Why would an A/C draw less current than normal and not work well?

[star882]

I'm troubleshooting a 4 ton Goodman A/C that has lost some performance (has difficulty cooling down house during the day). I already replaced the filter, cleaned the condenser, and inspected the fans. When I checked the condensing unit, it specs 19.7A but actually draws 14A. Voltage is normal (speced for 240v, measured very close to 240v). Near the indoor unit, there is a "liquid flowing" sound that varies periodically, so I think the TXV might be oscillating.

The A/C is just over a year old and worked great when it's new with similar weather and load.

[Peter_1]

Hearing a gissing/sissing sound can mean that the TXV isn't fed with 100 % pure liquid.
Lack of refrigerant perhaps.

What are your measured pressures and temperatures?

We have a Dutch quote for this
"meten is weten en gissen is missen" or measuring is knowing and guessing is missing but this doens't rhyme very well in English. :D

[The MG Pony]

Ah good you did sign up here! thees guys aut to help ya out!

oh and Wealkomen

[Lc_shi]

Less current means less power consuming,if the work is in normal state,which usually means less refrigerant in the sytem. Peter's experienced guy, i believe his judge is all right:)

regards
LC

[The MG Pony]

My votes on the low refrigerant as well due to the reduced current draw, that was the tip off and why I asked on another forum to see the Amperes going through.

But then again I have all so seen some stupidly simple things generate odd and misleading symptoms. So we shall await for the others with more experience to speak!

[MadApprentice]

Did you know that if your evap filters are blocked, the fan actually draws less current? I thought the college teacher was talking sh.it, untill he took us to the work shop and put a clamp meter on a fan then removed the filters and replaced them with ply wood. The reason? The fan has less air to move so therefore does less work so therefore draws less current. Dont believe me? Try it sometime!!!

[Peter_1]

Madapprentice, has somebody told here the opposite?
Star882 was talking about the compressor.
But, it's a good idea your teacher showed you this in practice. I think this man/women stood once int he field as a tech. Am I right?

But another question for you: what happens with a centrifugal fan when you remove it's outlet completely, so you remove the tube or the flex duct on that fan, what will happen then?

And a second one: with an axial fan - like the one your teacher was showing you I suppose - mounted in a condensor and the condensor coil is completely blocked due to dirt and we have hot weather, why is there a big chance that the motor will burn?

If the filter blocks in the indoor unit, what will happen to the current of the compressor and why?

Try to figure this out.

I already noticed you're not an average apprentice, you want to know why and how of what your learn and you don't believe allways what they're saying there in front of you.
That's for me the right attitude.
Don't just try to memorise what they learn you but try to understand it (like you do now and which is mostly the undertone of your questions), much better and you will never forget it.

[MadApprentice]

Well, i noticed that when theteach removed the access panel the current draw increased.

I realise that having blocked filters isnt a good thing, it would cause the motor to burn out from overheating due to lack of air flow over the fins on the motor.

No one here has told me the opposite, in my youthful ignorance , i just thought that having blocked filters cause more current draw, not less. I have a long way to go yet!

[MadApprentice]

I tell you what though,we learnt the three fan laws today, and having played around with the equations, i finally got the understanding! But it nearly sent me loopy in the process!

[Peter_1]

But another question for you: what happens with a centrifugal fan when you remove it's outlet completely, so you remove the tube or the flex duct on that fan, what will happen then?

And a second one: with an axial fan - like the one your teacher was showing you I suppose - mounted in a condensor and the condensor coil is completely blocked due to dirt and we have hot weather, why is there a big chance that the motor will burn?

If the filter blocks in the indoor unit, what will happen to the current of the compressor and why?

Try to figure this out.


You already thought on the answers?

[MadApprentice]

Hang on give me time !