Help! Possible flash gas problem

[Contactor]

Hello

Chilled cold room R404a set point 5 c

HP 20-25 bar

LP 1-2 bar

2-3 K subcooling

excessive superheat

Danfoss TEV changed using same filter and orifice

condenser has been relocated below evaporator 2.5m on a run of 17m

[Gary]

You will need to add refrigerant until the subcooling at the receiver outlet is 6.5-9.5K.

I would generally recommend 5.5-8.5K SC, but I added a little for the 2.5 meter lift.

[Gary]

Also, when the evaporator is above the compressor, the suction line should run up to the top of the coil and then down to the compressor. This prevents any liquid which may accumulate in the evaporator during the off cycle from dropping by gravity down to the compressor inlet, flooding on startup.

If the compressor is pumped down during the off cycle, then this is not necessary (but still a good idea).

[Andy]

Hello

Chilled cold room R404a set point 5 c

HP 20-25 bar

LP 1-2 bar

2-3 K subcooling

excessive superheat

Danfoss TEV changed using same filter and orifice

condenser has been relocated below evaporator 2.5m on a run of 17m

Hello Contractor.

Head is high, suction is low. My guess would be the expansion valve is too small.

Kind Regards Andy :)

[Gary]

Possibly air in the system... unless the condenser is dirty and/or the ambient is very high.

[Contactor]

The same system worked ok prior to being moved, we checked the orifice and changed the TEV anyway.

The HP stays high when fully charged, cutting out at 25 bar but holds steady at 15 bar when only half charged (LP always 1-2 bar) ambient 21c.

The condenser is now located approx 14m from the evaporator and 3m below, total run 17m.

Previously, the evaporator was located approx 1m below the condenser with a run of 17m.

[Andy]

The same system worked ok prior to being moved, we checked the orifice and changed the TEV anyway.

The HP stays high when fully charged, cutting out at 25 bar but holds steady at 15 bar when only half charged (LP always 1-2 bar) ambient 21c.

The condenser is now located approx 14m from the evaporator and 3m below, total run 17m.

Previously, the evaporator was located approx 1m below the condenser with a run of 17m.

Sounds a lot like a condenser problem. Fan running the right way? Air not recirculating?
Then you have some subcooling:confused:

I did see this or similar once on a freezer, when up in temp the unit would not pull down.

I cable tied the liquid line to the suction and increased the subcooling that way. Only gas going to the expansion valve was the problem.

Is the dip tube ok on the receiver?

Kind Regards Andy :)

[tonyelian]

hi
i agree with andy ur problem is in the high side u mention that u have change tev&orifice did u change filter drier check llt it should 12-15 degree above ambient air also air in air out temp the otherroom has the same dimension &heat load inside the room compressor capacity &nameof the expansion and orifice number

[Gary]

In order to get proper coil outlet superheat, there must be solid liquid at the TXV inlet. If the SC (measured at the TXV inlet) is 10-15F/5.5-8.5K, then there is solid liquid at this point, in which case the high SH at the TXV bulb means there is not enough liquid flowing through the TXV (plugged inlet screen, undersized orifice, superheat adjustment).

[chemi-cool]

I had a similar problem with a big air drier, HP 26 bar.
A cup tube expansion device.

All I did was to replace the drier and fill with new refrigerant and unit run like new 5.5 bar LP and 20 bar HP.

[Gary]

There seems to be a lot of confusion as to where the liquid line temp should be measured. In order for proper subcooling to be achieved, the liquid must travel through an area where it can be sufficiently cooled.

If the receiver outlet is in the path of the hot air leaving the condenser, then the liquid line temp must be measured further downstream in a cooler area.