MemberJuly 28, 2020 at 10:15 am
Got my T40 Delfield Blast Chiller giving me some trouble. It’s a 404A semi hermetic compressor (Model is: 3DB3F33KE-TFC)
Condensing unit is Trenton, Model#: W075L6-IT3A-3166
TXV is this one https://www.skh-kaeltetechnik.de/Exp…without-Nozzle
First indicator was short cycling, I happened to be walking by it and heard it go on and off repeatedly, I then went to check it out and here’s what I got.
Unit’s running, Sight Glass is full, I don’t see any rivering, flashing or anything.
Oil sight glass remains clear, I can see 3/4 of it is full and there’s no foaming or anything.
When I was checking it, I had it set to run to 38*F and then shut off, one of it’s settings, from my prior checks, it runs about 15-20 PSI suction over 227 PSIG head
Today it was running 5-8 PSI (-32.9*F Evaporating) over 337 PSI (125.8*F Condensing) SLT: 74.5*F this was after it ran for 5-10 minutes, which is way low head and way too high head, LLT is 217*F. S
Now, here’s what scared me. 107*F superheat.
Sounds really bad to me.
My first thought is a restriction, I didn’t feel a signifcant temp difference on the filter drier so I’m thinking it’s the TXV, when the unit shuts off the pressure stays so it’s not leaking by on the valves or the solenoid valve.
I was going to take the performance chart and check amps to see but my first thought is TXV. There’s no pressure tap at the txv so I can’t check SH at the evap.
Either the Drier is partially plugged or the TXV is shot, TXV is about $1000 so I really hope it’s not that.
What do you guys think?
MemberJuly 28, 2020 at 7:53 pm
First thing to check is why the high head. Air or water condenser? If air cooled, It should be no higher than 15F above ambient at the discharge of the condenser. How near full load is the compressor? Does it have a head pressure control? Have you checked for magnetic pull on the solenoid valve?
The compressor is obviously getting gas due to the high head. But is it cool enough liquid to properly meter.
Now if you can get it short cycling again, is it the high pressure switch (head) or the low pressure cutout tripping?
Also, check the hot gas cycling solenoid (defrost) to be leaking or open.
MemberJuly 28, 2020 at 8:11 pm
I forgot to ask you if the compressor has the modulating valve on it. The Copeland Discus units can modulate from 10% capacity to 100%. It’s on top of the head.
MemberJuly 28, 2020 at 8:34 pm
I forgot to mention that this compressor has a low oil safety. Make sure you can see oil in the crankcase sight glass.
Water condenser is what’s used. Split between inlet and outlet is 2*F on the loop, seems to be between 2-6*F on all the units we have, I checked the other ones for comparison.
It’s cutting out on low side I would think, but I could be wrong.
I pulled the charge today, cleaned the inlet strainer on the TXV and pulled the drier, had some trouble getting a new one but I could blow right through that drier with no problems, so I don’t think that was the problem.
Equalizer tube is not obstructed, liquid line seems unobstructed but I haven’t been able to get the TXV to do much with the bulb in my hand, it seems as if the problem was prior to the TXV, like it’s not getting a full column of liquid.
My SH as the evap was around 80* and at the compressor was over 100* so the evap is definetley starved.
I’m thinking it might have been the TXV orifice screen being 30-40% plugged from what I saw, it’s so small I imagine it makes a difference.
I see oil in the sight glass, that’s not a problem.
I also checked the defrost solenoid and the pump down solenoid and they both work and neither leak so those are fine as well.
MemberJuly 29, 2020 at 2:18 am
Check the evaporator coil and remove the TXV’s sensing bulb from the suction line. Check the subcooling, superheat and pressures again. If there’s no change, that’s a further indication of a TXV problem. Another test is to put the sensing bulb in ice water and checking the pressures superheat, and subcooling again
MemberJuly 29, 2020 at 9:19 am
Good point, I tried holding the TXV bulb in my hand and it didn’t seem to change much, but I figure that might be because it’s already wide open trying to feed but it’s not getting liquid.
I like the idea of the ice water on the bulb, I’ll give that a shot.
MemberJuly 29, 2020 at 10:40 am
Fired it back up with the same drier since I was curious of it was actually plugged, just for my own sake.
I got less than a 1 PSI drop through it and I’m seeing the same numbers I were before.
3 PSI suction, SLT is 80*F and superheat is over 100*
284 Liquid, LLT is 98*F and subcool is 15*
So, somethings restricted, my money’s on the TXV at this point.
MemberJuly 29, 2020 at 10:42 am
Electronic cold spray works better for freezers.
