Testing HVAC

[NCFORD]

I have a goodman packaged heat pump unit and want to check to see if it has the proper amount of coolant. I have a Yellow Jacket test manifold, but am not sure of the test procedure. I sure this is a standard procdure.

Thanks,
Tim

[LazyPup]

It would be inapproprate to even attempt to answer this question in a public forum because Federal Enviromental Protection Agency regulations prohibit anyone from transporting & dispensing refrigerants or from opening any valve or service port on a refrigeration system unless that individual has an EPA certified REFRIGERATANT HANDLERS CERTIFICATE in their possession. Merely connecting your manifold to an HVAC unit could subject you to federal fines of up to $10,000 per day for every day of proven offence.

In addition, while it is very easy to connect a manifold and take a pressure reading it requires a thorough knowledge of refrigeration theory in order to interpret the readings because there is no standard pressure, but rather, the operating pressures continually change in direct proportion to ambient air temperature & airflow at the condenser or air flow over the evaporator. In order to properly use a charging manifold a trained HVAC tech uses both the pressure readings and the temperature/pressure conversions on the refrigerant enthalpy charts to determine the condition of the unit under test.

[NCFORD]

I have the charts that you are talking about and a temp sensor. What I need is the general procedure. I don't really care about the regulations. I installed the unit myself and everything worked out great. It's been about a year and I would like to check it out.

[LazyPup]

I fully realize that you have the manifold guage and that you are anxious to try them out, however it would not be prudent for anyone to post information on the forum that would encourage the homeowner or DIY'er to circumvent established codes or public law.

Having said that, It is the intent of this forum to provide the homeowner or DIY'er the necessary diagnostic tools to perform thier own work where practicle. In this situation the task at hand is to periodically test your unit to see if it is functioning correctly, thereby saving you the cost of hiring someone to do that for you. To that end I can offer you an alternative procedure that would much better serve your purpose and provide a much more accurate result without requiring a full knowledge of the refrigeration process. In fact, due to the regulations involved with handling refrigerants most certified HVAC techs now rely upon other means of testing and only use gas pressure tests as a last resort when indicated by the primary testing methods.

Perhaps the simplest and most accurate test of your compressor unit is an Amperge Test. While the actual operating pressures may vary as much as 100psi depending upon temperature conditions, one fact will remain constant. If the refrigerant gas level is correct the compressor will be compressing at its full rated load therefore the compressor motor amperage draw will be constant.

In order to make an amperage test you would need an accurate snap on ammeter.

We must remember that the primary wiring to the condensing unit is supplying current to both the compressor and the fan motor, therefore we must take the compressor amperage test on the compressor wiring only.

When examining the compressor wiring you will find a wire to the compressor "Run" terminal which is usually a black wire running from "line 1" on the contactor to the compressor. You will also see a red wire running from "line 1" to a capacitor then from the capcitor to the "Start Winding" on the compressor. In theroy we could take an amperage reading on the run winding wire, then another reading on the start winding wire and add the two readings together to get a total amperage, but due to some variations in phase angle between the two windings we would end up with a slightly incorrect reading.

"Kirchoffs Law" states that the amount of current leaving a circuit is equal to the sum of all applied currents, therefore whenever testing for total current on an electric motor we must take the reading on the Common wire. In most cases the common wire will be a White wire running from the compressor to "Line 2" on the magnetic contactor.

In order to be finitely accurate you must begin by compensating for local voltage conditions. First test the voltage from "Line 1" to "line 2" on the magnetic contactor and compare your reading to the theoretical voltage listed on the compressor data plate. If they are both the same you can then proceed to take an amperage reading on the white wire and compare that reading to the theoretical Amperage reading listed on the compressor.

Occassionally we will find a substantial difference between the actual voltage and the theoretical voltage. I.E. the motor is rated at 220 volts but the actual voltage measures 240volts. In this case we must first mathematically compenste for the difference in voltage.

Wattage is determined by multiplying volts x amps, therefore we begin by multiplying the rated volts x the rated amperage as listed on the motor data plate to determine the total theoretical wattage. We then divide the theoretical wattage by the actual voltage measured at the contactor to determine what the correct amp draw should be for this installation.

By example, let us assume your motor is rated for 220v 10.5A.

220 x 10.5 = 2310watts.

Now let us assume your measured voltage was 240v. We then divide the theoretical watts by the measured voltage to determine the actual amp draw for this installation.

2310w / 240v = 9.6amps.

9.6amps then becomes the theoretical amperage for your installation. You then measure the actual amperage and compare the result to the the theoretical amp draw.

If the actual amp draw is substantially less than the theoretical amp draw it generally indicates a low refrigerant charge and would then warrant actually taking a pressure reading.

If the actual amp draw is substantially higher it is indictating a "High Head Pressure" condition, which primarily results from a restricted airflow over the condensing coil.

The most common causes of a restricted air flow are:
1. Dirty condensing coil.
2. Shrubs, vegetation, lawn furniture or other foreign objects close to the condensing unit that are restricting the airflow.
3. Loose or missing fan shroud or condenser cabinet components.
4. Broken, bent or Miss-positioned fan motor blades.
5. Defective fan motor.

If you suspect a problem with the fan motor you can use the same amperage test procedure to perform an operational test of the fan motor.

