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freezing

Just thowing this out there for the other guys.

I had a call bout five months ago,,, open case fresh case freezing product and bursting cans of energy drinks. Its a remote with a Carol electronic controller.

I arrive and the case is off. I restart it and observes operation. Verify that controller is set to southen specs. Deforst every hour, etc, etc.

I do make one change to the unit and raise the differential so that the box gets to 40 during the offcycle to make melts all ice off coil.

Oberve operation and make sure everything is gravy, manually defrost and record all temps to go with it.

Just this week I was replacing a dispensing valve on a fountain at said location and out of habit I walk around the store checking walkins and what not. On my way to the register I notice that the analog display on the case was reading 49 degrees. I whipped out pocket thermo to verify.... Its correct. I then notice that the walls on the case are frosted over. Hmmmmm. Remove the bottom cover to gain access to the electronic controler and it says that it is at 1 degree and currently in defrost. I can hear freon moving, its a remote so it's quiet under there. Give the suction line solenoid a love tap and it seals up and the the flow of freon stops. I verify on the top of the roof that the condensing unit has shut off and it has.

Four months ago I missed this cause the customer turned off the box and while i was there the problem never occured. I blamed the electronic controller and it's set points.

Needless to say contacted the company that sent me out and said I could not fix it cause the store did not issue a work order. I did defrost the box and restarted it and let the on duty manager know of the situation and what would be needed to fix it should it happen again.

Waiting for it to happen again.

And yes,,, it was a suction line not a liquid line solenoid.

Just wanted to thank everyone that helped out. Everyone had good advice.
This site is great and I'm glad I found it and will be here till it disappears.
Thanks again!!
On to the next project.

Thanks for the advice. I will try it and see what happens. Going to let this run over night with no product in it just to make sure the freezing up problem is taken care of.

With milk and fresh fruit, I'd still be looking for a cut out down in the low 30s.

You need to keep that product at the lowest temperature possible without freezing it.

Milk, fruit and juices have enough fats and sugars in them to lower their freezing point to below 32 degrees. I would not be afraid of a 30-32 degree cutout on that unit.

Not worried about the frost was just stating it was frost and not ice as before. That usually stock this cooler with 16oz milk on the top then juice. They have are those M&M pie slices and fresh fruit in there. 85% is juice and milk.

Originally Posted by mwright

New readings for today
Low side is running around 40
High side around 280
SH 11 at Evaporator
Pressure gauge set at 42 & 82 or close
Case is running at about 37 deg.
Shutting off at 37psi and turning on at 72psi according to my AK900
Pressures are off on the pressure switch!

Pressure switch scales are almost NEVER accurate. You must set them with an accurate gauge as you did.

Originally Posted by mwright

Running about 3 hours now.
Changed pressure settings, cut out at 42.2 and cut in at 84.8
Holding right around 40 deg.
Still frost by TXV but no ice
SH is about 15 when the compressor cuts out.
I'm thinking it may have been cycling too often which made the TXV freeze. Is that a logical explanation?

Why do you have a problem with frost at the TEV?

You've got a coil that is below freezing. Frost is an inevitibility. This is why we have a DE-FROST cycle.

IMO, 40 degrees is too warm for most medium temp applications. You need the product to remain below 40 degrees. To achieve that, you need to get that thing colder. Without knowing what product you're dealing with, I'm typically shooting for a high-20s, low-30s target for cutout.


Sounds like you've about got it whipped, though.

Running about 3 hours now.
Changed pressure settings, cut out at 42.2 and cut in at 84.8
Holding right around 40 deg.
Still frost by TXV but no ice
SH is about 15 when the compressor cuts out.
I'm thinking it may have been cycling too often which made the TXV freeze. Is that a logical explanation?

I readjusted pressure switch and it comes on at 81.7 psi and shuts off at 42.4.
When I read the SH when should I take the true reading? As the compressor is shutting down?

Case has been running about hour and a half now. Seems to be holding temp at 38 deg. Would like it to hold at about 41.
There's some frost forming at the TXV and towards the coil but not freezing up.

New readings for today
Low side is running around 40
High side around 280
SH 11 at Evaporator
Pressure gauge set at 42 & 82 or close
Case is running at about 37 deg.
Shutting off at 37psi and turning on at 72psi according to my AK900
Pressures are off on the pressure switch!

Originally Posted by mwright

So you are saying that
If there is a receiver there is no need to worry about Sub cooling? If so why is that? Also I should put in a sight glass, charge with correct amount of refrigerant and if sight glass is clear I'm good to go?

Yep, that's about the size of it.

Subcooling is what it is and only massively overcharging the unit will make it change.



That, of course, assumes that you've got a functional metering device.

Strike the balance and you're golden.

So you are saying that
If there is a receiver there is no need to worry about Sub cooling? If so why is that? Also I should put in a sight glass, charge with correct amount of refrigerant and if sight glass is clear I'm good to go?

Originally Posted by jpsmith1cm

Install one.

Once you put a receiver on a system, you don't need to worry about subcooling, you need to worry about a clear sightglass.


My mistake for not catching this earlier. I'm switching to AC mode and subcooling is part and parcel of that.

I'll take myself out back and whip myself 25 times with a refrigerant hose, now.

I'll furnish the hose.

Originally Posted by jpsmith1cm

How ya been, Cracker?

Howdy jp.

Originally Posted by mwright

Yes is does have a receiver but no sight glass.

Install one.

Once you put a receiver on a system, you don't need to worry about subcooling, you need to worry about a clear sightglass.


My mistake for not catching this earlier. I'm switching to AC mode and subcooling is part and parcel of that.

I'll take myself out back and whip myself 25 times with a refrigerant hose, now.

Yes is does have a receiver but no sight glass.

Does this thing have a Receiver and liquid line sight glass?

If so

You can forget all about that confusing subcooling

Originally Posted by jpsmith1cm

I'll be curious to see the actual subcooling.

Unfortunately I won't be able to get that until Monday. I will post as soon as I do.

Originally Posted by mwright

Yes between the compressor and the condenser coil but closer to the coil. Am I supposed to Benin the other side of the coil, the output side?

Incase you haven't figured it out I'm new to this and I appreciate all the help. Where I work doesn't have anyone with the time to train me so I'm digging in and learning as I go. :-)

Yes.


Measure subcooling on the outlet of the condenser, not the inlet.

What you were measuring was discharge superheat and, actually, that figure is a bit too low, IMO.

I'll be curious to see the actual subcooling.

Originally Posted by jpsmith1cm

Is that a typo or did you mean to say that you are measuring the temperature at the inlet to the condenser. At that point in the system, you will have superheated gas as you are supposed to, explaining your 'negative subcooling' reading.

Yes between the compressor and the condenser coil but closer to the coil. Am I supposed to Benin the other side of the coil, the output side?

Incase you haven't figured it out I'm new to this and I appreciate all the help. Where I work doesn't have anyone with the time to train me so I'm digging in and learning as I go. :-)

Originally Posted by crackertech

Yep 6 to 8 '' from the evap coil.

How ya been, Cracker?