Walkin Freezer Problem; R12 to R404a
danny
when changed to new 404a the oil should have changed 3 times , new driers
should have been installed , plus good evacuation . i remember once having
the same problem and it was moisture in the system , it would not go down
no matter what we did until we ran a vac pump for 5 hours changed all driers
, remember that poe oil sucks moisture , who can tell how long it was
opened to air when changing the valve . the fan its just normall , reason
its off its to prevent the moisture or any water left in the coil after
defrost being blown into the room plus giving the compressor a chance to
recover temp (lower) before turning the fan on .
defrost in our woods is 30 minutes every 8 hours , if real heavy use every
6, hours .its a good start also check the size of this new condenser unit
,you never know ..check what btuh it gives at your evap temp .
Kjobear151 <kjobe...@aol.comadd> wrote in message
news:20000106200816...@ng-fk1.aol.com...
> I went to a Dairy Queen today on a walkin freezer call. From what I could
tell
> from talking to the owner; the freezer was originally an R12 system that
had a
> R404a condenser unit installed when the compressor failed in the old R12
> system.
>
> There seems to be two problems with the system; (1) The lowest temp
that can
> be obtained even in the winter and with no door opening for hours, is
about 3-4
> F. & (2) The owner has to manually defrost the coil every 7 -10 days.
>
> We manually defrosted the coil which was very iced-up. Then ran the
system and
> found the following:
>
> Bubbles in sight glass w/ low load conditions; Added R404a till clear.
>
> And then had the following:
> Suction Pressure: 25 psi (ci/co set such that the condenser runs cont.
with
> a cooling call)
> Freezer Temp: Min 3-4 F (primary control; thermostat w/ pump down
solenoid)
> Superheat: 13 F @ compressor (Well insulated line ~ 30' from freezer to
> condenser)
> Dish Pressure: 245 psi (cond fan ran cont w/ call for cooling)
> Ambient 60 F
> Condenser Coil Clean
> Door gaskets in ok shape.
> Cool where freezer is located.
> All of freezer stock very well frozen.
> (I know: Is that all the info?)
>
> From talking to the owner; When he manually defrosts the evap coil, he
notices
> that there is steam coming from the defrost elements and the water he uses
to
> defrost the coil flows down the drain line. Also he noted that the evap
fan
> does not come on for a min or so after the solenoid opens on a call for
> cooling. He also told me that the company that did the c/o made many
visits
> after the installation and did at least the following: c/o the expansion
> valve, did superheat adustments, removed some of the refrigerant (may
explain
> the bubbles in the sight glass). He also told me that even after the
company
> tried many times to correct the problem, with no further adjustments, the
> temperature went from in the range of 15-18 F to 3-4 F. He needs 0 to -5
F to
> meet health department requirements.
>
> Do any of you have any experience w/ changing from R12 to R404a? From the
> Dupont literature I have this is not a recommended replacement for R12 but
it
> is for R502.
>
> I am thinking that possibly the first company may have had some internal
> problems due to the POE oil and mineral oil from the old R12 condenser
unit.
> That may be what led to the expansion valve replacement. Anyway, the 25
psi
> suction is quite high to achieve -5 F. That is only a 5 degree delta T.
And
> the 13 F superheat is rather high.
>
> I would appreciate any and all help on this problem.
>
> Thanks
>
>
>
>
> Keith Aubert Air-Care
Whitewater Jamboree
Kjobear151 <kjobe...@aol.comadd> wrote in message
system and
> found the following:
Is there a defrost clock present & operating properly?
> Superheat: 13 F @ compressor (Well insulated line ~ 30' from freezer to
> condenser)
I believe you could stand to be 20 F at the compressor, assuming you aren't
measuring so close you're picking up heat from the comp. Check the
superheat at the evap. outlet.
> Dish Pressure: 245 psi (cond fan ran cont w/ call for cooling)
> Ambient 60 F
Is there a head pressure control device?
> Do any of you have any experience w/ changing from R12 to R404a? From the
> Dupont literature I have this is not a recommended replacement for R12 but
it
> is for R502.
Have done several, no problems. Change cond. unit, TXV, be sure line sizes
are appropriate and run with it. The only problem I ever had was on a
reach-in I changed. The customer had turned the stat down all the way when
it went out. I didn't remember to set it back & left. He called me the
next morning bitching because all 4 doors had frozen shut (as it was -30 F)
oops. :-)
> I am thinking that possibly the first company may have had some internal
> problems due to the POE oil and mineral oil from the old R12 condenser
unit.
Possible, although if it wasn't a burn out, a little clean up and new driers
makes for a pretty smooth retro.
> That may be what led to the expansion valve replacement. Anyway, the 25
psi
> suction is quite high to achieve -5 F. That is only a 5 degree delta T.
And
> the 13 F superheat is rather high.
Sounds to me like it's a little low on the superheat at the comp. Copeland
usually gives you 20 there. You may be flooding. I could be wrong
(everybody tell me so please :-))
Good luck,
Robert
ftwhd
the evap fan thing suggests that the defrost circuit is not wired
right, did you check it? The fans should be running all the time
except for when its in defrost.
