I just came back from my neighbors unit, its a 14 SEER Rheem R22 split HP.
We walk our dogs together so he asked me if I could look at it tomorrow.
He said it wasn't cooling when he got home yesterday so he shut off
all night. I went & get my tools & checked it for him today. Water had been
coming out of his secondary overflow at the eave so I figured it was
probably the attic float switch. I used a wet vac on the secondary &
primary & the system started up O.K. Here's where things get screwy.
I checked the pressures & the system has fixed 25-30 degree
superheat(TXV) on the plate.
According to the chart the head pressures were right on
SP - 55 psi
HP - 225 psi
SH - 27 deg.
SC - 20 deg.
86 DB outside temp
80 DB inside temp
Temp across indoor coil 12 deg.
I originally thought the charge was low but I always check the unit specs
when available first.
Any other unit I would say would have a restriction
with high SH & SC but I've never seen a TXV that calls for such high SH.
It doesn't even have a subcooling reference at all.
Its pouring water out of the drain so its obviously doing some
dehumidifying. I'm going back to check in the morning when I'll actually
feel like working but curious if any one familiar with Rheem has ever run
into this funky TXV 25-30 deg. SH spec. on a residential unit.
Something is not right.. need model and serial numbers.
What are the model numbers for the heat pump and the air handler? The coil
model number would be good too.
As a rule, with Rheem stuff, you want 10 - 14 degrees of subcooling.
My first impression is that its overcharged....and there may be an airflow
restriction to complicate matters, and until I know what the model numbers
are, I really can't tell you much else.
Superheat's too high for low air flow. I'm thinking the screen at the TXV
is clogged or semi - clogged. Seems like the condenser's back up [high
sub-cool] and the evaporator is dry [not enough refrigerant]. low
performance [low TD on evap.] is also evidence that there's not enough
You should have a higher suction with the indoor temp. @ 80 deg., and a 10 -
14 deg superheat.
Check your TXV inlet screen.
Outside Model # RPNJ031JAZ
I'll probably get the indoor model numbers tomorrow.
I was in shorts & sandals & not about to go into the attic today.
I just came back from walking my dog again & he said everything was
working great. It's cold as ice in the house & it got to 90 degrees
outside after I left.
I might try another set of gauges tommorrow just to be sure but it has
specific charging instructions on the unit inside cover. They say that the
TXV used for cooling is non adjustible with a fixed 25 to 30 degree SH.
It doesn't have any subcooling specs but it gives specific head pressure
readings under outside ambient conditions. The SH just doesn't make sense.
My Suction line temp was 57 & air coming out was 68 which seems about
right. According to what's written on the unit I'd need to have about
47 psi on the suction line to get a good temp drop across the coil.
Most Rheems that I've worked on have a little higher than normal suction
pressures because they run well over 400 cfm's per ton.
Maybe this was one of Rheems experimental units.
I can't find it listed in ARI at all.
The correct TXV is non adjustable, and when properly installed, maintains
15 - 20 degree SH
Because its obsolete.
The RPNJ model was only made for about 5 years. It should be matched with an
RBHK-21 air handler (with ECM blower motor), and RCHJ-36A1 Multiflex coil.
According to the charging chart, at 80 degrees, your LLP should be right at
205psi with a 10 - 14 degree subcooling. Your SP is too low, your SH is too
high... is there a kink in the LL anywhere?? or dirty TXV screen, or did
somebody not properly install the TXV in the first place. When the TXV is
installed on those, the piston is changed to .120 along with installing the
TXV.(unless the coil/TXV were factory assembled). Just for grinns, when the
heat pump was installed, did the installer put in a filter/frier?? or did
the unit come with one internally??
I just had a thought(No, paul, it didn't hurt)... the problem with this
system...is constant?? or does it come and go??
As far as I know he's never had a problem in 8 years living in the house.
He says its working fine now too.
I appreciate all the info.
I'm sure if anything had to be field adjusted like the correct orfice it
wasn't done. When I check piston sizes in systems that need to be
field installed I'll find maybe one out of ten correct. Most guys
around here just install a system with whatever it comes from the factory
with. It's rare to even see a jumper on the defrost boards even changed.
The only thing that concerns me is that I don't want to go tearing into
the system just because it doesn't read the way I think it should. The
owner has no complaints & the numbers pretty much match the specs
written on the unit. Maybe I'll think clearer tomorrow.
