Copeland Compliant Scroll Problem
Kjobear151
Model RPLA-036JAZ, (11 SEER), outdoor unit with matching indoor unit and
expansion valve. The outdoor unit has a metering piston. The system is about
2 years old; But this is the first season it has been run very much in heat.
The house was a spec house.
The unit heats and cools great. The temps and pressures match the mfg.
charging curve. Checked in both heat and cool. Everything appears ok. The
unit defrosts normally. Amps are ok. The air flow is ok.
The problem is that the compressor makes a howling/moaning noise @ shut down,
when run in the heat mode at colder outdoor ambient temps, (less than 45 F or
so). It never does it in cooling and doesn't do it all the time even when it
is cold outside. The noise is so loud it can be heard inside. The unit sounds
ok while running.
Has anyone else seen problems with the Copeland Compliant Scroll making very
loud noises at shutdown??
Thanks in advance.
Keith Aubert Air-Care
DPai922851
saturated and at low pressures. Apparently the differential between HP & LP is
the culprit during these conditions. I haven't seen any deterioration of
performance due to this. I haven't had this verified by any factory reps.
though.
Good Luck
Dave Painter
P. O'Callaghan
If the valve is going back into the 'cooling mode' (for eg, becomes
de-energised when the thermostat is satisfied on heat (same time your
compressor shuts off)) then the pressures in the system (suction and
dischargs) have the chance to balance rapidly.
I doubt its your compressor, if it was, it would do it in cooling mode
too..
The reason that it is probably only happening in heating is that in the
cooling mode, the reversing valve isnt energised.
Phil.
Kjobear151 <kjobe...@aol.com> wrote in article
<19990114212356...@ng-cd1.aol.com>...
Kjobear151
>Its more likely to be your reversing valve.
>
>If the valve is going back into the 'cooling mode' (for eg, becomes
>de-energised when the thermostat is satisfied on heat (same time your
>compressor shuts off)) then the pressures in the system (suction and
>dischargs) have the chance to balance rapidly.
The reversing valve is still engergized at the end of a heat cycle.
Keith Aubert Air-Care
DPai922851
I forgot that Rheem/Ruud heat pumps energize the reversing valve during
heating cycle. I didn't pay enough attention to the type of sound, whooshing
noises are RV, clanking noises are compressor.
Sorry,
Dave Painter
John Tan
I posted something but never got through, so here goes again.
Copeland Compliant Scroll compressors inherently have low sound
and virbration characteristics.
At shutoff, the compressor may run backwards for a brief period
as the internal pressure equalize. A low mass disc type check
valve in the discharge tube of the compressor prevents the
compressor from running backwards for more than a second or two.
Also, though with the low level of vibration of scroll, a low
level of 'beat' frequency may be detected as noise coming along
the suction line into a house.
Copeland qualify that though with the relatively low pulsations
of the Compliant Scroll, individual system tests should be
performed to verify acceptability of sound performance (that is
OEM equipments manufacturers should do the tests).
However, if the said tests are not available, a hollow shell
muffler such as Alco ADP-1 will work quite well. The suction
muffler should be located 6" to 18" from the compressor. This may
required to add mass to the suction line to shift line resonance
away from excitation frequencies.
Hope this helps.
John Tan
John Tan
I'm sorry Dave...I couldn't find the original post, hence I have to
'tail' your post :-)
Hawkmeistr
not reseating fast enough on deenergization. We have found that there are two
styles of heatpumps made by most manufacturers. Depending on where you live,
there is some imaginery line across the US, your location above the "line" will
get you a unit that defaults to heat mode and below the "line" you will get a
unit that defaults to cooling. It does make some sense because you would need
heat more than cooling in the north on most days and vice versa for the south.
Of course you must specify which one you want as you may get one that has been
in the storage area, missent to the distributor. Check to see what mode you
are in when the reversing valve is energized verified by putting a voltmeter
across the coil of the reversing valve. We just put two new units on a high
school and through much troubleshooting and factory calling we found that the
units defaulted to different modes and had to rewire the thermostat for the
cooling default mode unit.