If the fan motor tests okay (indicting a good air flow) yet you still have a high head pressure it most likely is indictating a kinked or bent refrigeratant liquid line. Check the lines from the condenser cabinet to where they enter the house to determine if they have been damaged by lawn maintenance equipment or children & pets playing near the unit. If the lines are okay the problem is most likely caused by a stuck expansion valve or reversing valve and would require a trained HVAC tech to make the correction.

One of the best diagnostic tools you can have is simply a pair of dial type probe thermometers. Put one in the return air grille and a second one in a discharge air grille nearest the inside unit. During normal AC operation you should see a temperature differential of about 12 to 18degF depending upon the efficiency of your unit. The idea here is to place the two thermometers and leave them in place and periodically check the tempertures. Once you determine what the normal operating differential for your unit is, that differential should remain constant, by example, let us assume for the moment that your unit runs with a 16degF differential. It should then show the same 16degF whenever the unit is running. If the differential should drop considerably and remain there for a it is indicating a "Super cooling" condition. The primary cause of super cooling is a restricted air flow over the evaporator. The most common cause is a dirty air filter, but if left unchecked it will result in icing on the coil which further restricts the airflow.

If the temperature differential goes up substantially it is indicating a "starved refrigerant" condition and will require and HVAC tech to check it out.

[lonestarheir]

You go Lazypup - Good answer.

[KSever]

I have the charts that you are talking about and a temp sensor. What I need is the general procedure. I don't really care about the regulations. I installed the unit myself and everything worked out great. It's been about a year and I would like to check it out.

"I don't really care about the regulations" Is Not a good thing to say on this website or any open forum, especially when you don't know who the other guy reading actually is. Take me for instance, my cousin is a Director of one of the District EPA offices. I'm not going to say which one but I can prove it if need be. As for me I am a licensed refrigerant holder and do abide by any EPA laws set.
If I were you I would hide those gauges of yours and not be so proud of them and for sure I would not be letting everyone know you installed your unit yourself.

[LazyPup]

Technically speaking there is no regulation preventing a homeowner from installing their own unit providing that unit has a precharged lineset and they did not need to open the refrigerant system to top charge it or if they had an EPA certified HVAC tech perform the final top charge and setup.

On the other hand, as Kserver has pointed out, it is never a good practice to even attempt to open the gas portion of an HVAC unit unless you are an EPA certified refrigerant handler. Not only are the fines involved extremely severe, the EPA also pays substantial rewards for information leading to the arrest and conviction of unathorized people opening refrigerant systems. The fines can run as high as $10,000 per offence and often the reward is equal to 1/2 the fine.

In addition, the information on the rewards is public knowledge, well posted in most businesses that sell or distribute refrigerant or HVAC equipment and it is often published in many of the periodicals directed toward enviromentally conscious people. The bottom line, you never know when you may have a nosey friend or neighbor who would be more than willing to drop a dime to attempt to collect the reward.

Ask any EPA certified refrigerant handler and they will confirm that the regulations on refrigerants are extremely strict. Gone are the days when we just tossed the freon tank on the back of the pickup. In todays society we must keep extensive records on how much refrigerant we purchase, and very accurate records on where, when and how much we dispense. In addition, we must maintain records on how much refrigerant we recover and how we dispose of the recovered refrigerants. There mere acceptance of a refrigerant handlers certificate grants the EPA the right to inspect our records and perform an inventory of all refrigerants stocks in our possession confirmed by actual weight.

[lonestarheir]

"I don't really care about the regulations" Is Not a good thing to say on this website or any open forum, especially when you don't know who the other guy reading actually is. Take me for instance, my cousin is a Director of one of the District EPA offices. I'm not going to say which one but I can prove it if need be. As for me I am a licensed refrigerant holder and do abide by any EPA laws set.
If I were you I would hide those gauges of yours and not be so proud of them and for sure I would not be letting everyone know you installed your unit yourself.

Amen - just because you are able to do a job does not make you qualified to do a job. We invest lots of time and money to be able to do what we in the business do, so if you want to do it, do it correctly. I personally don't mind coming on some of these sites and helping people out, but there are certain things that a homeowner is not supposed to do - most are to dangerous, or have to due with rules and regulations. I don't really care for alot of the things that I am required to do, but I do them anyway. Do you think accounting for every bit of freon that my company purchases is a fun thing to do?? Absolutely not, but because of that I end up having to charge my customers a bit more overhead expenses so that I can log everything that I am REQUIRED to log.

Okay, off my soapbox now. Please understand that without knowing everything that you should know (which cannot be explained on this site) there are several different ways to determine the proper charge for your system. Your best bet it to call a company recommended to you by the factory that makes your unit. They should know your type of system and your area and what the proper factors are that should be considered for your situation.

[NCFORD]

Thanks lazypup,
I will use your method. I did amp check everything when I installed it, but not to the exact numbers. For the record my unit is a packaged unit so I did not have to do anything with the charge. I do care about the enviroment and would not attempt anything that I did not understand first. In fact the guy I borrowed the test manifold from installed his own spilt system including drawing a vacume and charging it. I Don't beleive it's that hard. From the stories I've heard from HVAC tech's, the "professionals" release far more bad stuff in the atmosphere than any homeowner. Just my
.02. Also, why can we work on auto AC? But not home AC?