Tick-tick-tick noise while off?

[Larry2]

What causes this noise several minutes after shutdown? I see this on two new systems. Both systems were properly evacuated during installation. I evacuated the second system down to 400 torr and valved it off and watched the gauges. The first system was on outdoor heat pump section only. The second system is all new stuff. It has new equipment all around with new piping from end to end. Brazing was accomplished with a steady flow of inert gas. There are no restrictions in the piping. I used a tubing bender for the bends and joined the lengths to fit neatly with straight couplings. Years ago, would have put a long elbow where pipes went around corners.

Once the unit shuts off, the outdoor section starts making a tap tap or tick-tick sound a few minutes later. The pressure gauge on the high side reflects this result on the needle. It is as though there is trapped refrigerant somewhere flashing to gas. The vibration is most noticable in the outdoor unit expansion valve.

This seems to occur when the system has been off a while, maybe three to five minutes. I haven't gotten around to installing the optional crankcase heaters. The will be installed before winter.

Superheat, subcooling, gauge readings, temperature readings are all on the mark IMHO. One is a fully matched new system with expansion valve. The other is a mismatched system, also with an expansion valve. They are both scroll compressor systems. They are Rheem/Ruud split system gear. One is 1.5 tons and the other is 3.5 tons.

One system was delivered new nearly empty of refrigerant. I suspected contamination, because the system required 90 percent of a full charge. That is to say, it contained only 10% of the factory supplied refrigerant. I wondered if the service valve had a leak, because the factory had overtightened it. It was really stuck. I worried my hex wrench would snap off in the valve. The second unit balanced to the charging tables to the oz after allowance for the piping length.

These are R22 systems.

[nike123]

Maybe scroll running backward until pressure equalize.

[Larry2]

This is not the typical Brrbpppttt noise they can make at shut down for a moment. This is a tap tap tap or tink tink tink sound it makes several minutes after shut off. The sound is one to several seconds between knocks. It lasts several minutes more at times. The service gauge pointer jumps with each sound.

[Don78]

What are your line set sizes, lengths, and amount of 90os.

[Brian_UK]

Could it be the sound of pipes contracting or expanding?

[Harrison]

I have noticed a ticking noise on split systems in winter when they have been off for a little while, i believe it is migration of refrigerant but its a pretty subtle sound. it can be pretty loud but never put the guages on to see what was happening.

[stefs_cruiser]

Do both systems use the same style of controll?

If it is an electronic expansion valve, it might be driven back to a home possition?
getting ready for restarting

[paddyaircon]

maybe your radio needs tuning?>lol

[nick uk]

daikins have electronic expansion valve clicks back to a diferent position few mins before start up

[SUBCOOLING]

i like daikins i could just rub one

[mad fridgie]

This is not the typical Brrbpppttt noise they can make at shut down for a moment. This is a tap tap tap or tink tink tink sound it makes several minutes after shut off. The sound is one to several seconds between knocks. It lasts several minutes more at times. The service gauge pointer jumps with each sound.

Had a similar problem with a Toshiba(s), it was one with a long indoor coil, the coil would expand and contract, causing the plastic casing to tap, tap the noise travel all the way through the system.
The basic fault was the screws were to tight hold the coil to the case, we loosened of a bit, all cured (many units)

[cadillackid]

if they are electronically controlled, sometimes ive found the computer boards are homing up the EEV, or the reversing valve clocks on and off if the board is reset..
-Christopher