bundysnake
20-07-2011, 09:59 AM
Ok so i have a residential ducted heat pump system that has a TXV at the FCU & at the COND unit (both valves have a built in one way bypass or check valve eg on heating mode the TXV at the FCU is bypassed and reverse for cool mode).
This unit runs fine on cooling but when switched over to heating and ran for around 1 hour a loud hammering sound is coming from the TXV at the FCU and the pressure on my liquid line is bouncing around like crazy.
I can't seem to figure out the cause of this issue, below is the steps i have taken so far along with some pressures temperatures i took on my last visit.
The system is a Unico small ducted system.
1) Pump down then flush lines & FCU with dry nitro
2) Verify the TXV is the correct tonnage both FCU & COND
3) Verified the system has the correct airflow
4) Change FCU TCV
5) Install bi flow liquid line drier & sight glass as the system didn't have these originally
After installing the drier the sound is much much quieter and takes longer to appear than previously.
Cond one way valve installed? Yes standalone/external
Cond Capacity 14kW
Filter drier & sightglass installed at FCU? Yes
FCU TX Valve CBBIZE-4 16A B15 16110 ZGA 45
Hot gas pipe at FCU 60degC
Discharge Temp 52degC
Discharge Pressure 380PSI
Liquid line temp at outdoor 31.2degC
Liquid line temp as it leaves FCU TXV 35degC
Liquid line pressure 400PSI
Subcooling on COOL mode 2deg
Superheat in HEAT mode 5degC
Suction pressure 100PSI
Suction Temp 5degC
FCU amps on HIGH 4.58
Number of Outlets 25
Supply Air Temp 41.4degC
Return Air Temp 18.3degC
Outdoor Ambient Temp 12degC
Average airflow per outlet 45l/s
Airflow l/s 1117 or 2366CFM
Any help you could provide would be much appreciated
This unit runs fine on cooling but when switched over to heating and ran for around 1 hour a loud hammering sound is coming from the TXV at the FCU and the pressure on my liquid line is bouncing around like crazy.
I can't seem to figure out the cause of this issue, below is the steps i have taken so far along with some pressures temperatures i took on my last visit.
The system is a Unico small ducted system.
1) Pump down then flush lines & FCU with dry nitro
2) Verify the TXV is the correct tonnage both FCU & COND
3) Verified the system has the correct airflow
4) Change FCU TCV
5) Install bi flow liquid line drier & sight glass as the system didn't have these originally
After installing the drier the sound is much much quieter and takes longer to appear than previously.
Cond one way valve installed? Yes standalone/external
Cond Capacity 14kW
Filter drier & sightglass installed at FCU? Yes
FCU TX Valve CBBIZE-4 16A B15 16110 ZGA 45
Hot gas pipe at FCU 60degC
Discharge Temp 52degC
Discharge Pressure 380PSI
Liquid line temp at outdoor 31.2degC
Liquid line temp as it leaves FCU TXV 35degC
Liquid line pressure 400PSI
Subcooling on COOL mode 2deg
Superheat in HEAT mode 5degC
Suction pressure 100PSI
Suction Temp 5degC
FCU amps on HIGH 4.58
Number of Outlets 25
Supply Air Temp 41.4degC
Return Air Temp 18.3degC
Outdoor Ambient Temp 12degC
Average airflow per outlet 45l/s
Airflow l/s 1117 or 2366CFM
Any help you could provide would be much appreciated