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Thread: 404a high pressure?
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14-01-2008, 07:16 PM #201
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14-01-2008, 10:09 PM #202
Re: 404a high pressure?
I would strongly recommend the insulated flexduct.
The bottom and front should be insulated as well. Hot air rises up from the condensing unit.
What I was seeing was essentially the same heat load being pumped by the condensing unit, but the evaporator load was much greater. In other words, the system was working about the same, but more heat load was entering, specifically in the return air. That return duct seems to be the achilles heel of this system.
You might want to open the TXV 1/2 turn. I would like to see the superheat back down around 12F.Last edited by Gary; 14-01-2008 at 10:22 PM.
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14-01-2008, 10:19 PM #203
Re: 404a high pressure?
im not sure how long it had been cooling when i took those measurements,, ill check it again in a little while, now that its had a chance to cool down inside the box.
and yes,, there are adjustments i can make to tweak this cooler,, and i will. but im still miffed as to why the sudden change. as i said before,, the txv was warm. before that,, despite all the inefficiencies,, the txv would always frost up,, and the pressure (or temp) at the txv was never that high.
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14-01-2008, 10:49 PM #204
Re: 404a high pressure?
The increased heat load warms the refrigerant, increasing its pressure/temperature. The warm refrigerant (40F) is not going to frost anything.
We know the return has been a problem all along. Why did the return suddenly decide to leak more heat than previously? I don't know.Last edited by Gary; 14-01-2008 at 10:54 PM.
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14-01-2008, 10:56 PM #205
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14-01-2008, 11:01 PM #206
Re: 404a high pressure?
Actually, the refrigerant going through the TXV is warm liquid which quickly flashes off to bring its temperature down to the saturation temperature (40F). So at that point it is not yet down to 40F.
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14-01-2008, 11:25 PM #207
Re: 404a high pressure?
but that liquid was no warmer yesterday,, than it was a week ago. wouldnt the liquid line have to be hotter to increase the pressure on the low side of the txv to where it was yesterday??
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15-01-2008, 01:42 AM #208
Re: 404a high pressure?
heres the latest,,
suction line at bulb 58f
liquid line at receiver 93f
evap in 47f
evap out 39f
cond in 71f
cond out 85f
ambient 74f
pressures at 60 and 265 psig
superheat at 35f
subcooling at 17f
it seems like were losing ground here,, but ill check in the morning
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15-01-2008, 02:38 AM #209
Re: 404a high pressure?
actually,, thinking about it,, im not sure how long it had been running for when i took those temps. it may have just started before i looked at it.
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15-01-2008, 04:41 AM #210
Re: 404a high pressure?
The low side pressure/temperature is regulated by the temperature and volume of the air passing through the evaporator.
The low side temperature (and thus pressure) was warmer yesterday because the airflow entering the evaporator was warmer.
The warm liquid leaving the TXV must drop in temperature to match the low side temperature. It is not the cause of the low side temperature/pressure. The heat from the air is.Last edited by Gary; 15-01-2008 at 05:17 AM.
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15-01-2008, 04:54 AM #211
Re: 404a high pressure?
Last edited by Gary; 15-01-2008 at 04:58 AM.
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15-01-2008, 05:46 PM #212
Re: 404a high pressure?
If you want to stick with the metal duct for the rigidity, you might seal it with duct tape and then insulate it with sheet Armaflex (closed cell foam).
An alternative would be several layers of Armaflex foam tape. Start at one end of the duct, spiral the tape around the duct, overlapping about halfway across the previous spiral, to the other end of the duct. Run the system for awhile. If the surface of the tape is cool to the touch, add another layer.Last edited by Gary; 15-01-2008 at 06:01 PM.
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15-01-2008, 07:32 PM #213
Re: 404a high pressure?
as is said before,, once i know the system is gonna be ok,, i will redo a few parts,, including teh evaporator chamber. i figure to eliminate that duct and just suspend the coil and draw air through it.
here are the latest readings,,,
ambient 74f
box 41f
suction line at bulb 34f
liquid line at bulb 97f
evap air in 45f out 36f
cond air in 77f out 89f
superheat 18f
subcooling 15f
pressures at 55/275 psig
lol,, this thing is bouncing around so much. if i can get a few steady readings,, im close,, i think
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15-01-2008, 10:10 PM #214
Re: 404a high pressure?
I would give it a layer of foam tape anyway, even if it's just temporary.
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15-01-2008, 10:16 PM #215
Re: 404a high pressure?
In your pictures, it looks like the duct "insulation" is a towel. I'm wondering if it got damp enough the other day to nullify it's insulating effect, then dried out and started working again.
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16-01-2008, 02:44 AM #216
Re: 404a high pressure?
there is insulation under that,, and no,, ive been trying to think of what happened when it warmed up,, but thats not it,,, everything was dry.
in my opinion,, in my vast experience,, i think the txv stuck open. it still provided enough resistance to keep the pressure under 100 psi, but not enough of a drop in pressure to provide cooling. all of the other factors seemed the same as any other day. it certainly got as warm,, if not warmer,, in the time we have been discussing that cooler. i can see no other significant differences that would cause that drastic of a change.
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16-01-2008, 03:45 PM #217
Re: 404a high pressure?
