Carrier condenser unit, loud buzz on start

SlamDunk

Hello All,
I noticed our 2011, 16 SEER, 3 ton Carrier condenser unit has an audible buzz on start up then it quiets down after 3 seconds. The buzz wasn't always there, just since last summer. I wouldn't be thinking about it right now if it weren't for the unit not starting on t'sat demand last night (neither fan nor compressor but I could feel fan trying). I replaced the start capacitor and everything fired right up and has been working fine since. Initial buzz is still present. Air temp out of vents is around 65-68 deg F.

It isn't the contactor or loose metal. It sounds like the compressor struggling to start. Is this normal with age?

mattmia2

did you measure the voltage at the condenser and look at the terminations to make sure one of them isn't loose/burned?

SlamDunk

Terminations look new and felt tight. No discoloration or evidence of burn marks. I didn't take any electrical measurements because it was just prior to bed time and large bugs were flying around my lantern.

I will measure volts and current draw after work.

ratio

I might throw one of those 2-second acid tests on it also. If it is a start issue with the compressor, it may have gotten things too hot already.

SuperTech

If possible test out the dual capacitor if your meter can measure microfarads. You might need a hard start kit if your unit isn't equipped with a start capacitor.

SlamDunk

2 second acid test?

It can and I will. the cap didn't have any bulge to it. I do not know if it has a hard start kit. None was added after purchase. I have heard bad things about them.

ChrisJ

How about a youtube video of it?

Is this a 2 stage scroll compressor?

SlamDunk

I don't have one but this is comparable. Line set goes up 12 feet and over 8 ft.

https://www.youtube.com/watch?v=L8JrXbpvP9w

ratio

https://www.johnstonesupply.com/storefront/product-view.ep?pID=B13-043.

I try and always have a few of these on hand, to help me decide if I'm going to throw the digital manifold on a system, or not.

SlamDunk

ratio said:

https://www.johnstonesupply.com/storefront/product-view.ep?pID=B13-043.

I try and always have a few of these on hand, to help me decide if I'm going to throw the digital manifold on a system, or not.

I think I'll pass. That's above my ability.

@ChrisJ It is not a 2 stage compressor.

ChrisJ

SlamDunk said:

ratio said:

https://www.johnstonesupply.com/storefront/product-view.ep?pID=B13-043.

I try and always have a few of these on hand, to help me decide if I'm going to throw the digital manifold on a system, or not.

I think I'll pass. That's above my ability.

@ChrisJ It is not a 2 stage compressor.

How are the compressor mounts?
All screws and bolts tight?

Any tubing rubbing on something it shouldn't?

SlamDunk

I'll have to check compressor mount bolts in the day light. Negative on everything else.

unclejohn

Is it a Bristol compressor. Give complete model number.

SlamDunk

Well, it sounds worse than I remembered. So much so that my wife was concerned enough to send me a video.

https://youtu.be/3jx-qtoiluE

Condenser unit is. 24ABC636A003

Ill be home to dig deeper in an hour.

SlamDunk

The video sounds worse than in person. Cant hear it from ten feet away. The cap died last night as measured <1microf. Volts 120 to ground, 240 ph to ph. Running load amps to compressor is 8A on each leg. Everything nice and tight. I'll add rubber pads under it. Sits direct on pad.

I'm going to call it normal operation and move on to my next problem. Appreciate the suggestions!

EBEBRATT-Ed

Contactor loose connections hard start kit

mattmia2

What about maybe burned contacts in the overload from when it wasn't starting with the bad cap?

SlamDunk

Contactor is fine.. actually, i replaced it a month ago for this buzz.. steady volts on top and bottom. The cap literally failed and found within an hour of failure