Compressor drawing FLA

[dtna13]

Ok guys ran into an issue today that I don't understand would like some more info on so that I can understand it better . I was checking a residential condenser saw the compressor was drawing its full rla which was 8.5 I was always told if its drawing what it is rated it high so I changed out the capacitor and ended up pulling 10 amps with a brand new cap. So that rulled that out called a more experienced tech let him know what was going on, and he had me check pressures my super heat was at 20 and my subcooling was at 34 the system was over charged. Inside the TD WAS 20 degrees. I understand that with caps you plus or minus 5%. The more experienced tech told me if the td is fine let it go. Is this common practice? Once i found that the system was over charged could that effect the amp.draws of the compressor to pull higher amps? Also, could it effect the overall life of the compressor?

[Poodle Head Mikey]

I can help you - but I have some questions for you to answer first:

1. Ambient temp
2. Head pressure
3. Air temp leaving the cond fan
4. Suction pressure
5. Suction line temp
6. Liquid line temp
7. Indoor air temp
8. Evap entering air temp
9. Evap leaving air temp
10. Compressor rated-amps
11. Actual compressor amps
12. Cond. fan rated-amps
13. Cond. fan actual amps
14. Blower motor rated-amps
15. Blower motor actual amps

PHM
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Ok guys ran into an issue today that I don't understand would like some more info on so that I can understand it better . I was checking a residential condenser saw the compressor was drawing its full rla which was 8.5 I was always told if its drawing what it is rated it high so I changed out the capacitor and ended up pulling 10 amps with a brand new cap. So that rulled that out called a more experienced tech let him know what was going on, and he had me check pressures my super heat was at 20 and my subcooling was at 34 the system was over charged. Inside the TD WAS 20 degrees. I understand that with caps you plus or minus 5%. The more experienced tech told me if the td is fine let it go. Is this common practice? Once i found that the system was over charged could that effect the amp.draws of the compressor to pull higher amps? Also, could it effect the overall life of the compressor?

[jpsmith1cm]

moved to tech to tech discussion

[cehs]

I agree with PHM, but it does not sound overcharged to me.
It sounds like dirty condenser, need more info.
SH is low, SC is normal.
If the OD temp is 100f, it will draw RLA exactly, or very close to it.

[catmanacman]

over charged also did you check for voltage drop across the contactor

[Poodle Head Mikey]

Good one!

I forgot to ask for voltage into and out of the contactor.

Thanks!

PHM
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over charged also did you check for voltage drop across the contactor

[dtna13]

Yesterday the temp was 90 degrees out on the beach it was a high rise on the beach voltage in and out was about 210, voltage drop across the contactor was 1. I was always told that if the voltage drop were to be 3 or more to replace, that only read 1. Also the condensing unit was up on the roof free from debris, coil was clean.

[Poodle Head Mikey]

So what about my other questions?

PHM
-------

Yesterday the temp was 90 degrees out on the beach it was a high rise on the beach voltage in and out was about 210, voltage drop across the contactor was 1. I was always told that if the voltage drop were to be 3 or more to replace, that only read 1. Also the condensing unit was up on the roof free from debris, coil was clean.

[dtna13]

So what about my other questions?

PHM
-------

honestly can not answer those after the rest of my calls yesterday and today I can not give you those answers but are dually noted for the next time I have a question to have all my bases covered. Thanks PHM

[SuperPro]

Not questioning your statement about coil being clean but I've looked at tons of coils that "looked" clean until I broke out the hose and coil cleaner and the stuff that'll come out amazes me.

[dtna13]

Very true, I did spray it down with a pump sprayer, not much power there. that could be a possibility, lets just say no visible debris.

[hvacrmedic]

I agree with PHM, but it does not sound overcharged to me.
It sounds like dirty condenser, need more info.
SH is low, SC is normal.
If the OD temp is 100f, it will draw RLA exactly, or very close to it.

SH could be spot on, we don't know. Not only do we not have any indoor and outdoor temperatures, but we don't know what the metering device type is either. SC OTOH is high by any standard. FWIW, the amperage at 100° ambient should be down around 80-85% of RLA for a 10 SEER unit, and less than that for higher efficiency condensers. Normally you wouldn't expect to see a compressor running at RLA unless the ambient temp is up around 115-120°.

[dtna13]

Thanks for the reminder medic the metering device was a txv. Hope it helps.

[hvacrmedic]

Thanks for the reminder medic the metering device was a txv. Hope it helps.

Yes, that helps a little. The amp draw would have dropped considerably if the charge had been corrected. I'm concerned that it went way over RLA with the new capacitor though. Are you sure it had the correct capacitance?

I'd like to reiterate, just because a coil looks clean that doesn't mean that it is.

[dtna13]

The original capacitor was a 35 mfd I replaced it with a cap of equal capacitance and did recheck it after I installed it to make sure. Is it possible that i put a bad cap on and made it worse I used my meter to check capacitance but that is not a very reliable method is it?

[dtna13]

Thanks to all you guys who replied to my question and those in the future you guys help out a lot and give me a better understanding of what I'm learning.

[hvacrmedic]

The original capacitor was a 35 mfd I replaced it with a cap of equal capacitance and did recheck it after I installed it to make sure. Is it possible that i put a bad cap on and made it worse I used my meter to check capacitance but that is not a very reliable method is it?

The capacitance check function is reliable enough. There are some meters that'll give strange readings on an open cap, but the odds of reading an open cap at anywhere near its rated value are probably a gazillion to one. I perform live tests on existing caps on a regular basis, but not because I don't trust the capacitance check function on my meter. The live test gives me more information (cap voltage) and on a running system it's generally quicker too.

The amperage jump could have been due to a change in conditions while the system was off, position of the amp clamp on the wire, or both. Did you test the old capacitor? Was it out of specs?

[catmanacman]

you should not have any voltage drop across the contactor .

[timebuilder]

A contactor is a switch, and as such, even under load, you should have a MAX of .3 - .5 volts drop across it. Of course, you have to eliminate any additional drop caused by not having a great connection between the meter leads and the terminals of the contactor. If you have to, use alligator clips to hold the probes on the terminals, and test again to get a more accurate reading.

To determine the cleanliness of the condenser coil, measure the difference in temp of the air entering and air leaving. the max value is 30° F. Average is 12- 15°.

34 Subcooling is too high. Someone overcharged the system, perhaps to raise suction pressure because they did not recognize a restriction. This is a common and bad practice.

You might want to print out the list of values to gather that PHM listed. More info can help you to find the real problems, quicker.

[Poodle Head Mikey]

Because 30º is more like "Danger Will Robinson" to me.

PHM
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. . . To determine the cleanliness of the condenser coil, measure the difference in temp of the air entering and air leaving. the max value is 30° F. Average is 12- 15° . . .