Mike
UA local 370
On 07 Jan 2000 01:08:16 GMT, kjobe...@aol.comadd (Kjobear151) wrote:
>I went to a Dairy Queen today on a walkin freezer call. From what I could tell
>from talking to the owner; the freezer was originally an R12 system that had a
>R404a condenser unit installed when the compressor failed in the old R12
>system.
>
>There seems to be two problems with the system; (1) The lowest temp that can
>be obtained even in the winter and with no door opening for hours, is about 3-4
>F. & (2) The owner has to manually defrost the coil every 7 -10 days.
>
>We manually defrosted the coil which was very iced-up. Then ran the system and
>found the following:
>
>Bubbles in sight glass w/ low load conditions; Added R404a till clear.
>
>And then had the following:
>Suction Pressure: 25 psi (ci/co set such that the condenser runs cont. with
>a cooling call)
>Freezer Temp: Min 3-4 F (primary control; thermostat w/ pump down solenoid)
>Superheat: 13 F @ compressor (Well insulated line ~ 30' from freezer to
>condenser)
>Dish Pressure: 245 psi (cond fan ran cont w/ call for cooling)
>Ambient 60 F
>Condenser Coil Clean
>Door gaskets in ok shape.
>Cool where freezer is located.
>All of freezer stock very well frozen.
>(I know: Is that all the info?)
>
>From talking to the owner; When he manually defrosts the evap coil, he notices
>that there is steam coming from the defrost elements and the water he uses to
>defrost the coil flows down the drain line. Also he noted that the evap fan
>does not come on for a min or so after the solenoid opens on a call for
>cooling. He also told me that the company that did the c/o made many visits
>after the installation and did at least the following: c/o the expansion
>valve, did superheat adustments, removed some of the refrigerant (may explain
>the bubbles in the sight glass). He also told me that even after the company
>tried many times to correct the problem, with no further adjustments, the
>temperature went from in the range of 15-18 F to 3-4 F. He needs 0 to -5 F to
>meet health department requirements.
>
>Do any of you have any experience w/ changing from R12 to R404a? From the
>Dupont literature I have this is not a recommended replacement for R12 but it
>is for R502.
>
>I am thinking that possibly the first company may have had some internal
>problems due to the POE oil and mineral oil from the old R12 condenser unit.
>That may be what led to the expansion valve replacement. Anyway, the 25 psi
>suction is quite high to achieve -5 F. That is only a 5 degree delta T. And
>the 13 F superheat is rather high.
>
>I would appreciate any and all help on this problem.
>
>Thanks
>
>
>
>
>Keith Aubert Air-Care
Mike
UA local 370
RonH
I have to go with the oil problems first, how did they go
about
removing the mineral oil out of the system? How long was the system
open to the atomshpere? I try and do not ever let a p.o.e. system ever
remain open to atomshpere any longer than it takes me to get that pipe
closed to air. P.O.E. is highly hydroscopic. Is their any indications of
air in the system?
RonH
Kjobear151 wrote in message
<20000106200816...@ng-fk1.aol.com>...
Kjobear151
turtle4air
this is turtle.
The problem was started with 404-A in place of 12 . Poor choice but
all the other problems just followed.
do check to see if you have the defrost running with the cooling mode
at any given time.
Like the others have said moisture in the poe type Eral .
TURTLE
--
Free audio & video emails, greeting cards and forums
Talkway - http://www.talkway.com - Talk more ways (sm)
Murdentech
"turtle4air" <tur...@worldnetla.net > wrote in message
news:yZcd4.26199$Mg.3...@c01read03-admin.service.talkway.com...
> On 07 Jan 2000 01:08:16 GMT kjobe...@aol.comadd (Kjobear151) wrote:
> > I went to a Dairy Queen today on a walkin freezer call. From what I
could tell
> > from talking to the owner; the freezer was originally an R12 system
that had a
> > R404a condenser unit installed when the compressor failed in the old R12
> > system.
> >
> > There seems to be two problems with the system; (1) The lowest temp
that can
> > be obtained even in the winter and with no door opening for hours, is
about 3-4
> > F. & (2) The owner has to manually defrost the coil every 7 -10 days.
> >
> > We manually defrosted the coil which was very iced-up. Then ran the
system and
> > found the following:
> >
> > Bubbles in sight glass w/ low load conditions; Added R404a till clear.
Now on 408A and 409A they specifically tell you to toss the sight glass out
the window, or just ignore it at any case. You will ALWAYS have bubbles in
sight glass (at least on 408 and 409) so check that out from your
refrigeration supplier...... You may have overcharged it. We did one with
409A and dumped a whole 30 lb cyliner in the thing until the bubbles
disappeared, the cooling effect disappeared right along with the
bubbles..... opps !
Didn't matter though as a week later the thing developed another leak and
lost all that precious magic gas.
> >
> > And then had the following:
> > Suction Pressure: 25 psi (ci/co set such that the condenser runs
cont. with
> > a cooling call)
> > Freezer Temp: Min 3-4 F (primary control; thermostat w/ pump down
solenoid)
> > Superheat: 13 F @ compressor (Well insulated line ~ 30' from freezer
to
> > condenser)
Forget superheat if it's a TXV system. You have to check SUBCOOLING, throw
superheat out the window if it's a TXV or not fixed orifice.... and don't
expect your temps and pressures to behave in any logical order from R-12,
THEY WON'T... They'll act as crazy as the Cincinnati City Council during
election year. You have to ask your supplier what they should be.