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16-01-2008, 04:21 PM #218
Re: 404a high pressure?
this mornings readings are,,,
ambient 77f
box 43f
suction line at bulb 41f
liquid line at receiver 99f
cond air in 74f / out 90f
evap air in 52f / 41f
pressures at 60/275 psig
superheat 18f
subcooling 13f
well,, maybe itll happen again
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16-01-2008, 08:58 PM #219
Re: 404a high pressure?
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18-01-2008, 03:42 PM #220
Re: 404a high pressure?
How is our wine cooler doing? Have we gotten the superheat down to 12F yet?
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18-01-2008, 03:48 PM #221
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Re: 404a high pressure?
Maybe his vine is properly cooled now and he enjoy his vine finally.
That is what I will do if that is my case.
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18-01-2008, 05:28 PM #222
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18-01-2008, 06:21 PM #223
Re: 404a high pressure?
hi flyboy , if its doing ok , PLEASE DONT TOUCH !!!
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18-01-2008, 07:15 PM #224
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19-01-2008, 02:31 AM #225
Re: 404a high pressure?
Whoaaaaa ? U mean this saga may come to an end ?
NO ! pls keep on toying with it , Flyboy !!
You've now got the " tamperitis" bug of fiddling with tx valves.
All us avid readers around the globe need our daily fix of this thread
Try and screw it up again so we can keep this project going .... if Gary was charging u for advice, it would have to go on record as the most expensive wine cooler in history!!!!
yuk yuk
regards
T-PRemember what Augustus once said:
"festina lente" - make haste, slowly!
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21-01-2008, 05:59 PM #226
Re: 404a high pressure?
hi honey,, im hoooome.
sorry guys,, ive been a little under the weather. anyhow,, these are the readings i took this morning,,,
ambient 74f
box 38f
cond air in 67f,, out 81f
evap air in 46f,, out 38f
liquid line at receiver 91f
suction line at bulb 40f
pressures at 50 and 255 psig
superheat 25f
subcooling 14f.
i opened the txv 2 turns and ill let it settle out and take the readings again in an hour or two.
theres plenty of time for that T-P,,, i believe its a god given right for a man to make a fool of himself,, and i excersize that right often.
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21-01-2008, 07:03 PM #227
Re: 404a high pressure?
I assume the suction line is insulated between the coil and the bulb... and the bulb heavily insulated?
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21-01-2008, 07:20 PM #228
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21-01-2008, 08:18 PM #229
Re: 404a high pressure?
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21-01-2008, 08:27 PM #230
Re: 404a high pressure?
I wonder if the high side gauge is off a few psi, leading us to believe that the subcooling is higher than it actually is?
Connect the high side gauge to your refrigerant tank. The pressure should agree with the temperature of the tank.Last edited by Gary; 21-01-2008 at 08:34 PM.
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21-01-2008, 09:10 PM #231
Re: 404a high pressure?
to be honest,, taking the suction line reading seems very fickle. sometimes i have to take the reading several times before i get a reading that seems right (i take the lowest reading).
no,, the suction line temp is very stable (within a couple degrees). here are the latest readings,,,
evap air in 46f (in reality this is probably lower)
evap air out 38f
cond air in 67f,, out 83f
suction at bulb 36f
liquid line at receiver 91f
pressure at 58 and 250 psig
superheat 14f
subcooling 14f
give me a little bit and ill check the accuracy of my gauges (does it matter if the bottle of 404a is like 10 degrees or would it be more accurate if i warmed the bottle up?)
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21-01-2008, 09:38 PM #232
Re: 404a high pressure?
It would be better if the bottle were warmed up and stable. That way we can calibrate to a temp that is closer to what we use the gauge for.
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21-01-2008, 09:49 PM #233
Re: 404a high pressure?
Last edited by Gary; 21-01-2008 at 09:54 PM.
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21-01-2008, 10:20 PM #234
Re: 404a high pressure?
i tried is with two gauges sets and the bottle of 404a was at about 35f. all 4 gauges were in the low to high 70sw psig. i have to remember to purge those gauges though, with the lossless fittings,, it doesnt seem to want to release the pressure as well.
ill check it again in a couple hours
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21-01-2008, 10:41 PM #235
Re: 404a high pressure?
Measure the temperature on the side of the bottle near the bottom. This is the temp that should agree with the gauges... and lose the lossless fittings.
At 35F, the gauge pressure should be 76 psi.Last edited by Gary; 21-01-2008 at 10:45 PM.
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22-01-2008, 02:50 AM #236
Re: 404a high pressure?
and here is the last set for today,,,
evap air in 44f,, out 39f
cond air in 70f,, out 87f
liquid line at receiver 93f
suction line at bulb 37f
pressures at 60 and 250 psig
supheat 14f
subcooling 11f
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01-09-2008, 05:18 AM #237
Re: 404a high pressure?
hi i am sptyagi from india . i have ref system with r23 and 404 a cascade system . same problem i also faced in r23 system after repairing the fitting and recharging. at last we analysised there was some air was trapped into the system during charging. i suggest to take out complete the gas and was the system with nitrogen then vaccume it properly and charge the fress gas. hope you will get good results.
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