Reach-In Freezer Fan

[VAV616]

Say we have a small reach in freezer.
ive evacuated it, vacuumed, and weighed in the charge.
and cleaned the condenser thoroughly. so i know that much is done.
yet i still seem to have problems getting the case temp much lower
than 27* at best. One thing that seems strange is that the air from the
E fan doesnt seem to be blowing very hard. This Hobart QF2 has only
One E Fan and discharges through a column in the back center of the
case. Is it likely the fan is not turning fast enough? Or i wonder if somebody in the past has replaced it with the wrong motor. Is there anyway to verify the fan speed short of an IR Tach gun?

??

[marter]

stick a zip tie in the fan and count very fast :p

other then that i wouldn't know of another way.. maybe easier to just get the motor its supposed to have and go from there

[monkeyman#1]

stick a zip tie in the fan and count very fast

LMAO. Agree wtih the rest of your response as well. Just verify if motor is correct via manufacturer,

[Poodle Head Mikey]

In the fan blade the correct rotation for the motor?

Is this a little open-frame fan motor?

PHM
---------



-------pitched for theCould
Say we have a small reach in freezer.
ive evacuated it, vacuumed, and weighed in the charge.
and cleaned the condenser thoroughly. so i know that much is done.
yet i still seem to have problems getting the case temp much lower
than 27* at best. One thing that seems strange is that the air from the
E fan doesnt seem to be blowing very hard. This Hobart QF2 has only
One E Fan and discharges through a column in the back center of the
case. Is it likely the fan is not turning fast enough? Or i wonder if somebody in the past has replaced it with the wrong motor. Is there anyway to verify the fan speed short of an IR Tach gun?

??

[VAV616]

stick a zip tie in the fan and count very fast :p



HaHa, :p

Now, i have weighed the charge in , filling my gauge hoses first , then zeroing the scale to be sure im not counting the 3 or 4 oz in the hoses. so im sure the charge should be about right. and i get
20# AKA 404a @ -16*
240#
with the case temp at 40* im not surprised to see the SH at 60+*(cap tube)
but what bothers me is with a return of 40* my supply is only 35* at best.
shouldnt i see more like 10* across the coil? and the normal operating temp of the evap should be -15*, yet would it already be that low when the case is far from its proper temp? i thought i might expect to see it higher than that untill the case gets a bit colder.

im pretty convinced now that ill just change the fan and see what difference it makes. But IDK how hard it will be to get the specs outa HOHOHObart

TY

VAV

[VAV616]

i havent taken a good look at the fan yet, is there a tendency of
open frame motors to slowly open up and slow down, or something?
I am sure that it turns the right way though, as the return goes in the
top of the case, and the supply comes out the center column down the
back of the box. but i have no way to verify what the proper blade pitch should be.
ty

VAV

[Poodle Head Mikey]

But rather the way the blade is suppose to turn. Is the blade turning so as to 'cup' or 'scoop' the air? If the blade or motor was replaced and do not match in rotation then the air flow will be much reduced.

That was my point.

PHM
---------



i haven't taken a good look at the fan yet, is there a tendency of open frame motors to slowly open up and slow down, or something?
I am sure that it turns the right way though, as the return goes in the
top of the case, and the supply comes out the center column down the
back of the box. but i have no way to verify what the proper blade pitch should be.
ty

VAV

[nateneff]

If the fan were spinning slower than it was designed to wouldn't that give you a greater air TD across the coil? If your evap fan is slow that would also give you a low heat load. With a low heat load your SH shouldn't be at 60* after running for a short while. Are you sure your evap is feeding properly? Is it a single capillary circuited evaporaor, or multiple? What does the frost formation look like on the coil? And how long did you let it run?

I have bought a new laser tachometer off of ebay for about $20 delivered a couple years ago and it works fine. I think the brand was nekko or neico or somethin like that. I wonder if it was made in china????LOL

[KB Cool]

Whats your SC? Sounds like you maybe stacking refrigerant in the condensor and need to change the partialy restricted cap tube.

[kmitech]

we take care of one QF2 and two QF3's. They all have 9 watt motor, 1550rpm, 115v, cw.

[VAV616]

Yes, it is a dual cap tube system. and i have not measured the SC.
/baddog
trying to solder captubes doesnot sound like fun.
I do now realize that less airflow would indeed make a Greater delta T.
So, i guess restriction makes more sense but, i thought with a cap tube restriction i might see an iceball forming at the point where the restriction is.

