R404A degradation (?)

[phil68]

Has anyone else come across this? We have quite a few Porkka walk-in freezers in the field & I've found that when I've been called to one that's struggling & everything else checks out if I change-out the refrigerant it restores performance back to where it should be. I usually know when it's needed because the gas smells like Frazzles crisps

[chillin out]

Are you sure it wasn`t short of gas?

And in changing the gas you inadvertantly repaired the fault?

Im not saying you were wrong, just giving you the chance to elaborate.


Chillin

[phil68]

Are you sure it wasn`t short of gas?

And in changing the gas you inadvertantly repaired the fault?

Im not saying you were wrong, just giving you the chance to elaborate.


Chillin

Nope, definitely not short of gas, I've had to do it quite a few times now, even on units that are still factory sealed. Fellow engineers have had to do it too. It only seems to afflict Porkkas, strangely.

[chillin out]

How did you put the gas back in?

Did you wiegh it?

The reason I ask is that Porka Freezer rooms have a habbit of not putting the correct gas charge in.

The label says 1kg but it really needs 1.3kg


Chillin

[phil68]

How did you put the gas back in?

Did you wiegh it?

The reason I ask is that Porka Freezer rooms have a habbit of not putting the correct gas charge in.

The label says 1kg but it really needs 1.3kg


Chillin

Hi Chillin, yep I'm aware of the incorrect refrigerant weights that Porkka stick on their rooms, I generally recharge them by 'feel'.

[phil68]

Also, the suction pressures are roughly the same prior to & after the gas change-out, which to me would indicate that the unit wasn't S.O.G.

[Johnny Rod]

What were the suction and discharge pressures before recovering the gas? Was it oily or notice anything else?

[phil68]

Did you carry out a leak test?

R404a is a blend of different refrigerants, each one separating if there is a vapour leak. The pressure may seem to be the same but the refrigerant has lost one or more of its components.

This problem normally arises when engineers top up the charge without checking for leaks and the blend is then incorrect or vapour charging only. Replacing the full charge in the liquid phase then rectifies the situation.

Yep, I usually check for leaks as a matter of course. When the gas smells like Frazzles crisps I change it out & it restores performance. It's usually O.K. after that & there's a couple of them running fine after doing this 18 months on. But only on Porkka walk-in freezers. Go figure

[Johnny Rod]

Welll you seem to have the nuts and bolts side covered and it looks like a recharge seems to fix it, so it's down to the refrigerant. You could get the old refrigerant analysed next time you find one of these, might help.

[Rob S]

Find this alot in wet systems. The HFC refrigerant, accually the POE, has a putred smell to it. In high load, undersized, or undercharged systems you can end up with plugged valves and yellow (or worse looking) oil. Only way I've found to solve this is to change the refrigerant to, drier, clean out the valve, then tripple evac. Not to mention any system changes if needed.