True GDM-72F ("F" Stands For F'in POS)

[markettech]

I'm pulling my hair out on this and need some advice.

Here's the specifics:

True GDM-72F
KATB-015E-CAV
Double cap tube fed
CRO-6-0/60
41 oz critical charge R404a
C-052S liquid drier.


Got called out yesterday on a GDM-72F - case temp warm.

Condenser was dirty so I brushed it clean and decided to check pressures. Suction 2 psig and head 210 psig (R404A).

Figured either low on gas, plugged cap tubes or restricted drier. Recovered approximately 4 lbs R404A from the system (knew system most likely had no leak at that point). Removed LL drier and brazed what would have been inlet to drier shut. Back blew system with nitrogen and felt pressure coming from cap tubes. Installed new drier - pressurize to 150 psig nitro - held for 20 minutes........evacuated to 400 microns - critical charged with 2 lbs 5 oz.

Started up - suction pressure now 0 psig, head 170 psig (or close to it, don't remember exactly).

Tried to adjust CRO - barely touched adjustment screw and suction pressure started bouncing around........figured it must be a CRO valve that's not throttling properly. Picked one up and changed it out. Evac - charge.

Start up - suction 1 psig head around 170 psig

Thought maybe one of two cap tubes partially restricted. isolated each cap tube and brazed 1/4" copper stub with access fitting on end of each. Pinched and brazed LL shut for pressurization. Pressurized with nitro through suction service valve - both cap tubes pressurized - both equalized to suction side pressure at the same time (which was fairly fast).

Its getting late at this time and my brain is getting tired - so - I was thinking maybe oil logged evap coil. Drilled small hole in lowest point of evap coil and blew through system with nitro. Best guess - maybe 2 oz of oil came out.

Re-hooked, evac, charge. Same result.

By this time I'm ready to pull my hair out. I brazed on access ports just upstream of cap tube and just downstream of where suction line exits the box. Liquid getting to cap tube and no pressure drop from discharge valve to inlet of cap tubes. Suction pressure at newly installed tap the same as inlet side of CRO which is the same as pressure at suction service valve.

WHAT THE HELL!!!

My thinking was restriction........and if its not before the cap tube or from the outlet of the case to compressor - then it's got to be the suction line inside the cabinet (figured maybe it got kinked somehow).

Pulled gas - repiped suction line external of box and tied in below. Evac, charge

Start up - 3 psig suction 180 psig head.

Enough already - I start slamming juice to the thing. 4 lbs 8 oz. and suction finally came up as high as 5 psig for a short time - head hovered around 225 psig......................But case temp starting to fall.

All 3 evap fans running - all rotation and fan blade correct. Evap coil clear.

I stopped back this AM and case is running at -10F, but it doesn't take a rocket scientist to know that 5/225 is gonna burn a compressor out.

I plan to call True on Monday..................Anybody got anything for me on this?

[skpkey9]

What do you expect its a TRUE piece of crap...:D :rolleyes: :D

[icemeister]

I assume this box is out of warranty or you would have called True at the outset.

It appears to me from what you described that both caps are partially plugged due to the cooked POE oil caused by the dirty condenser. If you call True, I guarantee that they will recommend changing out the cap tubes.

This is what I will tell you. You have two possible routes to take. One is to replace both cap tubes. The other route is to install a TEV in place of the capillaries. In either case of course, change the drier and change the compressor oil. The old oil is crapola at this point and will only plug up any new metering device.

I've done the TEV thing on the GDM-72F (The GDM stands for goddamned, BTW:D ) using a Sporlan QE2X4 valve with a KT-43SZ element and QC-2 cartridge. If you want to get real fancy you can add a receiver and a SG, although you don't actually need one because the condenser is fairly large. I made up a little distributor out of a piece of 1/2" copper and pinch in a pair of 1/4" for distributor tubes.

I like the way the case runs so much better with a TEV. With caps the suction is normally around 14# to 16# at a 0ºF box temperature and maybe a 40ºF suction line temp at the compressor. With the TEV it's up around 20# and suction superheat down around 30ºF.....nice and frosty.

I did my first one with a TEV back in 2001. It's still running great.

[the mojo]

Yep,Just get some crappy tubes from True. Drill a small hole in the back,in line with the inlet side. Chase the tubes in plastic.Or go to H.D. and p/u a flush electrical chase for a few $$$. That way when they plug again its easy.

[markettech]

I assume this box is out of warranty or you would have called True at the outset.

It appears to me from what you described that both caps are partially plugged due to the cooked POE oil caused by the dirty condenser. If you call True, I guarantee that they will recommend changing out the cap tubes.

This is what I will tell you. You have two possible routes to take. One is to replace both cap tubes. The other route is to install a TEV in place of the capillaries. In either case of course, change the drier and change the compressor oil. The old oil is crapola at this point and will only plug up any new metering device.