The coil forms ice begining from the side where the cap tube enters, and the build up starts in the middle of the coil on that side. It does seem to freeze up too soon. i have the clock set to four times a day for about 20 min, and actually i think it doesnt take quite that long to defrost. but i havent been able to sit and watch the unit to see exaclty how it behaves.
Ill go back today and measure the SC.

ty

VAV

[VAV616]

Ive heard some suggest replacing captubes with a TEV on this type of unit.
What do you guys think of that?

[crackertech]

Ive heard some suggest replacing captubes with a TEV on this type of unit.
What do you guys think of that?

You would need a reciver to do that.

[swinginutters]

I worked on that same model last week, running about 50 degress, felt the air movement, thought the evap fan wasn't even running. Took the top off ,evap fan was running fine. I think thats just how those are. I found a smal pinhole in one of the cap tubes, fixed it new LL dryer. Weighed in charge and it runs great. sounds to me like your cap tubes are restricted.

just a thought and another question, regaurding the last post, it sounds like a good idea to convert to a TXV but If your gonna convert to a TXV don't you need a reciever, or can You use a over sized dryer or is that considered Micky mouse?

[VAV616]

yes, this time i made sure that the coil was fully thawed, it seems my defrost setting was too short. but even after i know i had full defrost i start it up and get only 10# 220# and i do not have a liquid fitting to get a subcooling reading, instead it has only the king valve on the comp discharge, if i compare that to the liquid temp i get 14* sc, but i dont think that is acurate.

I did however notice that after running it for 20 min or so, i pulled the evap cover and saw that the captubes are sweating up to a point where they are coiled up, then they begin to freeze and everything past that is quite icy after only a short time.

So, you guys know the specs on the cap tubes? or will i have to take them off and take them to the supply house with me?
And this is an older R502 machine. someone at some point has put R404a in it , which is what ive been useing. So will the captube size be the same, or will it be a little different for 404?

thanks guys

VAV

[KB Cool]

I would call the manufacturer and get the correct size tubes. But, since yours has been altered. I would go by either a JB or supco chart. Using the HP of the compressor as a guideline instead.

[VAV616]

K i talked to HObart tech support.
for R404A its 9' @ .036" - 2 tubes 54" ea.
but none of the usual parts houses carry cap tube in
exactly that size. so i have to go through Hobart
and buy it :(

now when soldering cap tube do you unsweat it at the bulb on the end of the tube, or does the new bulb come with the cap tube usually?
and i wonder how far into the bulb i should insert the cap tube.
this unit does not have a LL Dryer on it(prob why i have little chunks of stuff in the cap tube) so i imagine ill go ahead and add one and a liquid line access fitting as well.

[ColdNH3]

You can take subcooling readings using the compressor discharge port, high side pressure should be the same across the board to the expansion valve, pretty close...the whole idea is a change in state at a given pressure thus giving you subcooling. Like you said, having the system open right now is a great time to add yourself a liquid line drier and an access fitting. I think you are on the right track, another way to check to see if your fan is moving proper air (ex. blades put on incorrectly) icheck the amp draw on the motor, is it close to anything listed on the motor nameplate? I know on some of those smaller or older motors that information isn't always available.

[tcape]

K
now when soldering cap tube do you unsweat it at the bulb on the end of the tube, or does the new bulb come with the cap tube usually?
and i wonder how far into the bulb i should insert the cap tube.
this unit does not have a LL Dryer on it(prob why i have little chunks of stuff in the cap tube) so i imagine ill go ahead and add one and a liquid line access fitting as well.

The bulb where your cap tubes is brazed onto is probably one of those spun copper LL driers. you will have to replace that with another type drier or an equivalent drier.

If you could get the hp off the compressor you could cross it over to a supco/jb captube of the right diameter and length as was already posted. However they have a note that says they might have to be fine tuned.

[ddlong]

I have done two cap tuge to txv changeouts, without adding a reciever. The thing I found out is the size of the condenser. If the condenser is too small, you don't have room for the extra refrig. I called both manufacturers decided to switch.

I noticed that some reach-ins have txv's without recievers. If the manufacturer can do it, I can to. The only caveat would be if the condenser is not large enough to hold extra refrig. and the manufacturer is the only one to tell you and he probably won't. I believe I called the manufacturer of the condensing unit to get info one time.

If you ever do switch, use a balanced port txv, personally I like Sporlan. And you do not need an external equalizer port, if you did, the manufacturer wouldn't be able to use cap tubes. This of course is based on my none engineering degree for all of the above advice.

Don in Moberly Mo

[VAV616]

Ty all for your advice

here is the continuing saga in a new thread

http://hvac-talk.com/vbb/showthread.php?p=3939322#post3939322

VAV