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How old is this system?

If its been running for a long time you can probably rule out have an issue with your bulb placement or a system design itself.

if the customers knows what the refrigerant is im sure he knows he has a leak and previous techs have just kept adding more because cheap customers never want to pay for the good fix, but techs have to stop offering temporary fixs so we can raise the industry standard and force people to make decisions based on the equipment and not their wallets.

id recommend pulling the charge and pressure test it. start at the begining like a new install. sounds like you have a leak and your loosing your charge. low sub cooling is a sure indication of low charge. if the sight glass was bubbling and your sub cooling was 15-18 id say your evap coil was blocked and probably needed to be cleaned.

the raise in high side pressure could be because your creating a new blend of refrigerant and depending on whats left in the system from previous fractionation your pressures would be all over the place.

Originally Posted by VTP99

How about a head pressure control stuck in bypass ? He could add gas till the cows come home and he still would be feeding the TXV with hot gas. Am I reaching for straws yet.

Its either this or contamination.
I'm betting its the headmaster, sure sounds like its stuck wide open to me.

Assuming you have a full system charge on sounds like to me you have a bad TXV. another thing you want to check is make sure you have the proper nozzle in your distributor. Check the distributor tubes for proper size. If they are 3/16 inch they are or were for an R-22 system. Your distributor tubes should be 1/4 inch. If your distributor tubes are wrong chances are your nozzle is wrong too.

Goodluck

Originally Posted by markettech

I was at first, too. But, with the OP adding refrigerant and observing a 100 psig increase in head pressure with only a 2 psig increase in suction....at a +20F outside ambient - something funky is going on.

How about a head pressure control stuck in bypass ? He could add gas till the cows come home and he still would be feeding the TXV with hot gas. Am I reaching for straws yet.

Originally Posted by VTP99

Personally I have never seen a refrigeration system using R410a. (excluding a/c refrigeration) Also I would not expect any refrigeration tech to think that R410a would be a possibility as a refrigerant in such a system. Now R22 or R407 that could happen and there was a thread just on here in which that happened.
Oh....I'm going with low on charge theory

I was at first, too. But, with the OP adding refrigerant and observing a 100 psig increase in head pressure with only a 2 psig increase in suction....at a +20F outside ambient - something funky is going on.

Personally I have never seen a refrigeration system using R410a. (excluding a/c refrigeration) Also I would not expect any refrigeration tech to think that R410a would be a possibility as a refrigerant in such a system. Now R22 or R407 that could happen and there was a thread on here in which that happened.
Oh....I'm going with low on charge theory

Originally Posted by malcor

You misunderstood what I wrote.

I stated that if R404a were contaminated with R410a or R407c (or any other refrigerant) that it would be highly possible. That is because there would be a lot of uncertainty where blends were mixed, resulting in a new unknown refrigerant type. I never compared R410a to R404a and am not sure why you thought I did either.

Re-re-reading your post, I see that, now.

I wouldn't consider it fractionation, though, but a mixed refrigerant. Fractionation describes a very specific phenomenon and it isn't nearly as common as some people think that it is.

Timebuilder, I agree that that is part of it. Sure we have become a less civil society, yet, I know in my personal experience that I am a little less aggressive if people know it's me posting an attack. On other boards that I discuss politics and rural living, I post with my actual name, and I weigh every word I say. This isn't a topic that inspires my wrath to begin with, so I'm not inclined to start ripping into anyone. If someone is bent on doing something that time has taught me to be bad, I accept that I will not prevent their continued use of a practice I disagree with. That doesn't compell me to get up in anyone's face. If they have a heat pump gage set with a set of six foot hoses, and they are bent on checking a small ice machine with it everyday, ultimately that is between them and their customer. I will share that I use a very short hose with the gage that can withstand the harvest cycle and a valve, but, if they are bent on doing things their own way, that is their business. While I fully understand what is the reasoning behind Navy 06. I use to have to frequently reclaim all the refrigerant from a system, weight it and PT the bottle to verify the blended refrigerant was good, even though I knew the problem was electrical, because the unit felt it was to be done. I learned in the service, as well, though on the outside we get a little more flexiablity. At the point that post appeared, it appeared a possibility, though probably not the next check. I understand where that comes from. Like I already said even though I know many who tweek a little gas into an ice machine or small appliance, I usually still reclaim everything, put a vacuum to it and weigh a charge into the unit. That is what I was taught and it is pretty acurate. Some of those service habits will likely be with him forever, some will probably not. It certainly isn't a stupid idea.