Eight years? Did he have the coils cleaned, in that time?
Another idea. Many times, when I'm diagnosing, the amp draw is the number
that sheds light on the matter. see how hard the compressor is working.
Water coming out the secondary drain is always a concern, to me. Makes me
wonder, if the primary drain is clogged.
Since he had the unit turned off over night, it's possible the evaporator
was frozen over. Not as likely with a TXV coil, though. High super heat may
be from humidity removal.
Good idea to check the temperature of the liquid line leaving the condensor.
I'm finding that most of the systems I am asked to service have dirty
condensors. Many times, some condensor cleaning is all the system really
needed. Please let us know what you find.
Outdoor unit Model RPNJ031JAZ man. date 10/99
Air Handler Model RHBHB-21J11NFAA
Coil model RCHJ-36A1G
Things look a little better today:
Getting about a 14 degree drop.
75 db inside
85 db outside
S Pres 64
S Temp 59
H Pres 210
LL Temp 87
So I'm running about 23 deg. SH & 18 deg. SC
I reread the charge plate & it definitely says:
"system equipped with non adjustable fixed TXV's - 25 -30 degree
superheat cooling & 10-15 deg. superheat heating"
Also on the unit it specs 10 -15 deg. liqid line temp above outdoor
ambient. Since I'm only 2 degrees above that suggests an overcharge.
I did notice a 1/4" liquid line set which was smaller than both indoor &
outdoor line set connections. So it should be 3/8" line set or at least
5/16". Plus its probably over 50 ft. line sets. That might account for the
higher than normal SC.
Well the owner is happy & it's cooling the house fine so I'm not touching
it for now. I'll still keep researching.
1/4 inch LL?? Is this the second system since the house was built?? If it
is, was the first system a Lennox?? That 1/4 inch LL will make for a high
SC, and high LLP.
BTW, your correct...over 50ft does require a 3/8LL. the RBHB air handler is
not the correct one for that heat pump(at least not for it to be 14SEER),
the one needed for that heat pump is either an RBHJ or RBHK with the ECM
blower motor....the coil is ok, it was added as the air handler didn't come
with a coil installed...
If your neighbor wants you to replace his 2 1/2 ton system in the future,
try this out for size...
RPNL-030JEZ heat pump with an RHLL-HW3617JA air handler. ARI rates it as
15SEER with 9.25HSPF. ARI REF# 823415
The original system was an old GE which probably had 1/4" LL but when this
system was put in I would've thought they ran all new copper. They moved
the condenser to the other side of the house & ran the copper down a
closet from the attic to the crawl space. Anything's possible though, they
could have saved the old copper & reused it.
I'd be curious if you could find any specs on the TXV with that AH coil?
I still can't figure out why it calls for 25 - 30 deg. SH on the condenser
no tellin.... I got no idea about the specs on the TXV... I checked the
archives and it doesn't give specifics. The training I recieved on Rheem
systems with Multiflex coils says 10 - 14 degrees SC to ensure a solid
column of liquid refrigerant to the expansion valve.
BTW.. a little more info on that system as its configured(this is what not
having the correct air handler will do)....
12SEER, 10.8EER, COP 3.3, HSPF 6.95...not even close to the advertised 14
OTOH, the RPMC-030JAZ (12 SEER)with the RBHK-21 air handler with an
RCHJ-36A1 coil will net
13.8SEER, 11.85EER, COP 3.52, HSPF 7.15. Maybe picking nits, but....
THe RPMC heat pumps with the RBHK air handlers were my premium line for many
years, and I sold a lot of them.
That's interesting because the one thing the owner told me was that he
never saw much of a difference in his electric bill going from an old 8 or
so SEER unit to a 14 SEER that he was sold. So given the small lineset
his 12 SEER might even go down to a 10 SEER close to where he started.
Did the liquid line set loop several times, at the one end or the other?
Some of the really early systems, they used the lineset as a metering
device. Should not be the case, with the TXV coil. I think you're on to
something, try a 3/8 liquid line.
When the guys on the list aren't calling me a F' hack, they may agree. Clean
the condensor is rapidly becoming my favorite thing to do to a system.
Gary, I presume you cleaned the condensor? Even if it appears clean, it can
still be running way under efficiency.
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