In the past few postings, we have been discussing the refrigerant cycle and some diagnostics. We have discussed how important looking at the whole system is to assuring a properly operating system.
We have looked at troubleshooting using temperature and pressure readings, super heat and sub-cooling , checking proper CFM, and what they mean as part of that diagnostic. Hopefully, we have made the point that most problems are external of the refrigerant side of the system.
So, how do we know what pressure and temperatures a particular system should be operating at? One way is a good understanding of psychometrics — being able to plot various conditions on the psychometric chart and seeing how the system is operating. This is usually more than the average tech can do. Thankfully, manufacturers publish this data to save time and assist the technician in making proper diagnostics.
York does have an Application Guide for both air conditioners and heat pumps. The heat pump data is available for both heat and cooling operating conditions. This application guide provides Service Data and Condenser Data for our outdoor units. The SERVICE DATA TABLES are presented in the first half of the Guide where refrigerant temperature and pressures, indoor delta temperature, proper CFM ranges, indoor wet bulb temperature, and unit operating current (amp draw) for a range of operating condition and temperatures are included. The data is based on a nominal matched indoor coil / condenser combination. It is important to note: these tables are intended to provide ball park figures for troubleshooting for the outdoor unit operation in the field and should not be used as the final answer. They will however, get you very close to what you should be seeing on a particular unit at particular conditions.
You still need to do a complete diagnostic of the system especially if your actual site conditions and the tables are not close.
The second part of the Guide presents data that can be used for coil matching by cross plotting the condenser date with third part coils manufacturer’s data.
This Guide is just another tool to help you make a proper diagnosis of a system that may or may not be operating properly. You do need to keep in mind, that this Guide and the troubleshooting chart I posted in a previous blog are only a part of having the proper tools to work on an air conditioner or heat pump. Your gauges and hoses must be kept in good condition. You need an accurate thermometer or thermocouple to read suction and liquid line temps and temperature drops across the coils. You need an accurate psychrometer to measure the wet bulb temperature so you know the load on the coil. You need an accurate scale to weigh in refrigerant to a system. You need an accurate multi-meter to read voltages and amperage. You need an accurate manometer or magnahelic gauge to check for proper air flow. And most importantly, you need to know how to use all these tools, including the Guide, properly.
I hope you find the Guide a valuable tool and make use of it. Spring is here and, hopefully, we’ll have a hot summer and having this guide makes your job easier. The guide can be accessed on www.upgnet.com