Charging with Liquid or Gas? (A Worthwhile Tip)

[Grizzly]

We all know that the fastest way to add refrigerant
is to add it in liquid form.
And the many ways of achieving this have and are, being discussed on this forum.
But I have never seen mentioned the point that in some circumstances.
Initial charging with Liquid Refrigerant, even on the high side can cause extensive damage.
EG.
If you have a water cooled shell and tube condenser or evaporator.
ALLWAYS INITIALLY CHARGE WITH VAPOUR!!
Bringing the system up to it's refrigerants temperature / pressure of around or preferably just above freezing.

Because if you have a system with a poor water / glycol flow.
There could be insufficient heat load around the internal copper tubes.
And adding liquid Refrigerant can cause Ice Crystals to form around the tubes and crush them.

This not fiction I have seen it done.
In fairness it was a Frigate in dry dock, where one of the chillers had major repairs which involved removing the refrigerant.
This was then re-added upon completion of the repairs.
Sadly the Engineers concerned had forgotten the fact that the condenser cooling medium was Sea Water.
As the ship was in dry dock being refitted there was no sea water available to in this case to absorb the negative temperatures being applied!
The End result was a very costly Condenser change.

This could just of easily happened if say you had poor water flow and the flow switch was still made.

If you charge from scratch through the Evap, then the same could happen there.
So the simple answer is charge with vapour (or liquid that is flashed off whilst it enters the system)

Until your system has reached that refrigerants
pressure / temperature for just above freezing!

Sorry it's so long winded Guy's, but I couldn't think of a shorter way of explaining what I mean!

Hopefully someone will benefit from this snippet?
Cheers Grizzly

[The Viking]

Ok, sound advice as always Grizzly.

But be aware, with modern blended refrigerants, unless you charge a whole cylinder you will have to take it from the cylinder in liquid state.
Otherwise you would change the mixture and the characteristics of the gas.

The trick in those circumstances is to charge slowly enough so the liquid boils off before it reach any critical parts of the system (until you reached the refrigerant's saturated pressure at 0 degrees C, after which you can whack it in to the liquid side of the system).

[Grizzly]

OK, sound advice as always Grizzly.

But be aware, with modern blended refrigerants, unless you charge a whole cylinder you will have to take it from the cylinder in liquid state.
Otherwise you would change the mixture and the characteristics of the gas.

The trick in those circumstances is to charge slowly enough so the liquid boils off before it reach any critical parts of the system (until you reached the refrigerant's saturated pressure at 0 degrees C, after which you can whack it in to the liquid side of the system).

Ditto with the sound advise Viking.
With the described above in mind you could also minimise the risk by ensuring that the cooled or cooling medium is flowing.
Cheers Grizzly.

[expat]

Definitely a worth while tip. I never would have thought of this.

Are you talking about a little water still being in the shell, and when the liquid refrigerant starts evaporating it freezes the water which upon expanding crushes the refrigerant piping or is it a more complicated problem?

[Grizzly]

Definitely a worth while tip. I never would have thought of this.

Are you talking about a little water still being in the shell, and when the liquid refrigerant starts evaporating it freezes the water which upon expanding crushes the refrigerant piping or is it a more complicated problem?

Spot on!
In fact the less water present the higher the risk in creating the ice crystals needed to crush the tubes.
I first encountered this problem cutting my teeth on Halls Aqua-chills!
But there are plenty of other scenarios where it could apply.
Grizzly
Grizzly

[NH3LVR]

I prefer to charge through the liquid line. Shut off the King (Receiver) Valve and put the liquid in through a port in the liquid line. I worked in a plant that had been charging R502 gas into the suction on four 60 Horsepower units for years. It took forever.
It was a yearly thing as we took the refrigerant out at the end of each season. I installed the valves and we could recharge all four in the time it took to do one through the suction.