I'm not convinced that screen names are the root cause of friction. I DO think it has to do with the limited nature of written communication, and the lack of writing most guys have done who are under 40 years old, because it became less emphasized in the past 30 or so years in public schools.

There ARE times when I read something, and I have to ask if the poster is even a tech, just based on the way the information is given, and what conclusions are being drawn in the questions asked by a poster. Hopefully, it doesn't seem condescending when I do that, as knowing the experience level often helps one to GIVE help, where that assistance is warranted. Obviously, we don't want this to be a DIY site, but we also have to bear in mind that there is a WIDE range of experience among us. There are guys here that have a lot of great experience, and I come here often, looking for tidbits that make me a better tech, because there is always a chance that someone has looked at something differently than I might, merely by their own life experiences being different than my own. That's what I love about this place.

I'd say we should all put down the long knives and say "apology accepted," and move on.

If the OP has more questions about this issue, we can help.

From the handful of posts I have read, franctionalizing or mixed refrigerants would not be my guess, unless the owner had told me that he or a friend had tried to add gas, or if perhaps I saw a jug sitting out back...

Originally Posted by malcor

The problem with typing here on the forums is that you don’t get the visual and tonal cues that you get from a normal face to face conversation. I'm not a condescending person at all and I really meant no offence. Perhaps it’s my writing style or the way I expressed what I was trying to say, that gave that impression. I actually came to this web site with the mindset of having a technical rumble in the dirt with my peers. I didn’t come here to offend anyone or to make trouble. And that’s the truth.

Just between us on this board, I think screen names play a part of why sometimes someone gets hostile or such. Often we might bite our tongue when we talk with people who know who we are, but here we are Malcor & Bobbycold. I suspect people know that my name isn't Bobby Cold. Some may know me as Johnny Cold in real life (LOL). If you offend people here, what are we going to do about it. It isn't like we're coming to burn down your village and slaughter your goat. We don't even know who you really are. With such anonymity, it has to be tempting to unload on people.

Originally Posted by markettech

I honestly could care less why you purposely entered a certain word or made a specific statement.

That said, I am rather curious as to the purpose of your condescending attitude earlier in this thread...which was apparently directed at individuals who responded to the OP prior to you. Regardless of the reason, hopefully it fulfilled whatever emotional need you had at the time.

The problem with typing here on the forums is that you don’t get the visual and tonal cues that you get from a normal face to face conversation. I'm not a condescending person at all and I really meant no offence. Perhaps it’s my writing style or the way I expressed what I was trying to say, that gave that impression. I actually came to this web site with the mindset of having a technical rumble in the dirt with my peers. I didn’t come here to offend anyone or to make trouble. And that’s the truth.

After noticing hostility towards me I started reading around the other topics here. I have come to realise that people who are learning the trade are encouraged to ‘get their post count up’ with posts that have technical content. Now that I realise that, I can see that my first post in this topic (#9) was uncalled for and out of line. It was a misunderstanding on my part and showed poor judgment.

It wasn’t my intention to offend anyone and I certainly didn’t want to discourage anyone from participating here, especially someone who is here specifically to increase their knowledge. I made a error in judgement and I apologise for any offence that I may have caused Navy06 and to anyone else that I may have offended too.

Originally Posted by malcor

You should re-read what I wrote. I wrote about -40’F, about being the operative word. I intentionally wrote about because the actual set value of the particular TXV's superheat is unknown.





You misinterpreted what I wrote. I didn’t dismiss the possibility of there being refrigerant contamination. I clearly stated in a few posts back... “So we can rule out refrigerant contamination for now.”

If you re-read what I wrote, I was saying that contamination of the refrigerant would not likely be the cause of the particular problem. As in the particular problem that the OP posted about. You have misinterpreted what I have written as a general blanket statement regarding refrigerant contamination. That’s not the case at all and if I were to make such a ludicrous blanket statement then my mind would have to be equally blown too.

Let me make it a little clearer.

The OP stated that the system was running with a suction pressure of between 3 to 5psi. Frost only forming after the TXV to the evap. Discharge air temp from the FDC was about 10 to 15’F, which is not really a proper indication of the overall evaporator temperature but gives a rough indication. Also, the box temperature was abnormally warm, hence the reason why they were called out in the first place I imagine.

In order for the suction pressure to be so low there would be two likely possibilities, given the data, observations and actions taken by the OP. Either the temperature at the TXV sensor was cold enough to cause the TXV to throttle back so much or the TXV had issues and was starving the evaporator. Considering the box temperature was abnormally warm it is reasonable to presume that the evaporator temperature was likewise abnormally warm for the given suction pressure. Otherwise, it would have been doing a better job of cooling the box.

