gage set hose on backwards

bill498326 · 04-29-12, 05:36 AM

I installed my first mini split it did not go as planned.

I did a nitrogen purge and then a pressure test at about 25 psi.. I then vacuumed the line set and indoor unit for several hours.

I then released the refrigerant into the lineset , opening both the high and low side valves,and all seemed to be well.

When I removed the gage set hose I discovered that it was on backwards and so the schrader valve was not depressed, meaning that the lineset had not been evacuated.

When I discovered this I did the pump down procedure for 30 minutes, closed the high and low side valves , and vacuumed the lines for 15 minutes and then re opened the high and low side valves.

Am I completely screwed? Did the nitrogen in the lines get into the outdoor unit to raise havoc?

The unit seems to be functioning ok. A very small amount of the r410a refrigerant escaped while I was messing around with it.

BradC · 04-29-12, 09:12 AM

If you had 25 psi in the line set then, yes you will have a considerable qty of nitrogen in there. Please tell me I'm wrong.

If not then you are going to need a friend with a recovery unit and cylinder to get the non-condensibles out.

Edit: could you monitor the pressure when you released the refrigerant?

And another thing. Pump down for 30 minutes?!? Where did that time come from? I'd have thought you'd toast the compressor with 30 minutes of no refrigerant flow.

bill498326 · 04-29-12, 05:24 PM

I could not monitor the pressure when I released the refrigerant. I could hear it rushing in.

The instructions said something about running the outdoor unit on maximum cool for up to 30 minutes to return all the refrigerant to the unit. I don't have the instructions here with me.

I am pretty sure that there was 25 psi. in the line set.

BradC · 04-29-12, 08:05 PM

Quote:

Originally Posted by bill498326

I could not monitor the pressure when I released the refrigerant. I could hear it rushing in.

The instructions said something about running the outdoor unit on maximum cool for up to 30 minutes to return all the refrigerant to the unit. I don't have the instructions here with me.

I am pretty sure that there was 25 psi. in the line set.

Right. Firstly, to pump down a unit you close the liquid line service valve. You then run the unit in cool mode while monitoring the pressure in the line set. You run it until the pressure drops into a slight vacuum, close the vapor line service valve and shut it off. Should take a couple of minutes at most.

A Hermetic compressor relies on the return of cool vapor to absorb its heat. Without a refrigerant flow, a compressor will rapidly heat up (imagine a compressor drawing a kilowatt and not being able to reject that heat anywhere). As the compressor gets hotter, the discharge (what little of it there is) gets hotter and eventually reaches a point where the refrigerant will begin to break down and generate acids. It's all pretty nasty.

Now, as for your problem. You have two options. You can leave it as it is, which implies you will have a couple of hundred PSI of nitrogen living in the top of your condenser reducing the effective surface area and therefore efficiency. *or* you can get the unit evacuated and re-charged.

This requires a recovery unit and cylinder. You suck all the refrigerant into the cylinder with the reclaim unit. You then leave the cylinder to settle for a few hours (or overnight). Pop your gauge set on the cylinder and note the difference between the bottle pressure and the theoretical correct pressure based on the temperature of the bottle. The bottle pressure will be higher due to the nitrogen, so you vent a small qty of gas from the bottle, lather rinse and repeat until your pressure is correct. Then dump it back into the system.

Now, if you can get your hands on a recovery cylinder and a couple of kilos of dry ice you can do it without the recovery machine.

bill498326 · 04-30-12, 04:39 AM

After reading your post about pumping down a unit, it jogged my memory and I think that I performed approximately the correct procedure.

I was in slight panic mode at the time, but I now remember that the instructions said to close one valve and open the other one turn. The gage needle went pretty close to the peg on the vacuum side of the scale.I think now that it only took a few minutes, but it seemed like an eternity!

I noticed that when the unit runs in heating mode, both the big pipe and the small pipe are quite hot to the touch, and about equal in temperature.

Does this mean that the coil in the indoor unit is filled with non condensible gas that prevents good heat transfer?

How does one use dry ice to take the place of a recovery machine?

BradC · 04-30-12, 05:00 AM

Quote:

Originally Posted by bill498326

Does this mean that the coil in the indoor unit is filled with non condensible gas that prevents good heat transfer?

Possibly. What sort of heat are you getting out of it when it is wound up to maximum?

Quote:

Originally Posted by bill498326

How does one use dry ice to take the place of a recovery machine?

So glad you asked!.

Dry ice sublimates at approximately 77 Degrees C. R410a (Or R22 or Propane) is a liquid at atmospheric pressure at somewhere around 45 degrees C (give or take for the differing gasses).

You take the recovery cylinder and vac it out, then pack it in a cooler with dry ice and wait for it to get really cold (I wrapped the cooler with towels and filled it with alcohol to aid the heat transfer). Simply hook it up to the patient and open the valves. The refrigerant will naturally migrate to the bottle as it wants to condense in the coldest part of the system. Eventually (might take an hour or so) you will note the system pressure ventures toward a vacuum, and you're done.

Now, your system pressure may well not venture into vacuum as you have a snot load of nitrogen in there, and it takes more than dry ice to condense that, but it should pull all the R410a out.

