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Originally Posted by onetime

Could you explain the extremely high sub-cooling causing overfeeding, I don't to a lot of refrigeration but I've not seen that or maybe I didn't know to look!!

onetime,

Be glad to.

The TEV selection process is based on BTUH capacity at a given SST, liquid line refrigerant temperature and pressure drop across the valve.

With sub-cooling we get a temperature drop without a drop in pressure. Since we’re discussing sub-cooling we’ll take out two of the three; pressure drop and BTUH capacity.

The Sporlan “G” valve, nominal 2 ton for R404A is rated for 2.17 tons at a 20 degree SST at 100 degree liquid line temperature.

Here are the correction factors that apply for lower LL temperatures

60 F 1.43 x 2.17 = 3.11 tons
50 F 1.54 x 2.17 = 3.35 tons
40 F 1.64 x 2.17 = 3.56 tons
30 F 1.74 x 2.17 = 3.78 tons

With an increase of sub-cooling we would also have a gain of 1/2 % capacity from the refrigeration system for every 1 degree of sub-cooling.

Extremely high sub-cooling could result in an oversized TEV or an undersized evaporator which would allow liquid refrigerant to flood to the compressor. What if the TEV was oversized to begin with but worked ok due to low SC. In this example it might be best to use the 1.5 ton “G” valve if the LLT was 30 F to 40 F.

I realize this situation would be rare but it is possible with extremely high SC and sodd seems to have a very unique problem which is why I brought it up.

Originally Posted by powell

Dang Sodd,

That's a wierd situation. Maybe there was some sort of debris stuck in the ports that dislodged when you worked on the valves. How about moisture or ice?

Extremely high sub-cooling would also cause the valves to overfeed but that problem wouldn't have gone away with a power head change.

Let us know what you find.

Could you explain the extremely high sub-cooling causing overfeeding, I don't to a lot of refrigeration but I've not seen that or maybe I didn't know to look!!

dome could be slightly ovaled,casing the needle to be out of adjstment, the needle has a 1/16 of an inch travel

Originally Posted by thegoodhumorman

Did you find my dime that I filed down and stuck into the powerhead to "get it thru the night"?

I like Neds thought about the LPRV possibly being adjusted or perhaps you have a low temp element on a med temp case?
Perhaps (stretching it here BUT...) a couple welds were completed in the vicinity of these two sensing bulbs and the gas pressure within the bulb deformed the metal membrane, distending it outwards towards the pushrods so much so that it never fully receded- sounds somewhat far fetched but this is a first for me as well in that it began flooding again after reinstalling the heads- doesn't explain why not flood initially but perhaps it was but an EPR or rack target kept velocity down enough to keep it hidden.
Just a thought...

I think that trick is to cool...sucks that I didn't think of it on my own

Originally Posted by thegoodhumorman

Did you find my dime that I filed down and stuck into the powerhead to "get it thru the night"?...

Now that's funny...true , but funny

Assuming the TEV was working properly after its original installation, there is no "failure" of the power head that would cause the valve to flood... as noted in previous posts.

Other than the obvious, a loose sensing bulb, the only other likely explanation I see is something getting lodged between the pin and port preventing the TEV to modulate in the closing direction. And in the process of replacing the power head, the obstruction gets cleared. I suspect in above stated cases simply removing and reinstalling the original power head would have worked also.

Originally Posted by sodd81927

Thanks Kelly at least I know thier is someone out there thats seen this happen. This does not mean I'm not nut's it just means I'm not alone....

You gota be nut's to do what we do.

Originally Posted by Kelly T

I have had the same thing happen to me here in guam, it never gets cold here, I never did figure out why the power heads caused this but the units did work after i changed the powerheads, this was 2 years ago and never had a problem since, I worried over it for about 6 months then chalked it up to evil spirits, I would be very happy to see someone figure this out

Thanks Kelly at least I know thier is someone out there thats seen this happen. This does not mean I'm not nut's it just means I'm not alone....