I've done the TEV thing on the GDM-72F (The GDM stands for goddamned, BTW:D ) using a Sporlan QE2X4 valve with a KT-43SZ element and QC-2 cartridge. If you want to get real fancy you can add a receiver and a SG, although you don't actually need one because the condenser is fairly large. I made up a little distributor out of a piece of 1/2" copper and pinch in a pair of 1/4" for distributor tubes.

I like the way the case runs so much better with a TEV. With caps the suction is normally around 14# to 16# at a 0ºF box temperature and maybe a 40ºF suction line temp at the compressor. With the TEV it's up around 20# and suction superheat down around 30ºF.....nice and frosty.

I did my first one with a TEV back in 2001. It's still running great.

Interesting....I was actually talking to a friend of mine who's also in the trade this morning and one of the ideas that came up in conversation was to eliminate the cap tubes altogether and just install a txv - it's nice to know someone else has gone down this road with success.

Yes, the unit is out of warranty and it is an '05 compressor - so it has been changed at least once. From the smell of the refrigerant, the compressor is not long for this world - makes me think this thing has been operating with low suction for quite some time.

This is going to sound like a remedial question I'm sure, but - if I install the txv and no receiver, should I pipe in a LL sight glass and charge to clear glass, or should I charge via subcooling - or what?:confused:

This case WILL work as designed, I don't care what I've got to do to it. It's now a matter of principle.

You're gonna laugh, but I started on the call at 1:30 yesterday and got kicked out of the store at 11:45 last night. After investing this much time and effort, I will tear the thing down to the bare sheetmetal and rebuild it again if need be - but it will work when I am done by God.

- talk about a freekin nightmare service call:eek:

[the mojo]

Ice two methods same madness. Should have said to bring a can of POE, MT.:o

[the mojo]

And MT I'll join you come Monday a new CU going in on a GDM-72F. Less than 1 week old.:eek:

[markettech]

And MT I'll join you come Monday a new CU going in on a GDM-72F. Less than 1 week old.:eek:

I'm glad there are others out there "suffering" as well.......I don't feel so alone now:D

The unfortunate thing about my nightmare call is that this was the first service call I have gotten at a new account. Just picked up the chain of 5 convenience stores.

I walk in trying to "slam dunk" my first service call and look like a hero............end up looking like a zero:o .............Thank you, True:mad:

[the mojo]

The design alone has given me even more grey hair.:(

[icemeister]

This is going to sound like a remedial question I'm sure, but - if I install the txv and no receiver, should I pipe in a LL sight glass and charge to clear glass, or should I charge via subcooling - or what?:confused:

You can add a SG but I found the nameplate charge to be right on. But of course it's always best to check for positive subcooling when there's no receiver.


This case WILL work as designed, I don't care what I've got to do to it. It's now a matter of principle.


Yes, it'll work OK with new cap tubes, but as I said it runs a heck of a lot better with a TEV......and I'm sure with some decent suction cooling for a change that K-Body will live to a ripe old age (iffin' they keeps the condenser clean).

[markettech]

Yes, it'll work OK with new cap tubes, but as I said it runs a heck of a lot better with a TEV......and I'm sure with some decent suction cooling for a change that K-Body will live to a ripe old age (iffin' they keeps the condenser clean).

I said work as designed - what I should have said was maintain temperature without cooking the pump;) I will be installing that valve.

Most of the "hard" work is already done when I repiped the suction line - now it's just a matter of extending the liquid line and installing a tx valve.............sounds so simple and easy, maybe I won't even go back and just send one of the new guys to finish up.:D :D

[icemeister]

It would probably be better if you finished it yourself. Otherwise the customer will think the other guy was the one who finally fixed it.

One hint. I found there wasn't a lot of room inside the evap housing to locate the valve so I extended the distributor tube straight to the left outside of the housing and hung the TEV right there. It's up high, nobody sees it, and most importantly it's real easy to adjust and clean the screen if need be.;)

[selfemployed]

Have had our buts kicked around on the cap tube thing since the new oil came along. I've replaced more cap tubes in 6 yrs. than the other 24. 404a plates the cap tube inside. 134a the drier beads restrict the cap tube for about 14". When you pull the cap tubes out I bet you will find tick truds on the ends if they don't fall off when you remove them.

[k-fridge]

I'd add a receiver and site glass if you convert to a TXV.

[270wsm]

I saw a GDM today outside a store in the 90* heat. I didnt think these things were meant to be ouside in the heat.

[Dowadudda]

no no no no effin no.

Just fix it the right way.

You mis diagnosed a partially blocked cap tube first off. A delta T measurment of your condenser, a superheat measurment at your pump, and a discharge temperature measurment would have told you your not picking up any heat in the evaporator.

A cap tube(s) is easily replaced by routing the new tube up the back wall, pentetrating the box and stabbing into the coil.

