– Urgent – Blast Chiller Problems – Urgent –

[fixbear]

That would fall under a cooling tower.  Why; Because the heat exchange would still have to have a column of water above it to prevent air entrancement and to allow expansion and replacement of coolant.  A pressure tank can be used for the expansion and minor makeup,  But there still has to be a column above the cooling tubes to vent en-trained air that could impede circulation.   Don’t confuse “cooling tower” with “evaporative cooling tower”.  Different animal that now has to be treated very carefully due to Legionnaires virus. 

[alnelson]

Hi

[alnelson]

If your condensing unit has a receiver, you don’t need to check subcooling. Since excess liquid refrigerant can stack in the receiver, subcooling doesn’t do much to help determine if you have a full charge or not.

 

Look for a clear sight glass and check the receiver level to determine if you are low on refrigerant.

 

When you are adjusting the txv, check superheat on the suction line right at the evaporator.

[olivero]

Well, there is some argument on the SC with receiver, been through it before but in theory you can tell if you have sub cooling between the outlet of the condenser to the receiver but after the receiver it won’t be accurate due to the equalization of pressure and temp that can occur in the receiver.

 

I don’t even think this unit has a liquid receiver despite it being described in the diagram, there are 2 tanks near the compressor, 1 is an oil separator which is on the liquid side and there is what seems like an accumulator on the suction side but could also be an oil separator (wrapped in insulation so I can’t tell). The outlet of the condensing unit that goes to the filter dryer and SG has no receiver on the platform and I doubt they mounted one halfway down.

 

Oh and get this, they sat the unit on the floor, no legs, no nothing, unit defrosts water gets out the door or someone cleans it and the water gets under it… can’t clean it……………………… could have been installed better IMO.

 

Sucks for the cleaners, hoping to one day move it somewhere else and have it raised off the floor by at least 5″ per NSF/FDA code.

[alnelson]

Oh ok.

 

The wrapped tank on the suction side is probably an accumulator. 

 

If no receiver definitely go by subcooling.

 

Does sound like you got it by adjusting the superheat.

 

If you have a sight glass with no receiver, the intermittent flashing of the sight glass is probably just from when the txv opens or closes. As long as the glass clears out and you’ve got the correct subcooling it’s all good.

 

Most txv’s have a screen on the Inlet, sometimes those can plug up and cause high superheat as well.  

[olivero]

Okay cool,

 

I figured it was, don’t understand why the liquid line has no receiver, you would think it would since its load can vary so much.

 

Yeah SG bubbling and no bubbling is making me think its not low, and I am seeing a good SC so I think I am okay. I think i need to iron out the operators a little to make sure they pick the right type of chilling or freezing depending on the type of food as that will also play a role, unit might think its not getting cold enough but if they pick a soft cooling cycle to cool down roasted pork, it ain’t gonna happen.

 

I would have to recover all the refrigerant, vacuum and recharge to clean the screen on the inlet?

 

I have been thinking about this unit for the last couple of days, I would think running 2 separate lines each with its own solenoid would be logical for this unit, 1 would open on the blast cooling and soft cooling cycle and the other would have a receiver and would open on the blast freezing cycle, they would also each have their own TXV so they could be fine tuned for optimum performance.

 

Right now it’s the same line, same TXV feeding the evap on freezing temps or cooling temps which to me, is not that logical.

 

I am not an expert in any way, I am actually fairly new to all this fancy schmancy removal of heat systems but to me, that would seem better.

[alnelson]

Yes with no receiver there’s no way to pump it down so you would have to recover the charge to clean the txv screen, so probably don’t want to do that unless you absolutely have to. 

 

Sounds like you’re on the right track. Just need to make sure they set it right and keep the door shut. 

[olivero]

Yup Yup.

 

luckily its got a reed switch on the door so as soon as it opens, unit shuts off, not good for the compressor to flap the door open and closed, they don’t do that but it wouldn’t be good if they did.

 

Thanks for the input Alnelson.

[fixbear]

olivero, It does have a receiver. It is that big shell tube condenser that it sets on.  It holds 56 lbs’s of refrigerant if you are wondering. BTW that condenser is a low temp unit designed to run at a max -5F,  55,000 BTU’s and drop to 25,000 at -40F.  Some other things you might want to know about that condenser. Max water in temp is 80 and out 105.  A shell tube condenser has a tremendous amount of space available volume wise between the outside of the tubes and inside of the shell.  There also is a lot of room between tubes due to the meat needed on the end plates. Normal ones I’ve worked on have three passes for the water

 

Right now it’s the same line, same TXV feeding the evap on freezing temps or cooling temps which to me, is not that logical.

 

I am not an expert in any way, I am actually fairly new to all this fancy schmancy removal of heat systems but to me, that would seem better.

That would put the compressor in overload due to higher suction pressure,/ temp. 

 

    If you follow this linc it will tell you about suction accumulators and show you the inside. http://orders.sidharvey.com/IMAGES/specs/3706.pdf 

 

I was also surprised to find a Trenton installation and maintenance manual for the T-40 condenser.  Trenton #1068156.  Never seen one nor do I know what it contains. It is active on Trenton parts for that condensing unit. 

[alnelson]

Yes, good point fixbear, I forgot that the shell/tube condenser is the receiver.