Trane AC's

Techman

I believe that in the Trane Educational World, they have a rule for calculating Head Pressure. They have a name for it but I don't recall what it is at the moment.Well anyway, Trane simply adds 30* to the existing ambient temp and ,this is for their "lesser SEER" units.

pecmsg

In the old school that was probably true just like Beer Can Cold
& 500 Sq Ft per Ton. I also believe that was cooling only and in the summer time. (Which can not get here soon enough I might add)
Today SH / SC / Scale according to manufactures recommendations

GW

I am very curious where you're getting that information, Trane is not a joe-schmo manufacturer...all ac systems are charged with sub cool (txv) and super heat (fixed orifice).

Yes, the manufacturer give pressure charts based on outdoor temps but it's for reference only.

unclejohn

By lesser SEER you mean <6.

Techman

I think it was called the "Approach Method", ring any bells w/ anyone? uncle john , on AC that would be 12 seer and under.
GW-How many new AC systems are not TXV these days? Am I wrong about a 70* day = 95* condensing temp and a 95* day = 125* cond temp. What is it w/ todays 16 SEER units ? a 95* day will give about a 120-122*cond temp w/ 410a?. And refrigeration has a SEER of ??????
pecmsg- there are lots and lots of "old school" units out there . and this "new school"stuff was based on "old school" stuff

pecmsg

I use that method on water cooled equipment and chillers but never thought of it on A/C.

Techman

Now I believe I was wrong about part of what I said. It was Lennox with the "Approach Method" of charging AC units. I'm still looking for the other stuff.

GW

Yes Lennox has "approach" numbers...i haven't heard of someone getting confused "aproach" with initial charge setup though. Perhaps I misunderstood the original comment on this.

The approach (Lennox) number is more like 3 degrees (in single digits anyways ), you must be confusing your nunbers with older 10 seer r22 numbers. "Beer can" days...yes. Today's systems with higher seer and txv, no.

Techman

Well you heard it now. What is the difference between initial setup readings and a middle of the summer service call readings using the "Approach Method", being old school and all, the #'s don't apply? I did say 12seer and under.With all this new fangle stuff, what pressure do you see on a regular scroll comp 16seer r410a, residential, on a 70* day and the same for a 95*day? r12r22r502r134r401r404r407r408r409r507 ALL operate under the same temp rule, r22 ac and r410a ac follow the temp rule or damn close to it, old/new school

GW

I'm truly afraid I don't understand the context of this entire post, or what your point is.

Techman

I hope that is not contagious.
This and several other recent threads are about people who( or people who are curious about) work with freons in the cold ambients ,AC, Refrigeration,Ice people.
Ok ,how about this summer ,if you record some temps of the day and the pressurers of a few of your AC systems and see . Still have a few of the old school r22 units around? Check the new school r410a Pressure /Temps against the old stuff and the temps will be real real close.

unclejohn

Tech, In my beginner days 1976 it was rule of thumb 30* above ambient and sweating right up the the compressor. Now most of the equipment back then was under 9 SEER. And most were 6 or under, On those real tall Carriers you charged them to a clear sight glass at I think I remember correctly 300# head. My brother in law said he knew a guy in Colorado when he worked out there that did not carry any refrigerant gauges, just two glass thermometers and he could charge a unit using the approach method spot on. I don't know how well that method works in the DC area with the high hu-mighty. Some rat stole my Brown Trane book. I started looking through the Blue Trane book but haven't found any thing yet.