> > Dish Pressure: 245 psi (cond fan ran cont w/ call for cooling)
> > Ambient 60 F
> > Condenser Coil Clean
> > Door gaskets in ok shape.
> > Cool where freezer is located.
> > All of freezer stock very well frozen.
> > (I know: Is that all the info?)
> >
Head seems awful high, and the cond. fan should be controlled by head
pressure, might cycle at 60' ambient, depends on load.
> > From talking to the owner; When he manually defrosts the evap coil, he
notices
> > that there is steam coming from the defrost elements and the water he
uses to
> > defrost the coil flows down the drain line. Also he noted that the evap
fan
> > does not come on for a min or so after the solenoid opens on a call for
> > cooling.
Evap. fan should run all the time except on defrost with electric defrost
elements energized.
He also told me that the company that did the c/o made many visits
> > after the installation and did at least the following: c/o the
expansion
> > valve, did superheat adustments, removed some of the refrigerant (may
explain
> > the bubbles in the sight glass). He also told me that even after the
company
> > tried many times to correct the problem, with no further adjustments,
the
> > temperature went from in the range of 15-18 F to 3-4 F. He needs 0
to -5 F to
> > meet health department requirements.
> >
You may want to try shorter defrost cycles with more defrost cycles per day.
And check your defrost heaters to make sure they are doing their job.
> > Do any of you have any experience w/ changing from R12 to R404a? From
the
> > Dupont literature I have this is not a recommended replacement for R12
but it
> > is for R502.
> >
I have used the 408A (which is for 502) in and R-12 freezer with no problem,
so if 404 is also for freezer application, you should be okay.....
They talk about temp glide accros evap. coil. each one has a different
"glide" which might cause one side to be colder than the other side of the
coil. If you have a defrost termination sensor that may be your problem. I
had to eliminate the defrost termination sensor on one unit to get it to act
right.
> > I am thinking that possibly the first company may have had some internal
> > problems due to the POE oil and mineral oil from the old R12 condenser
unit.
> > That may be what led to the expansion valve replacement. Anyway, the 25
psi
> > suction is quite high to achieve -5 F. That is only a 5 degree delta T.
And
> > the 13 F superheat is rather high.
Forget the oil, that's hogwash, as long as there is oil in the system and no
moisture you'll be fine.
> >
> > I would appreciate any and all help on this problem.
> >
> > Thanks
> >
Hope this helps a little.... I'm trying to not let refrigeration become a
habit, but the faster I run the louder they hollar...... every time I almost
have a day off someone's damn refrigerator gets in the way.
--
Jeff Murden
Cincinnati, Ohio
www.murdentech.com
"Quality is worth every dime".
Kjobear151
Yes it is advancing and the elements do come on and the fans do cycle off
during the defrost and back on w/ a delay after the defrost. Have not checked
yet if the defrost is adequate to clear the coil. We plan to ck back w/ the
owner and make another followup call.
>Is there a head pressure control device?
Yes.
>Sounds to me like it's a little low on the superheat at the comp. Copeland
>usually gives you 20 there. You may be flooding. I could be wrong
>(everybody tell me so please :-))
>
We will check the superheat at the evaporator. Flooding would make some sense.
The evap pressure is just way too high.
Keith Aubert Air-Care
Kjobear151
>the evap fan thing suggests that the defrost circuit is not wired
>right, did you check it? The fans should be running all the time
>except for when its in defrost.
>
Really dont know for sure what was done before we were called in. Not even
sure it was R!2 before just have to go by what the owner knows of the system.
The fans do run cont except during the defrost and a short delay there after.
I reread my post and I realize that it was not worded very well. I did not
mean to say that the fans cycle each time on a pump down but only delay after a
defrost. The defrost is set for 4 per day and have a term stat w/ 17 min
safety c/o.
Keith Aubert Air-Care
Kjobear151
>at any given time.
We will check that. Dont think so but anything is possible.
Keith Aubert Air-Care
Kjobear151
You think she might be heating the thing up?? :-)
>Now on 408A and 409A they specifically tell you to toss the sight glass out
>the window, or just ignore it at any case. You will ALWAYS have bubbles in
>sight glass (at least on 408 and 409) so check that out from your
>refrigeration supplier...... You may have overcharged it. We did one with
>409A and dumped a whole 30 lb cyliner in the thing until the bubbles
>disappeared, the cooling effect disappeared right along with the
>bubbles..... opps !
It could be overcharged. One thing I did notice that I did not mention in my
original post was that the suct was at 20 psi w/ the bubbles and w/o bubbles it
was at 25 psi.
Just for info:
There is a cooler right next to this freezer that we changed a compressor on
and went w/ 409a. It works great w/ no bubbles in the sight glass.
Also we changed a compressor in a 404a soft serve icecream freezer and it works
great w/ no bubbles in the sight glass.
