# Thread: Just line temp.

1. Professional Member*
Join Date
Oct 2013
Posts
292
Post Likes

## Just line temp.

I was wondering can we find out the psi in a line just by the temp of that line?

I have a sealed system (freezer - reachin - turboair) I measured the line temp:
lowside - 51.5' and highside - 151.9'
P-T chart R134a reads (lowside - 49psi and highside - 263psi)
P-T chart R404a reads (lowside - 109psi and highside - 453psi)

My freezer stats R404a but it can't be? I called the manufacture and they stated that it is correct.
Would you please inlighten me on this.. please....... BTW the freezer is working fine.
This thread is not to ask for repaire just to get educated.

2. Professional Member*
Join Date
Oct 2013
Posts
292
Post Likes
I guess what he said make sense, refrigerant in a tank at room temperature is different then a refrigerant being pushed around by a compressor. P-T chart is only referring to refrigerant that is not being pushed around by the compressor...

3. If there is a liquid/vapor mixture you definitely can use a pt chart, though a compressor definitely influences the pressure and temperature of the refrigerant in the system with the dynamic forces upon the gas.

Suppose you have an r404a jug and you just finished charging every drop of liquid from the jug into a small compressor pack, now the jug is only vapor. With all vapor there will be superheat present, and that will throw away the usefulness of a pt chart (pt relationship won't exist with pure vapor)

4. Professional Member*
Join Date
Oct 2013
Posts
292
Post Likes
Would that apply to all liquid justlike all gas?

5. Originally Posted by the_4rs
Would that apply to all liquid justlike all gas?
all liquid? that would be hard to answer, liquid does subcool at 100% quality while staying at the same pressure (for example, like the liquid line of a home ac unit or mechanical subcooler of supermarket). If you have to know the pressure and temperature of a refrigerant at a given location in the system, you absolutely need a thermometer of a pipe-clamp type and a refrigerant pressure gauge, and using superheat and subcooling calculations (basic math), you'll know exactly what's going on in your system.

You could have 50 psig on the low side of an ac system with 15 degrees evaporator superheat (considered ideal), or 50 psig and 0 degrees evaporator superheat (could be dangerous for compressor)

6. Professional Member*
Join Date
Oct 2013
Posts
292
Post Likes
without knowing the PSI, can we use the temperature splits from the evap and the condensor to get a good enough idea of the charge in a sealed system? Split at evap 15.4' and the split at condensor 11.3' also the box temp is 13.3'....

7. Professional Member*
Join Date
Oct 2013
Posts
292
Post Likes
I see... Thank you...

8. I think sub cool and super heat would add a few isues https://www.youtube.com/watch?v=DGYL...e_gdata_player

Sent from my SPH-L720 using Tapatalk

9. Originally Posted by TACKERDOWN
I think sub cool and super heat would add a few isues https://www.youtube.com/watch?v=DGYL...e_gdata_player

Sent from my SPH-L720 using Tapatalk
This is the best video I've seen about superheat/subcool

10. Professional Member*
Join Date
Oct 2013
Posts
292
Post Likes
Thank you

11. Originally Posted by TACKERDOWN
I think sub cool and super heat would add a few isues https://www.youtube.com/watch?v=DGYL...e_gdata_player

Sent from my SPH-L720 using Tapatalk
Excellent video. Thanks.

12. I was going to try and explain but im more of a hands on type. Glad to help.

Sent from my SPH-L720 using Tapatalk

13. Professional Member*
Join Date
Oct 2013
Posts
292
Post Likes
Originally Posted by the_4rs
without knowing the PSI, can we use the temperature splits from the evap and the condensor to get a good enough idea of the charge in a sealed system? Split at evap 15.4' and the split at condensor 11.3' also the box temp is 13.3'....
What is every ones ideal splits on Evap and Condensor?

Page 1 of 2 12 Last

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•

## Related Forums

The place where Electrical professionals meet.