[Dowadudda]

you go through all that bull $hit for to put in a TXV and still not done your job the way your suppose to, and that's put the unit back together and working as it was designed.

I have a alot of respect for Icemeister, but I absolutely disagree with his thing on this subject.

[markettech]

You mis diagnosed a partially blocked cap tube first off. A delta T measurment of your condenser, a superheat measurment at your pump, and a discharge temperature measurment would have told you your not picking up any heat in the evaporator.

A cap tube(s) is easily replaced by routing the new tube up the back wall, pentetrating the box and stabbing into the coil.


It is obvious to anyone reading the OP that I mis-diagnosed the problem (more than once). I didn't start this thread to get beat over the head with the fact that I was wrong.

Hopefully as I learn more, I will no longer mis-diagnose a system or make any mistakes.........................in short, be more like you.

Tell me, how would a superheat and subcooling reading help me definitively determine that

one cap tube is completely blocked and the other one feeding fine.
one cap tube is completely blocked and the other one partially restricted
both cap tubes are partially restricted
The suction line is restricted somewhere inside the cabinetIf you can tell me how I walk up to a cap tube system that is already running warm and check a couple of pressures/temperatures - then make a hard and fast determination as to the cause of failure on a call like this - you are hands down a refrigeration GOD.

Yes, I made mistakes.........but that's not the point. There is no doubt I dropped the ball in changing the CRO valve. It was one of those things where in my mind I justified the part being bad because I didn't look at the big picture (and was hoping to get the hell out of the store in a timely manner).

I will install a TXV on this system. My thinking is that if I have gone through all this work already, I'm not going to take the chance on plugging up another cap tube(s) in a year or two. When I walk away and give this system my blessing..................I'm not one that enjoys coming back for a "redo".

[icemeister]

My advice to markettech was that he had two options: Either replace the cap tubes or install a TEV. Because of my experiences of repeated cap tube failures with this specific model True reach-in, I prefer the TEV route because of the improved performance, serviceability and extended compressor life.

Don't get me wrong on this.....I'm not a big fan of re-engineering any self-contained system. The GDM-72F will run fine with the factory twin cap tube feed, but I had this one case (the one I changed to TEV in 2001) that had been kicking my butt for several years. It went through two sets of valve plates, two sets of cap tubes (and a burnout in there somewhere as well). Each time it was put back together right, as per factory design. Each time the customer (owner of two high end gourmet markets) was getting more upset with this freezer (and increasingly so with me). I couldn't afford to dick around with this any more.

When the one of the caps partially plugged yet again I decided to go with the TEV. I had the valve parts in the truck, I didn't have the cap tubes, I had already run the LL up the inside LH corner with the little white cover from True, so what the heck? It worked like a charm and that's when I realized it ran much better with the expansion valve and I actually got some reasonable suction cooling on the pig. I certainly don't think it was wrong to accomplish that. Is it end justifying the means....well, yes. I'd would do it again if I see the same problem.

[Airmechanical]

My advice to markettech was that he had two options: Either replace the cap tubes or install a TEV.Don't get me wrong on this.....I'm not a big fan of re-engineering any self-contained system. The GDM-72F will run fine with the factory twin cap tube feed


just out of curiousity, did you add a receiver and sight glass when you changed it to tev?



.

[markettech]

you go through all that bull $hit for to put in a TXV and still not done your job the way your suppose to, and that's put the unit back together and working as it was designed.

I have a alot of respect for Icemeister, but I absolutely disagree with his thing on this subject.

There are several threads on this site addressing the idea that the design/manufacturing processes used be some OEM companies is such that the equipment gets to the end user with as little cost into the refrigeration system as humanly possible.

One of the reasons cap tubes are installed in the first place is because it is much more cost effective than to install a receiver, liquid line sight glass and TXV.

It is widely known that True puts out some of the cheapest pieces of crap in the industry. If True Mfg. had a sound design - there would be no need to stray from the factory set up.

I for one will not blindly take any OEM's design or recommendations as gospel (unless it already fits into what I believe) until said manufacturer has established a proven track record.............True is far from a proven leader.

[k-fridge]

no no no no effin no.

Just fix it the right way.

You mis diagnosed a partially blocked cap tube first off. A delta T measurment of your condenser, a superheat measurment at your pump, and a discharge temperature measurment would have told you your not picking up any heat in the evaporator.

A cap tube(s) is easily replaced by routing the new tube up the back wall, pentetrating the box and stabbing into the coil.
Good grief Dow, take a chill pill dude. Granted we need to be careful about re-engineering equipment but you of all people should know t hat it's sometimes necessary. There are times when the OEM parts are not available requiring a substitution and there are times like this when the original design was compromised due to price and with a few extra bucks of replacement parts you could actually improve upon the performance and reliability.