Keith Aubert Air-Care
Kjobear151
>They talk about temp glide accros evap. coil. each one has a different
>"glide" which might cause one side to be colder than the other side of the
>coil. If you have a defrost termination sensor that may be your problem. I
>had to eliminate the defrost termination sensor on one unit to get it to act
>right.
This sounds like something we might want to look at.
Keith Aubert Air-Care
Whitewater Jamboree
Murdentech <rjmurde...@murdentech.com> wrote in message
> Forget superheat if it's a TXV system. You have to check SUBCOOLING, throw
> superheat out the window if it's a TXV or not fixed orifice.... and don't
> expect your temps and pressures to behave in any logical order from R-12,
> THEY WON'T... They'll act as crazy as the Cincinnati City Council during
> election year. You have to ask your supplier what they should be.
?? TXV maintains a fairly "constant" superheat. Superheat should be set as
close to the minimum stable signal point. (Setting that causes smallest
sensible change in the bulb temperature.) Practically speaking, close to 10
F at the outlet. If system is flooding, suction pressure will be too high,
limiting the temp that the system can reach.
Robert
JohnTan
Have not seem your post for sometime.
Actually R404A is not a closed replacement for retrofit to R-12 system
( capacity to capacity )......but down the line, the contractor may
have considered other constraints like availability of R-134a
components,etc.
Maybe you can provide us the details:-
a) compressor brand/model from the nameplate
b) txv. model
c) is condenser coil "original"....properly sized condensing unit
rather than using back the old R-12 condenser coil.
Some retrofit check list for your reference:-
http://www.genetron.com/bul/404ab.html
http://www.genetron.com/rg/404arg.html
temp. pressure chart:-
http://www.genetron.com/temp/404a.tempf.txt
Meantime:-
a)ensure system is using POE oil ( mineral oil not misicible with R404A
may "logged" and "insulate" the evaporator coil causing poorer heat
transfer. Flush the coil from any logged oil.
b)try not to "top-up" R404A; preferably to draw out all existing R404A
and charge with in liquid the new R404A.
c) proper evacuation is necessary and crucial.
c))try change the liquid driers at least twice using the better known
Sporlan or Alco driers ( properly size and for the new refrigerants
application ). Field feedback shows that running the system with a new
drier for a day and subsequently changing to a new drier will be ideal.
Hope this helps.
Cheers.
John Tan
On 07 Jan 2000 01:08:16 GMT kjobe...@aol.comadd (Kjobear151) wrote:
> I went to a Dairy Queen today on a walkin freezer call. From what I could tell
> from talking to the owner; the freezer was originally an R12 system that had a
> R404a condenser unit installed when the compressor failed in the old R12
> system.
>
> There seems to be two problems with the system; (1) The lowest temp that can
> be obtained even in the winter and with no door opening for hours, is about 3-4
> F. & (2) The owner has to manually defrost the coil every 7 -10 days.
>
> We manually defrosted the coil which was very iced-up. Then ran the system and
> found the following:
>
> Bubbles in sight glass w/ low load conditions; Added R404a till clear.
>
> And then had the following:
> Suction Pressure: 25 psi (ci/co set such that the condenser runs cont. with
> a cooling call)
> Freezer Temp: Min 3-4 F (primary control; thermostat w/ pump down solenoid)
> Superheat: 13 F @ compressor (Well insulated line ~ 30' from freezer to
> condenser)
> Dish Pressure: 245 psi (cond fan ran cont w/ call for cooling)
> Ambient 60 F
> Condenser Coil Clean
> Door gaskets in ok shape.
> Cool where freezer is located.
> All of freezer stock very well frozen.
> (I know: Is that all the info?)
>
> From talking to the owner; When he manually defrosts the evap coil, he notices
> that there is steam coming from the defrost elements and the water he uses to
> defrost the coil flows down the drain line. Also he noted that the evap fan
> does not come on for a min or so after the solenoid opens on a call for
> cooling. He also told me that the company that did the c/o made many visits
> after the installation and did at least the following: c/o the expansion
> valve, did superheat adustments, removed some of the refrigerant (may explain
> the bubbles in the sight glass). He also told me that even after the company
> tried many times to correct the problem, with no further adjustments, the
> temperature went from in the range of 15-18 F to 3-4 F. He needs 0 to -5 F to
> meet health department requirements.
>
> Do any of you have any experience w/ changing from R12 to R404a? From the
> Dupont literature I have this is not a recommended replacement for R12 but it
> is for R502.
>
> I am thinking that possibly the first company may have had some internal
> problems due to the POE oil and mineral oil from the old R12 condenser unit.
> That may be what led to the expansion valve replacement. Anyway, the 25 psi
> suction is quite high to achieve -5 F. That is only a 5 degree delta T. And
> the 13 F superheat is rather high.
>
> I would appreciate any and all help on this problem.
>
> Thanks
>
>
>
>
> Keith Aubert Air-Care
Polleke
The sightglass can have bubbles as this is gas in the liquid.
If the condenser is just a little colder as your sightglass you will
always see bubbles whatever the charge.
so please do check the charge.
This will only have effect on the condensing pressure tho
so if temp is lower as pressure for the stuff inside you will have to
take a little out.
