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Old 07-15-16, 12:35 AM   #11
STM
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On the capacity loss issue, wouldn't changing the cap tube out for a TXV help alleviate some of that? This is the one I was looking at.

https://surpluscityliquidators.com/p...-txv-hp80.html

Externally equalized but it's flare fittings so maybe less chance of burning it up.

Another option:
https://surpluscityliquidators.com/p...weat-r134.html

Internally equalized so one less joint, but brazing a heat sensitive component is risky. Going to practice brazing before I work on the system but I'll still be pretty green.

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Old 07-15-16, 01:27 AM   #12
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R134a in a R410a compressor isn't going to work that well, even after accounting for the possibly higher condensing temperature. R22 or something similar (including R290) will be more optimal and still allow you to run the evaporating temperature higher without overloading the compressor. Get a R22 TXV that is adjustable since you'll probably have to tweak it for use with R290 or a R290 based blend.
http://ecorenovator.org/forum/geothe...ssor-r290.html

I did a design running R433b in a R410a compressor and got it working quite well. I did a few advanced things like tuned PID loops and ejector cycle with two evaporators to boost dehumidification efficiency, but in your case, it would be easier to just plumb the existing condenser as a second evaporator between the existing evaporator and the TXV, then remove the evaporator side fan and foam insulation/air guide and hard wire the fan to low. (That would hopefully give the best overall efficiency without adding fancy electronics.)
http://ecorenovator.org/forum/geothe...er-heater.html
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Old 07-15-16, 01:53 AM   #13
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So propane is better than R134a? What about the R152a from electronics dusters? Just read a little bit on that and people are claiming better performance than R134a.

How do I tell if the TXV is adjustable? I thought they all were.

https://surpluscityliquidators.com/p...n-valve-1.html

That one is an R22 labeled as -20 to 50*F. I'm assuming that's evap temperature. It's internal equalizer, is that acceptable or should I go for external for better efficiency? I was thinking about increasing evaporator capacity, either by adding the existing condenser as an extra evap or pulling the evap off of a larger A/C.

Edit: I see what you were saying, leave the condy in its physical place, then remove the squirrel cage and turn the system into a linear straight flow through with the original condenser replumbed in series before the original evap. Pull air through existing evap, over compressor, then out through condenser, right? That could work but I would have to do something with that original fan, it leaves a huge dead spot in the air flow right in the middle of the condenser.
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Old 07-15-16, 04:20 AM   #14
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http://www.sporlanonline.com/literature/10/10-10.pdf

The F series are adjustable.
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Old 07-15-16, 06:05 AM   #15
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Ok from what I can gather this is an adjustable, pressure limiting TXV. I think that's what I need after reading on what the pressure limiting does. Apparently it allows the system to work wider temperature range. I think...

https://surpluscityliquidators.com/p...equalizer.html
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Old 07-15-16, 09:21 AM   #16
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Pressure limiting is to keep the suction pressure from going too high, which is a feature not needed or desired in your application. You'll want the pressure to be able to go high since that increases efficiency.

Once you more than double the evaporator capacity, any further improvements in capacity are likely to be well into diminishing returns.
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Old 07-15-16, 11:01 AM   #17
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Alright, learned another tidbit then. So I should choose one with a listed temperature range.

For instance a Sporlan EFV-1/2-c is an Adjustable superheat valve, R22, with an internal equalizer and sweat connection 1/4 inlet 3/8 outlet with a charge for commercial refrigeration at -10*F - 50*F

Can the lines be adapted to the size of the TXV or should I find one with exactly the sizes I need?

Would external equalizer be better? I can't imagine much pressure drop across the evap on a system that small.
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Old 07-15-16, 03:53 PM   #18
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I should kick myself, I just checked the dehumidifier, it is 410A as well. So I guess I don't have the perfect size available. BUT I will keep my eyes open.

I used internal equalized txv, haven't had a problem at all. I would say go with the cheapest on for 1/2 half R22 and call it good. No adjusting really needed.
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Old 07-15-16, 04:16 PM   #19
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It's cool, I got the 5k emptied last night by the A/C guy from work. Should be sitting full of nitrogen now. Picked up 1/2lb of Sil-Flo at the hardware store today but my normal torch head isn't getting up to temp even with Mapp. Need a turbo torch or break out the O/A. I'll order that EV-1/22-C, looks like a decent choice.
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Old 07-15-16, 05:51 PM   #20
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the adjustment is the superheat control. I usually dont mess with it much on smaller units. The gas in the sensing bulb determines your maximum operating evaporator pressure, most have charge gas that limits this value no matter how hot your supply air is. Look around the threads, this topic has been covered before.

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