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Old 09-15-2011, 11:31 PM   #1
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King valve as expansion valve...


Hi all! Newbie to the forum and beginner to the topic. I just wanted to get a little discussion and feed back on a cheap (just make it work) method. So here's what I'm working with, this is my single mothers house and she's been living with just window units for four or five years now. She has a 1978 built home with all original equipment with exception to the condenser unit. Split gas furnace with a 3 ton r22 goodman 10seer condenser (replaced around '96) and a rheem coil (orifice tube valve) and the pan is rusted out. Well about six years ago it sprang a leak somewhere, just had it filled once and after the bill my mom said Not doing that again and got the window units. Well after just completing a r410a condenser and evap on my home, my confidence is high. So two weeks ago I figured I would try to swap her system to r134a, put some stop leak in it, change the oil and see what happens. Put it in and I'm getting a 20F split at the closest vent but her run time is 14-15hrs/day with temps over 100F outside 76-78 inside and the inside humidity hangs around 55%. I've adjusted my charge significantly but can't get the humidity down and run times are too long. So here my plan, I'm going to put my old (good condition) 4 ton coil on hers to prevent flood back and use a king valve to vary the flow as needed. All the numbers I'm getting from the system are pointing me to it needs more flow. No evidence of leaks. Have at it, issues, concerns, advise...

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Old 09-16-2011, 08:01 AM   #2
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General comments

Not quite following the reasoning behind switching to 134a. By using an R-22 compressor and using 134a you are pumping less #'s of refrigerant through the system (vapor density's of refrigerants are different) and also running at significantly lower pressures meaning less refrigerant entering the coil through the metering device.

The downside to just putting more refrigerant into the coil using a manually operated king valve is that you will increase the suction pressure in the evaporator and therefore raise the saturation temperature of the 134a, making the coil warmer instead of cooler. It will also require constant adjustment as the outdoor ambient temp changes. A TXV would be a better option for control of flow to maximize cooling effect and minimize superheat to compressor.

I further wouldn't change to a larger (4ton) coil without the use of a 3 ton TXV, but that being said, why not use your 4 ton coil, put on a 3 ton (R-22) TXV and switch back to the R-22 the system was designed for?

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Old 09-16-2011, 10:02 PM   #3
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King valve as expansion valve...


The whole point of the r22 to r134a swap is because I don't have a license handle, so r22 is out of the question for me. Not only that but i've been trying to find a serious discussion on a viable r134a swap for all the diy'ers out there that wont touch a system because they have to have a license... I know it's completely doable but no info really exists that I have found. Anyways so since sticking to the r134a is my only option/ most readily available option, using a r22 txv I dont think is a good idea. I imagine that if I did use an r22 txv with r134a in the system it would keep my temp difference in a very close range to optimum flow but I would probably run into the same problem- just slightly off. So that's why I feel the use of a manually adjustable expansion valve is my best option to optimize my flow rate. I'm completely aware of pressure versus temp issues on in the evap, so I'll just dial back until I'm happy. As far having to adjust the valve due to varying weather conditions, I'm not too worried about that since of course oriffice tubes are fixed metering devices also... I'll just give myself a good safety margin with the superheat and combined with the oversize evap I feel like I'll have a safe and great running setup. Ofcourse thats my take on the idea... What do you think any future prospective buyers or their inspector would say about such a system?
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Old 09-16-2011, 11:06 PM   #4
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Originally Posted by Danman5000 View Post
The whole point of the r22 to r134a swap is because I don't have a license handle, so r22 is out of the question for me. Not only that but i've been trying to find a serious discussion on a viable r134a swap for all the diy'ers out there that wont touch a system because they have to have a license... I know it's completely doable but no info really exists that I have found. Anyways so since sticking to the r134a is my only option/ most readily available option, using a r22 txv I dont think is a good idea. I imagine that if I did use an r22 txv with r134a in the system it would keep my temp difference in a very close range to optimum flow but I would probably run into the same problem- just slightly off. So that's why I feel the use of a manually adjustable expansion valve is my best option to optimize my flow rate. I'm completely aware of pressure versus temp issues on in the evap, so I'll just dial back until I'm happy. As far having to adjust the valve due to varying weather conditions, I'm not too worried about that since of course oriffice tubes are fixed metering devices also... I'll just give myself a good safety margin with the superheat and combined with the oversize evap I feel like I'll have a safe and great running setup. Ofcourse thats my take on the idea... What do you think any future prospective buyers or their inspector would say about such a system?
What a nightmare! Can I drive this house?

Last edited by Doc Holliday; 09-16-2011 at 11:08 PM.
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Old 09-17-2011, 02:00 PM   #5
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Probably... I'll be finishing up this afternoon, i'll let you know how it goes!
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Old 09-17-2011, 04:18 PM   #6
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76 inside, 100 outside 55%rh...I don't think I would touch anything. You had a serious stroke of luck..walk away.....