Now even if there were refrigerant contamination, the temperature at the TXV sensor would still need to be cold enough to make it throttle to cause a suction pressure of 3 to 5psi. In fact, it wouldn’t matter what refrigerant was in the system, the temperature at the sensor would still need to be corresponding cold for the TXV to throttle to cause such a low suction pressure. Otherwise, the TXV would have issues/be faulty.

That was my reasoning for measuring the temperature at the TXV sensor, to determine if the TXV was working correctly or not for the given suction pressure.





The measurements and observations given by the OP didn’t point to there being irregularities with those. And as far as the TXV strainer, that is a part of the TXV and is why I said ‘TXV issues’.

I gave my systematic reasoning leading up to checking the TXV. I don’t haphazardly hork around and am not sure what I wrote to give you that impression.

Also, I didn’t second guess the abilities or aptitude of the OP in providing his observations and intentional omissions, even wrote “One of the most useful tools you possess is your powers of observation, and that is something that can’t be substituted for in a remote diagnosis.”

I honestly could care less why you purposely entered a certain word or made a specific statement.

That said, I am rather curious as to the purpose of your condescending attitude earlier in this thread...which was apparently directed at individuals who responded to the OP prior to you. Regardless of the reason, hopefully it fulfilled whatever emotional need you had at the time.

Originally Posted by malcor

I'm curious, do you actually repair commercial refrigeration equipment?

Don't mean to be rude but your recommendations, and a couple of others, really has me wondering...

With a screen name like NAVY06, I'm guessing he started working refrigeration the same place I started, the Navy and then the Coast Guard. They were funny about that stuff. It didn't take a lot for someone up the chain to decide that since there is a blended refrigerant that the next step (it may be the first step for a compressor has no power at contactor, if the Cheif Engineer was a fine arts major) is to reclaim the charge, weight the bottle and PT it to insure the blend is correct. Over time since retiring from the service, PTing the reclaimed gas is not my first step for troubleshooting, though in most cases I still reclaim critical charges that are low charge and refill by weight whenever the charge is suspected of being low. If NAVY06 stays at it, he will get past those extremely excessive, and unproductive things we all had to do in the service. Let me tell you a story from back when I was active duty. The Coast Guard had a Modspace trailer, and the authorized PM's included a weekly check of the suction pressure. It doesn't matter to the service that every time you put the gage set on it you take two 6 foot hoses of gas out of the system, someone had a bright idea, and I must obey. I requested the short hose and single suction gage, but it never appeared. After about a month and a half of faithfully preforming my duties, as you can guess, the suction pressure was below the very ridged standard set out in the same instruction that required gages on a perfectly fine operating unit. One unit had such a requirement for an ice machine, but after talking to the chief, it was felt that we could skip that. I have no doubt that NAVY06 probably did this awhile with the Navy, and will likely break the bad service methods as time continues.

There is reason to suspect that there may be a seperated blend, but I don't think it would be my next check. If the blend seperated, I doubt it was from use. Most likely the owner charged as a gas.

Originally Posted by jpsmith1cm

How would you say that R410a can fractionate with a 0.3 degree glide yet say that 404a cannot with a 1.1 degree glide?

Either refrigerant CAN fractionate, but it isn't likely for either to do so in actual use.

You misunderstood what I wrote.

I stated that if R404a were contaminated with R410a or R407c (or any other refrigerant) that it would be highly possible. That is because there would be a lot of uncertainty where blends were mixed, resulting in a new unknown refrigerant type. I never compared R410a to R404a and am not sure why you thought I did either.

Originally Posted by 2sac

I agree. If there is an inclination, especially from the equipment owner, the charge is messed up, put new gas in it and remove the doubt from the equasion.

Here's the thing. In the restaurant business, most of your owners and managers who have been in the business for awhile, know what's involved in refrigeration repairs. This is why the tech not only needs to have a knowledge of his craft, but also of customer relations. The second I hear "Well, maybe this is wrong", I know someone else f'ed with it. They called me now because the guy who f'ed with it is no longer around for whatever reasons. Of course they want to save money and you will hear about it, over and over. If you fix it right they will call you back. To play guessing games with the customers money is setting yourself up to lose the customer. Be honest with them up front.

I agree with you.

I just said that if a customer told me that they thought that ‘such and such’ was wrong with their equipment that I would verify their claim.

