Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit https://heatinghelp.com/contact-us/.

superheat

 hello

     several times on ac systems with cap tubes or piston metering devices I need to add freon to raise the evap pressure  to 60#. but in so doing I get too low a superheat reading. normally I expect the suction line to be slightly cool to the touch. but when the suction line gets very cold I think its because of the freon I added in order to raise the suction pressure to a point high enough to keep the evaporator from freezing. the system will work this way but I don't like that cold suction line.                                   any suggestions of insights?

                                                                thankyou

                                                                 dennis

Comments

  • JStarJStar Member Posts: 2,752
    ...

    Why do you try to get 60# suction on every system? It should be different for every system depending on a number of factors.
  • TechmanTechman Member Posts: 2,144
    superheat

    Having a lower than 60psi is a" it depends " situation. A rule of thumb here might help,so,what is the outdoor air temp? Not lower than 70-72*.What is the indoor air air temp? again ,not lower than 70-72-74* Is this your 1st time on this unit?Oversized? Dirty evap,filters,blower wheel?Duct sizing wrong?Supply registers not open?And checking the charge is better done by the subcooling,not the superheat.
  • TechmanTechman Member Posts: 2,144
    dennis

    Got your e-mail. I TOTALLY agree with you about Profressor Silberstein' book "Pressure Enthalpy without tears" very good but can't say I grasped all of it .LOL LOL. Again,a rule of thumb, on cool days you can get fairly close pressure readings. On a 50-60* I place a plastic tarp around the cond coil to raise the head press press up to 95* condensing. [r-22 is about 182psi] and then charge the low side upto 60psi or so ,depending on the other rule's of thumb.It's close ,but better than waiting for all of the units  for a warmer day. It's kind of like a motormaster head press control.
This discussion has been closed.

Welcome

It looks like you're new here. If you want to get involved, click one of these buttons!