Flushing Walking Cooler with TXV in Place

[ajdelange]

The compressor for my walk-in went TU and when the replacement arrived the first thing I saw was a big sticker on it warning that it is filled with POE oil. That means I'll have to flush the lines when I install it (which is probably a good idea anyway after 15 years and I don't really know how the compressor failed). The catch is that everywhere I look it says to remove the TXV when flushing for fear that something will come loose and lodge in the orifice. Well removing the TXV, wedged in as it is into a very small space, probably exceeds my skill level with a torch so here's what I plan to do. I'm going to take apart the TXV in place by unscrewing the spring/needle assembly and then blow the flushing solution into the TXV body backwards through the orifice into the liquid line (front seated suction service valve prevents any from going through the evaporator at this point). Then I'll repeat the process with the liquid line closed off with the suction line open.

Any refrigeration guys on here with a comment?

 

[vonski]

The compressor for my walk-in went TU and when the replacement arrived the first thing I saw was a big sticker on it warning that it is filled with POE oil. That means I'll have to flush the lines when I install it (which is probably a good idea anyway after 15 years and I don't really know how the compressor failed). The catch is that everywhere I look it says to remove the TXV when flushing for fear that something will come loose and lodge in the orifice. Well removing the TXV, wedged in as it is into a very small space, probably exceeds my skill level with a torch so here's what I plan to do. I'm going to take apart the TXV in place by unscrewing the spring/needle assembly and then blow the flushing solution into the TXV body backwards through the orifice into the liquid line (front seated suction service valve prevents any from going through the evaporator at this point). Then I'll repeat the process with the liquid line closed off with the suction line open.

Any refrigeration guys on here with a comment?

What refrigerant and pic of the txv?

 

[ajdelange]

R22

Camera held horizontal. Liquid line at bottom (I think I can get that one and will do that if I can't push enough flush through the orifice in the valve body. The bright silvery rectangular thing at the lower left is the electrically operated (by the thermostat) liquid valve. Line with the tie wrap on it is the one I'm not so sure I could get. But as that line comes out of the body with no aperture there really isn't any point in undoing that connection that I can see.

TXV is Sporlan.

 

[vonski]

The TXV has a body , cartridge and powerhead. If you would like to disassemble the TXV I would recommend disconnecting the sensing bulb, rolling up the bulb w/ copper to the power head. Support the body with a wrench and with another wrench unscrew the powerhead. Sporlan sells a special wrench large and skinny. Use an allen wrench to remove the cartridge, might be a funky triangle (special tool) my guess is an allen. They also have special install Lube... use the old comp oil to reinstall.
Most definitely change the filter drier. With poe oil, you can run r407a or the more popular 407c. Way cheaper then r22 and no tvx swap. Do not expose poe oil to moisture.

 

[ajdelange]

Thanks for the reply! Questions/comments:

The TXV has a body , cartridge and powerhead. If you would like to disassemble the TXV I would recommend disconnecting the sensing bulb, rolling up the bulb w/ copper to the power head. Support the body with a wrench and with another wrench unscrew the powerhead. Sporlan sells a special wrench large and skinny. Use an allen wrench to remove the cartridge, might be a funky triangle (special tool) my guess is an allen.

The object isn't so much to disassemble the TXV as it is to get access to the lines for flushing without having to de-braze the TXV and eliminate the risk of orifice blockage. The photo clearly shows that the power head can be removed from this TXV but I was thinking of attacking from the other end as in this photo:

Thus my first question is as to why you recommend working from the power head end. Are you thinking that I might not be able to inject flushing liquid fast enough from the adjustment end because of the orifice? If that's the case I think I would de-braze the liquid line rather than take off the power head because it would be simpler (I can reach that joint) and I don't think I can get the injector gun into the body of the TXV from the power head end.

Or is it because the insides of the bottom of the Sporlan TXV don't resemble those in the photo in this post?

They also have special install Lube... use the old comp oil to reinstall.

The object here is to get rid of the old oil.

Most definitely change the filter drier.

I always install a new filter/drier whenever I open the system.

With poe oil, you can run r407a or the more popular 407c. Way cheaper then r22 and no tvx swap.

The compressor is specified for R22 only and I have about 27 lbs of that on hand so I'll be sticking with R22.

Do not expose poe oil to moisture.

I am not planning to add any oil beyond what is in the new compressor and I will not be removing the seals from the new compressor until just before connecting it to the system. The system will be purged with nitrogen for brazing. I may install A/C-Renew. If I do that it will be done via a sealed injector.

