hey so i did some maintenance on my parents system and found head pressure at 580 with 34 degrees subcoolingin heat check it at ac on 70 degree day and had 5 degrees in cooling . have correct return air, clean filters clean coils. any ideas txv operational on outdoor unit has me stumped 4 ton unit any input would be appreiated thanks
Danny
i would love to help! however your lack of punctuation and lack of information hinders me. Delta T accross both coils, high and low side pressures, superheat and subcoolig are all basic assets when asking for AC help.
You had a heat pump running in the heat mode on a 70º day?
What was the indoor temperature?
Low indoor airflow, overcharge, possibly both?
if you had a 80 degree return air and 70 degree outdoor temp might be perfect ,also thermostat does not show correct RA temp
yeah sorry for lack of punctuataion. like i said i checked the subcooling in ac on a 70 degree day and had low subcooling, however in heat mode on a 40 degree day i had 34 degrees. Since you check heat pumps with txvs rather than pistons in subcooling not superheat i did not include that info. I can get the delta t across coils, however head pressure of 586 on a 40 degree day seemed to me to be problematic one way or another. could be wrong. Fan was running and there is 1670 cfm of return air on a 4 ton unit. and please no comments from people who try to put others down with above quotes to make themselves feel better. No disrespect justr don't have time or patience for it. Thanks
Danny
od temp 40
heat mode
suction 120
head 586
subcooling 34
410a unit
4 tons
So you have a outdoor txv ? And a communication variable speed that shows the 1670? Doesn't always mean you are getting it. Not saying that is the problem here though.
Please provide model and serial of units.
yeah i thought about the unmatched possibility ill get the m/s numbers but no i got the trurn air with a ductulator duct is sealed and not kinked so i figured it was pretty close thanks for the tip about superheat though. makes sense.
This may be a whole nother thread worthy but you how are you using that ductulator?
Sounds to be over charged in heating.
You need 450cfm/ton for heating mode.
You will have a higher subcooling in heating mode because the ID coil is smaller then the OD coil.
You're head pressure is too high in heating.
What are your pressures when you checked in cooling?
70* is a little cool. If you had lower head pressures this would be why you have lower SC.
If airflow checks out and you know charge is good (check in a/c) then i would recommend adding a VPS to the OD fan. Carrier used these back in the day on their 410a h/p. If you turn OD fan off it should lower your head pressure.
[QUOTE=gravity;15287331]Sounds to be over charged in heating.
You need 450cfm/ton for heating mode.
Where do you get this number? I do heatpumps all the time and have never got them to pull 450cfm/ton and they work great. All specs i have ever seen say 375 -400 a ton is fine. Or am i wrong?
The SST is warmer than the outdoor air.
The possible causes I can think of are overcharge, metering device over feeding & low indoor airflow.
We can eliminate the outdoor TXV over feeding so there's not much left. I wouldn't be surprised if it had both low airflow & was over charged.
Gary
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heating needs more airflow because the coil is smaller. look it up
I did and in every rheem air handler manual i looked into they show the same cfm for heat or cool mode with a chart that shows cfm compared to static pressure and not one is over 400 cfm/ton and they will even accept as low as 350cfm/ton. Also we are regulated in california by calcerts and they never test for anything over 350cfm/ton period.
Where are you seeing this?