You can see this fairly easy to check it by putting your hand on the
condenser from top to bottom on top it will be hot and on the bottom
it should have same temp as the liquid line.
if only small top is hot to much charge is in.
just connect a empty bottle to liquid line and check the discharge
pressure if it drops let it drop until ok.
a 13 F superheat is very good.
maybe the unit is just a little small and cant keep up.
please check the motorcurrent too as this can be a good indication of
level of capacity the unit is doing.
feel the heads of compressor for heat maybe one cilinder not working
next visit make a diagram and do the simple theory. do it every day
and also nice explanation to owner. Normally i ask the owner what he
thinks is the problem.
switch of the fan on the evaporator and check the suction pressure if
it drops compressor too small.
check for nice free airflow on the evaporator.
ftwhd
If it is a Bohn coil chances there is a orifice in the distributor
that will need to be changed. Use the one for 502.
One other thing that may have happened is the unit accidentally was
charged with gas instead of liquid. This could account for the high
head and lack of cooling.
As far as the defrost goes it sounds ok except I would give it a 25-35
min defrost time instead of 17 min. Pull the wire off the X terminal
set the defrost for 4 a day at 35 min a day and see if the icing
problem goes away. If it does, increase the length of time on the
termination stat, put the wire back on X make sure all the heaters
work and the door gasket seals tight, and it should be fine. The fan
delay after defrost is right.
Did you check to make sure the condenser is sized right and that the
TXV is the correct one for the evap? You said you had a superheat of
13F, I assume this is on the evap and not at the compressor. Where
did you take the coil temp measurement at, and did you take the glide
into consideration? What you really want to see on low temp is 5-6F,
that seems to work the coil fine and getting temps below 0 should be
no problem. What is the TD across the evap? How does the frost
pattern look? normal?
Charging by sight glass is wrong with blends as you will tend to be
overcharged. I usually charge it by superheat and normally although
not all the time, the SG is about half full.
Is the compressor a tin can or semi hermitic? If it is a semi then I
would change the oil 2 more times to get the mineral oil down to an
acceptable level. If its a tin can, changing the oil is a bit more of
a PITA but it still should be done, just tell the customer to expect a
good size bill for what he may see as a waste of money. I don't think
the small percentage of mineral oil left in the system is the problem
however. Let us know what the real problem turns out to be ok?
Mike
UA local 370
danny
404 a will run normally at 250 to 300 psi on an 80 f day . about your
statement of the oil , i would ask you to read a little more on equipment
containing 134 ,404 , 507 . with all due respect , this is probably the most
important thing in the system , if that oil contains moisture it will become
acid , and you will have a dead compressor in your hands , if it was a b oil
i would not even worry after the first oil change , but poe oil will bite
you back if it is allowed to come in contact with air . i have taken 404a
to minus 50 f , it is a great refrigerant . so - 15 f should be no problem
. you may have lots of mineral oil in a system but what good is it if it is
not compatiable with your refrigerant .news:Lefd4.8097$x02.1...@typhoon2.kc.rr.com...
danny
funny you should mention that . we did one years ago were the guy said it
would never be colder than o f here , the next day he had to demelt the door
, it got to -40 f . and the moisture from the bottom of the door froze shut
, when i got there there was 3 blocks full af trucks waiting for fish . all
i did was shut the unit off ,while he used hot water at the door.
Whitewater Jamboree <whitewate...@yahoo.com> wrote in message
news:s7ajca...@corp.supernews.com...
>
> Kjobear151 <kjobe...@aol.comadd> wrote in message
> system and
> > found the following:
>
>
to
> > condenser)
>
aren't
> measuring so close you're picking up heat from the comp. Check the
> superheat at the evap. outlet.
>
> > Ambient 60 F
>
>
the
> > Dupont literature I have this is not a recommended replacement for R12
but
> it
> > is for R502.
>
sizes
> are appropriate and run with it. The only problem I ever had was on a
> reach-in I changed. The customer had turned the stat down all the way
when
> it went out. I didn't remember to set it back & left. He called me the
> next morning bitching because all 4 doors had frozen shut (as it was -30
F)
> oops. :-)
>
> > problems due to the POE oil and mineral oil from the old R12 condenser
> unit.
driers
> makes for a pretty smooth retro.
>
> psi
> > suction is quite high to achieve -5 F. That is only a 5 degree delta T.
> And
> > the 13 F superheat is rather high.
>
Copeland
> usually gives you 20 there. You may be flooding. I could be wrong
> (everybody tell me so please :-))
>
> Robert
>
>
Kjobear151
>Is their any indications of
>air in the system?
No. Nothing indicates non condensibles in the system.
Keith Aubert Air-Care
Dan Murphy
you just about where you are. It sounds like an undersized unit. Bubbles in
the sight glass support this. You need at least a 20 psig suction, and most
likely a 15 psig suction since most freezer coils are sized with a 15 degree
TD. Your superheat sounds ok. The fan delay is normal. Your icing problem is
most likely a separate issue, such as terminating too quickly or too short a
defrost. Discharge pressure is high unless you have winter condensing pressure
control valve. If you don't have a flooding valve, the condensing pressure
points again to an undersized unit if it is 60 degees outside.