 

[vonski]

I don't recommend taking the txv body apart. The body is factory pre set. Pulling the power head off and removing the cartridge will grant easy access to the circut.

I would never add old oil, just a tiny bit enough to wet the txv cartridge o-rings and power head mating service to reinstall.

Your plan is on point, I hear nitrogen purge and I'm all in. R22 is 3 times the price of it's replacments. I don't have $500 for a 30lbs jug of r22. With poe oil your options open up to run multiple r22 replacment refrigerants.

you can cut the suction line at the evap to let oil drain instead of trying to push it to the c/u.

The silver thing is a solenoid valve w/ coil is normally closed, please energize open when flushing the system. Flush as planned and swap the compressor.

Not sure on your application but the vertical distance between the comp and evap are important. Heatcraft recomends a p trap on the suction of the evap. One p trap out of the evaporator and every 20 ft of vertical rise. Helps with oil returning to the compressor.

 

[ajdelange]

Once again, thanks for sharing your expertise. Again, some comments:

I don't recommend taking the txv body apart. The body is factory pre set.

According to Heat Craft's "Ten Tips for a Successful Installation" (and this is a Heat Craft fan coil unit) that is a commonly held misconception. One removes the hex cap at the left end (pic in #3) to expose the end of a stem which adjusts the spring interior to the body (see the pic in #5) thus allowing the tech to adjust super heat. The reason I got onto DIY refrigeration repair is that the guy who installed this TXV did not know how to set it properly and left the job with a frosty suction line at the compressor. The guy's boss kept calling him every half hour to tell him that he was spending too much time on the job. I really felt sorry for the guy but figured I'd better learn how to do this sort of thing myself. It's been kind of fun, actually.

Pulling the power head off and removing the cartridge will grant easy access to the circut.

That would be true except that the power head is too close to the sheet metal to allow me to get the flush tool in there so I'm kind of stuck with taking off the left end. If this TXV is anything like the one pictured in #5 I shouldn't have any problems taking it apart, reassembling it and setting super heat. But I will continue to research this to see if this Sporlan valve is different from the one in #5.

I would never add old oil, just a tiny bit enough to wet the txv cartridge o-rings and power head mating service to reinstall.

There are no O-rings in the TXV in #5 and I hope there are none in the Sporlan at the adjustment end.

I don't have $500 for a 30lbs jug of r22.

I don't either but I do have the R22 which I bought as a hedge against a day like today. I used to have 2 A/A heat pumps, 3 A/Cs and this cold room all of which used R22. I figured I'd better stockpile some and am glad I did.

you can cut the suction line at the evap to let oil drain instead of trying to push it to the c/u.

The suction line run to the condensing unit is short and vertical and terminates in an SAE fitting and is, thus, draining while the system is sitting idle.I shouldn't have to cut anything which is good news to me because any braze I do is a potential leak.

The silver thing is a solenoid valve w/ coil is normally closed, please energize open when flushing the system.

Automatically taken care of as the system is off and the T-stat is asking for cooling.

Not sure on your application but the vertical distance between the comp and evap are important. Heatcraft recomends a p trap on the suction of the evap. One p trap out of the evaporator and every 20 ft of vertical rise.

Compressor is below the evaporator and only 3 - 4 feet below. Heatcraft's recommendations are for vertical vapor flow i.e. when the compressor is above the evaporator or when the suction line rises above the top of the evaporator before heading down so I think I'm OK WRT p-traps (I don't have any).

[Edit:]Found a cutaway drawing of the Sporlan in their catalogue which confirms that internally it is very much like the unit pictured in #5. Thus I expect no problems with disassembly/assembly from the adjustment stem end. Even looks as if the orifice can be screwed out, were I to be so bold. And there are no 0-rings to worry about.

[Further Edit:]From further browsing in the Sporlan catalogue I see that you are thinking of Type EQ valves (with cartridge). This is a Type EF (no cartridge). Super heat can be adjusted on either.

 

[daewooo10]

Two things you may not have to "debraze" it if you habe enough room to cut the pipe before and after the txv. The system is r22 which means using two couplings you can solder it with silver solder and not have to braze. That uses a lot less heat.

Second thing if you don't have a vacuum pump rent one not sure if the nitrogen purge was in place of pulling it down into a vacuum. I work with an old school guy and he has some get it done quick practices that never really work.


Sent from my SM-G930P using Home Brew mobile app

 

[ajdelange]

That's something to think about. Thanks.