What make and model TXV does it have? Does it have a bypass tube? What charge is on it? And last, with a 33,000 BTU unit, There has to be a distributor head and several feed tubes into the evaporator. Inside that distributor there is a orifice before the cone. I assume this has a remote condenser. What size liquid line and how long. Is it possible that it got damaged?
MemberJuly 29, 2020 at 10:47 am
Oh, and has there ever been a burn up? Or multiple additions of refrigerant/oil in the past?
MemberJuly 29, 2020 at 11:08 am
I believe it.
It’s an ALCO TIE SW, 800 552. 404A unit in case I had not mentioned it.
It’s externally equalized.
MemberJuly 29, 2020 at 11:10 am
Never a burnout, I added some refrigerant 2-3 years ago after finding and fixing a leak on the liquid service valve.
Lineset is probably 100′ or more, I don’t know how anyone would’ve damaged it, I doubt that’s the case.
It’s a direct feed, there’s no distributor, just the outlet of the TXV going into a split tube for the evaporator, tees off the bottom and goes 2 directions.
MemberJuly 29, 2020 at 12:47 pm
going into a split tube for the evaporator, tees off the bottom and goes
Interesting. a old way of flooded eveporator system.
In that case, you have a orifice on the inlet of the valve.
Your valve is not a standard, but a 800534 orifice/strainer should work ok . The charge is a SW liquid because they have a hot gas defrost. Liquid charges are very fast acting vs. gas charge. But they can not be made with maximum pressure limiting. There fore be very careful adjusting it. I ruined a 12 hp compressor some years ago flooding it due to this same type of problem. A bad charge that I couldn’t get a Sporland “Z” charge replacement and used a regular. Problem was that the valve was cranked open during troubleshooting and when the new charge was installed it flooded so quick I couldn’t stop it.
Alco uses a very small diaphragm on their charges. So if it has lost any liquid, It will not open the valve at all. I’d be looking at that as the number one problem.
If your interested, here is the Data Sheet for your TXV
MemberJuly 29, 2020 at 1:43 pm
Thank you Fixbear,
I spoke to Sporlan and we were able to get one made up from their parts.
Power head will be: KT43SZ
Cartridge is a BQC-B (1 1/4 – 2 Ton)
Body is an EBQE with external equalizer.
I spoke to Delfield and they said it’s probably the TXV.
MemberJuly 30, 2020 at 1:40 pm
Replaced the TXV, same problem if not worse.
Keeps cutting out at 1 PSI on the low side, high side over 300 PSI.
Took the solenoid valve apart, clear as day, pulled the diapraghm just to be sure, didn’t change a thing.
I can hear the TXV whistling or whatever it’s called.
What else could it be? Pulling my hair out here.
MemberJuly 30, 2020 at 5:27 pm
The TXV you mentioned is a bit on the small side. You have a 2.75 ton system.
I asked you about charge top off. If you have added more than 10 to 20 percent of the total charge, and if the leak was on the low side, The R404 is no longer in spec. being a zeotropic mixture with glide it will split.
The high head bothers me. Especially since it;s not to capacity. This is usually non-condensables in the system. or a dirty heat exchanger. ie. low water flow or scale.
Now the lack of flow through the evaporator can be a liquid block due to the high vertical rise of vertical evaporator tubes I have seen this with the system oil blocking off the flow from wrong viscosity. Polyoester is a touchy oil. Very hydroscopic. Also oil will not return reliably more than 3 ft without traps. Is it possible the your suction line has a minor pitch that the oil floods the evap?
Because this is a remote condenser, I would install a tap or sight glass just prior to the TXV. I always installed a tap on the tail coil for adjustment of the TXV.
MemberJuly 30, 2020 at 6:56 pm
I spoke to Delfield and they said it’s probably the TXV.
And what specific questions did they ask you?
MemberJuly 30, 2020 at 7:04 pm
<div>I can hear the TXV whistling or whatever it’s called.</div>
That means you already have bubbles in the liquid before it gets to the valve and a very rapid expansion/boiling at the valve
MemberJuly 30, 2020 at 8:43 pm
They didn’t ask me much, I told them what I was seeing with high head and low suction and he was convinced it was the TXV.
According to Alco, the orifice in that valve was a 21,155 BTU orifice, so just shy of 2 tons.
I only added 2.6 lbs, barely anything and I don’t think I needed to, I was a bit newer to this 3 years ago.
I broke off the feed line to the evap from the TXV, that’s 2 seperate lines, both closed with access valves and then pressurized through either side of the coil and there’s plenty of flow through both sides of the evap.
I then went from one side of the evap all the way to the valve on the compressor and there’s plenty of flow through there as well.
I attached a simple picture of the layout of this unit.
I also attached how I isolated the evap and tested both sides.
I put nitro in through press tap 1 with press tap 3 open, I have flow. Then I closed press tap 1 so it’s sealed.
