Oversized system excess superheat TEV dilemma theory help

[Contactor]

Hi Everyone

I have a system which I think is both oversized and suffering from very low load.

It's on R404 4c set point LP 1 or 1.5 bar, superheat always 15c or more

The superheat is excessive and not responding to the TEV (internally equalised) being opened, in fact I think this may just be making things worse.

I'm wondering if the evaporator is actually being flooded due to the extreme low load and whether or not to CLOSE the TEV in order to push back the dew point and bring about a good superheat.

I cant be sure that the condensing unit is oversized but think it probably is, so presumably without the TEV superheat set up correctly the compressor is at risk of pulling liquid regardless of how big it is?

I realise this will be a case of trial and error but wondered if anyone agrees with my theory or would like to comment?

Thanks

[monkey spanners]

For excessive superheat i would be thinking that the tev was underfeeding, or there is a restriction either in the tev or drier etc, especially if the system superheat can't be lowered by adjusting the tev. (assuming system has enough or correct type of refrigerant)

If the whole system was oversized and hence had a low load, i would also expect to see a low superheat, and a high td across the coil, similar if just the condensing unit was oversized. If just the evap was oversized i would expect a low td across the coil, a higher than expected suction pressure and i think a low superheat also but having a job getting my head round this one

[Peter_1]

You measured the SH where?
SH must always within a range of 7K to 8K (evaporator SH), even id system is over- or undersized. A TEV doesn't see if the components doesn't match with each other.
Do you have types of compressor and evaporator?
You can make the study work again and look what should have been installed.

[Tesla]

Hi Contactor
From what you say there could be either a restriction in the liquid line, SOG or the comp is not pumping properly. Remeasure the operating parameters - LP, HP, SH, SC, Air on and off coils, current and perform a comp efficiency test ie will it hold a vacuum and how long for. Feel around the system for temp drops. Let us know what you find. Feel down the return bends of both coils you should be able to notice where the boiling and condensing points are. If it has high SH the evap can't be flooding unless there is (rare) a restriction in the suction line. The basics should point you in the right direction HP LP SH SC and feeling the pipes.
Just thought of a few other considerations - restricted air flow and miss matched components.