Almost on a daily basis I get told what is wrong with a system on arrival to a job, ranging from kitchen staff to building engineers. I am used to sifting through the information and verifying any valid concerns. I just don’t outright take their word for it blindly. That would be irresponsible and unprofessional on my part, after all they are paying me to diagnose and repair their equipment. They don’t call me so they can tell me how to repair their equipment.

Originally Posted by markettech

I know how a TXV works.

I also know a low temp TXV is not adjusted to achieve 0F superheat at the outlet of the coil before the valve starts throttling closed.

You should re-read what I wrote. I wrote about -40’F, about being the operative word. I intentionally wrote about because the actual set value of the particular TXV's superheat is unknown.

What blows my mind here is how you've dismissed the possibility of mixed refrigerant in the system based on nothing more than wild assumptions...with virtually zero quantifiable data to back it up.

You know how a TXV works - and with this knowledge are able to definitively determine whether or not a system is contaminated with mixed refrigerant?

You misinterpreted what I wrote. I didn’t dismiss the possibility of there being refrigerant contamination. I clearly stated in a few posts back... “So we can rule out refrigerant contamination for now.”

If you re-read what I wrote, I was saying that contamination of the refrigerant would not likely be the cause of the particular problem. As in the particular problem that the OP posted about. You have misinterpreted what I have written as a general blanket statement regarding refrigerant contamination. That’s not the case at all and if I were to make such a ludicrous blanket statement then my mind would have to be equally blown too.

Let me make it a little clearer.

The OP stated that the system was running with a suction pressure of between 3 to 5psi. Frost only forming after the TXV to the evap. Discharge air temp from the FDC was about 10 to 15’F, which is not really a proper indication of the overall evaporator temperature but gives a rough indication. Also, the box temperature was abnormally warm, hence the reason why they were called out in the first place I imagine.

In order for the suction pressure to be so low there would be two likely possibilities, given the data, observations and actions taken by the OP. Either the temperature at the TXV sensor was cold enough to cause the TXV to throttle back so much or the TXV had issues and was starving the evaporator. Considering the box temperature was abnormally warm it is reasonable to presume that the evaporator temperature was likewise abnormally warm for the given suction pressure. Otherwise, it would have been doing a better job of cooling the box.

Now even if there were refrigerant contamination, the temperature at the TXV sensor would still need to be cold enough to make it throttle to cause a suction pressure of 3 to 5psi. In fact, it wouldn’t matter what refrigerant was in the system, the temperature at the sensor would still need to be corresponding cold for the TXV to throttle to cause such a low suction pressure. Otherwise, the TXV would have issues/be faulty.

That was my reasoning for measuring the temperature at the TXV sensor, to determine if the TXV was working correctly or not for the given suction pressure.

If it were me, I'd be checking my LL drier, TXV inlet screen, look into the possibility of a condenser flooding valve issue....and whatever else I could think of, before haphazardly horking around with the TXV adjustment stem just for drill.

The measurements and observations given by the OP didn’t point to there being irregularities with those. And as far as the TXV strainer, that is a part of the TXV and is why I said ‘TXV issues’.

I gave my systematic reasoning leading up to checking the TXV. I don’t haphazardly hork around and am not sure what I wrote to give you that impression.

Also, I didn’t second guess the abilities or aptitude of the OP in providing his observations and intentional omissions, even wrote “One of the most useful tools you possess is your powers of observation, and that is something that can’t be substituted for in a remote diagnosis.”

Originally Posted by jpsmith1cm

How would you say that R410a can fractionate with a 0.3 degree glide yet say that 404a cannot with a 1.1 degree glide?

^^^

I think if R410a is the contaminant then the mixture (If R404a was the primary) my fractionate more than say if R22 was the containment, due the bigger difference in pressure at a fixed temp.
A frosted/frozen expansion valve and distribution legs, is not at all uncommon, especially on electric defrost on pump down systems, and coil sensed defrost termination. If no pump down, less likely seen as refrigeration vapour will move back to the valve when being heat in the coil.

Originally Posted by malcor

In my experience with R404a I would say a definate no.

However, fractionation would be highly possible if the refrigerant was contaminated with say R407c, R410a or even any other refrigerant I suppose.

To rule fractionation out as the cause it would be a simple matter of measuring the suction pressure and temperature at the TXV sensor on this particular system. If contamination were the case I would expect the refrigerant to be contaminated with R410a.

The symptoms and measurements provided by the OP don't point to it in my opinion.

How would you say that R410a can fractionate with a 0.3 degree glide yet say that 404a cannot with a 1.1 degree glide?

Either refrigerant CAN fractionate, but it isn't likely for either to do so in actual use.