RTHD , oil return issues .

[servicetrane]

keep the vent valve closed

[Tech Rob]

If migration due to water flow or the room's temperature control is the issue, maybe isolation valves or a different thermostat setting are the answer...?

[svc]

Do you have condensor water regulating valves controlled by the ch530? Maybe settings are different between the 2 machines. Could it be that the chiller having the issue is starting up under different conditions than the other? If the condensor water regulating valve is N.O. vs N.C in the off state. All the rthds I have started up since 2009 have had this valve. I was thinking that they made this required.

[svc]

keep the vent valve closed

Say What?
The valve is closed during shipping. It is opened at start up.

[txhvac]

Do you have condensor water regulating valves controlled by the ch530? Maybe settings are different between the 2 machines. Could it be that the chiller having the issue is starting up under different conditions than the other? If the condensor water regulating valve is N.O. vs N.C in the off state. All the rthds I have started up since 2009 have had this valve. I was thinking that they made this required.

I've only heard of the regulating valve as an option, same as the RTHC.

[svc]

I looked it up. You are right it is in option! However it would be a requirement under certain conditions for the chiller to operate within its design envelope. RTHD chillers rely on differential pressure between the compressor discharge and suction to move oil through the compressor rotors and bearings for cooling and lubrication. It also requires an oil pressure differential in order to load the compressor. Lower temperature and pressure in the condenser (and higher temperature and pressure in the evaporator) can reduce the chiller’s differential pressure below the minimum required for proper cooling, lubrication, and loading. The chiller is protected from compressor damage by the CH530 control system. However, inadequate pressure differential will keep the chiller from operating. The most effective way to maintain the required differential pressure during chiller startup and operation is to apply condenser water temperature control.

[txhvac]

I looked it up. You are right it is in option! However it would be a requirement under certain conditions for the chiller to operate within its design envelope. RTHD chillers rely on differential pressure between the compressor discharge and suction to move oil through the compressor rotors and bearings for cooling and lubrication. It also requires an oil pressure differential in order to load the compressor. Lower temperature and pressure in the condenser (and higher temperature and pressure in the evaporator) can reduce the chiller’s differential pressure below the minimum required for proper cooling, lubrication, and loading. The chiller is protected from compressor damage by the CH530 control system. However, inadequate pressure differential will keep the chiller from operating. The most effective way to maintain the required differential pressure during chiller startup and operation is to apply condenser water temperature control.

Agreed 100%. The Carrier 30HXCs are the same way, the machine is not sold with a regulating valve, but one can be field installed, set-up, & the chiller will control the valve. People really need to have to have good control of their towers w/ these machines.

[Phisher]

Trane recomends controling the condenser bypass based on the pressure difference between the condenser and evaporator. A minimum of 23# delt-p between the condenser and evaporator needs to be maintained for proper oil flow. The condenser water needs to be 17deg higher than the chill water with in 2 min of startup. A 25deg. deta-t must be maintained.

[latchingfault]

try setting your delta P to 240kpa (2vdc) min and 480kpa (10vdc) max for your cond regulating valve

[milkyway]

yep., there are 5 reasons why this machine need this control
and 4 methods of control.