evaporator problem

[billdozza]

I have a r-22 3 ton heatcontroller evaporator that kept freezing up. I removed piston and installed a 3 ton xpansion valve. I notice all 6 spider tubes getting wet yet only 4 0f the 6 3/8" suction tubes leading into the 3/4" suction manifold are getting wet. I put the sensing bulb in warm water and the valve opens up , but those 2 tubes still remain dry. Could it be a partial restriction in those spider tubes.

[mikeref]

Billdozer, is this a freezer room or coldroom and does the evaporator partially ice up, say bottom 1/3 or fully ice?..mike

[billdozza]

residential A/C system its no longer freezing up now, but 1/4 of the coil is dry

[joe magee]

I have seen restrictions where the tubes are brazed into the distributor. Some of the braze ends up in the tubes.Would need more info though. Superheat/subcooling temps splits etc etc etc

[billdozza]

pressures 170 over 58
outdoor temp-80f
indoor wet bulb-58f
indoor temp-68f
return air temp-69f
supply air temp-55f
tempreture suction line @ service valve 56f
indoor/outdoor coils sparkling clean.
no pleated filters.
removed sensing bulb off TXV and tested in both ice and warm water and valve reacted accordingly.
compressor rated for 13 RLA unit running at 10.5, System has no leaks pressurized for 1 month at 250 PSI and held. Vacuumed for 5 hours and microned to 400, held up to 700 for a hour. New liquid line filter dryer and sight glass with moisture indicator. Periodic bubbling, valve does not hunt. 1 more thing i would like to mention the unit is cooling the first floor but the return is in basement, is it possible that the colder air in basement throttling my TXV and giving me my high super heat.

[nike123]

Did you fitted externally equalized TXV, and is distributor placed vertically? Could you make photo of that TXV-distributor setup?

[billdozza]

yes xternal equalizer and b4 sensing bulb & the bulb is mounted horizontally @ 8:00

[FEISTY]

Here's my 2 cents worth. If all your technical readings are still holding steady, and the rated RLA is truly for the compressor only, you seem to be running head pressure somewhat low for R22. Watch your amps and add some ***** to reach 220-230. Your coil sounds like it is frosting from bottom up and dist. tubes are starving. All of the other bases have been covered so give this a try. Hope it helps. Good luck.

[nike123]

Your superheat at service valve is (56°F-38°F)=18°F. If we presume that pressure drop from evaporator to compressor (service valve) should not exceed equivalent of 4°F, you still have 14°F of evaporator superheat. That is high for R22. It should be around 10°F.
Check that TXV (if adjustable) is at factory setting (measure with number of turns or with sliding ruler).

[nike123]

is it possible that the colder air in basement throttling my TXV and giving me my high super heat.

Nope, superheat will remain at preset value if you have liquid refrigerant at valve inlet and if TXV is fully functional, no restriction and properly installed.

[lana]

Hi there,

If two of the distributor tubes behave differently then there is a problem of pressure drop difference between those tubes. As mentioned be by joe magee, it could be partial restriction in the tubes or the length of the tubes are not the same which gives different pressure drops.
Cheers