knkreb
31-03-2008, 12:38 PM
Okay, here it goes. I've exhausted everything I can think of on this system.
Specs:
Carrier 38AK044 (40ton A/C unit) Split system
R22
Witt LVL25 Air Handler (approx 30 ton capacity according to manufacturer)
Originally set up to to have Alco 22 ton twin TXV's on both circuits.
The condenser coil was a mess when I first got to this unit. Over half of the coils were bent over, dirty and not allowing good air flow. After straightening coils, and cleaning it, it required a good amount of refrigerant to be added to it to clear the site glass. It only runs in the summer time, and is in a very dirty environment, so I wasn't real concerned about winter/cold operation, so I kept the charge light enough in case the coils clogged up early.
The unit ran amazing well after that, but would trip off on oil pressure every so often. It would flood at start up. Found also that the solenoids were not wired properly and were "open" any time that the thermostat called for cooling. Carrier provides a relay to only open the solenoids while compressor is running, but it was not used. I corrected this, and thought that I had it.... turns out it keeps doing it.
That's when I called the manufacturer, to find that the coil was only rated for 30 tons. A little bit of math for summer time operation turns out that 22 ton valves have nearly 30 tons of capacity (approximately). So, I changed the expansion valves to two OVE-15GA's. These would have about a max capacity of 21 tons each when the head pressure is up at it's highest.
Still it tripped oil pressure. It was a mild day that it did this, and has tripped several times on mild days. So, next I added time delays to the solenoid valves. Now it will: open hot gas valve immedately, stage 1 solenoid at 30 seconds, and stage 2 at 5 minutes. This would provide a "pump out" of any liquid in the system, and only bring on one valve at a time. In my thoughts, this would reduce the possibility of flooding from both valves bringing down the coil to temp at the same time. Oil in the site glass is running extactly where it needs to be at while compressor is operating.
It still tripped oil pressure even after this. So, at the last visit, I charged according to the chart, and will be checking in to see if it's still running.
One other note, the compressor valves are leaking back, so it's equalizing on the off cycle. I was hoping the "pump out" would help reduce this issue somewhat, but don't know yet how much headway I've made.
One last note, the hot gas valve is a 6 ton valve bypassed into an aux side connector on stage 1 distributor.
Thoughts of anything left to look at?
Specs:
Carrier 38AK044 (40ton A/C unit) Split system
R22
Witt LVL25 Air Handler (approx 30 ton capacity according to manufacturer)
Originally set up to to have Alco 22 ton twin TXV's on both circuits.
The condenser coil was a mess when I first got to this unit. Over half of the coils were bent over, dirty and not allowing good air flow. After straightening coils, and cleaning it, it required a good amount of refrigerant to be added to it to clear the site glass. It only runs in the summer time, and is in a very dirty environment, so I wasn't real concerned about winter/cold operation, so I kept the charge light enough in case the coils clogged up early.
The unit ran amazing well after that, but would trip off on oil pressure every so often. It would flood at start up. Found also that the solenoids were not wired properly and were "open" any time that the thermostat called for cooling. Carrier provides a relay to only open the solenoids while compressor is running, but it was not used. I corrected this, and thought that I had it.... turns out it keeps doing it.
That's when I called the manufacturer, to find that the coil was only rated for 30 tons. A little bit of math for summer time operation turns out that 22 ton valves have nearly 30 tons of capacity (approximately). So, I changed the expansion valves to two OVE-15GA's. These would have about a max capacity of 21 tons each when the head pressure is up at it's highest.
Still it tripped oil pressure. It was a mild day that it did this, and has tripped several times on mild days. So, next I added time delays to the solenoid valves. Now it will: open hot gas valve immedately, stage 1 solenoid at 30 seconds, and stage 2 at 5 minutes. This would provide a "pump out" of any liquid in the system, and only bring on one valve at a time. In my thoughts, this would reduce the possibility of flooding from both valves bringing down the coil to temp at the same time. Oil in the site glass is running extactly where it needs to be at while compressor is operating.
It still tripped oil pressure even after this. So, at the last visit, I charged according to the chart, and will be checking in to see if it's still running.
One other note, the compressor valves are leaking back, so it's equalizing on the off cycle. I was hoping the "pump out" would help reduce this issue somewhat, but don't know yet how much headway I've made.
One last note, the hot gas valve is a 6 ton valve bypassed into an aux side connector on stage 1 distributor.
Thoughts of anything left to look at?