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T40 Blast Chiller not running properly
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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.
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I spoke to Delfield and they said it’s probably the TXV.
And what specific questions did they ask you?
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<div>I can hear the TXV whistling or whatever it’s called.</div>
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That means you already have bubbles in the liquid before it gets to the valve and a very rapid expansion/boiling at the valve
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Fixbear,
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.
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I’m starting to think it’s non condensables.
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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.
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Interesting,
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.
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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.
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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.
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That sounds a bit light for that machine. Especially with a remote condenser. What diameter is the liquid line?
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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.
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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?
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