Problem with R409A system

[bennybluetoes]

Hello all! Need some help. I have been working on a R409A system, it is 130 psi head, and around 27 pound suction. First call out I got was unit was tripping out on lp, drier was 100 years old (as always), moisture in system, tx had iced up so I replaced tx and orifice (probably didnt really need to) and did some filter changes every couple of weeks (ran fine). But customer had complained that evap always ices up (for last four years) . I know if unit is to small it will ice up, but checked unit, not to bad could be a little bigger but power is and issue, but distributor on this system will ice up about one minute after running, and evap coil will ice straight away as well. Now i have new drier, only other thing between drier and valve is sight glass, I have new tx valve, correct orifice (I have checked). and recently bypassed heat exchanger because I thought it may have had a small leak and was not getting full liquid line. But no joy! Distributor is not blocked. So would anyone know why this system would ice up so quickly? It is really starting to do my head in.

[nike123]

What is superheat, subcooling, air temperatures, evaporator fins distance? Make full measurements if you wish some well taught answer!

[chillyblue]

Check air flow over evap, (fan rotation), is the cond unit oversized e.g evaporating far to low with a big TD over the coil, this could cause icing, other thing to check is the humidity in the room far higher than it should be???

CB

[kooler]

Just about every system I've used R409a in ran with a head pressure of 150-180psi range to get satisfactory suction pressure and system charge... The sight glass didn't always clear up either but there's too many variables to address here without more data like nike is talking about...

[taz24]

Hello all! Need some help. I have been working on a R409A system, it is 130 psi head, and around 27 pound suction. First call out I got was unit was tripping out on lp, drier was 100 years old (as always), moisture in system, tx had iced up so I replaced tx and orifice (probably didnt really need to) and did some filter changes every couple of weeks (ran fine). But customer had complained that evap always ices up (for last four years) . I know if unit is to small it will ice up, but checked unit, not to bad could be a little bigger but power is and issue, but distributor on this system will ice up about one minute after running, and evap coil will ice straight away as well. Now i have new drier, only other thing between drier and valve is sight glass, I have new tx valve, correct orifice (I have checked). and recently bypassed heat exchanger because I thought it may have had a small leak and was not getting full liquid line. But no joy! Distributor is not blocked. So would anyone know why this system would ice up so quickly? It is really starting to do my head in.

I may have read it wrong but did you change
the refrigerant for new? 409 is a blend and if
it has lost any of it's composition it will work
differently to how you expect it to work.

Just a thought.

If it has had new gas in then it's not that, if it is
on the original refrigerant then I would replace it
for new.

Cheers taz

.

[bowral fridgy]

check fins aren't blocked restricting air flow

[Brian_UK]

It would be kinda nice if the original poster came back with some sort of reply to the help he is being given.

[hd88]

409 is crap. sounds like the txv needs to be opened up or replaced. It is starving the evap. dont be scared of that valve. open it (turn it counterclockwise) and watch the frost disappear and then check and adjust the superheat, if you know how. you will need a full column of liquid to that txv. (full sightglass)409 is the worst and was the first R-12 drop in refrigerant made. good luck.