Last edited by Master of Cold; 09-17-2011 at 04:20 PM.
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Old 09-17-2011, 04:53 PM   #7
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An inspector would say its a Frankenstein system and needs replaced.

R134A in a designed for 22 system will lose a lot of capacity. Probably around 25%. Your mother is probably better off with the window units.
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Old 09-17-2011, 09:43 PM   #8
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Master of Cold - not with 14 to 15 hr run times per day. That's way too long for my taste...
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Old 09-17-2011, 10:07 PM   #9
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King valve as expansion valve...


I've got good new though!!! It's frigging perfect! No leaks, outside temp was 85f and 86% humidity(just rained) and inside started at 78f and 58%. In just 50 min it dropped down to 74f and 48% right where I want it. Maybe with a little more run time the humidity will get down to 42-46% range. Got a 22F split at the closest vent. I left it there for now but I'll check on it tomorrow to check the run times. That king valve takes some fine adjustments but with that high humidity I could make a small adjustment and see the condensation build up on the low side in a matter of two to three seconds. Its quite amazing to have that much contol of the system!
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Old 09-17-2011, 10:43 PM   #10
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I'll give a run down on the install... Swapped in a 4ton goodman coil and bypassed the existing txv(r22). The only pain in the ass I had was the line set was 3/4 soft copper and the evap had 3/4 hard copper which I was told by a wonderful old man at ace hardware they are measured differently so that's why the same size doesn't fit. Thankfully I found a soft copper 3/4 to 1/2 addapter and a hard copper 3/4 to 1/2 addapter. You would think the 1/2 would be a diifernt size also but they fit perfect. Don't be alarmed by the downsize, the inner diameter of the 1/2 hard copper is nearly a perfect match to the inner diameter of the 3/4 soft copper. Everything else seemed to go together no problem. Little pain on taping up the underside, the whole system just had a very low clearance. Pulled the vacume down to 500 microns, left it there for an hour and half, ended around 600, completly within spec. I had parked the r134a in the condenser, so I just added 3 more ounces of oil and slowly released the refrigerant. I started with the kxv( king expansion valve) closed, after releasing the refrigerant I just opened it up to equalize and then left it barley open. Started the fan first to check for significant air leaks, found minor ones, no big deal. Turned on the condenser, checked my pressures, checked my kxv, let it out until I could feel the low side get cold and the started checking all my numbers and making fine adjustments. Everything is right where it should be, definitely not a compromised system. If anything I would say thing thing outperforms an r22 setup.
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Old 09-17-2011, 10:58 PM   #11
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There is no size difference between 3/4" soft drawn and 3/4" hard drawn ACR copper. The evap, is not 3/4" ACR, its 7/8" ACR.