Is weird alright

Originally Posted by sodd81927

I told y'all this was a head scratcher. I thought about moisture and the subcooling and maybe someone screwing with valves i ruled all that out early in the game. I did not want to work today but since I was caled out anyway I went by the store all was fine I reinstalled one of the old power heads and the flooding came back, reinstalled new back to 8deg superheat so I'm convinced its the power heads but cannot explain why. I have never in thirty years seen a P/H get stronger It defies logic.Thank you all for your input I may try to send one back to Sporlan and explain what happened just to screw up there day.

I have had the same thing happen to me here in guam, it never gets cold here, I never did figure out why the power heads caused this but the units did work after i changed the powerheads, this was 2 years ago and never had a problem since, I worried over it for about 6 months then chalked it up to evil spirits, I would be very happy to see someone figure this out

that is not far fetched. But close to it.

Break it down. The element is pushing on the pin. Why. Dunno. But it is pushing on the pin.

Did you find my dime that I filed down and stuck into the powerhead to "get it thru the night"?

I like Neds thought about the LPRV possibly being adjusted or perhaps you have a low temp element on a med temp case?
Perhaps (stretching it here BUT...) a couple welds were completed in the vicinity of these two sensing bulbs and the gas pressure within the bulb deformed the metal membrane, distending it outwards towards the pushrods so much so that it never fully receded- sounds somewhat far fetched but this is a first for me as well in that it began flooding again after reinstalling the heads- doesn't explain why not flood initially but perhaps it was but an EPR or rack target kept velocity down enough to keep it hidden.
Just a thought...

What is the systems refrigerant? And what is the flooding valve element say on it?

I just got done going through a system where the valves were 404, and the gas was 22. Flooding the rack like something fierce.

Originally Posted by powell

Dang Sodd,

That's a wierd situation. Maybe there was some sort of debris stuck in the ports that dislodged when you worked on the valves. How about moisture or ice?

Extremely high sub-cooling would also cause the valves to overfeed but that problem wouldn't have gone away with a power head change.

Let us know what you find.

I told y'all this was a head scratcher. I thought about moisture and the subcooling and maybe someone screwing with valves i ruled all that out early in the game. I did not want to work today but since I was caled out anyway I went by the store all was fine I reinstalled one of the old power heads and the flooding came back, reinstalled new back to 8deg superheat so I'm convinced its the power heads but cannot explain why. I have never in thirty years seen a P/H get stronger It defies logic.Thank you all for your input I may try to send one back to Sporlan and explain what happened just to screw up there day.

Originally Posted by jonny in La

what a dumb@$$ I am of course the closing force of the spring will close the valve if the element fails sorry dudes got dyslexia on the brain thinking in reverse.

/

Knew you would figure it out!!!

what a dumb@$$ I am of course the closing force of the spring will close the valve if the element fails sorry dudes got dyslexia on the brain thinking in reverse.

Tweakers

Never overlook a tweaker. An adjustable wrench a small amount of knowledge and a large amount of curiosity (usually a kid) could cause a seriously out of whack TXV in some random fashion like you describe. Or a fairly smart disgruntled employee either way can give a service man a perplexing headache.

ok if the spring force overcomes the dome force what happens because you got three pressures acting in unison and against one another.

When you lose the "Hisser", it pumps down.

did you cut the cap tube to the bulb and get the hisser out of it. As i understand elements they contain a charge warm it up it applies more downward force on the needle to open the valve cool it down it contracts closing the valve so if you dont have any gas in the element how is it going to apply downward force on the dome to open the valve.

Dang Sodd,

That's a wierd situation. Maybe there was some sort of debris stuck in the ports that dislodged when you worked on the valves. How about moisture or ice?

Extremely high sub-cooling would also cause the valves to overfeed but that problem wouldn't have gone away with a power head change.

Let us know what you find.