r410a leak detecting / get working again.

[phs]

ok iv got a few thoughts id like to bounce around for the best way to approach this.

domestic a/c 8kw reverse cycle .

leaks detected 5/8 suction line compression join. only on high pressure heating cycle. before lines where charged it was holding 1500 kpa presure nitrogen steady over a week
(regulator would not pump past 1500kpa)
still operating correctly heating and cooling works fine, temp drop over coil is good.
but better getting it sorted now rather than later. installed a year ago.

approach tactic 1. store gas back into outdoor unit. tighten join, apply oil or reflare ? re test with nitrogen 400psi over night. or 600psi for an hour. (problems i can see, nitrogen can leak through the valves and mix with gas at those pressures ???). vac down.. hold below 400 microns for 30 mins open valves run unit.

approach tactic 2. reclaim gas (i only have old gas cylinder) pump up as stated above
fix leaks hold pressure. re gas with new gas.

so id want to take tactic 1 but if people think with a new MHIAA unit that nitrogen could sneak by the valves and mix with the r410a its not really worth the risk..

[Tesla]

Hi phs I would personally go for option 2 to save the possibility of doing the job twice. If it was the old R22 and had a fitting to purge non condensables (into a bottle) then it would be different.

[phs]

yeah i dont want to do any thing twice.

ok so ill get the gas out first, what about my testing procedure ? is it better to hold 400psi over a few days or 600psi for a few hours with the gauges connected that was no gas gets lost disconnecting re connecting through the service valve.

just want to make sure its sorted first time and for good

[stufus]

I would pump it down to the condenser. Be sure you dont pump down to vacuum due to the leaking flare. The valves on the unit are rated for system test pressure passing shouldnt be an issue providing the install was well done and no swarf was leftin the pipe work. With regards test pressure 600psi is fine for 1 hour test indoor and out door flares and any joints along the pipe run. Vac it run it and add refrigerant if required to replace lost charge.
Cheers
Stu

[phs]

thanks stu...

ill leave a little with of gas in it so no air can suck back into the unit...

there is no swaft it was all cut with tube cutters and blasted with nitro after purging.
600 for an hour cheers ...

[phs]

It's got me stumped it was leaking from a flare joint on heating the other day .. Now I can't get the same joint to leak at 600 psi ..

[Tesla]

phs it could be a different type of leak such as temperature or vibration dependent leak - what was the conditions just before you detected the leak?
You could try the (wrap leak area in a plastic bag with tape supporting) test and come back a few hours later, slice a little hole in the bottom of bag then check for leak with detector.

[phs]

Ok good idea I nipped the joint up with a bigger spanner got only the slightest turn out of it ... I vacuumed it down to 200 microns and started it up I noticed 200 psi closed by the time the inverter ramped right up it was at 60 psi, is that a tad low ?? This unit is at my place and I do have a second exact same unit in the lower part of the house I might check to see what it drops to when running .. It's got me buggered 600 psi for 2 hours spit on vacuumed down to 200 microns and held it fine. how common is this leaking while running only ??

[phs]

It definitely not running right only half the normal temp drop over the coil when running .. I'll have to get an empty cylinder and weigh it but it will definitely be low