Did you drain the old oil from the compressor and put in all new oil so its compatible with R134A?
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Old 09-17-2011, 11:13 PM   #12
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Substitute Refrigerants and Oils
Refrigerant Blends
The American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) has a specific numbering system (based on the chemical structure) to designate refrigerants. This organization also maintains a list of approved refrigerants and details on their composition and safety on the ashrae.org website.
Refrigerant blends are also numbered according to the ASHRAE system. Blends are comprised of two or more refrigerants that have different physical characteristics. Refrigerant blends that are composed of two different refrigerants are called binary blends. Refrigerant blends that are composed of three different refrigerants are called ternary blends.
Types of Refrigerant Blends
Blends are divided into two classifications, azeotropic or non-azeotropic (also called zeotropic), depending on the temperature glide characteristics of the blend.
Azeotropic Blends
An azeotropic refrigerant mixture acts like a single-component refrigerant over its entire range. Under normal conditions, azeotropic blends do not separate.
Non-Azeotropic or Zeotropic Blends
Like azeotropic blends, non-azeotropic (zeotropic blends) consist of multiple refrigerants blended together. However, a non-azeotropic refrigerant mixture still acts like a mixture of refrigerants after blending and does not behave like a single refrigerant.
These blends cannot be treated like a pure refrigerant during servicing. You can only charge them as a liquid, and when the system has a leak, you cannot top off the refrigerant. The reason you cannot top off non-azeotropic blends is because these blends fractionate during a leak (or during vapor charging). Therefore, the characteristics of the blend change because the more volatile refrigerant boils off in a greater ratio during a leak (or during vapor charging). This dramatically alters the composition and the properties of the refrigerant.
These non-azeotropic refrigerants are given a 400-series ASHRAE refrigeration designation.
Near-Azeotropic Blends
Another informal classification of refrigerant blends is called near-azeotropic. Near-azeotropic blends are non-azeotropic blends that have a very small temperature glide. That is, they change volumetric composition and saturation temperatures in nearly the same way as azeotropic blends. The temperature glide is so small you would not be able to detect it in the field. See the example below where the temperature glide of the non-azeotropic R-410A is only 0.2°F making R-410A a near-azeotropic refrigerant blend.
Although you can treat R-410A and other near-azeotropic refrigerants as an azeotropic refrigerant, most manufacturers recommend that you still charge them as a liquid, but they can be topped off, and this is a significant benefit.
Blended non-azeotropic refrigerants leak from a system in uneven amounts due to different vapor pressures, so these systems cannot be topped off. Instead, you need to recover all of the refrigerant and send it to a reprocessing (reclamation) facility. The system (after repairs) must be recharged using only liquid (not vapor) charging.
Tip
The ASHRAE numbering system does simplify things somewhat because you know you can service any 500-series refrigerant like a pure refrigerant without any concern about fractionation. You can charge 500-series azeotropic refrigerants as a liquid or a vapor, and after a leak, you can top off systems containing this type of blended refrigerant.
Charging a Refrigerant Blend
In general, 400-series non-azeotropic blended refrigerants should be charged as a liquid. Because these non-azeotropic refrigerant blends are a mixture of different refrigerants with different volatilities, if you charge them as a vapor, the refrigerant with the highest vapor pressure (most volatile) will be charged into the system at a higher proportion than the other refrigerant components. The only way you can be sure the non-azeotropic blend is charged properly and does not fractionate during charging, is to charge it as a liquid.
Changing to a Different Refrigerant
According to EPA, there are no “drop-in” service replacements for any refrigerants. The term drop-in replacement means that the refrigerant provides exactly the same cooling, efficiency, pressure ratio, and other performance factors as the original refrigerant with no changes to existing equipment. Despite what some sales materials claim, every replacement refrigerant requires some change to the system. However, some changes are only minor, and the performance differences can be minimal.
Using Synthetic Oils
Ester Oil
The type of oil that is most commonly used in stationary refrigeration applications with HFC refrigerants, such as HFC-134a and HFC-410A, is ester oil. The most common ester oil is polyolester (POE) oil. Although HFC refrigerants are typically compatible with most existing refrigeration and air-conditioning equipment parts, they are not compatible with the mineral oils that were used in a system. Instead of mineral oils, you can use any appropriate synthetic oil.
Caution
Do not mix ester-based oils with any other oils except in waste disposal containers. In general you should never mix different types of oils in a system.

All synthetic oils (including POE ester, PVE and PAG oils) are extremely hygroscopic, which means they readily absorb moisture. When working on a system with any synthetic oil, be especially careful not to let excess moisture get into the system. For example, while mineral oil has a water saturation limit of only 25 parts per million (ppm), the new synthetic oils absorb much greater concentrations of water. POE oil has a saturation limit of 2,500 ppm, which is 100 times the limit of mineral oil. PVE has a saturation limit of 6,500 ppm, which is 260 times that of mineral oil, and PAG has a saturation limit of 10,000 ppm, which is 400 times that of mineral oil. With the potential for so much more water in the system, you have to be careful to avoid moisture entry into the system, and you have to rigorously follow triple evacuation methods.
Alkylbenzene and Mineral Oil
For HCFC refrigerant installations and conversions, you can use mineral oil, alkylbenzene (PAG) refrigeration oil, or a combination of the two. Alkylbenzene is a synthetic refrigeration oil and is more expensive, but it can be used with all halocarbon refrigerants. PAG oils cannot tolerate even very small amounts of chlorides, and chlorides can come from coatings in tubing, outdated flushing methods, or residual amounts of CFC refrigerant that might have been in the system.
The synthetic lubricant commonly used with blends containing HCFCs is alkylbenzene.
The synthetic lubricant commonly used with HFC refrigerants and HFC blends is POE ester oils.
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Old 09-18-2011, 12:02 AM   #13
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There is no size difference between 3/4" soft drawn and 3/4" hard drawn ACR copper. The evap, is not 3/4" ACR, its 7/8" ACR.

Did you drain the old oil from the compressor and put in all new oil so its compatible with R134A?
Yeah your right, I just forgot that one. Anyhow, all the adapters matched up so no harm. As far as the oil, that was step one for me. I know the issues, mineral oil and r134a, it will coagulate in the suction line and just adhere to the walls of the lines.
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Old 09-18-2011, 12:14 AM   #14
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I take that back, the adapters I bought were both 3/4 to 1/2 and both of the 3/4 ends were different sizes and the 1/2 ends were the same. I don't know the technicals on copper tubing, I just made sure the matched up properly. I've still got the receipt...
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Old 09-18-2011, 11:18 AM   #15
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Plumbers use inside diameter, refrigeration uses outside diameter.
If you ever get fittings and pipe at a plumbing supply you have to keep this in mind.

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