Manifold Guages

[jakb21599]

What are some of the causes that the needle bounces irriratically on the high side gauges. It,s on a 5 hp semi hermatic compressor. The system is working fine and at temp. 35F
SC is 11 and SH is 36. Uses R22 gas for a meat case display.
The last time i had guages on it the needle did not bounce like it is now. It was steady. Now it is bouncing around so much that i cant even see the needle at times. The best judgment call on looking at it when you can see the needle is around 275-300 psi. low side is 26 psi and steady. site glass after liquid line filter is full and no bubbles. It was during a hot pull down, but once the case reached temp the bouncing did not stop. just slowed down, but not steady.
Just curious as to why it is doing this and should it be a concern? thanks for your help

[monkey spanners]

On reciprocating compressors is normal to get gauge flutter every time the piston reaches the top of the cylinder, the degree of flutter depends on a lot of things, how hard the system is working, if the connection port is only just open or wide open, etc.
If you can connect onto the liquid line instead of the compressor discharge valve you should have a much more stable pressure reading.
I use oil damped gauges to stop this, but even the sometimes there is a little movement.

[jakb21599]

I was thinking about getting the field piece sman 3 digital gauges. Will the digital gauges bounce around like the regular gauges ?

[jakb21599]

On reciprocating compressors is normal to get gauge flutter every time the piston reaches the top of the cylinder, the degree of flutter depends on a lot of things, how hard the system is working, if the connection port is only just open or wide open, etc.
If you can connect onto the liquid line instead of the compressor discharge valve you should have a much more stable pressure reading.
I use oil damped gauges to stop this, but even the sometimes there is a little movement.

would thier be any other reasons why that i need to investigate other than what you had said ? Just want to be on the save side and not loose a compressor for something that i may have could prevented. Thanks

[martinw58]

you cantry back seating the valve slowly untill the bouncing stops

[jinxycat]

yup what he said, just crack the service valve, you will see the flutter reduce as the valve is closing, also you cant beat a set of refco manafolds

[glenn1340]

Just a word of caution, excessive pulsataion will damage the bourdon tube in the gauge. As others have said, try just cracking open the valve or maybe a dedicated glycerine filled gauge that`ll smooth out the pulsations