> > I went to a Dairy Queen today on a walkin freezer call. From what I could
> tell
> > from talking to the owner; the freezer was originally an R12 system that
> had a
> > R404a condenser unit installed when the compressor failed in the old R12
> > system.
> >
> > There seems to be two problems with the system; (1) The lowest temp
> that can
> > be obtained even in the winter and with no door opening for hours, is
> about 3-4
> > F. & (2) The owner has to manually defrost the coil every 7 -10 days.
> >
> > We manually defrosted the coil which was very iced-up. Then ran the
> system and
> > found the following:
> >
> > Bubbles in sight glass w/ low load conditions; Added R404a till clear.
> >
> > And then had the following:
> > Suction Pressure: 25 psi (ci/co set such that the condenser runs cont.
> with
> > a cooling call)
> > Freezer Temp: Min 3-4 F (primary control; thermostat w/ pump down
> solenoid)
> > Superheat: 13 F @ compressor (Well insulated line ~ 30' from freezer to
> > condenser)
> > Dish Pressure: 245 psi (cond fan ran cont w/ call for cooling)
> > Ambient 60 F
> > Condenser Coil Clean
> > Door gaskets in ok shape.
> > Cool where freezer is located.
> > All of freezer stock very well frozen.
> > (I know: Is that all the info?)
> >
> > From talking to the owner; When he manually defrosts the evap coil, he
> notices
> > that there is steam coming from the defrost elements and the water he uses
> to
> > defrost the coil flows down the drain line. Also he noted that the evap
> fan
> > does not come on for a min or so after the solenoid opens on a call for
> > cooling. He also told me that the company that did the c/o made many
> visits
> > after the installation and did at least the following: c/o the expansion
> > valve, did superheat adustments, removed some of the refrigerant (may
> explain
> > the bubbles in the sight glass). He also told me that even after the
> company
> > tried many times to correct the problem, with no further adjustments, the
> > temperature went from in the range of 15-18 F to 3-4 F. He needs 0 to -5
> F to
> > meet health department requirements.
> >
> > Do any of you have any experience w/ changing from R12 to R404a? From the
> > Dupont literature I have this is not a recommended replacement for R12 but
> it
> > is for R502.
> >
> > I am thinking that possibly the first company may have had some internal
> > problems due to the POE oil and mineral oil from the old R12 condenser
> unit.
> > That may be what led to the expansion valve replacement. Anyway, the 25
> psi
> > suction is quite high to achieve -5 F. That is only a 5 degree delta T.
> And
> > the 13 F superheat is rather high.
> >
> > I would appreciate any and all help on this problem.
> >
> > Thanks
> >
> >
> >
> >
> > Keith Aubert Air-Care
Dan Murphy
on. It happened to me once.
RAC
but you still must have correct super heat in order to control the cooling of
the compressor and also maintain the designed BTU evaporative rate of the coil.
The two are complete different subjects and have nothing to do with each other.
Is their something I'm missing here????
Rich
Murdentech wrote:
Jeff...@webtv.net
nice.Some freezer evaporators like Larkin have gizmos that won't
energize the fan until the coil gets 0.
Sonofdawra
>it drops compressor too small.
To my way of thinking, any system where you shut off the evaporator fan, the
suction pressure will fall. This has nothing to do with the compressor being
too small but has to do with the amount of heat is being absorbed by the
evaporator.
Low air flow over the evaporator coil will always drop the suction pressure.
Sonofdawra
>safety c/o.
I would set the defrost time to around 30 minutes. I assume you have a Paragon
timer or comparable with a termination solenoid. If the defrost termination
thermostat is set properly, then the defrost cycle will run as long as needed,
but at 17 minutes, you may be terminating on time instead of coil temperature.
If you are defrosting 4 times per day, then it is unlikely that your cycles
would need to exceed 30 minutes.
Sonofdawra
>condenser)
>Dish Pressure: 245 psi
>Anyway, the 25 psi
>suction is quite high to achieve -5 F. That is only a 5 degree delta T.
By my chart, 25 psig for R-404A is a -9F boiling point which with a 3 to 4
degree F box temperature would equate to more like 12 or 13 degrees TD.
>And
>the 13 F superheat is rather high.
Not really at all since you indicate that is at the condensing unit-----what is
the superheat at the outlet of the evap coil----much more important data.
Superheat of 6 degrees F or slightly less at the outlet of the evaporator would
be in line for low temp.
The 245 psi head pressure sounds high to me. What is your subcooling? Normal
or excessive? I would bet on the system being overcharged and running
excessive subcooling.
Isn't it fun trying to clean up someone else's mistake :o)
Have a nice day, Ron
Kjobear151
I have been reading the group all along just have still not been able to catch
up since I fell behind from the busy summer. But I am still working on it.
Keith Aubert Air-Care
Razoreye
any higher level.
2. Proper TXV and orifice and is it adjusted to above SH?
3. Any pres drop in low side from coil to Comp?
4. Change over to 507 it's good stuff and will perform well in Low temp sys.
5. Evap coil sized correctly or blocked at all?
RW- Rep of Tx
ba...@ptd.net
>I went to a Dairy Queen today on a walkin freezer call. From what I could tell
>from talking to the owner; the freezer was originally an R12 system that had a
>R404a condenser unit installed when the compressor failed in the old R12
>system.
