Capillary size

[kssoin]

Hi All,
I hav replaced a rotary compressor in a window Ac. The first one had stalled. The replacement comp is manufactured by Siam Compressor Industries Thailand. The original comp was by same company. The Ac is a 1,5 TR unit.
Before starting the unit i want to make sure that the capillary is right. The unit has two caps of .064 " ID having length of 41.5 inches.

What is the correct cap size for the compressor having model no RH313VADT

Thanks in anticipation.

[Brian_UK]

I don't think that you can base the size of the capillary line on the size of the compressor.

[kssoin]

Hi Brian,
How do I ascertain that the cap size is correct.
I ask this because the unit had low low side pressure of 54 psig at hi pressureof 200 psig, and the unit was running at full load amps.
Appreciate your response.

[sendhilkmar]

Kssoin,
If you have replaced the same model compressir then there could not be any problem with the cap. size . Capillary size should be caluculated based on mass flow rate and operating pressures/ temperatures. Your AC suction and discharge pressures are too low. Have you changed the old filter frier and capillary?

[kssoin]

Kssoin,
If you have replaced the same model compressir then there could not be any problem with the cap. size . Capillary size should be caluculated based on mass flow rate and operating pressures/ temperatures. Your AC suction and discharge pressures are too low. Have you changed the old filter frier and capillary?

Hi Sendhil Kumar,
It is a hyundai 1.5 TR. The original comp was 19*** BTU/Hr manuf by M/s Siam Compressor Industries.
I could not get that comp. Got this one which fits the foundation bolts perfectly. This is a 18500 BTU/Hr comp.
this is a 31.3 cc per rev as per the spec.
So what should the cap size be?
Yes i replaced the filter drier and the caps, i dont know jf they would suit this compressor.
I have also changed the orientation of the drier. Previously the cap tube end was 90 Deg vertical. Now I have made it abt 20 to 60 Deg downwards. (A Learning from this forum).
If i increased the pressures to abt 60 psig at the suction(after the evap. the unit drew current over the max value of 9.4 Amps. At peak ambient (43 Deg C )at midday the current was abt 11 Amps.

Appreciate your response.

[sendhilkmar]

you may cut down the length; Try with 32" length #2 of the same bore. what was the discharge pressure @ the time of 60 Psig suction?

[kssoin]

you may cut down the length; Try with 32" length #2 of the same bore. what was the discharge pressure @ the time of 60 Psig suction?

Hello Sendhil Kumar,
Thanks for the reply,
At 60 psig the high pressure was abt 225 psig.
Now that compressor had failed. I got the compressor cut from a local machinist,
The bearing at the bottom is stuck at a particular point in the revolution.
Yes i will try with 32".
Tell me what should be the suction line pressure after the evaporator, given the high ambient we have in delhi abt 42 - 44 Deg C, also a low evap temp will cause freezing during high humidity days coming ahead.
Regards

[sendhilkmar]

Kssoin,
At 45C ambient the discharge pressure goes around 300 Psig and suction would be around 85 Psig. Frosting will take place at lower suction pressures (below 55 psig).

[kssoin]

Kssoin,
At 45C ambient the discharge pressure goes around 300 Psig and suction would be around 85 Psig. Frosting will take place at lower suction pressures (below 55 psig).

Hi Sendhil Kumar,
I fixed the caps yesyterday and charged the ac with abt 1 Kg R 22.
By the time i finished it was evening. I am getting 63 psig after evap and 250 psig at the liquid line. I measured the subcoolong it was 4 to 5 Deg K and the the super heat was abt 12 and the lowest was abt 9 Deg K. There was a lot of sweating on the suction line. The compressor current was 8 Amps. I will now check these values in the morning. The lowest evap in air temp was 17 Deg C.
Since subcooling is low can some more of refrigerant be charged ?

[sendhilkmar]

You can charge little bit refrigerant; but maintain the superheat min. 10 C. Do you mean return Ait temp 17C or wet bulb temp. 17C

[kssoin]

You can charge little bit refrigerant; but maintain the superheat min. 10 C. Do you mean return Ait temp 17C or wet bulb temp. 17C

17 deg C was the lowest Air in at the evaporator.

[kssoin]

I don't think that you can base the size of the capillary line on the size of the compressor.

Hi Brian,
I had contacted the compressor manufacturers and they've sent me a pdf manual for the rotary compressors. it is a 2.9 MB file that cannot be posted. There is a section on Capillary tube selection of six pages that are abt 700 KB . I will post these six pages on yor PM .
As per these from chart 1
i get for a cooling of 2300 Kcal/hr i get a cap tube length of 1.8 meters for an ID of 0.064".
From chart 2 for condensing temp of 45 Deg C and 5 Deg C of subcooling gives a correction factor of 0.8. so the length is 1.8*0.8= 1.44 meters. (Two number capillary tubes.)
In chart two we have subcooling lines and Dryness % lines. What is Dryness % in this context.
Regards
I cannot attach the pages in pdf form as each is larger than 100 KB. How do I post these?