Your system has a TXV for its metering device. The correct charge is determined by subcooling. The superheat still needs to be checked to verify that there are not other refrigerant circuit related problems though.
Depending on the model, your system has 1 or 2 factory installed liquid line filter driers inside the unit, there should not be one installed outside the unit.
Many people charge a system with the refrigerant bottle turned upside down, and either throttle the refrigerant in with the valve on the refrigerant manifold, or use a small device that goes inline with a refrigerant hose that insures the liquid flashes off before it makes it to the system.
You walked up behind a guy, who had his attention focused on something else, and you are concerned that he was startled when you said something?
I do understand your concerns though.
Only a very small percentage of installers and service techs actually flow nitrogen through a system when brazing the refrigerant lines. This despite it being a specific requirement in virtually every manufacturers installation instructions.
Only a minority of installers/techs who actually use a micron gauge during evacuation, again, this is despite clear manufacturers instructions regarding vacuum level requirements.
Depending on who's study you look at, between 56% and 73% of newly installed systems are incorrectly charged at startup, most by more than 10%.
Last edited by mark beiser; 03-16-2008 at 10:49 AM.
Twilli says who said anything about DEEEtroit or the Pistions
Originally Posted by beenthere
No Heat No Cool You need Action Fast
Originally Posted by twilli3967
Every single time I hook up my gauges to the unit my very next move is attatching my pipe clamp thermocouple and checking s/h and s/c.
Even if the charge is "weighed in", s/h and s/c will still need to be calculated to be sure the system is running correctly.
Maybe he was using the "Beer can cold method"!!
Leading industry experts agree that the integrity of the refrigerant system should not be compromised unless a problem is suspected and that gauges are not required for preventative maintenance.
James Bergmann has documented this in the TESTO AC and Refrigeration Application Guide available at
Originally Posted by hvac-master
Well then I guess I have been doing it wrong all of these years. Maybe those "experts" should look up the meaning of "preventative maintanence". By putting your gauges on a system you are not compromising the integrity of the system. Can you imagine what would happen if I went out on a PM and the home owner saw me put no gauges on the unit?? Over time things change....units were built by man and will fail. If I can catch it soon enough to avoid a hassle and maybe save the home owner some time and money....I am all about it. My gauges go on every time and always will.
I need a new signature.....
You should be checking your refrigerant charge by subcooling like everyone is saying and to do that you have to hook up your gauges. By checking superheat you're basically checking whether or not your txv is doing its job.
Originally Posted by hvac-master
this is true and has been know for a long time. As this may be true you still cant get a complete story with just takeing temps. Gauges are a very important diagnostic tool and should never be underestamated or pushed to the side just because we are only doing a pm and it isnt important
With proper subcooling and superheat how do you know if you have a weak valve without gauges.
Bergmann's article has a lot of good stuff in it. I don't agree with everthing in it, but still a pretty good article. If I could benchmark systems and not worry about somebody else putting gauges on it after I left it, then I would. The reality is however, that customers aren't in general loyal to a given company. Some even mess with the system themselves in between, or let their brother's buddy who used to do auto AC 20 years ago come over and work on it. People are trying to save a buck whenever they can. Also there are a lot of one time visits. What good does it do to benchmark a system you might never see again? Must be different in other parts of the country, Bergmann's part of the country I mean. Truth is, even if I could find such an ideal world as his, I'd still put my gauges on it.
Last edited by hvacrmedic; 03-23-2008 at 11:00 PM.