# Thread: what is superheat ?

1. ## what is superheat ?

R-134a with spring pressure 9.5 psig =5.5* and evap 30.5 psig =35*
how to calculate the superheat?

2. Professional Member
Join Date
Mar 2005
Location
N.J.
Posts
448
Post Likes
WHAT??????????????

3. call a tech. save yourself some money.

4. Originally Posted by cfe
R-134a with spring pressure 9.5 psig =5.5* and evap 30.5 psig =35*
how to calculate the superheat?
Bulb pressure equals spring pressure plus evap outlet pressure, so
P_bulb = 9.5 + 30.5 = 40psig

SH is the bulb saturated temp minus the evap saturated temp (assuming that bulb temp is equal to suction line temp)

From the P/T chart
SH=45-35=10°

5. Originally Posted by hvacrmedic
Bulb pressure equals spring pressure plus evap outlet pressure, so
P_bulb = 9.5 + 30.5 = 40psig

SH is the bulb saturated temp minus the evap saturated temp (assuming that bulb temp is equal to suction line temp)

From the P/T chart
SH=45-35=10°
thanks hvacmedic.
i thought there is no way to figure out SH with the info provided or just when evap in equilibrium only and maybe cross bulb charge will have different SH reading.

i did the same calculation but end up with 5 SH. i misread 30.5psig to 35.5 psig=40*. 40psig=45*

i always rely on thermometer and gauge to get SH ans SC reading.

6. Originally Posted by cfe
thanks hvacmedic.
i thought there is no way to figure out SH with the info provided or just when evap in equilibrium only.
i did the same calculation but end up with 5 SH. i misread 30.5psig to 35.5 psig=40*. 40psig=45*

i always rely on thermometer and gauge to get SH ans SC reading.
Yes, that was assuming stable operation, and an ideal TXV. Of course no such TXV exists, so this was all correct only on paper.

#### 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.