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Old 07-29-2010, 05:50 PM   #16
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A/C Not blowing cold air!


Test the capacitor with your volt meter. After disconnecting the wires to the cap, discharge it by making a connection between the two terminals with a screwdriver blade. Next, with your electrical meter set to ohms, connect one lead wire to each of the terminals. If the ohm reading starts high, then drops to a lower reading, your capacitor is charging. Next, remove the leads from the terminals, switch your meter to DC Volts (not AC), then again connect one lead to each terminal. The reading should start high and slowly drop. If so, your capacitor is discharging. If this is not happening, replace the cap. ALWAYS use the same voltage as the original cap, but you can increase the mfd (micro farads) rating by 10%.

Test the amp draw of the compressor on start up and running - remember, the compressor has two sets of windings, start and run. Just because one is good doesn't mean they both are. And make sure your system is not overcharged with refrigerant as well. This can lock the rotor and cause the wires to overheat, increasing resistance, causing more heat, etc.

Has anyone checked that the basic incoming voltage is okay? Look for between 208 and 240 Vac.

http://www.completeheating.ca

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Old 07-29-2010, 06:07 PM   #17
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Mr. Glen this is awesome information for me. All this is new and it would've been great if someone had shared this with me before. I must admit defeat, I finally gave up and called someone. However, I did take notes from your information so I will know what to do next year, because this seems to happen every summer. Yes, of course, I need a new AC but who the heck can afford those things right now.

I will post tomorrow and let everyone know the end results. I do have to say I am rather proud of myself for being able to replace a simple thing such as burnt wires.

Thanks again Mr. Glen!
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Old 07-29-2010, 06:16 PM   #18
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Quote:
Originally Posted by Glen McIver View Post
ALWAYS use the same voltage as the original cap, but you can increase the mfd (micro farads) rating by 10%.
I agree with everything you said except for the above.

You can (and should IMHO) increase the voltage tolerance of a cap. Using a 440V instead of a 370V is percectly acceptable and will likely be a better cap from a reliability standpoint.

However I would not increase the capacitance unless it's only temporary. The manufacturers chose these capacitance values for a reason. I would stick with them if possible. What if the value was originally 50 mfd and a tech substitutes a 55. Now the next time another tech. substitutes a 60 instead of a 55. Now you're well over 20% out of spec. Don't assume techs. doublecheck manufacturer's schematics when replacing components.

If a tech. has to deviate from the original value they should clearly tag it showing the original value. This practice probably never happens during the rush to get these systems up and running and on to the next call.

Last edited by hennyh; 07-29-2010 at 06:27 PM.
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Old 07-29-2010, 06:22 PM   #19
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OK, so my current cap has 440 VAC/B on it. If it is replaced I should make sure it's replaced with the same. Did I understand this correctly?
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Old 07-29-2010, 06:29 PM   #20
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OK, so my current cap has 440 VAC/B on it. If it is replaced I should make sure it's replaced with the same. Did I understand this correctly?
Yes, same or higher. (never lower)
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Old 07-29-2010, 06:39 PM   #21
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Originally Posted by hennyh View Post
I agree with everything you said except for the above.

You can (and should IMHO) increase the voltage tolerance of a cap. Using a 440V instead of a 370V is percectly acceptable and will likely be a better cap from a reliability standpoint.

However I would not increase the capacitance unless it's only temporary. The manufacturers chose these capacitance values for a reason. I would stick with them if possible. What if the value was originally 50 mfd and a tech substitutes a 55. Now the next time another tech. substitutes a 60 instead of a 55. Now you're well over 20% out of spec. Don't assume techs. doublecheck manufacturer's schematics when replacing components.

If a tech. has to deviate from the original value they should clearly tag it showing the original value. This practice probably never happens during the rush to get these systems up and running and on to the next call.
By incresing the voltage rating you also increase wattage thereby overheating and shortening the life of the start windings. Yes, it will work, but only for a short time. If you do this, budget for a compressor swap in the near future.

A tech should also be able to run the numbers on the unit to determine the original cap. If not, they can always read the schematic wiring diagram.
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Old 07-29-2010, 06:43 PM   #22
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Originally Posted by hearmeroar874 View Post
Mr. Glen this is awesome information for me. All this is new and it would've been great if someone had shared this with me before. I must admit defeat, I finally gave up and called someone. However, I did take notes from your information so I will know what to do next year, because this seems to happen every summer. Yes, of course, I need a new AC but who the heck can afford those things right now.

I will post tomorrow and let everyone know the end results. I do have to say I am rather proud of myself for being able to replace a simple thing such as burnt wires.

