Off cycle pressure

[frostedflake]

Hi RE people!

I have a troubleshooting question here, hope not to sound as an idiot but...

can we tell if a system is short on refrigerant by the off cycle pressures?

I once read here a thread i can't been able to find where you talk about refrigerant tanks having same pressures at different filled amounts but don't know if same applies to an air con with cap tubes and r22.

thanks in advance

[sedgy]

the simple answer is no , each gas has its own standing pressure, at different temps< if there is any liquid in the system<

[acnerd]

Definitely no. As Sedgy said, each refrigerant will have its own standing pressure. If the unit has been off for a long time, the pressures will be lower; if it ran recently, the pressures will be higher. If the building is hot, the pressures will be higher; if it's freezing outside they'll be lower.... You get the picture!

Obviously if you only have an equalised standing pressure of 10 PSI or lower, it probably is short ;)

[frostedflake]

thanks for the responses!

heres the thing:

i've been playing with three r22 tanks all of them weight different, and they all have the same temperature (ambient temperature of 30º C / 86º F) and i get the same pressure measure for two of them while on the fullest one i measure a higher pressure, but by now i figure its not an experiment, rather a waste of time...

[Gary]

thanks for the responses!

heres the thing:

i've been playing with three r22 tanks all of them weight different, and they all have the same temperature (ambient temperature of 30º C / 86º F) and i get the same pressure measure for two of them while on the fullest one i measure a higher pressure, but by now i figure its not an experiment, rather a waste of time...

The third tank could be overfilled, containing only liquid (very dangerous) or more likely it may contain non-condensables (air) which will add to the pressure.

[frostedflake]

thanks for taking the time to read this post.

reading the post where you talk about the tanks iced on the bottom and heated on the top helped me a lot to understand what happens to the refrigerant when it is not being pumped and what's its relation to temperature.

best regards

[sedgy]

rostedflake, you need acompariter for each gas you work on , there is no other way, to see whats going on inside the system=pressure =tempriture relationship

[sedgy]

not a waist of time it is giving you a consept of bottled gas, <its temp = its psi,, tell me whats the diff between r134and r12? please give psi at24c

[frostedflake]

I check with pt chart, but when actually measuring some bottles of these refrigerants at that given temp. it varies a bit when tanks are overcharged or contain other gases or oil

R134 @ 24º C (75º F) = 78.9 psig

R12 @ 24º C (75º F) = 75.2 psig

thanks

[sedgy]

correct sir but they should NOT have other gasses or be overcharged should they? keep it going you will get there