TXV Expansion valve insulation - InspectionNews

Gene South · #1 (**permalink**) 07-01-2009, 05:05 PM

I usually write up TXV's that are not insulated. How many of you do the same ?

Gene

Jim Luttrall · #2 (**permalink**) 07-01-2009, 05:36 PM

Well Gene if there is condensation, it should be insulated. Typically this will just be the outlet of the valve and of course the suction line where the bulb is attached.

Gene South · #3 (**permalink**) 07-01-2009, 07:14 PM

Jim thanks, I guess I thought the bulb should be insulated, thinking that would make the TXV more efficient. Maybe I am wrong.

Jim Luttrall · #4 (**permalink**) 07-01-2009, 07:34 PM

The bulb is just a temperature sensor clamped to the tail of the evaporator coil. The portion of the suction line exposed outside the cabinet (not the usual method) should be insulated to prevent condensation. If you are not getting a good thermal bond, the valve could malfunction and over or under feed the coil which would effect the operation and overall unit efficiency. Insulation would be a good thing at the bulb in that respect.

Dan Hagman · #5 (**permalink**) 07-01-2009, 07:54 PM

Hey Gene Jim is correct, the expansion valve bulb needs to be insulated because it is operating the valve to maintain the superheat of the evaporator. Normally the TXV valve itself is not insulated, but the suction line after the valve needs to be. Some TXV valves are automatic and some are adjustable to adjust the superheat. If the valve is inside the cabinet then don't worry about it, although some are on the outside of the cabinet or A-Coil.