[txdave]

Was checking out a Carrier 5 ton package today. Co-worker had found orifice restricted last week and he removed the evaporator header and orifice tubes and installed txv. He said he weighed in charge according to name plate. He went back yesterday and didn't like pressures so recovered some refrigerant. I got call today that unit wasn't cooling. 64 degree supply, 80 degree return, pressures: 85-90 low,320-340 high, 20 degree superheat. Adjusted txv and got 15 degree superheat but txv started hunting. Delta T never changed. Added a couple pounds of refrigerant but didn't help. Possible wrong txv?
TXV: SVE4 CP100...gonna checkon that tomorrow. Though about recovering all refrigerant, pulling vacuum and weighing in charge myself just to be sure it is right. Had a 30 degree condenser split so I cleaned condenser coil, knocked pressures down a little for a little while. Not sure if co-worker cut out orifices when he removed the header, so much solder every where. OK, guess I'm rambling trying to figure this out. If anybody has any suggestions I would appreciate it.

 

[Aircooled81]

TXV obviously opening to provide high suction, but head preasure could be high - what is a ball park of the outdoor ambient?
Not removing the orifices would probably haved drop suction preasure, not raised it.
and overcharge could have lowered split and raised discharge preasure.
Small equip like this, you are on the right path. Pull the charge and weigh it in. call the manufactur/suphouse and ask what the recomended subcooling is, and the charge. the amount to weigh in may have changed slightly due to the metering device swap out.
quick checks since you are following through on someone elses work;
High fan speed/too much cfm could provide low split, check mtr amps.
Bulb placement, tightness to suction line, and insulation.
good luck

 

[codgy]

I know the design sucks but you can't change over to expansion valve that easily, need the right distributer and equal length tubes. Even then the total charge will change. Clean condenser coil even if it looks clean!! Why did you not install new orifice header?

 

[txdave]

Don't know why a new orifice header was not installed. Ambient is around 85*.

 

[txdave]

Thanx for the replies and suggestions. Gonna check it today with a more clear head . Yesterday I was baffled as to why the orifice heaer was not replaced. I work with some silly people who are always doing silly things. LOL

 

[mikelcs]

I know the design sucks but you can't change over to expansion valve that easily, need the right distributer and equal length tubes. Even then the total charge will change. Clean condenser coil even if it looks clean!! Why did you not install new orifice header?

very true. you need a distributor with the correct number of feeds and all distributor tubes must be the same length. this means that you need to be very careful when positioning the assembly into the coil. when properly installed, the retrofit works very well. make sure that you mark the unit with the new charge for the next guy.

 

[txdave]

Thinking about taking txv out and installing correct orifice header but co-worker squeezed evap. tubes down onto distributor tubes so I don't know if I can straighten tubes out enough to install header.

 

[mikelcs]

i would cleanup and check the expansion valve installation and stay away from the factory header, the factory header restrictions are very common.

 

[t527ed]

once the unit was re-engineered in the field you can forget about weighing in the charge.