equalizing time??

[philjd26]

hi,
on a vrf system say with about 25 units off it, whilst pressure testing field pipe work, do you allow for equalizing time...??

iv a real pup on my hands here, the system is fairly big with excessive pipe runs...i left the system at 35 bar last night and it had dropped 5 psi...

i am leaving it again tonight and hoping it equalized...there are bs boxes etc..but thing is i fed nitrogyn down all 3 pipes and enabled all units in cooling.

also 4 degree temp differance between before and after pressures...

i am going to be chasing this tommorrow,shyite!!!:mad:

any thoughts??

[DEVIL]

Hello
The problem is like this,mainly all VRV/F s indoor units and bs boxes come with pre seated all expansion valves to open, so the equalization process should take only minutes , but if you gave power to the indoor units, everything is reseated to normal working process.
So to do a pressure test after that you have to give power, to the outdoor unit, and in the manual you can find how to set the unit to "refrigerant recovery or pressure test" or however the process is called, and that dose the thing that prepares the unit to do like they came from the factory.

And the temperature influence on the nitrogen is like this, for 10 deg C derivations you have 1 bar pressure modification at 39 bar testing pressure.

But it's important that the temperature is modified were the pipes run, or make an average not the outside temperature.

[philjd26]

hi devil

thanks for reply, i might be in luck according to your statement. i made adjustments on outdoor to open all valves an pmvs ,however did not adjust indoors..... the outdoor units were exposed to the ambient change of 4 degrees so might have got a little drop on this and with an extended equalize time it could be (i hope) ok in the morning...

i watched pressure yesterday @ 30 brg for 6 hours and did not drop.. i decicided to up the pressure to 35 for the night @ 35 brg..left sit for an hour, recorded pressure and headed off..

came back and 5 psi down.. fingers crossed it will hold..

rgrds phil

[marc5180]

P1/T1 = P2/T2..... You could work it out using this formula


Edit...What were your temperatures last night and today?

[philjd26]

7c yesterday and 2c this morning...

[marc5180]

Ok by using that formula and with a pressure of 35bar, if it had dropped to 2 Deg C then your pressure this morning should have been 34.375Bar.

[philjd26]

Ok by using that formula and with a pressure of 35bar, if it had dropped to 2 Deg C then your pressure this morning should have been 34.375Bar.


thanks marc, looks like i could be ok...

rgrds phil

[defender1be]

maybe stupid remark, but have you made the system vacuum before you put nitrogen on it?

[nike123]

maybe stupid remark, but have you made the system vacuum before you put nitrogen on it?
Why would you do that? What is the point of vacuum drying when you don't know if your system is air tight?

[1torr]

Hi, perhaps he means recovering remainder of refrigerant until say 5 inches achieved and then pressure testing. If there's a couple of psi pressure of refrigerant in it still before pressure test, it could cause more of a pressure/temp change.

[nike123]

Hi, perhaps he means recovering remainder of refrigerant until say 5 inches achieved and then pressure testing. If there's a couple of psi pressure of refrigerant in it still before pressure test, it could cause more of a pressure/temp change.


hi,
on a vrf system say with about 25 units off it, whilst pressure testing field pipe work, do you allow for equalizing time...??


But we are speaking here about commissioning new VRF system. There is no refrigerant left in pipes since it is not introduced yet.

[1torr]

Hi, I didnt see anything in his post to say it was pressure testing a new install

[nike123]

Hi, I didnt see anything in his post to say it was pressure testing a new install
Yep, you are right, my mistake! I saw something what was not there.:confused: