discharge superheat????????

[SkyWalker]

hi guys we had a techie from a "certain" manufacture come to our site the other day to look over a DX condenser, he did the usual Superheat + sub cool ect, but he also checked discharge superheat :confused:?

not sure how he worked it out or why? what help is this in diagnosing a system and how did he work it out? discharge temp against what saturation temp?????, its new to me?

[TRASH101]

The discharge superheat is calculated the same way as any other superheat/ subcool on a system. By measuring the discharge superheat you can subtract the suction superheat and that then leaves you with a figure of how much superheat the compressor has given through compression and mechanical /electrical inefficiencies.
So if you have the operational envelope data for the compressor you can use the reading to diagnose faults that may not be apparent through other means.

[Peter_1]

Discharge superheat gives you an idea of what's happening inside the compressor.
Checking also this way for non-condensables or a cross check or security check for other measurements.

[SkyWalker]

By measuring the discharge superheat you can subtract the suction superheat and that then leaves you with a figure .

thanks for the reply, I don't really follow the above though? if we are working out the discharge superheat we cant use this measurement in out calculation?? am i missing something?

would we measure discharge temp and subtract suction superheat?

[marc5180]

Hi SyWalker, to measure discharge superheat,
1)take the discharge pressure and convert to temp using comparator then
2) take the discharge temperature

subtract 1 from 2 and that will gve you your discharge superheat.

[TRASH101]

The discharge superheat is usually the total super heat of the system or more accurately the superheat reading taken at the place when no more energy is gained or lost.

This is still measured as refrigerant temp - saturated condensing temp for the measured pressure (all measured from same test point) this can be subtracted from (or added to) and shows enthalpy gains or losses to the refrigerant caused by the system.

The above assumes that the system is balanced and mass flow is steady at the times of readings.

I hope that explains it.

So Yes you can add and subtract superheat readings if the system is balanced.

And No we wouldn't take discharge temp. and subtract suction superheat.

[SkyWalker]

thanks Marc and trash, trash your answer is a bit on the technical side but I understand the basics of what your saying, I presume you have studied refrigeration at university?

[TRASH101]

trash your answer is a bit on the technical side but I understand the basics of what your saying, I presume you have studied refrigeration at university?


I haven't studied at university but perhaps oneday, before I'm too old.

Cheers

[icecube51]

I haven't studied at university but perhaps oneday, before I'm too old.

Cheers
A good tech is never to old to study, its in his blood to study. When our blood becomes refrig, than we stop our studies.:cool: Than we have to, because we are dead than.:rolleyes:

Ice

[icecube51]

So if you have the operational envelope data for the compressor you can use the reading to diagnose faults that may not be apparent through other means.
And all the manufacturers love to give us this data, because they don't want there one technicians to have to much work.:D

Ice

[nike123]

http://www.achrnews.com/Articles/Feature_Article/f89050b539a5a010VgnVCM100000f932a8c0____

http://www.fridgetech.com/articles/recipfailmodes/highdischargetemps.htm

[icecube51]

its good comment Nike, just wondered on the first link were the picture has gone?(LOL)

Ice