>
>There seems to be two problems with the system; (1) The lowest temp that can
>be obtained even in the winter and with no door opening for hours, is about 3-4
>F. & (2) The owner has to manually defrost the coil every 7 -10 days.
>
>We manually defrosted the coil which was very iced-up. Then ran the system and
>found the following:
>
>Bubbles in sight glass w/ low load conditions; Added R404a till clear.
>
>And then had the following:
>Suction Pressure: 25 psi (ci/co set such that the condenser runs cont. with
>a cooling call)
>Freezer Temp: Min 3-4 F (primary control; thermostat w/ pump down solenoid)
>Superheat: 13 F @ compressor (Well insulated line ~ 30' from freezer to
>condenser)
>Dish Pressure: 245 psi (cond fan ran cont w/ call for cooling)
>Ambient 60 F
>Condenser Coil Clean
>Door gaskets in ok shape.
>Cool where freezer is located.
>All of freezer stock very well frozen.
>(I know: Is that all the info?)
>
>From talking to the owner; When he manually defrosts the evap coil, he notices
>that there is steam coming from the defrost elements and the water he uses to
>defrost the coil flows down the drain line. Also he noted that the evap fan
>does not come on for a min or so after the solenoid opens on a call for
>cooling. He also told me that the company that did the c/o made many visits
>after the installation and did at least the following: c/o the expansion
>valve, did superheat adustments, removed some of the refrigerant (may explain
>the bubbles in the sight glass). He also told me that even after the company
>tried many times to correct the problem, with no further adjustments, the
>temperature went from in the range of 15-18 F to 3-4 F. He needs 0 to -5 F to
>meet health department requirements.
>
>Do any of you have any experience w/ changing from R12 to R404a? From the
>Dupont literature I have this is not a recommended replacement for R12 but it
>is for R502.
>
>I am thinking that possibly the first company may have had some internal
>problems due to the POE oil and mineral oil from the old R12 condenser unit.
>That may be what led to the expansion valve replacement. Anyway, the 25 psi
>suction is quite high to achieve -5 F. That is only a 5 degree delta T. And
>the 13 F superheat is rather high.
>
>I would appreciate any and all help on this problem.
>
>Thanks
>
>ll
>
>
>Keith Aubert Air-Care
If you want the headache your first thing is proper orfice with proper
distributer, next you need externally equalized expansion valve to
start with. Then, deal with the oil issues that everyone else has
talked about. But, by the time you add up your labor cost to
straighten this mess out why don't you go get an R-12 low temp
condensing unit, R-12 expansion valve, and a filter drier. Evacuate
and charge with 409 A and get the hell out of there and save your self
a weeks worth of headache and you 'll you will look like a hero.
Murdentech
available reading), but you won't be able to get accurate superheat until
the box is running under "normal" conditions. I've been told to charge using
sub-cooling with TXV. I do like to check superheat once the thing is running
and balanced out as close as you can get it. The sight glass is not a good
way to check charge when using new refrigerants, because each one has it's
own charicteristics.
As for the oil, I may have misspoke. They want you to change the oil, POE is
subject to moisture problems. But it is compatible with mineral to an
extent. I did say "as long as you don't have any moisture in the system". I
have been told that "complete" oil change isn't as critical as "they" want
you to think. (unless you are using 134A or something, which is why 134A is
mostly seen in new systems and not so many retro-fits).
There are a lot of folks with more "hands-on" using newer gasses, so I'll
sit back and just listen.... hell I still have 3 jugs of R-12 on the
shelf..... :)
Jeff Murden
"RAC" <lib...@lrbcg.com> wrote in message
news:3876B4FC...@lrbcg.com...
RonH
>>I went to a Dairy Queen today on a walkin freezer call. From what I could
tell
>>from talking to the owner; the freezer was originally an R12 system that
had a
>>R404a condenser unit installed when the compressor failed in the old R12
>>system.
>>
>>There seems to be two problems with the system; (1) The lowest temp
that can
>>be obtained even in the winter and with no door opening for hours, is
about 3-4
>>F. & (2) The owner has to manually defrost the coil every 7 -10 days.
>>
>If you want the headache your first thing is proper orfice with proper
>distributer, next you need externally equalized expansion valve to
>start with. Then, deal with the oil issues that everyone else has
>talked about. But, by the time you add up your labor cost to
>straighten this mess out why don't you go get an R-12 low temp
>condensing unit, R-12 expansion valve, and a filter drier. Evacuate
>and charge with 409 A and get the hell out of there and save your self
>a weeks worth of headache and you 'll you will look like a hero.
Sorry , I have to disagree with you on a point here, 409a is not a good
choice of refrigerant's below 20deg, and the man said they need
to run the box at 0 to minus 5. Like 404a ,408,507,etc. etc.
RonH
RSCamero
>I went to a Dairy Queen today on a walkin freezer call. From what I could tell
>from talking to the owner; the freezer was originally an R12 system that had a
>R404a condenser unit installed when the compressor failed in the old R12
>system.
Did they change the txv to a 502 txv ?
