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Fieldpiece ASX14 & Troubleshooting  Could you please provide…

Customer Question
Fieldpiece ASX14 & Troubleshooting                                 ...
Fieldpiece ASX14 & Troubleshooting                                 

Could you please provide me with step by step instructions on how to use the Fieldpiece ASX14 to check superheat and re-charge freon? Should I turn off the power to the condenser before re-charging or checking pressure? Do repair people ordinarily turn off the electricity before testing the electricity for handlers and components in general?   Since the ASX 14 can be used to measure superheat/subcooling and charge/discharge freon, I don’t think I would need gauges. Is that right or would I need additional equipment.

I am in training for HVAC repair. In my training materials, it says that I should refer to the documentation of the condenser about what superheat or subcool settings to use.   Also, I can obtain the electric schematics for troubleshooting. However, where do I obtain this documentation? Is there a particular website or book that has a collection of this information?

I was told that I should measure air volume (and some other troubleshooting steps) before recharging Freon. However, I haven’t seen this done in real practice. Do HVAC professionals truly check the air volume before re-charging a condenser? In reality, do HVAC repair people calculate superheat using both the “superheat charging method” and the “suction vapor superheat method”?

Lastly, is there an easy way for me to tell if a system is a TXV system by looking at the condenser. If I have to look at the air handler (to determine it’s a TXV system), how can I quickly check?
Submitted: 8 years ago.Category: HVAC
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Answered in 19 minutes by:
6/26/2010
HVAC Technician: Douglas, HVAC Technician replied 8 years ago
Douglas
Douglas, HVAC Technician
Category: HVAC
Satisfied Customers: 3,089
Experience: Manufacture Rep for Major Brand, Technical Trainer, NATE
Verified
Hi, I'm Douglas and I am here to help you resolve problems with your heating and cooling equipment.

First lets cover the airflow.... In the real world, not near enough techs measure the actual airflow because they dont know how or dont know any better. In a nut shell airflow is the most critical part but also the most misunderstood. In the end, if you dont have proper airflow, the charging charts are worthless anyway. All the charging charts are based on 400 CFM per ton of airflow and 80% of the ducted systems in the US lack airflow.

You will need gauges. The Field piece is simply designed as a tool to make reading superheat and subcooling easier for the less experienced tech. A set of gauges tell you not only poressure but the saturated refrigerant temperature. These physics are always there. If we take R-22 for instance. If your suction gauge shows 70 psig. That means the saturated temperature of the refrigerant is 40 degrees. Superheat is the difference between the saturated temperature and the actual temperature of the suction gas. So you would measure you suction line temp. If the suction line were 53 degrees, you would have 13 degrees superheat.

Each model is different. You cant just guess at what the superheat should be. If the unit has a fixed metering device, you would need the specific chart for that unit. If it has a TEV, then you would consider most TXVs are set to between 10 and 15 degrees superheat. In this case you would need to validate that you have a solid column of liquid going to the valve. You do this by measuring the subcooling.

Subcooling is measured similar to superheat in that you look at your liquid pressure and convert that to a temperature via your gauge. So, if memory serves me for R-22 200 psig is about 100 degrees. If your liquid line were 94 degrees, then you have 6 degrees subcooling.

The reality is that there are no cutting corners and be very careful what you learn from other techs. I train techs for a living and even the guys who have been doing this for 30 years have alot of bad habits and dont know really why they do what they do. Experience is not always the best. I tell my students that I have been playing golf longer than tiger woods. The reality is, he has great experience by focusing on the mechanics and fundimentals, and I just keep picking up bad habits along the way. He makes millions playing golf and I just flat out suck. BotXXXXX XXXXXne is in order to be a true expert you must first learn how something works and then and only then can you tell when something is wrong and how to correct it.

The only way you will know if a system has a TXV is by looking at the indoor coil and seeing one. Most everything made today has a TXV on it but 3 years ago, only 1 in about 6 had them.

There is no magic web site. If you really want to know this stuff, you seek out an instructor or mentor who will take the time to teach it properly. Check with the local distributors and see if they are holding any classes andattend as many as you can.

In the mean time, pick up the book "modern refrigeration and air conditioning"... you can get it at Amazon or other online retailers. it will be your bible for the vast majority of your carreer.

http://www.amazon.com/Modern-Refrigeration-Conditioning-Andrew-Althouse/dp/1590702808


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Customer reply replied 8 years ago
I appreciate your time and expertise when answering my question. I agree that there are no cutting corners and am in a HVAC training program now. I would like to award you the $ for this question. My original question has some unanswered things:

* Could you please provide me with step by step instructions on how to check superheat and re-charge freon with the Fieldpiece ASX14? I am looking for instructions like “1. turn off power to the condenser. 2.Attach pipes to ASX14 and vapor line 3. Loosen nut to start flow” I don't need to know the calculations.

* Where do I obtain the electric schematics for troubleshooting in general, superheat and subcooling charts for various AC units? Is there particular websites or books? If so which ones?

* Turning off Power- Should I turn off the power to the condenser before re-charging or checking pressure? Do repair people ordinarily turn off the electricity before testing the electricity for air handlers and components in general?

* For clarity- you mentioned that TVX are ordinarily set to 10 to 15 degrees of superheat. Since we usually check subcooling with TVX systems, do you mean 10 to 15 degrees of subcooling? If you mean 10-15 degrees of superheating, then I should measure both superheating and sub-cooling in TVX systems?

* For clarity- when you say that I should “look(ing) at the indoor coil and seeing one.” Do you mean I should just look for a thin coil in the air handler or look for more things? Couldn't the thin coils be used for something else?


* Do HVAC repair people calculate superheat using both the “superheat charging method” (this method uses the wetball, dryball and outside temp) and the “suction vapor superheat method”?

Customer reply replied 8 years ago
Relist: Incomplete answer.
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