Thanks again Mr. Glen!
You're welcome. Post the make, model and serial # tomorrow, along with your service person's diagnosis. Also ask for liquid line and vapour line pressures, outdoor and indoor air temp (wet or dry bulb) and a coil temp drop.
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Old 07-29-2010, 06:46 PM   #23
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Great ! While we are at it what else should I make sure he does correctly? And is $38 a lb for refrigerant expensive?
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Old 07-29-2010, 06:52 PM   #24
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Originally Posted by hearmeroar874 View Post
Great ! While we are at it what else should I make sure he does correctly? And is $38 a lb for refrigerant expensive?
R22 or R410a? US dollars?

Quote:
Originally Posted by hearmeroar874 View Post
Great ! While we are at it what else should I make sure he does correctly? And is $38 a lb for refrigerant expensive?
.......................and clean the contactor.
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Old 07-29-2010, 07:08 PM   #25
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Don't know what type of refrigerant yet and yes, US Dollars.

I will post everything tomorrow.
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Old 07-29-2010, 09:45 PM   #26
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By incresing the voltage rating you also increase wattage thereby overheating and shortening the life of the start windings. Yes, it will work, but only for a short time. If you do this, budget for a compressor swap in the near future.
What????

Voltage tolerance is the max. safe voltage to avoid damage to the cap. Capacitance determines current flow based on the impedance of the circuit.

Its like substituting a 10 watt resistor in place of a 5 watt resistor. Or using a 16 AWG extension cord in place of a 18AWG extension cord. Tolerance is a different concept then capacitance. The circuit will be just as happy but it'll cost a tad more and take up a tad more space.

Maybe you should take a refresher course in basic electrical circuits.

P.S. Maybe we should tell Amrad that their replacement 440V Turbo Caps are putting millions of HVAC systems at risk.

Last edited by hennyh; 07-29-2010 at 10:20 PM.
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Old 07-29-2010, 09:58 PM   #27
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Quote:
Originally Posted by Glen McIver View Post
By incresing the voltage rating you also increase wattage thereby overheating and shortening the life of the start windings. Yes, it will work, but only for a short time. If you do this, budget for a compressor swap in the near future.

A tech should also be able to run the numbers on the unit to determine the original cap. If not, they can always read the schematic wiring diagram.
On a run cap. The voltage rating. is the insulation value in the cap. Not its charging voltage.

So going from a 370 to a 440 has no effect on the winding of the compressor.
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Old 07-30-2010, 03:40 PM   #28
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Originally Posted by hennyh View Post
What????

Voltage tolerance is the max. safe voltage to avoid damage to the cap. Capacitance determines current flow based on the impedance of the circuit.

Its like substituting a 10 watt resistor in place of a 5 watt resistor. Or using a 16 AWG extension cord in place of a 18AWG extension cord. Tolerance is a different concept then capacitance. The circuit will be just as happy but it'll cost a tad more and take up a tad more space.

Maybe you should take a refresher course in basic electrical circuits.

P.S. Maybe we should tell Amrad that their replacement 440V Turbo Caps are putting millions of HVAC systems at risk.

On an AC sinewave we know that Eav= 0.637 Epk. We also know that your voltmeter reading is actually an effective (rms) value as opposed to an instantaineous or peak-to-peak (Single phase only) Vac value, so we can apply the formula of Eeff = 0.707 Epk.

Next, let's add the parameters of 240 Vac (rms) +/- 10% (as allowed by the power authority) to find Vpk, within the rms range of 208 - 264 Vac. Simple enough. Your house current's true range of voltage (not the measured range on your meter) is between 294.2 and 373.4 Volts.

So what happens during voltage spike when you add capacitor that allows for a higher voltage that the system was designed for? (Hint: C = Q/E) Using a higher voltage capacitor will work, but why would you remove the safety factor?

Why do you think the insulation on your house wiring is rated at 600 volts? Why do you think you can't find household electrical items that comsume more than 1500 watts when a 15 amp circuit can supply 1800 watts before tripping the breaker? Simple. A margin of safety is factored in.

And maybe I should take a refresher course in basic electrical circuits, after all, it's been 19 years since I earned my degree.
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Old 07-30-2010, 04:45 PM   #29
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Ok, boys back to your corners !

So this is my bad news... one of windings (if my terminology is incorrect please accept my apologies and correct me gently) in the compressor terminal is "wide open" measuring very high, the other two were around 2.6ohms and 1.3ohms. (Tech measured these) Also the orange wire (run wire? is that right) was connected to the bad winding and burnt up like a piece of paper! Results NEED A NEW COMPRESSOR!!!!! So to cut expenses I am looking for a good used compressor because I'm broke like the majority of the world! My tech referred me to someone but I can't get a hold of this guy. Two weeks of no AC in humid ass Florida is cause for an act of insanity!!!!
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Old 07-30-2010, 04:55 PM   #30
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take a rubber mallet. And smack the compressor. It might reset the internal over load, if its stuck. if it doesn't, then the winding may have burnt up.

Used equipment is often a bad idea.

I know where you can get one real cheap though. Your's, its used.

Find out what warranty you get with it.

Also, have your tech find out why yours burnt up.

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