reading manifold

[ruffus]

well this might be a dumb question but i don't want to muck things up
i just need to know what markings to go buy the psi markings or do i go by the markings for the refrigerant that i am using please help

[4Qman]

Originally Posted by ruffus

well this might be a dumb question but i don't want to muck things up
i just need to know what markings to go buy the psi markings or do i go by the markings for the refrigerant that i am using please help

Mate no disrespect but its a bit of a Noob question when playing with refrigerant and material that can be dangerous if not used properly.

90% of the time its safe but thats when you know whats going on, not when your stuck deciding what part of the gauge your reading I mean this in the kindest possible way dude. A few people may be more strict on such a question as saftey is a big factor on this forum. "As it should be"

[tim-]

well, the pressure is what you look at, you get the temptures by using a thermometer.

[ruffus]

ok my system is running and i know what temp it is running at and i know what temp i am going for but my gages have markings fro r404a r134a and r22 plus the psi markings know i have been told that the markings that r marked for the refrigerant or for mixing and to just use the psi markings for charging and tunning is this right

[Big SturL]

Pressure is pressure. When using low pressure gasses, any manifold will do. For higher pressure gasses (such as used in cascades) need stronger, an more expensive, manifolds.

[ruffus]

so does this mean that i just go by the psi markings

[tim-]

yes, kind of.. the temptures on the manifold describs evaporating tempture at specific pressure.

use the termometer to check temptures and use the manifold for pressure.. that's what I do and that's the way I'm learn to use it.

the tempture on the highpressure side of manifold describs if it's possible to condens the refrigrant to liquid or not by comparing tempture at specific pressure with the tempture on outlet of condenser.

[ruffus]

thanks tim i just did not want to put my compressor in to too much of a vac as it would muck it up

[wdrzal]

4Qman how can you be so harsh on a question most,including you ,and the rest who posted plus those who didn't answer or don't know the answer too.

ruffus welcome to XS


as you can see their are many scales on your hi & low side gauges.

First always remember this:If you know the pressure you know the temperature,if you know the temperature,you know the pressure.this applies as long as liquid and gas are both present, the % is lower than 1% so thats a safe number,thats another topic.


your gauges have pressure scales usually psi & bar . They also have temperature scales for the 3 refrigerants you listed. lets use 134a and psi and Fahrenheit for temperature.

I don't know why but psi is imperial as Fahrenheit,as is bar & centigrade
metric system

Here at XS most read psi for pressure and centigrade for temperature.(I suspect until -40 where they are the same its easier to get to -20C than -20F)

now the explanation useing the imperial system ,PSI & Fahrenheit,you can google up a temperature & pressure converters .


first say you have a tank or system that has >1% liquid is at ambient temperature(room temp) put hose on tank of 134a and read pressure say pressure is 70 psi now follow the needle to the 134a inner scale (Fahrenheit) use can use a piece of paper as a straight edge ,set edge of paper on 70 psi and run to needle center pivot pin. or just imagine a straight line as if the needle was there. It will cross the F scale @ exactly 69 degrees F. providing refrigerant is stabilized and it a pure 134a mix. A lot of guy here mix refrigerants, don't do that. how did I know that ,reread bold print.

your gauge has a built in pressure/temperature chart for those 3 refrigerants.

yes you can use that manifold on other refrigerants but,you then just read pressure and consult a P/T (pressure/temperature) chart.

To sum up as long as liquid and gas are present, you can read pressure and know temperature or read temperature and know pressure.

so now add accurate thermometer to tank it is 70 psi so its temperature is exactly 69 Fahrenheit.

Read up on pressure/temperature charts. Then read up on sub-cooling and superheat. thats another day in the future.

[wdrzal]

your low side gauge goes to -29.92 hg vacuum always rounded and marked 30 hg vacuum then goes to 0 the to ultimate high pressure for low side gauge,usually around 350 psi.

the high side gauge works the same way for reading pressure and temperature.starts at 0psi and goes to 500 to 800 psi depending on manifold set.

[mytekcontrols]

wdrzal stated... 4Qman how can you be so harsh on a question most,including you ,and the rest who posted plus those who didn't answer or don't know the answer too.

Very good point

I think many of us need to be less harsh about what we say to others on this forum. Just because some one thinks they are an expert, doesn't mean they need to be critical of others, or what they are sharing. We are all here to learn, to share, and to hopefully teach. Let's just remember how it feels to be starting out, and how exciting that can be.

[ruffus]

ok thanks alot this helps me out alot

[runmc]

Originally Posted by tim-

well, the pressure is what you look at, you get the temptures by using a thermometer.

If you are using r404a and you gauges are scaled for r404a, then the pressure/temperature scales will correspond and be accurate.

If your using R22 and your gauges are not scaled for r22 you can get a P/T chart for r22 and match the pressure from you gauges to the pressure - temperature reading on the chart and find out your temperature that way.

You don't need a thermometer. Under normal circumstances, a refrigerant is a specific temperature and a specific pressure.

[wdrzal]

you do need a thermometer to measure sub-cooling and superheat as I mentioned, Thats another thread, when you don't know the exact charge to weigh in ,or measure by volume, sub-cooling superheat is your best choice to charge by, a sight glass or ultra sonic sight glass (i found to work well)will also do on suction tube. any refrigerant leaving the evap as liquid and boiling off does the evaporator little good.

I still believe sight glasses gives noobs a visual of whats happening in the tubes. A picture is worth a thousand words

Have a happy and proud memorial day Ron and other members in the U.S.A.and our allies.

[Athanatos]

http://www.xtremesystems.org/forums/...d.php?t=144603

[[XC] 2long4u]

Does anybody have a t/p chart for R290?

[wdrzal]

I just noticed , that some companies as Refco gauges are oppisite of what I described above, the principal is the same but someone posted a pic of a gauges that had the Temperature scales in the outer rings and pressure scales on the inner rings

This is oppisite to all my equiptment just the scales are oppisite. pressure look for psi & bar................temperature look for Rxxx number refrigerants......you read them the same as described.