View Full Version : Seeking R404A Advice & Tips

20-05-2015, 08:18 AM
Hi everyone,

I have recently changed jobs and have been looking after a few cool rooms (never had previous refrigeration experience except for when I did my course 8 years ago)

I had a compressor burn out on a R404A unit. I installed a new compressor, new driers, burnout drier, etc etc.
After giving the unit a vacuum I weighed in the same charge as what I originally pulled out.

Once I ran the unit I had a normal looking head pressure but a low suction pressure.
I've ended up adding a touch more gas and had a play with the TXV (winding it out around 1 and a quarter turns) before I had pressures that looked better.

When I left the coolroom it was reaching temperature (set at 3 degrees Celcius) though it felt it is taking a bit longer to reach than before.
My suction pressure at the condenser is 60ish psi (around -5 degrees Celcius). Head pressure is around 250-260psi.

On the Evap I have a 1 degree Celcius suction pipe temperature and a -5 degree saturated suction temperature/pressure.

Does this sound about right for the R404A gurus?

I have a very slight ice build up on the inlet of the Evap and the suction returning is very cold but not sweating.

Air off the fans I was getting less than 2 degrees Celcius.

I am a bit worried about why I had to adjust the TXV and add more refrigerant when I put an identical compressor in it. My concern is maybe the TXV is failing..

Any advice welcomed :)


20-05-2015, 03:54 PM
It's always good practise when changing a compressor to change the txv,most reputable compressor rebuilders insist on it for warranty.

20-05-2015, 03:59 PM
And an add on,you ask why did the original fail? if it's single phase change the starting electrics if it 3 phase always ! change the contactor and overload,seen so many instances of a contactor taking out a replacement compressor.

20-05-2015, 08:44 PM
Contactor and all starting electrics were also replaced.
Original compressor had a winding down to earth causing an instant trip.


monkey spanners
20-05-2015, 11:16 PM
Evaporating temperature seems a bit high, but it would depend on many things is its ok. Too high an evaporation temperature will slow down cooling or even prevent the room reaching temperature.

21-05-2015, 12:56 AM
Hi Jonesy.
A quick check is to read air onto evaporator and compare to SST at evap, evaporator super heat should be 60>70% of that value.

21-05-2015, 06:54 AM
Thanks guys,

I'll check the air on next time I'm on site. I was there today and it appeared to be running well. Wasn't icing up, was reaching temperature and holding all day.

Ill recheck it again next week!