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What is a Nomograph Chart ?

It has something to do with SubCooling!


  • SpenceSpence Posts: 316

    It is the factory chart inside your unit regardless of sub cooling or superheat. If my "x" is ???, then my "y" should be ????. For example, at an IWB of 63, at an ambient of 80, the intersecting lines may indicate 70 PSIG of vapor pressure.
  • TechmanTechman Posts: 2,143
    edited May 2013

    Hi Spence, I am not sure if that charging chart is a Nomograph or not, But I was referring to this "Subcooling compensating chart" kindof nomograph chart. Carrier AC Co. has this chart in their "Handbook of Air Conditioning System Design" book. Knowing what the actual press is at the TXV is critical, yea,like anything on this chart isn't critical

    OK you Wetheads, hydronics has a "static head" for that hot water pipe going "UP" to that 2nd-3rd-4th floor.What is it 1psi =2.31' ? Well, we ReferHeads  have 1psi=2' for R22. 
  • SpenceSpence Posts: 316

    Real classics, here! Way too cool; keep them in good condition! What has happened since these wonderful publications is the manufacturer making things more simple for us in the field. A perfect example is practically everyone charges their OD units for the condenser, a 15' lineset, and the smallest AHRI matched ID coil. Then they tell you to add "x" ounces for each foot over 15, up to a certain TEL. Here is where your wonderful nomographs came in, yet they are now on proprietary software programs. You enter the conditions in the field and the program tells you if your LL and SL PDs are OK and what you need to do to make them happy. Upsizing tubing usually is the answer and the software also tells you how much refrigerant to add. If you don't have the software a call to your local distributor gets you your info.
  • TechmanTechman Posts: 2,143
    edited May 2013
    Nomograph chart

    Hi Spence, Happy Mothers Day to you and yours! I totally agree with you about the info the mfrg gives in their guide lines, that is the 1st step in doing it right. I've been thru 23-30 schools/classes that say the very same thing. I AGREE, but,  it doesn't make sense to me that the SC on an AC w/the evap in the basement is the same as an evap way up there  above the ceiling in a 3 story house/office .IF the mfrgs magic SC # is good for that attic job then its also good for every other elevation under that .All bases covered! Simple!. So,  1st fl TXV inlet press would be almost = press at King valve,so maybe a SC of 1 is needed, 3rd fl attic TXV inlet press drop =  LL press drop + 1psi drop for every 2' of riser, around 12-13 SC is needed. As the LL backs up in the cond coil while the SC increases, the condensing space is decreased so the head goes up. Your way works for you and many, many, many others! My way works for me and only a few others!! Enjoy the day!!!

    A couple of ice cold brews would have been nice during this conversation.
  • SpenceSpence Posts: 316
    No is

    Thanks for the good findings, and to you likewise! I see your point about evaporators up or down. On the typical residential application, as long as the TEL is within specs and the correct amount of compensating refrigerant has been introduced, your maker's SC guarantees a full liquid line. In your mile-high example I'm totally with you; engineering is needed. That's when I pop in the maker's software; getting too lazy to lug around those groovy old manuals like your Carrier set (you know, the folks who practically invented air conditioning). Wouldn't it be great if these situations were only on new jobs, instead of having to rectify the OPMs? (Other people's messes)
  • TechmanTechman Posts: 2,143
    Vertical Height Limitations.

    In my newer Rheem/Rudd manuals I see many cond units are limited to 25' of vertical separation. I see LOTS of cond units that break that rule. What to do? What to do to get one those "rule breakers" up and running as well as possible!What are some of the "VHL" on the equipment that you guys sell?
This discussion has been closed.


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