I then put nitro in through press tap 2 with press 3 open, I have flow.
I then closed Press tap 3 and put nitro through press tap 2 up to the comp’s red area which is it’s service valve and verified flow through there.
I had the line at 3 PSI and then pressurized up to 40 PSI full flow with the service valve open and I could feel and hear the flow increase, so I don’t think it’s a restriction there.
That pretty much covers the entire low side and leaves the compressor, discharge valve and condenser and condenser valve.
MemberJuly 30, 2020 at 8:52 pm
I’m starting to think it’s non condensables.
MemberJuly 31, 2020 at 9:32 am
High head is only achieved by non-condensables, overcharge, or lack of heat removal.
Non condensables are gases like air, nitrogen etc. that the pressure/temperature is not sufficient. This can also be a refrigerant that the system is not designed for.
Overcharge means there is not enough space in the condenser for all the gas to condense.
That leaves heat removal. Any barrier to the heat of the refrigerant not being removed fast enough will cause this. Wether air movement, water movement, anything impeding the transference of heat. With a water cooled system this can be water differential temp to close to the operating temp, water pressure, or internal scale in the heat exchanger. Anytime water has heat added to it scale precipitates out. Much slower than other kitchen equipment, but it is happening.
As I mentioned earlier, The high head is what I was most concerned with at the beginning of this thread. If you have high head, you’ll never achieve designed capacity. Especially with a freezer.
I’ve never seen a tap put on a bypass tube before. Normally you want it just downstream of the sensing bulb to get the most accurate calibrations.
Years ago (before R502) low temp units had a vent tap at the highest point of the condenser. This was a necessary due the the machine operating in a vacuum on the suction side. We saw a lot of non-condensables back then. You shut the compressor off and cracked the vent as a normal practice before topping off. Of course we didn’t have good vacuum pumps back then let alone micron meters. And all R-11 centrificals have a bleeder on the top of the condenser for the same reason.
MemberJuly 31, 2020 at 9:39 am
At this point I believe the refrigerant to either be partially or totally contaminated.
The high head is odd and it could very well be due to non condensables, I think it’s a reasonable decuction based on what we’re seeing.
I added it on the equalizer line since I had no way to drill a hole into the suction line and blow out the particles whereas the equalizer line I could, considering they are the same pressure, I figured it wouldn’t matter.
Good to know on the venting of non condensables.
MemberJuly 31, 2020 at 2:08 pm
If you think it has been contaminated, you’ll want to; do a acid test, change the oil, remove the refrigerant, change the dryer again, vacuum to below 700 microns, and recharge liquid phase with new R-404A. Never add R-404 refrigerant without inverting the bottle. In the gas phase it will split.
MemberJuly 31, 2020 at 5:14 pm
Sounds good, I just pulled all the refrigerant, only about 16 lbs in there, had enough room in my cylinder with a good old ice bath.
I verified flow from the discharge valve to the filter drier, pressurized it, noticed an increase in flow immediately, so it’s not the condenser.
It might just be bad juice, man that would suck.
MemberAugust 1, 2020 at 9:02 am
That sounds a bit light for that machine. Especially with a remote condenser. What diameter is the liquid line?
MemberAugust 1, 2020 at 9:56 am
After thinking on this a bit, Where are you measuring the head pressure? I ask because you have a oil separator in the system. If before the separator it may read high due to the coalescing screen in the separator or the float not returning oil and more was added.
There are electronic field units out there today to test refrigerant gas for type and blend quality. I’ve never bought one, but maybe someone else can relate there experience with them.
MemberAugust 1, 2020 at 10:20 am
Well, butter my biscuit.
God damn, seems like it was leaking and non condensables that did it. I ended up charging it 37 Lbs and I took out 14.5 Lbs, must’ve been the non condensables rocking that head pressure upwards making me think it had plenty charge when it really was missing 2/3rds of it’s charge.
It even said it had SC when the bad refrigerant was in there, man what an evil trick.
Got her running now, 13-15 PSI suction and 245 Liquid or so, bout -23*F evaporating over 103-106 * condensing or so, just recalling the numbers.
SC is about 2-4*, I want to raise it but I emptied my last 2 jugs of 404….. Didn’t think she would need this much.
SH at the comp is about 55* and about the same after the evap so I know I need more juice or feed more juice through the TXV, but I should raise my SC before looking at upsizing my cage in the TXV right?
MemberAugust 1, 2020 at 10:39 am
I don’t know what the suffix numbers of you compressor relate to, Depending on that it’s real BTU’s may be as low as 28,000. The T-40 manual that I’ve seen calls for 45 lb’s. I know that that compressor has to be special to cover both medium and low temp applications. So it will have a bit smaller bore than a standard one. Now I understand why they cost $28,000.
