TXV icing up

[jayryu]

In walk-in freezer, What is the reason of TXV icing up? TXV body, sensing bulb and peripherals usually covered with thick and hard ice. At this time the box temp is not normal or takes very long time to pull down to normal temp. After melting the ice block, it takes only a week to find the same ice block around TXV. I am suspecious there is something wrong with TXV. Any idea? The walk-in freezer has been in service almost a year and this problem is happening from abt a month ago. :mad:

[taz24]

.

It is common in most freezers and has a lot to do with the moisture in the air, not the valve itself.

There are reasons why the valve might do this, that could mean a fault but most low temp cold rooms
do the same. You might find putting armaflex insulation around the valve and the phile (bulb) slow down
the ice build up, but the valve is the coldest part of the system and any moisture in the air will freeze
onto the valve and create a large bulb of solid ice.

It becomes a problem if the ice interferes with the heat exchange across the phile (bulb) because if
the ice builds up around the phile then it can give a false reading to the valve and make it think the
system is satisfied, so the valve shuts down. hen the valve shuts down the refrigerant is starved
inside the evap and therefore the system does not perform.

Make sure the bulb is firmly fixed then insulated to the suction.

If the room struggles to pull down you need to look at the bigger picture.

Door opening rates
Air movement inside room
Defrost intervals
setpoint temps.

Then check running pressures and set the system up to the most optimum you can.

All the best

taz.

Ps valve do fail but don't always jump in and adjust or replace the valve. Nearly always
somthing else is wrong and masking the symptoms.

taz

.

[Tradewinds]

Moisture in the refrigerant can cause this as well. As the moisture passes thru the TXV it begins to freeze and cause a blockage. This restriction then lowers the outlet temperature of the valve and causes excessive ice to build up. If there is only a small amount of moisture in the system you could simply change the liquid line drier cores, however you may need to remove refrigerant, pressure test, triple vac and recharge.

[FRIDGE]

is there a lot of icicles in the room? that would mean there is a lot of moisture in the room.

if room is very dry and no signs of moistre, i would suspect moisture in refrigeration system.

what refrigerant are u using and what are the operationg temps and pressures?
does your back pressure run down to vacuum?

[jayryu]

After my first post, I tried insulating txv body, sensing bulb itself and cleaning inlet screen but no changes. I was very sick of doing and checking, finally I have replaced the TXV(GSE-1-Z) two weeks ago and observed the TXV for 2 weeks and found there was almost no ice build-up around the valve except screen of strong(?) frost and it looked very nice. Thanks for every gentlemen.