cellar cooling

[SkyWalker]

hi guys, i visited a cellar cooling sytem the other day, it was the first i had been to, just wondered what you guys thought of 3c air on/off TD on evap?

system was a hubbard premium 200 (R407c), twin evap, common 3/8 liquid T into 2x 3/8" liquid, common 7/8" suction T into 2x 5/8" suction (as per install manual i found on site) air on evap 14c off about 11c, superheat was 10K, suction pressure 65psi, full sight glass, compressor draw reading from its name plate said 14.1A Max, was running at 8.1A. there was slight frosting on the distributor's of both evaps but nothing to write home about. outdoor ambiant about 22C i think. round about 10k sub cooling also.

danfoss T.E.V's both 04 orifice. i checked the tev and both are 3 1/2 turns in, (starting from the full outward position)
the cellar was 6m x 3m about 2.4m ceiling height.

there where no complaints the system wasnt holding the cellar at 12c its just i aint seen a cellar system before and wasnt sure if this was a low indoor TD? thought it do at least 8C or so. also is 10k superheat high? if this was like 5k woudnt this mean more liquid in the evap's? better td's?? or would 5k be too small?

i normaly work on a/c and hold my hands up, i know how to take and make the readings but dont know if my readings are as they should be?

didnt intend this post to be so long but any help/education would be much appreiciated, cheers guys

[Gary]

What is the design temperature for the box?

[SkyWalker]

hi Gary, what do you mean by box? if you mean the cellar then i presume it was designed to hold at 12c as this is target temp.

i had no involvement in the design and in all honesty not sure if the person who did design it had a clue!

the amp draw was taken from contactor and not on the common wire btw, just realized that now.

[nike123]

hi guys, i visited a cellar cooling sytem the other day, it was the first i had been to, just wondered what you guys thought of 3c air on/off TD on evap?


Temperature difference at evaporator entering and exiting air is not TD! That is dT (or Δt).

TD is difference between suction saturation temperature and temperature of air entering evaporator and it should be between 5-10K depending on desired humidity and actual air flow of evaporator.

http://www.refrigeration-engineer.com/forums/showpost.php?p=92775&postcount=5




system was a hubbard premium 200 (R407c), twin evap, common 3/8 liquid T into 2x 3/8" liquid, common 7/8" suction T into 2x 5/8" suction (as per install manual i found on site) air on evap 14c off about 11c, superheat was 10K, suction pressure 65psi, full sight glass, compressor draw reading from its name plate said 14.1A Max, was running at 8.1A. there was slight frosting on the distributor's of both evaps but nothing to write home about. outdoor ambiant about 22C i think. round about 10k sub cooling also. 14°C air on and 65psi (5°C SST) gives you 9K of TD which looks right.



danfoss T.E.V's both 04 orifice. i checked the tev and both are 3 1/2 turns in, (starting from the full outward position)
the cellar was 6m x 3m about 2.4m ceiling height.

there where no complaints the system wasnt holding the cellar at 12c its just i aint seen a cellar system before and wasnt sure if this was a low indoor TD? Since your dT is 3K and for refrigeration is normal 3-5K I would say that your dT is also normal.


thought it do at least 8C or so. also is 10k superheat high? if this was like 5k woudnt this mean more liquid in the evap's? better td's?? or would 5k be too small?Superheat could be high becaose of high load. If you measured your superheat at near design temperature, than you should have around 4-5K evaporator superheat.
Where did you measured superheat?

Your 10K subcooling is high but you should firct cover portion of condenser to achieve 40°C condensation, and then make your measurements again. If then subcooling is still 10K than you should remove some charge until you got around 7K subcooling.

[SkyWalker]

o.k nike, thanks for the input, i did know about delta T, but didn't know Td was something completely different. im trying to learn all i can and you guys help me alot, much appreciated.

superheat was measured at evap coils, pressure and temps, room was about 14c when superheat reading was taken. how come the compressor draw seems low, would it be because i took the reading on the contacor and not the common, not sure if this system had Run Cap.

[Gary]

hi Gary, what do you mean by box? if you mean the cellar then i presume it was designed to hold at 12c as this is target temp.

I have no idea what a cellar cooler is... must be a euro thing. I'm thinking a walk-in cooler, but at a higher target temp.

The superheat is probably a little high for this close to target temp, but if you can wait until it gets down to target temp you can more accurately adjust it.