The "brazing" I'm referring to is done with Sil-phos 15 which isn't really that hard to work with but I'd rather not have to braze or de-braze anything if I don't have to. Every joint is a potential leak and what you are suggesting introduces 4 of those. The liquid line connection is much more accessible than the nozzle side so I could cut the liquid line. The nozzle side is pretty tight (see photo) but I could probably get one of those little cutters in there.

WRT the nitrogen: I intend to first blast (high pressure) nitrogen through the system to dislodge any flakes of anything that may be in there. The hapless fellow I mentioned in my last post tried to braze a leak with refrigerant in the system and did not flood it with N2 when he subsequently re-brazed the connections after opening it. That, I think, was pretty much standard practice as R-22/alkyl-benzene apparently won't dislodge copper oxides but R-410A/POE will so I think N2 flushing is pretty much universal now.

The second mention of nitrogen refers to establishing a gentle flow of nitrogen through the system while brazing in the new compressor and filter/drier in order to prevent formation of oxides which the POE oil will dislodge.

Thus the N2 is used to remove/prevent particulates - not as a substitute for evacuation. Running the system with non condensible N2 in it would not be a good idea.

 

[vonski]

R22
View attachment 570874
Camera held horizontal. Liquid line at bottom (I think I can get that one and will do that if I can't push enough flush through the orifice in the valve body. The bright silvery rectangular thing at the lower left is the electrically operated (by the thermostat) liquid valve. Line with the tie wrap on it is the one I'm not so sure I could get. But as that line comes out of the body with no aperture there really isn't any point in undoing that connection that I can see.

TXV is Sporlan.

Pic looks like a Q body style txv. Here is the install instructions. I don't mess with the body settings when the superheat and sup cool are already setup.

 

[ajdelange]

Pic looks like a Q body style txv.

It looks just as much like an EF which I am assuming it is based on what it replaced. But it could be a Type Q. I won't know until I take it apart. I am hoping it will be an EF as I will then be able to remove the orifice from the adjustment stem side. I don't think I'll be able to get tools in there to remove it from the power head side as there isn't much room between that end of it and the fan coil enclosure wall.

I don't mess with the body settings when the superheat and sup cool are already setup.

I don't recommend taking the txv body apart. The body is factory pre set.

Putting those two together I assume you are referring to equipment such as a reach-in that come preassembled as a single unit. In such a case I would expect the TXV to have been properly set at the factory and I wouldn't fiddle with it either. But with a split system such as a walk-in it is a different matter. This condenser goes with that fan coil, this line set and the other box. The system isn't integrated and tested until it is installed on site. In such cases it is necessary to set the super heat and the TXV is, thus, going to have to be adjusted. The valves do come "preset" from the factory - with the stem half way in - but the liklihood that this setting will give the correct superheat in a given installation is going to be small.

The fact that you have an empty package for a TXV suggests that you must have installed one. Did you not adjust the stem after installation? Or did the system come to the proper SH with the stem half way in (or out if you prefer)?

 

[ajdelange]

The new compressor is installed and running and the system was more or less flushed. The low side was easily flushed (or relatively easy as the 'gun' with the flushing kit was defective) through the TXV as the port to the nozzle opens directly into the lower part of its body. This is fortunate as I'm not sure I'm skilled enough to debraze in such tight space without ruining something or starting a fire. The liquid side was a different story. The fluid just did not want to go backwards through the orifice (check valve?) and so I wound up doing what daewooo10 had suggested (cutting the liquid line) except that instead of using couplers I expanded one end of the cut tubing when I put things back together.

The new compressor is so quiet compared to the old one I wasn't even sure it was running (which it wasn't at first because I forgot a wire in the start circuit) so I guess the old one really was coming apart inside. I'll probably autopsy it today.

Needless to say with the new compressor the old TXV setting was wrong. Adjusting it properly is going to be a neat trick as the compressor only runs 3 minutes in its normal cycle when the door is closed. The condenser unit was probably oversized (5500 BTUh) for my little walk in. Guess I'll just keep cranking the stem in until S/H is at least 10° at all times at the condenser unit.

My next question is as to what, if anything, you all know about AC Renew. I got taken in by the hype and bought a bottle. Does it really do what it says it does? Should I install it?

 

[ajdelange]

The problem with the compressor that caused me to replace it was a leaky inlet valve. The photo below shows the piston side of the head plate with the inlet valve spring, inverted so the mating surface of valve and seat are shown. The leak is on the right hand port at 9 o'clock. Wonder what caused it.

Looking forward to a cold beer with dinner!