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what should i charge to when replacing the TXV
Mcro1986
Member Posts: 8
long story short lennox unit bad txv wouldn't adjust 30 degree superheat found brass shavings inside the txv.
I ended up flushing the lines changing the filter dryer and txv. i used an Emerson txv instead of another lennox txv. now my question is, do i charge the system to the condenser requirement of a 6 degree approach and 3 subcool or what Emerson wants a 10 degree subcool?
I ended up flushing the lines changing the filter dryer and txv. i used an Emerson txv instead of another lennox txv. now my question is, do i charge the system to the condenser requirement of a 6 degree approach and 3 subcool or what Emerson wants a 10 degree subcool?
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Comments
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In my experience 10 degrees of sub cooling will rarely get you in trouble no matter whose unit you are working on.good luck0
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I'd go with the equipment manufacture recommendations. But as Zep said 10* sub cool shouldn't hurt.0
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Mcro, There aren't too many places in a system to get brass shavings, possibly they were copper?
Yea , KindaSorta, 10*SC will cover your butt for every AC for every brand . So going by the CYA rule then you will be OK. So, if your system "needs" only 2*SC , CYA and get 10*SC, or if your system "needs" 8*SC then 10*SC will still CYA. Its a "catch all" rule, for "typical" installs, that fall within the "piping height vs length" chart of each Mfrg . Don't a few CU say on their nametags 6*SC is their "target SC", 6*SC sure limits the piping "H vs L" thing.
Q here, the ACTUAL REQUIRED SC of a 50' horizontal lineset is the same REQUIRED SC as a 50' lineset that goes up vertical 35'. NO WAY ,NO WAY, NO WAY.
My BIGGEST concern was/is the fact that lots and lots of Techs don't know the REAL story of SC , or worse they DON'T CARE. If all they do is typical residential/light comm then they CYA and do the "Target SC thing" and they are "good to go", I agree mostly/ some times. I come from a more Commercial/Industrial background (Carrier, Governaire) and "knowing" how to FIGURE OUT SC was/is normal. Now, all of these #'s and charts and guidelines are ALL FOR ONE REASON ONLY, and that is to ensure that the TXV/metering device has a "FULL LL " feeding the TXV, under all "normal" operating conditions. Having a full SGMI at the CU does not guarantee a full SG at the TXV. I've put SGMI at the TXV and CU on some systems "just to see" or I use my "electronic SG tool" to "see" whats happening at the TXV.
There are still Techs that say that just USING a SGMI WILL cause the system to be overcharged. HOGWASH. Overcharging a system is due to an "un-knowledgeable" Tech, plain and simple1 -
WOW all the abbreviations......... Yea, I'm lost. Print it in Aerobic. At least I can go on line a decipher it...:-) Hey Terry Only kidding. What is a CU?, You are talking 1 adem 12....0
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Evacuate, weigh in the appropriate charge. Adjust for pipe length and airflow to achieve proper indoor delta T. Lennox has the charts and info. Weigh in gets it right every time.0
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Lennox does like a lower subcool than some. We put in an Allied heat pump the other day, under the conditions, called for 1° subcool! Personally I think do what the condenser manufacturer calls for, they know the system.0
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John am I reading you right? 1 *Sub/cool? Min 8* 10-14 w/ tx more like it. If that were the case, ( not knowing what you are actually looking at) Just pipe the discharge line into 4 linear foot of coil and there you go. I respectfully would like to know your source of that information because it is and makes no sense.
Peace'
Mike T.
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I have never seen a 1* S/C.......
Peace;
Mike T
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That was correct, they wanted 1° subcool under the conditions we had at the time. We were surprised. It's a chart right on the door of the unit. 2 ton 14 SEER heat pump.0
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I see a range of 8-10 subcool on the Trane 410a stuff, nomenclature states plus or minus 3. Finding 12 is the sweet spot, with low 50s discharge temps. Recently got the SMAN3, we have a tempestuous relationship, as I'm acclaimating to the precision of it, learning to trust it!0
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