Brazing in a fully charged system

[rubafish]

If you use a couple of ball valves in line with a liquid line dryer, one before and one after the dryer so you can isolate and change the dryer without having to recover the charge, should you use a flare connection to attach the dryer or braze it in? If you braze the dryer in how far from the valve would you place the dryer in order not to adversely effect the refrigerant in the liquid line while brazing?

[KeyResults]

The ball valve thing seems to me a bad practice unless you have a schrader on the dryer to evac.

I never like fittings where I can solder. Adds cost in brass fittings.

[Green Mountain]

If you use a couple of ball valves in line with a liquid line dryer, one before and one after the dryer so you can isolate and change the dryer without having to recover the charge, should you use a flare connection to attach the dryer or braze it in? If you braze the dryer in how far from the valve would you place the dryer in order not to adversely effect the refrigerant in the liquid line while brazing?

If you shut off the valves on either side of the drier you are still going to have refrigerant in the drier and the connecting pipe. You have to relieve that pressure/refrigerant before you put the heat to the drier.

That little bit of refrigerant will build a lot of pressure when heated. You should always vent any vessel when brazing. If you shut the valves and drilled a hole in the drier that would be safer. But I reccomend using a flare drier to do what you want to do.

Most condensing units are properly valved so that you can pump-down the system and change the drier without losing the charge. So I don't know why you are trying to do what you are describing.

[tocss]

sounds like a bad idea.you are just asking for problems what if someone or something closed the valves. and you cant be certain that all moisture or air are not going to be removed from the system.and if using fittings that thay might leak over time.best bet would be to remove the refrigerant. or pump down. braze the new dryer in. nitrogen. and vac the unit.then weight in new refrigerant.

[wildtech]

Iv'e seen that done alot on large cond units but they all had schrader ports, what I did was recover the refrigerant into the suction line, take apart the filter housing replace the filter core(s). Evac and move on

[jpsmith1cm]

Iv'e seen that done alot on large cond units but they all had schrader ports, what I did was recover the refrigerant into the suction line, take apart the filter housing replace the filter core(s). Evac and move on

Ditto that.

On the larger equipment that I work on, removing the entire charge is largely impossible and definitely impractical.

On smaller, residential sized condensing units, it is possible, but what would it be worth? If you are that worried, a single liquid valve, a flare drier and a few tools would accomplish the same thing.

Heck, if you wanted to get REAL fancy, you could pipe a 3 valve bypass arrangment, allowing you to change the drier 'on the fly'. I have that setup on some of the newer equipment. No need to do a big pump down, just close 2, open 1 and pump it out. Driers in and out in maybe 15 minutes.

[rubafish]

Let me be alittle clearer on what I'm concerned about. After replacing a locked compressor I want to put in a liquid line dryer to clean up the system and protect the compressor. I want to be able to change this filter at a later date without having to recover the charge so I plan on using ball valves to isolate the dryer from the system. I am concerned that if the dryer is too close to the full charged liquid line on the other side of the ball valve, not the side that the dryer is on, will I expose this line to too much heat while brazing in a replacement dryer?

[t527ed]

how do you plan on flowing nitrogen while brazing in the new drier?

sounds like a bad idea, just pump the unit down at the service valves.

[rubafish]

I would put in some schraders but recovering the charge then replacing the dryer sounds like the best way to go.

[Mr Chesapeake]

What he asked above, how do you plan on flowing nitrogen while brazing in that new drier?

[rubafish]

Through the schrader. This set up would allow me to change the dryer on the fly. I would place the dyer in the liquid line so that it see liquid in both heating & cooling modes. On opposite sides of the dryer I would put a ball valves with schraders on the dryer side which would allow me to recover the refrigerant from the filter before changing. It would also allow me to flow nitrogen while brazing. But I am still concerned about the heat transfer along the liquid line passed the ball valve to the charged side of the system while brazing so I'm not going to do this.

[beenthere]

Use refrigeration valves that require a wrench to shut and open them, along with either filters that have schraders, or install an access fitting so you can check to make sure you have the refrigerant pumped out.

[jpsmith1cm]

If you are that dedicated to changing the drier, install a replacable core type.

No nitrogen needed.

[Green Mountain]

I don't get it. What capacity is this system? Is this a RTU and it has no service valves?

Okay I'm going out on the limb here. If you pump down a system. Have the new drier already to be brazed into the line. Then I would, check and make sure there is no pressure left in the liquid line. Vent the liquid line through the service port of the service valve. Quickly un-sweat the old drier and braze in the new one. Without a nitrogen purge.

Then pull a vacuum. Charge the liquid line. Open the service valve and you are done.

I contend that the liquid line will only have vapor in it during this process. No air will enter the line during this process. Therefore there is no need to purge nitrogen during a simple drier change.

(there this ought to start a discussion.)

[Shophound]

If you are that dedicated to changing the drier, install a replacable core type.

No nitrogen needed.

Ditto that, or go with two refrigeration valves (that must be operated with a wrench) and flare the pipes feeding the drier. Use a liquid line drier with a schrader, or just sweat one onto one of the lines between the valve and the drier if you don't want to be stuck with always buying a drier with a schrader on it.

Caveat with replaceable core driers...install them correctly so they don't become oil traps.

[coolestacman]

putting valves on both side of the drier would require a safety valve to be installed between the valves so the drier doesn't become a bomb

[frozensolid]

I don't get it. What capacity is this system? Is this a RTU and it has no service valves?

Okay I'm going out on the limb here. If you pump down a system. Have the new drier already to be brazed into the line. Then I would, check and make sure there is no pressure left in the liquid line. Vent the liquid line through the service port of the service valve. Quickly un-sweat the old drier and braze in the new one. Without a nitrogen purge.

Then pull a vacuum. Charge the liquid line. Open the service valve and you are done.

I contend that the liquid line will only have vapor in it during this process. No air will enter the line during this process. Therefore there is no need to purge nitrogen during a simple drier change.

(there this ought to start a discussion.)

I agree, no need to over complicate things.

[crmont]

Flare it in. Ball valves/schrader port optional. Allows for any type of swap later.

[Joe Harper]

I have done this on voyager units. Place a ball valve on both sides of the drier, and braze in flare nut stubs. If it is a LL drier, use a "t" and braze in a pressure port. On the suction side, use a drier with a schrader port in it.

It is much cheaper for the customer to do this rather than pay for another recovery, and vacuum.

[Joe Harper]

I don't get it. What capacity is this system? Is this a RTU and it has no service valves?

Okay I'm going out on the limb here. If you pump down a system. Have the new drier already to be brazed into the line. Then I would, check and make sure there is no pressure left in the liquid line. Vent the liquid line through the service port of the service valve. Quickly un-sweat the old drier and braze in the new one. Without a nitrogen purge.

Then pull a vacuum. Charge the liquid line. Open the service valve and you are done.

I contend that the liquid line will only have vapor in it during this process. No air will enter the line during this process. Therefore there is no need to purge nitrogen during a simple drier change.

(there this ought to start a discussion.)

Most commercial package units dont have service valves.