Pump-Down Procedure....

NY_Rob

Need to relocate one of the indoor units on my Panasonic mini-split.

In looking over the Pump-down procedure in the service manual- it outlines the procedure for all four zones but makes no mention if you just want to disconnect one zone. I will be disconnecting "Zone A".

Question 1) With that in mind- should I just carry out the procedure as outlined for all four zones then just re-open the service valves for the three remaining zones once I pull and cap the disconnected zone?

Question 2) "Start cooling operation".... does it matter which indoor unit I activate to start the "cooling operation"? Do all four indoor units have to be active/on? Can I activate just the zone I will be removing (Zone A)?

Thanks!


Service manual excerpt follows.....

unclejohn

It should work if none of the others zones are calling for cooling. I have no experience on mini splits due to being and old dog. I guess you have to pull the disconnect to stop the unit when the pressure gets low. I guess there is no low pressure cut off on those units which seems odd.

HVACNUT

Do you know if any refrigerant was added during the installation? Pretty much need to be D.O.B.A. with the refrigerant charge.
You will need to pump down/recover all 4 circuits.
The correct way is to recover, nitro, evacuate, and weigh the refrigerant back in in ounces.

NY_Rob

^ Thanks @HVACNUT...
No refrigerant was ever added, the system was under the 150' lineset factory precharge length even with all four indoor units setup.

One indoor unit is getting relocated to a different room and the lineset will be maybe 25' now vs the 40+ ft lineset it had for the past 5yrs. The other three indoor units are staying where they are now. Their linesets will not be disturbed.

I was thinking that I could use the outdoor unit's pump-down procedure- cap & remove the one indoor unit and it's lineset. Set it up in it's new location with the shorter lineset, N2 purge and triple evac just that circuit, then open it's service valves releasing the captured refrigerant (from the condenser pump-down procedure) in the outdoor unit.

If you're saying that I have to recover all the refrigerant from the condenser and recharge by weight.... I will have to have a HVAC tech come in and do that. I have basic tools, a (two stage) vacuum pump, a micron gauge, manifold set and a nitro regulator... but I don't have a refrigerant scale or R410a tank to recharge.

newagedawn

mini splits are one circut even tho there are 4 evaps, you need to reclaim all refridgerant and recharge, weigh in the charge as mini splits are very sensitive to charge, and dont forget to pull a vacuum

ratio

Doesn't need to be that hard. Kill the power to the system, close only the valves on the lineset to move, recover only that lineset into another lineset, do your work, vac it, & open the valves back up. You shouldn't need to recover the whole machine. I've done this before without issues. I don't think you'll need to weight in a charge unless you have a booboo while recovering. (Done that before too!)

Note that a recovery machine is necessary either way you go, as a scroll can't safely pull down into a vacuum. The pumpdown feature is only a quick start on recovering the system, not a replacement for it.

NY_Rob

Thanks to all who replied!

Since it's clear I'll have to have my HVAC tech come over after installing the new LG mini-split (on the other end of the house) to add some refrigerant due to lineset length... I'd like to do it all in one visit if possible.

With the above in mind, can I:
-Use the Panasonic mini-split pump-down procedure then remove the one lineset/indoor unit that needs to be moved... then seal & cap it's service valves. In the meantime I would still be able to use the other three indoor units connected to the Panasonic condenser.
-Once the new LG mini-split is setup, have the HVAC tech come over and add refrigerant to the LG and at the same time recover and weigh the refrigerant from the Panasonic mini-split with the fourth zone now connected up in it's new location.

NY_Rob

Wanted to re-visit this thread since I'll probably be disconnecting the one zone (zone A) that's gong to get relocated this weekend....

Since I'm only disconnecting one of the four zones- can I close the service valves (both liquid and gas) for the other three zones then perform the pumpdown procedure using the outdoor unit for just the one zone I'm temporarily removing?

The procedure would be as follows:
-Close liquid and gas service valves for zone B, C, D..
-Close liquid service valve for zone A.
-Run compressor in cooling mode till zone A gas service valve reads between -15 to -30 in Hg on manifold set.
-Close zone A gas service valve.
-Disconnect power at compressor.
-Remove linesets from zone A, cap liquid and gas service valve ports.
-Open service valves for zones B, C, D to resume normal operation with remaining three zones.

Thanks... Rob!

ratio

Is it a scroll compressor? They can't be run very far/at all into negative pressures. The winding start to arc over & pretty soon you need a new compressor. It's my understanding, however, that recip compressors don't suffer from this.

How big is the charge? If there's an extra 10 lbs of juice in there, you might have a hard time getting it all into the condenser. I think you could leave the liquid valves open on the heads that aren't moving, that would give you more volume to stash the juice in.

pecmsg

I would not use the compressor to pump down that low.
1) If theirs a leak you've contaminated the entire system
2) The compressor in that system may not pull down that low.

Follow the manufactures pump down procedure, recover remaining refrigerant into a recovery tank.

Personally for the small amount in one head just recover into a clean tank.

ratio

You can get away without a recovery juggy by recovering into one of the other linesets; but honestly if it were mine I would just pump it down to zero & loose whatever fumes were in the line.

NY_Rob

Thanks everyone... it was super easy... took 4min

Ran the zone I was removing for a few min till it got cold... closed it's liquid line service valve... watched the vapor line pull down to -30in Hg on the manifold gauge set (took four min)- closed the vapor line service valve, pulled power on system. Didn't see any pressure rise after a few min...Done.
Removed the indoor unit and bracket, taped over the hole in the wall. Disconnected the tray cable at the outdoor unit. Whole thing took 25min or so.
A little sheetrock and paint work/siding work and that room is done.

This weekend I'll reinstall that indoor unit in it's new location... plan on reusing the lineset (will cut re-flare ends) and tray cable, only need about 20' out of the 45' available.

Thanks again to everyone who offered advice...

NY_Rob

Followup.....
Installed the above removed indoor unit in it's new location last weekend.
Ran the leak/bubble test at 400PSI with nitro overnight... no leaks. Triple evac'd and nitro'd the (reused with new flares at both ends and now 20' shorter) lineset.
Final evac for just one lineset started at 225 microns and finished at 240 microns 20min later. Had to end the test 10min short due to rain!
Ran the indoor unit with a digital thermometer on top and bottom air ducts.. 24F split in temp, it was 60F outdoors and 70F indoors.
The other three indoor units running nominally.

Think I'm done here!

briski58

Hello I have a similar task to complete with my Mitsubishi Mr Slim 410a system / 3 heads and 1 compressor. I turned to Angi's list looking for someone to recover the refrigerant so that I could move the compressor to repair water damage to the home. I have been told by more than one technician that due to a reverser valve that they cannot just recover the refrigerant. Others have told me to just move the unit as far as possible with lines connected.
I did read the posts on this subject and there was mention of a recover machine. Will such a machine be needed to complete this task? I'm looking for any professional advice I can get. Thank You

pecmsg

You can move it with the lines connected but that’s about it. 

Anything to do with hooking up gauges. Needs to be done by a licensed technician. EPA Regulations. 

briski58

Thanks for the reply. I'll probably be using this site to find a qualified tech. Moving it with lines attached sounds too risky to me. One careless worker while doing repairs could cause me big headaches.

HVACNUT

Forget the pump down. Reclaim all into a fresh cylinder on a scale. After the triple vac and reconnect, it will need a few ounces of new refrigerant because you'll never get it all back out of the reclaim jug.
Cover all refrigerant pipe openings. No dirt, dust, pollen, nothing gets in.
Mark all pipes and wires A,B,C etc.