So... What's the problem here?

[jpsmith1cm]

Picture was taken at the case. Liquid pressure taken between drier and TXV.

I suspected a big pressure drop, so I tapped the case expecting exactly what you did.

Pressure drop between rack and case is nominal (<5# on the liquid side). Hard to be definite as it is hard to be two places at one time.

[cold spell]

Case nozzel is for R22

[icemeister]

An R22 nozzle would certainly give similar symptoms.

[dangpgt97]

Is the liquid line large enough to feed the evap?

[Herb1025]

In the ref systems we work on we control and look at every temp and pressure . The ref and building system is on 24 /7 . This is the way of the future ref tech you see what the system is doing before it take's week to control the product or store heating and AC failure When you walk in to the place you have a head's up or you were at home at 2 am and not in your truck

[flange]

incorrect placement of sensing bulb for tx, or some other effect upon it?

[jpsmith1cm]

The assumption is that there was something wrong with the refrigeration circuit.




I called Tech support and when the guy called me back, I laid out the scenario that has been outlined for you guys.


He asked me this question:

"What is your AIRFLOW?"

I took the Alnor and checked air velocity. Read 600FPM at several spots across the Honeycomb. I did this with him on the phone and read the readings off to him.

Case airflow is rated at 220 FPM.

I choked off the return air to provide as little airflow as possible (got it down to 300FPM) and all readings dropped to normal.

With the higher airflow, I was lucky to see 10 degrees supply air temperature. When I choked it off, it dropped so fast that my Fluke could barely keep up with it.


Apparently, at some point in this case's history, the wrong fans were installed.

I am waiting for the correct parts to arrive, but this fix is functional enough for now.

[jpsmith1cm]

In the ref systems we work on we control and look at every temp and pressure . The ref and building system is on 24 /7 . This is the way of the future ref tech you see what the system is doing before it take's week to control the product or store heating and AC failure When you walk in to the place you have a head's up or you were at home at 2 am and not in your truck

I have been a strong advocate for more data for the tech to see. Give me more data about the operation of a system and I am more able to tune it to optimum efficiency and am more able to make quicker repairs and spot trends in operation.

I'd LOVE to see the systems that you are describing.

[Herb1025]

So is the factory going to pay ? I have had store ref people adjust fan blades to adjust air flow but to replace fan motors and blades just can not buy it Should look at case history

[mccool]

TXV was wide open at the time this picture was taken.

All heating vents were already checked and aimed away from this case. (Yes, it is an open air single-deck type case)

Not to be a jerk, mccool, but how would low airflow contribute to this problem?


Ok. Time for another hint. It hasn't worked right in a very long time if it ever worked right. Our company didn't install it, but we got saddled with the repairs.

Oh now I see the high superheat on your guages...don't own a fancy set like that,,,,,but would have caught the problem before case was even started, when I noticed the wicked pitch on the fan blades.....just kidding.

[icemeister]

The assumption is that there was something wrong with the refrigeration circuit.

I called Tech support and when the guy called me back, I laid out the scenario that has been outlined for you guys.

He asked me this question:

"What is your AIRFLOW?"

I took the Alnor and checked air velocity. Read 600FPM at several spots across the Honeycomb. I did this with him on the phone and read the readings off to him.

Case airflow is rated at 220 FPM.

I choked off the return air to provide as little airflow as possible (got it down to 300FPM) and all readings dropped to normal.

With the higher airflow, I was lucky to see 10 degrees supply air temperature. When I choked it off, it dropped so fast that my Fluke could barely keep up with it.


Apparently, at some point in this case's history, the wrong fans were installed....

What a great lesson JP.

Now I get your hint about how the HVAC guys might get the answer right away.

I totally missed the airflow aspect...even after I posted a comment about using the Testo 410 for case velocities just yesterday.

DUH....

[KB Cool]

Wow!!! who would have thought too much air flow on a refer case. I usually just check to see if the coils frozen, motor is working and spinning the right way. Nice find though and glad you shared it with us. I'll have to keep it in mind. May need it someday.

[jpsmith1cm]

So is the factory going to pay ? I have had store ref people adjust fan blades to adjust air flow but to replace fan motors and blades just can not buy it Should look at case history

I wish I had the full case history.

I don't know about payment or anything, I just want this case to work properly.

As I said before, my company did not install this case. We took this store over about 18 months ago and this is the first that this problem was brought to our attention.

Oh now I see the high superheat on your guages...don't own a fancy set like that,,,,,but would have caught the problem before case was even started, when I noticed the wicked pitch on the fan blades.....just kidding.

Is OK. What you are looking at in that picture is the new AK-900 coming from Digicool. Once you get used to the display, you can absorb all of the system information at a glance. They're AWESOME!

If I started the case, I'd have caught it, too, when I set the SH. Apparently, not all companies do this.

What a great lesson JP.

Now I get your hint about how the HVAC guys might get the answer right away.

I totally missed the airflow aspect...even after I posted a comment about using the Testo 410 for case velocities just yesterday.

DUH....

That is EXACTLY why I posted this and why I milked it along as long as I did.

It seems that, as a market guy, I tend to ignore airflow as a potential problem. If a case is delivering a decent air curtain, then the airflow is fine. Nothing more need be checked. I *ASSUME* that it is correct. I have the instruments to measure it, I just don't.

I can just about promise that this one won't slip by me again.

I think that the 410 just crawled a few slots up the tool list...