To be honest, if you hook a vacced out bottle up to the liquid line you'll probably suck 2/3rds of the charge out before it even starts to get cold. When I recover my big unit here now, I hook up a vacced bottle to the liquid line and start 'er up in cool mode. The system practically flushes the refrigerant right into the bottle. It leaves much less to pull out for the painstaking (relatively) vapor recovery.

All temperatures given here are rough approximations from memory, however they're close enough that the principle works. I've recovered 3 systems doing it this way (before I bought a recovery machine).

bill498326 · 04-30-12, 04:36 PM

The air coming out of the indoor unit felt toasty warm. The room started out at 60 degrees F and warmed up to 80 degrees F after a few hours.

The dry ice method sounds doable. What happens to the lubricating oil?
Does it stay in the unit, or leave with the refrigerant?

Thank you for all your prompt responses, they have been most helpful.

BradC · 04-30-12, 07:08 PM

[QUOTE=bill498326;21520
The dry ice method sounds doable. What happens to the lubricating oil?
Does it stay in the unit, or leave with the refrigerant?[/QUOTE]

You won't get a lot of oil in the transfer. The trick is to make sure the recovery cylinder is nice and clean, then when you re-charge the refrigerant you do it as a liquid with the cylinder upturned rather than through the liquid port. This ensures everything in the bottle gets bombed back into the system.

04-29-12, 05:36 AM	#1
bill498326 Lurking Renovator Join Date: Apr 2012 Location: delaware Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	gage set hose on backwards I installed my first mini split it did not go as planned. I did a nitrogen purge and then a pressure test at about 25 psi.. I then vacuumed the line set and indoor unit for several hours. I then released the refrigerant into the lineset , opening both the high and low side valves,and all seemed to be well. When I removed the gage set hose I discovered that it was on backwards and so the schrader valve was not depressed, meaning that the lineset had not been evacuated. When I discovered this I did the pump down procedure for 30 minutes, closed the high and low side valves , and vacuumed the lines for 15 minutes and then re opened the high and low side valves. Am I completely screwed? Did the nitrogen in the lines get into the outdoor unit to raise havoc? The unit seems to be functioning ok. A very small amount of the r410a refrigerant escaped while I was messing around with it. Last edited by bill498326; 04-29-12 at 05:43 AM..

04-29-12, 09:12 AM	#2
BradC Apprentice EcoRenovator Join Date: Dec 2010 Location: Western Australia Posts: 148 Thanks: 1 Thanked 48 Times in 34 Posts	If you had 25 psi in the line set then, yes you will have a considerable qty of nitrogen in there. Please tell me I'm wrong. If not then you are going to need a friend with a recovery unit and cylinder to get the non-condensibles out. Edit: could you monitor the pressure when you released the refrigerant? And another thing. Pump down for 30 minutes?!? Where did that time come from? I'd have thought you'd toast the compressor with 30 minutes of no refrigerant flow. Last edited by BradC; 04-29-12 at 09:17 AM..

04-29-12, 05:24 PM	#3
bill498326 Lurking Renovator Join Date: Apr 2012 Location: delaware Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	I could not monitor the pressure when I released the refrigerant. I could hear it rushing in. The instructions said something about running the outdoor unit on maximum cool for up to 30 minutes to return all the refrigerant to the unit. I don't have the instructions here with me. I am pretty sure that there was 25 psi. in the line set.

04-30-12, 04:39 AM	#5
bill498326 Lurking Renovator Join Date: Apr 2012 Location: delaware Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	After reading your post about pumping down a unit, it jogged my memory and I think that I performed approximately the correct procedure. I was in slight panic mode at the time, but I now remember that the instructions said to close one valve and open the other one turn. The gage needle went pretty close to the peg on the vacuum side of the scale.I think now that it only took a few minutes, but it seemed like an eternity! I noticed that when the unit runs in heating mode, both the big pipe and the small pipe are quite hot to the touch, and about equal in temperature. Does this mean that the coil in the indoor unit is filled with non condensible gas that prevents good heat transfer? How does one use dry ice to take the place of a recovery machine?

04-30-12, 04:36 PM	#7
bill498326 Lurking Renovator Join Date: Apr 2012 Location: delaware Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	The air coming out of the indoor unit felt toasty warm. The room started out at 60 degrees F and warmed up to 80 degrees F after a few hours. The dry ice method sounds doable. What happens to the lubricating oil? Does it stay in the unit, or leave with the refrigerant? Thank you for all your prompt responses, they have been most helpful.

04-30-12, 07:08 PM	#8
BradC Apprentice EcoRenovator Join Date: Dec 2010 Location: Western Australia Posts: 148 Thanks: 1 Thanked 48 Times in 34 Posts	[QUOTE=bill498326;21520 The dry ice method sounds doable. What happens to the lubricating oil? Does it stay in the unit, or leave with the refrigerant?[/QUOTE] You won't get a lot of oil in the transfer. The trick is to make sure the recovery cylinder is nice and clean, then when you re-charge the refrigerant you do it as a liquid with the cylinder upturned rather than through the liquid port. This ensures everything in the bottle gets bombed back into the system.