MemberAugust 1, 2020 at 10:43 am
<div> 245 Liquid or so, bout -23*F evaporating over 103-106 * condensing
So what is the water temp’s into and out of the condenser?
MemberAugust 1, 2020 at 3:02 pm
Started another freeze cycle after defrosting.
14 minutes into it.
Box Temp -11*F
Coil Temp -16*F
Suction: 8.2 PSI (-32.4*F)
SH: 76.5* (At compressor)
Liquid side: 261.2 PSI (107.0*F)
25 Minutes into freeze cycle.
Box Temp: -17*F
Coil Temp: -19*F
Low side: 7.2 PSI (34.2*F)
High Side: 261.7PSI (107.1*F)
40 minutes into freeze cycle.
Box Temp: -21*F
Coil Temp: -22*F
Low side: 7.1 PSI (-34.4*F)
High Side: 250.7 PSI (104.1*F)
What do you guys think?
MemberAugust 1, 2020 at 4:08 pm
1 hour and 10 minutes into a freeze cycle.
Box temp is -22*F
Coil temp is -23*F
Low pressure: 7.1 PSI (-34.5*F)
High Side: 246.7 PSI (102.9*F)
Compressor discharge line right before it enters the condenser: 147*F (2 feet or so from the compressor discharge valve)
Condenser outlet is 102*F
Condenser water inlet to the condenser: 102*F
Condenser water outlet of the condenser outlet 103.2*F
MemberAugust 3, 2020 at 8:29 am
Why is you cooling water so hot? Whats the ambient of your cooling tower?
That’s were the capacity is lacking. Incoming water should be lower than 95F to come near capacity.
MemberAugust 3, 2020 at 9:22 am
Ambient around here is close to 100*F at the moment, there’s a large condenser outside with 3 fans mounted on the top of it.
There’s not really a cooling tower.
MemberAugust 3, 2020 at 8:11 pm
If you have a 100 ambient, 103 is really good.
I recall from a year or so ago that you had a closed water recirculating system. That means a pump, expansion chamber above the heat ex changers, They are commonly referred to as cooling towers because they have to be above the other equipment they cool for head purposes.
MemberAugust 3, 2020 at 8:22 pm
When it is real hot, if the humidity is below 70%, you can drop the water temp by adding a mist of water to the air just before the heat exchanger. Think evaporative cooling.
40 min into the freeze cycle with how many pounds of load? Flash freezer should be down to -40 in a hour.
Any high moisture product like meat or fish has to be flash frozen to protect texture. If the cells are frozen slowly, they burst and ruin the texture. Think mushy. If flash froze, The cells remain intact and the quality is very near fresh state.
MemberAugust 4, 2020 at 12:22 pm
The above numbers were done with no load, just an empty box, or, it had 2 potatoes I put in there, but that was it.
The refrigerant temp would have to be lower to hit -40*F, I imagine -50*F at least to get a delta t where there’s a chance of making it that cold.
Low side would have to be barely above 0 PSI to make it.
MemberAugust 5, 2020 at 6:35 am
What is your suction pressure control cut out point?
And where was the leak?
MemberAugust 5, 2020 at 9:11 am
Currently it’s set to around 4 PSI
Leaks were in the condenser outlet service valve and the suction service valve, fixed the packings, pressure test, vacuum, etc. All went well.
MemberAugust 5, 2020 at 9:42 am
Do you tighten and maintain the valve service caps and gaskets? I’ve seen more of them missing over the years than installed. The older metal ones had a copper seal gasket. Some of the newer plastic ones don’t do much except prevent ice from forming and stretching the packing. They also form a corrosion that sometimes makes very difficult to remove them. Same for the Schrader valves. I like the brass caps that are hex type. Next to that the brass knurled ones. Can’t even guess how many thousands of them I’ve replaced. The good valves for refrigeration have the green viton seal and stronger spring than automotive. Found many of them in systems over the years as well
MemberAugust 5, 2020 at 9:51 am
Occasionally I do, I’m not very well frequented to them.
I added the Teflon seal repair whatever it’s called and that sealed it up.
MemberAugust 5, 2020 at 11:55 am
The problem is with the back seat. They are a tapered hard steel valve against a softer body. When back-seated tightly it close’s off the test port and the stem packing. But often they wear or get foreign material in them. The Rotolocks are not a problem to replace, but the receiver valves are usually welded on. I’ve seen many a compressor suction valve placed incorrectly so that the line is on the top. Water gets in them from condensation and late in the cycle it freezes. Every compressor cycle. This crushes the copper and can pull the flare out or reduce the capacity of the line. Line should be sides or bottom, never the top.
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