Hawk
Craig
I think Carrier changes reversing valve default by tonnage. I cant
invision a northern and a southern heat pump design. Do you think its
the Mason-Dixon line thats the determining factor? :o)
Craig
ftwhd
I think the southern version is the Turtle brand :)
Above the 37th parallel the heating load is greater than the cooling
load and below the 37th parallel the cooling load is greater than the
heating load. Thats why HP are sized for the heatoing load in the
north and the cooling load in the south.
Regards, Mike
Hawkmeistr
Mexico, Virginia and some more places on the Uncle Sam plan. I am a retired
Master Sergeant from the US Air Force and did HVAC my entire 23 year career.
My current working partner and I have run across this problem here in New
Hampshire (he's originally from New York) and only after troubleshooting
thoroughly did we come across the fact that we have units that default
separately. It's not that the reversing valves have been replaced as we have
found this problem in brand new units, as I stated originally. I know it
sounds very odd but, we have seen default to heating mode in person.
Hawk
Craig
Im not disputing the fact that a unit can default to heat or cooling on
shut down or loss of power to the reversing valve. It can probably
happen in the same model line from the same manufacturer. The reason it
is done is because some overpaid engineer needs to do something to prove
his worth not because of the geographical location of the heat pump.
Craig
Sonofdawra
>required to add mass to the suction line to shift line resonance
>away from excitation frequencies.
>
>
>Hope this helps.
>John Tan
John,
I think the Republicans will go into detail on this later next week in the
Senate:o)
How's the economy doing this week over your way. Any signs of an upward move?
John Tan
Uncle Ron,
The information was obtained from Copeland periodic updates if you need
to know the source.
Gee, I hope they will get over this thing swiftly.......the issue is
getting stale .....the media is probably looking for other sensational
stories.
Economy seems to be bottoming since the Asia crisis from the mid of
1997......lots of casualties since then......AC&R trade affected somehow
in the construction sector but maintainence/repairs services still doing
well. Economists are predicting a general improvement from the mid or
end of 1999.
Looking further at Brazil recently, one wonders if hedge funds
activities need to regulate as they are blamed for the currency crisis
in Asia.
Cheers.
John Tan
Kjobear151
>> >This may
>> >required to add mass to the suction line to shift line resonance
>> >away from excitation frequencies.
Would changing the resonant frequency of the suction line dampen the noise both
while running and @ shutdown??
There have been several responses that suggest that the reversing valve is
shifting at the end of the heat cycle and causing the noise. The reversing
valve solenoid stays energized at the end of a heat cycle and the valve is
not shifting at the end of a heat cycle.
One respondent suggested it was related to a near saturation conditon at the
compressor suction at low ambients. This does seem to be what is happening;
The unit's pressures and tempertures do fall on the charging curve. But I
wonder what could be causing this loud noise. The supplier's troubleshooter
has been in consult w/ us on this and he says he has never seen this before.
The only thing close was a noisy scroll while running and not at shutdown. The
outdoor unit was making the noise but it turned out to be a indoor coil c/o
that solved the problem.
The noise is definately coming from the compressor. The supplier's
troubleshooter who hasnt been out to see the installation is too not sure.
I sure would hate to c/o a compressor and it not solve the problem.
Any further help would be greatly appreciated.
Thanks
Keith Aubert Air-Care
Craig
My gut feeling is changing the compressor wont solve the problem. I
dont know what to suggest for a remedy though. Ive had some heat pumps
make some weird and loud sounds before also. Usually it was the
reversing valve though.
Craig
John Tan
>
>
> Would changing the resonant frequency of the suction line dampen the noise both
> while running and @ shutdown??
>
> troubleshooter who hasnt been out to see the installation is too not sure.
> I sure would hate to c/o a compressor and it not solve the problem.
>
The information is obtained from Copeland updates.
The recommendation is to add a muffler if you read my post again.
If you're very sure that the noise is coming from the compressor rather
than from the reversing valve........then go for it.
I'm interested in the outcome if muffler is added or reverse valve is
changed.....please update.