Dimension of liquid and suction pipe

[Fegner]

Hallo,

I need help.

We got to refurbish an existing A/C-System and have to change from R-22 tp R-407c. The build in liquid pipe is 28mm(diameter). The build in doubleraiser (suction) pipe is about 42mm and 64mm. I can´t replace them so I have to use them. I want to install a new outside unit with a cooling capacity from 100kW. In 2 steps about 50kW/50kW.

Can I still use the pipes, and does the oil still finds its way back to the compressor?

I got an existing pipe length from about 36m. The geodatic hight difference is about 17m. The evaporator is placed in the basement, the compressor is placed on the roof.

Condensing temperature: 45 `C
Evaporating temperature: 4´C

I´m thankful for every help.

[frostedflake]

I think the compressor oil always circulates through the whole system with the refrigerant (even in the best of cases) so a complete flushing/cleaning/filtering is needed to remove the previous oil from the system.

You need to retrofit and take these considerations:

R-407C uses POE lubricant since its components are not miscible with the mineral oil or alkylbenzene lubricants found in most R-22 systems. When retrofitting, a lubricant flush procedure is necessary to reduce the original oil content below 5%.

Retrofitting Procedures
1. Establish baseline performance. Note the oil type in use and any system operating data (if system is operating properly). Check for existing leaks and identify any needed repairs.
2. Recover the existing refrigerant charge (DO NOT vent to atmosphere). Weigh the amount of refrigerant removed.
3. Drain existing oil from the compressor sump, suction line accumulators, etc. Record the amount of oil removed. Add an equivalent amount of OEM recommended POE oil.
4. Recharge the system with the recovered R-22 charge and run the system (at least 1 hour) to circulate the new lubricant.
5. Recover the R-22 charge again and check the residual oil content of the lubricant. The amount of the original lubricant in the POE must be less than 5%.
6. Repeat steps 3 – 5, as needed, until the required oil purity level is reached. Once the oil flushes are completed, standard maintenance should be conducted (i.e. filter-drier change, leak repairs).
7. Evacuate the system (less than 500 microns) and ensure it maintains a vacuum. If vacuum is lost, it may indicate that leaks are present in the system.
8. Charge system with R-407C refrigerant. Remove refrigerant as liquid only from cylinder. The initial charge weight should be approximately 90% of the standard charge for R-22, charging up to 95% if necessary.
9. Adjust TXV set point and/or refrigerant charge to achieve the desired superheat. Low side pressure control settings may also need to be adjusted.
10. Monitor oil level in the compressor. If necessary, adjust oil amount to attain normal operating level (mid-sight glass).
11. Label system clearly, indicating the type and amounts of system refrigerant and oil.