Superheat Question

desol

Hey guys,

I have a question about Superheat. I'm just starting my AC ticket; i already have a Gas ticket. When(and if) a system is low on refrigerant, the suction line will start to freeze up near the compressor(if i remember right), this apparently will be reflected by a high superheat measurement. How can you have high superheat ie: High suction line temp - gauge pressure/temp...and have a line freeze? If the suction line has high line temp, wouldn't it prevent it from icing up?

What am i missing/confusing here?

Thanks,

D.

delta l

SuperHEAT is a relative term. It refers to a higher temperature than the saturated (gauge) temp. Still pretty damn cold.

Delta

NickTech

superheat doesnt mean super hot, its just the amount of sensible heat above saturation (boiling point). the BP is determined by the pressure. if the system is low on refrig. the evap is starved, meaning it is lower in pressure than normal. with the pressure lower, the BP is lowered toward freezing temps. so if your looking for an evap temp of 40 deg, the BP is 40 deg. if the BP subsiquently drops due to loss of refrig then the evap temp drops to lets say...24 deg. superheat is sensible heat (readable heat)above the BP, so your temp at the evap outlet may read 45 deg which is 21 deg superheated 11 deg higher than what you want if the the evap was at 40 deg.
40 deg. sat------------- 24 deg. sat
50 deg at evap ----------45 deg at evap
----------------------------------------
10 deg of SH-------------21 deg. of SH

beenthere

Pretty much what the others said.
Super heat. Is the amount of heat above saturation temp, that the gas has absorbed.
A walk in freezer with a remote condenser. May have a super heat of 5°F, but its saturated temp is still -20F°.
If it was low on charge. It may have a saturated temp of -35°F, and a super heat of 40°F. Meaning the temperature you measured on the vapor line was 5°F. But its still a high SH.
So a high SH is the amount of temperature above the refrigerants saturation temperature.
Not how warm it is to us.

Okewhat

Is this a book question or real life? If this is a book/test question then please disgard my post. If not first you need to know if the system has a device which shoots for a constant superheat ex. txv. If so then u should b measuring subcool not superheat.

Geno54

Although the suction line is seen freezing at the compressor. the start of it is normally at the beginning of the evap. It starts freezing there and works its way back to the comp

NickTech

not to be rude, but what the fuuuk is an ac ticket??

flashheatingand

How do you know that you have high super-heat with a fozen coil. lets's say you have low press of 20 and the l.s. is caked with ice. Unless you placed a sensor on the pipe and the ice covered the sensor, you don't actually know what the line temp is. Eh??

Odds are that if the line-set freezes, the coil coil could use a cleaning as well.

Anybody have any killer techniques in thouroughly cleaning a coil w/out opening the lines? I never have been a fan of Most of the "cleaners" because you still need to wash. The brushes work alright if the space is big enough. Not crazy about those coils that Rheem made, or the w coils.

OK, I will admit, I have considered pulling out the h.e. but never acted on this.

beenthere

Don't bother to check it. Until the coil is thawed.

NickTech

:w00tsorry, i was drinking some that day