Transicold in public transportation

[Niko_B]

Hello,

Have a bus with transicold a/c system with these simptoms:

Refrigerant: R134, TXV

Temperature inside the bus: 80F
Outdoor temperature: 92F

Suction pressure: 24psig
Head pressure: 220psig

Subcool: Temp measured at sightglass 104F
Superheat: didn't measure

Sight glass shows low on charge.
No significant temperature drop across the filter drier (no service valves for pressure drop measurement)

Condenser: Clean/ish , all fans running in good direction.
Evaporator: Not so clean (maybe 20% airflow restrictive)

Insuffitient cooling is the problem.
Help me understand high subcooling, sightglass not full, low suction, high head :confused:

Thank you.

[chillerman2006]

Does this help

[chillerman2006]

Took me a while as i work in bars & degees celsius

But buy the figures you give I would say you are low on refrigerant or you have a very low superheat and bringing liquid back

Check the super heat if its high your low on refrigerant

[Niko_B]

Temperature inside the bus: 80F (27C)
Outdoor temperature: 92F (33C)

Suction pressure: 24psig (1,65Bar)
Head pressure: 220psig (15Bar)

Subcool: Temp measured at sightglass 104F (40C) (that gives us 18C subcooling)
Superheat: didn't measure


It's obviously a bit low on refrigerant although no much superheat, (compresor suction was ice cold)
The thing that bothers me is high head pressure which should be around 11-12Bar (160-170psig) and high subcooling which would indicate overcharge.

I'm thinking maybe restriction or dirty filter although the filter didn't show much temp drop across it.

????

[Niko_B]

Thinkg that evaporator coils need to get cleaned properly, so does the condenser alhought it looks cleans, after that, measurments should be taken.

[chillerman2006]

Thinkg that evaporator coils need to get cleaned properly, so does the condenser alhought it looks cleans, after that, measurments should be taken.

illiminate non-condensables as well by recovering the charge and only charging the liquid back in + leave 1/2 kg in the bottle, new drier, good vac then after you have cleaned the coils you can weigh in correct charge, if needed top up with virgin,

Charging liquid + leaving 1/2kg in bottle will ensure any non condensibles are in bottle

[chillerman2006]

(compresor suction was ice cold)

Measure the superheat - ice cold means nothing - what is the temperature