>
>There seems to be two problems with the system; (1) The lowest temp that can
>be obtained even in the winter and with no door opening for hours, is about 3-4
>F. & (2) The owner has to manually defrost the coil every 7 -10 days.
1.) I had the same problem with a R-12 W.I. freezer converted
to 404A. Never could get that box below 0* F. We use R401B for
these conversions now.
2.) Not enough defrost time or under charged. Does the coil
ice up uniformly or just on one area of the coil ?
>Bubbles in sight glass w/ low load conditions; Added R404a till clear.
May not have been necessary.
>
>And then had the following:
>Suction Pressure: 25 psi (ci/co set such that the condenser runs cont. with
>a cooling call)
>
>Freezer Temp: Min 3-4 F (primary control; thermostat w/ pump down solenoid)
>Superheat: 13 F @ compressor (Well insulated line ~ 30' from freezer to
>condenser)
SH seems a little low to the compressor. What is it at the
sensing bulb ?
>Dish Pressure: 245 psi (cond fan ran cont w/ call for cooling)
>Ambient 60 F
>Condenser Coil Clean
>Door gaskets in ok shape.
>Cool where freezer is located.
>All of freezer stock very well frozen.
>(I know: Is that all the info?)
>
>From talking to the owner; When he manually defrosts the evap coil, he notices
>that there is steam coming from the defrost elements and the water he uses to
>defrost the coil flows down the drain line. Also he noted that the evap fan
>does not come on for a min or so after the solenoid opens on a call for
>cooling. He also told me that the company that did the c/o made many visits
>after the installation and did at least the following: c/o the expansion
>valve, did superheat adustments, removed some of the refrigerant (may explain
>the bubbles in the sight glass). He also told me that even after the company
>tried many times to correct the problem, with no further adjustments, the
>temperature went from in the range of 15-18 F to 3-4 F. He needs 0 to -5 F to
>meet health department requirements.
>
>Do any of you have any experience w/ changing from R12 to R404a? From the
>Dupont literature I have this is not a recommended replacement for R12 but it
>is for R502.
You might want to try a R-502 txv. The pressures run closer
to 502 than they do to R-12. I wouldn't guarentee it because I don't
know what the evap. coil was designed for.
>
>I am thinking that possibly the first company may have had some internal
>problems due to the POE oil and mineral oil from the old R12 condenser unit.
>That may be what led to the expansion valve replacement. Anyway, the 25 psi
>suction is quite high to achieve -5 F. That is only a 5 degree delta T. And
>the 13 F superheat is rather high.
25 psi on my charts that I use say that the saturated suction
should be at -9* F. The 245 psi on the head side is good or at least
it is what I shoot for.
>Thanks
>Keith Aubert Air-Care
...Ron
--
1968 CamaroRS (winter is here and time to hibernate)
1986 MonteCarlo (you know the one... long enough to be
a land yacht without actually being called one)
rscamer...@frontiernet.net
barr
>>
>>>I went to a Dairy Queen today on a walkin freezer call. From what I could
>tell
>>>from talking to the owner; the freezer was originally an R12 system that
>had a
>>>R404a condenser unit installed when the compressor failed in the old R12
>>>system.
>>>
>>>There seems to be two problems with the system; (1) The lowest temp
>that can
>>>be obtained even in the winter and with no door opening for hours, is
>about 3-4
>>>F. & (2) The owner has to manually defrost the coil every 7 -10 days.
>>>
>>>Bubbles in sight glass w/ low load conditions; Added R404a till clear.
>>>
>>>And then had the following:
>>>Suction Pressure: 25 psi (ci/co set such that the condenser runs cont.
>with
>>>a cooling call)
>>>Freezer Temp: Min 3-4 F (primary control; thermostat w/ pump down
>solenoid)
>>>Superheat: 13 F @ compressor (Well insulated line ~ 30' from freezer to
>>>condenser)
>>If you want the headache your first thing is proper orfice with proper
>>distributer, next you need externally equalized expansion valve to
>>start with. Then, deal with the oil issues that everyone else has
>>talked about. But, by the time you add up your labor cost to
>>straighten this mess out why don't you go get an R-12 low temp
>>condensing unit, R-12 expansion valve, and a filter drier. Evacuate
>>and charge with 409 A and get the hell out of there and save your self
>>a weeks worth of headache and you 'll you will look like a hero.
>
>Sorry , I have to disagree with you on a point here, 409a is not a good
>choice of refrigerant's below 20deg, and the man said they need
>to run the box at 0 to minus 5. Like 404a ,408,507,etc. etc.
>RonH
>
Works as well as R-12, remember it was an R-12 system that was
retrofitted
ftwhd
409 is as good as choice as any for an 12 retrofit. It will easily
get you too zero and below.
Mike
UA local 370
RonH
ftwhd wrote in message ...
Mike,
I'm not disputing how it work's, but when wanting the lower
temp.'s 0 deg. and below, it isn't recommeded. 409A work's better
at refrig. temp's (36-40degf) in my experience. I was told you shouldnt use
it below
20 deg f unless changing out the oil also. And if your going to that trouble
why not use a refrigerant designed for lower temp's?
As before remember he's wanting sub-zero temp. check the retrofit
chart's , which one would you choose? not 409a
Just my opinion
RonH