Causes for low delta T over evap?
Can't wrap my head around something for some reason today, any ideas.
With good subcooling (14) and superheat (13) and good airflow (350 per ton verified) what could be the cause of a low split? (13)
entering wet bulb 65
return air 75
all taken at unit.
I considered a restriction in the evap coil/metering dervice (TXV) but superheat should have been lower (coil) or higher (TXV) and pressure were close to normal 345/120.
Cond. delta t was 10, ambient 95.
I can see there is a problem but what I'm just not seeing.
try putting probes in dif locations...maybe pocket of swirling air?
Please, Please Please......keep the Factory Smoke in the Wires!!!!!
Is it Rum'Oclock yet???
Check electric heat. If it has some.
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My first guess would be leak in the return somewhere, if you measured your WB at the return air grille, it would not effect the reading, if your leak is between the return grille and the AH/Furnace.
Originally Posted by 0351
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I have always heard 10 degrees is a good rule of thumb subcooling and you are getting more than a 3/1 ratio out of your compressor. Great on efficiancy but could be a sign of a slight charge offset?
could be humidity in the air of the house
What size unit is it?
It sounds like you're picking up heat in the system.
If its a 4 or 5 ton I'd say you've got 5 kw strips running.
If its a 2 ton I'd say you've got hot air leaking into the return.
An engineer designs what he would never work on.
A technician works on what he would never design.
R410A at 345PSIG is 107°F, with 14°F SC, that brings your liquid line temp down to 95°F. Your outdoor temp was also 95°F. That should you give you an idea of where to look for a restriction.
Yuppers liquid at ambient or below=liquid line restriction was my first thought, I was just excepting higher high side.
Originally Posted by beenthere
Refrigerant cycle dxing is definitely a weak point for me as it’s so nebulous.
I guess its one of those thing that you may or may not see high high side?
It is a 5 ton A/C + furnace R410A, just had the ducts sealed so they "should" be good.
Never thought about the electric heat issue, I'll keep that in my toolbox if I see the same issue on a fan coil.
It was wet in house for the area but my airflow calcs said it should be an 18 split.
Thanks for the help guys, sometimes being new to the trade I'm hesitant to make a call, glad to know I wasn't completely off in left field.
Non-condensables will cause low split. Have to monitor pressures, SH, and SC for a while and see if you get fluctuation. I use min/max feature on digital guages. Can also use temp. clamp meter.