experience
2) should I be worried about frost on suction lines?
3) and what should I tell a customer who has been informed that if he see's frost on his lines it will damage his compressor?

Why do I make this request?
I am an apprentice. Another apprentice who was visiting our area and is well known and trusted by our company went with 3 of us to a new supermarket customer to make some suggestions on rack maintence(which I might add was very helpful and informative). And when I say "us" read my profile.

I have limited rack experience and he( visiting apprent.) strictly does supermarkets.When he saw layer of frost/ice on some suction lines and portions of the header (low temp rack)he said "liquid flooding" and "compressor damage" and my boss promptly informed the customer. When I saw sweating on comp bell housing around SSV I agreed it was possible.
Now i've been in that room several times and never worried about the frosting lines and was starting to feel dumb. The other apprent said it's NOT NORMAL and must be a open TXV or evap fans down. So we check superheat at header...404A ..suction line 20 psig and line temp 22*f.
Even with SH of 37* he still didn't feel right about it and put it into defrost, and assured me it's not normal, somethings wrong with the measurements there must be liquid there. Now he has more supermarket experience and saw the confused look on my face and apologized for confusing me...now I felt really dumb. I got another set of guages and temp different temp probe and same readings. I found a thread on this confirming my thougts that frost is common but on printing it out and revealing my findings it was mentioned that "guys on here are HVAC and well it's not the same thing". Which is why I have made the above request.

I have been working on racks for 15 years.

He is an idiot. You are right.

[Phase Loss]

He is an idiot. You are right.

x2

[nate1701]

he mentioned that the racks he works on are commonly 507
would that make a difference?

[engineerdave]

NATE -

I "dabble" in both supermarkets and hvac. Not real good at either.

Your buds are correct when they say they're NOT the same trade. However, your T/P Chart does not lie.

You're running 404 LT at 20 psi. That's not out of line for market racks. Some might even call it slightly warm.

Surely there is some humidity in the ambient air...

Humidity is.... what? Water vapor, no?

Water freezes at +32f, so some frost is to be expected.

Go run through your checks, you'll see, bud.

[intellitech]

For any shady repair I wait to submit the bill till the problem clearly shows itself or the corrections I did eliminates it.In my market that's the most effective way to keep customers happy.
If I rushed to submit the bill and it turnes out I was too hasty,I eat the subsiquent trips..

That's a great point......I had a call to Ponderosa once on a Traulsen 2 door cooler with the Intellitraul electronic control. I had never worked on one of these. The complaint was that the day before it was freezing the product but of course as soon as I approach the unit it cycles off at 34 degrees and comes back on accordingly. So I call Traulsen and am told to check the temp sensor (thermistor) that senses the return air side of the evaporator. It is what tells the compressor to cycle on and off. So I check the sensor by putting it in ice water and watching the digital read out drop accordingly. After playing with it for a while it is cycling perfectly....

I inform the customer of the situation and that was that. I did not bill them that day and have never been called back to that unit. So they did get billed after some time went by.

So to make a long story short, in our field of light commercial refrigeration, this method seems to work out.

[intellitech]

I would like a reply stating the following:

1) you have supermarket rack experience
2) should I be worried about frost on suction lines?
3) and what should I tell a customer who has been informed that if he see's frost on his lines it will damage his compressor?

Why do I make this request?
I am an apprentice. Another apprentice who was visiting our area and is well known and trusted by our company went with 3 of us to a new supermarket customer to make some suggestions on rack maintence(which I might add was very helpful and informative). And when I say "us" read my profile.

I have limited rack experience and he( visiting apprent.) strictly does supermarkets.When he saw layer of frost/ice on some suction lines and portions of the header (low temp rack)he said "liquid flooding" and "compressor damage" and my boss promptly informed the customer. When I saw sweating on comp bell housing around SSV I agreed it was possible.
Now i've been in that room several times and never worried about the frosting lines and was starting to feel dumb. The other apprent said it's NOT NORMAL and must be a open TXV or evap fans down. So we check superheat at header...404A ..suction line 20 psig and line temp 22*f.
Even with SH of 37* he still didn't feel right about it and put it into defrost, and assured me it's not normal, somethings wrong with the measurements there must be liquid there. Now he has more supermarket experience and saw the confused look on my face and apologized for confusing me...now I felt really dumb. I got another set of guages and temp different temp probe and same readings. I found a thread on this confirming my thougts that frost is common but on printing it out and revealing my findings it was mentioned that "guys on here are HVAC and well it's not the same thing". Which is why I have made the above request.

I applaud you for doing your own research and verifying your measurments. Nothing can be more frustrating than dealing with experienced ignorance...that is guys with years and years of experience (or just a few for the sake of this discussion) based on wrong information. I suggest posting on this site as much as possible and you will get the correct information based on guys with REAL experience and not just arrogant know it alls.

Please do not take my commets as negative or cynical......I just deal with this nonsense alot too and it gets old .

[stonewall]

Saturation temperature - The boiling point of a liquid

SUPERHEAT - Heat added to a substance above it's saturation temperature.

SUPERHEATED GAS - A gas temperature higher than the evaporation temperature at the exiting pressure.

SUPERHEATED VAPOR- Refrigerant vapor heated beyond its saturation point.


So if a vapor is superheated above its saturation temperature, then there can be no liquid remaining.

1) you have supermarket rack experience I have supermarket rack experience.
2) should I be worried about frost on suction lines? I worry more if there is no frost on low temp suction lines.
3) and what should I tell a customer who has been informed that if he see's frost on his lines it will damage his compressor? That he was misinformed by an idiot.

[Dowadudda]

hussmann remote headers. What a friggen POS those are.

[nate1701]

thanks for pics stonewall, they may come in handy if the issue comes up again.

[icemeister]

Attached is a little ditty I put together a while back for posting in the local supply house....just to see what kind of response it would get. As expected, most guys immediately say it's flooding back.

(The picture....along with the operating conditions...was posted on HVAC-Talk last year by Smilies)

[jpsmith1cm]

he mentioned that the racks he works on are commonly 507
would that make a difference?

Nope.

refrigerant is refrigerant and superheat is superheat.

[jpsmith1cm]

Nothing can be more frustrating than dealing with experienced ignorance...

I love that. Funny $hit.