In any case, this forum is a place that we can share our knowledge and experience with each other, hopefully without getting flamed for it.

[icemeister]

just out of curiousity, did you add a receiver and sight glass when you changed it to tev?

Nope.....just the TEV. In that instance, I simply charged per the dataplate, checked for positive subcooling and adjusted the superheat. The condenser is generously sized on that box and has enough extra volume to handle the ebb and flow of the TEV without problems.

Ideally however, you can't go wrong adding a receiver and sightglass.

[KB Cool]

This is where I meant to post.:D
Markettech,
Don't you have one of those thermal engineering "cap-checks"?
If you do you should use it on this box. I would love to hear the results.

[markettech]

This is where I meant to post.:D
Markettech,
Don't you have one of those thermal engineering "cap-checks"?
If you do you should use it on this box. I would love to hear the results.

Busted!!:eek:

Yes, I do have one somewhere in mini-warehouse full of refrigeration stuff. I have been mostly working on racks so had no need to carry the thing around.

I should probably try to dig it out. That said, I'm not sure how it would've worked in a situation like this. The cap tubes aren't plugged really - I guess it would have been worth a shot.

[KB Cool]

Busted!!:eek:

Yes, I do have one somewhere in mini-warehouse full of refrigeration stuff. I have been mostly working on racks so had no need to carry the thing around.

I should probably try to dig it out. That said, I'm not sure how it would've worked in a situation like this. The cap tubes aren't plugged really - I guess it would have been worth a shot.


You need the "chaser kit" for partially restricted tubes.

[wannafreeze]

I wonder if you had measured the pressure upstream of CPR valve..Maybe it would have saved you little bit time if it mattered at that point.
Other than that I have no techinical knowledge to add.
But I had a freezer with plugged double cap tubes recently.
I gave my price to replace them and told the owner that there is a tail light guarantee and no money back.Plus it's an indication that oil is going bad,another spending is pending.
He bought a TXV freezer.
The only stupid thing I did was I didn't give the phone number for him to call so I could make a nice commmission wihtout him even knowing.:mad:

[Dowadudda]

no no no no.

I wasn't to do anything. your reading my post wrong and maybe I am not writting correctly.

I would change both Pat.

Ice, you know me. And it wouldn't be a surprize then that I would disagree with you on this cause I have in the past. Your not wrong. Your just not doing it the way I would. That's all. I got reasons as you do.

Pat, now hear me and feel me here okay?

I am a little surprized. Your ten times better a tech than that. 20 times. Take the a$$ chewing from a freind and a fellow colleague. You got ahead of yourself, you know it. Take the next one in much more stride and not be so quick to nail it and move on. Your stressed out, your whole life is upside down in ways at the moment. You missed it cause of all that, not cause your stupid, or inexperienced or anything. Your coming on hear and not telling the whole story about doing upteen million hours, running the show, putting up with all the BS of running the show and then on a True GDM POS. I understand why you got quick about it. I am busting your balls cause I am your friend.

You asked me how you would figure which one. I'd tell you if it was me I wouldn;t even try to guess. Rip them both out. And replace them. If you really wanted to know which one was plugged, I might try to turn the fans off, and see which one flashes. Sometimes you can sometimes you can't.

[icemeister]

I'm cool with all that.:cool: :cool: :)

I just wanted to let you and the others know the story behind what drove me to rework this case.

Diagnosing which of the dual cap tubes is plugged is really kinda a waste of time. If one is messed up, it's likely the other one isn't far behind. It 's only practical to change out both........while you're at it.

For what it's worth, I have noticed that if one cap plugs up you will either get fans or no fans due to the placement of the fan klixon. So with fans and 1/2 an evaporator, the compressor runs at close to 0# and the case can't get below 20ºF. If the other tube is plugged you often will get no fans at all, the back side of the coil freezes up and if the fans do eventually come on you got no airflow because of the already iced up evap.

[markettech]

Pat, now hear me and feel me here okay?

I am a little surprized. Your ten times better a tech than that. 20 times. Take the a$$ chewing from a freind and a fellow colleague. You got ahead of yourself, you know it. Take the next one in much more stride and not be so quick to nail it and move on. Your stressed out, your whole life is upside down in ways at the moment. You missed it cause of all that, not cause your stupid, or inexperienced or anything. Your coming on hear and not telling the whole story about doing upteen million hours, running the show, putting up with all the BS of running the show and then on a True GDM POS. I understand why you got quick about it. I am busting your balls cause I am your friend.

Thanks;)

I have been a little edgy lately - got a lot going on............(don't we all).

Hey Dow - We fell into a helluva deal on a 4 bedroom 2 bath so after only 4 months we're moving again.:eek: Poor kids barely got their rooms set up - but this will be the last one for a LONG time................unless you're looking for a partner to start a refrigeration company with up there:D :D