defrosting of freezer system [-40°]

[Shaukat]

with water cooled condenser freezer cooling coil defrostining system with hot gas by pass is not performing properly? whay to do? - shaukat

[Tycho]

with water cooled condenser freezer cooling coil defrostining system with hot gas by pass is not performing properly? whay to do? - shaukat


The condenser is getting to much water. check if the watervalve is working properly, or if it's there at all.

[Tycho]

The condenser is getting to much water. check if the watervalve is working properly, or if it's there at all.

if that's not it, let us know how the HP line is designed, what valves there are and what kinda valves there are around the freezer.

[Sridhar1312]

Condenser discharge water will be best for defrosting as it is simle and only care to be taken care in Piping the drain as well as defrost header.Check in Roy J Dossat Book the slope is clearly given

[chemi-cool]

The condenser is not a part of HG defrost so its not relevant if its cooled by water or air. If your evaporator is flooded one, allow time between LSV closed and HG valve opening to empty all the liquid out. Check the operating of KVL, some of them have strainers on the enterance and if blocked or even partialy, you don't get good suction.

Is this a sudden problem, or it has been for a long time?

[Shaukat]

tanx, during the defrosting ,water pump is 'off' condition ,

[Shaukat]

Condenser discharge water will be best for defrosting as it is simle and only care to be taken care in Piping the drain as well as defrost header.Check in Roy J Dossat Book the slope is clearly given
at -40°c , we may not use water to defrost cooling coil, as i know there 2 option 1- hot gas ,2- electric heater. do you know any other option.

[Shaukat]

The condenser is not a part of HG defrost so its not relevant if its cooled by water or air. If your evaporator is flooded one, allow time between LSV closed and HG valve opening to empty all the liquid out. Check the operating of KVL, some of them have strainers on the enterance and if blocked or even partialy, you don't get good suction.

Is this a sudden problem, or it has been for a long time?
at -40°c , we may not use water to defrost cooling coil, as i know there 2 option 1- hot gas ,2- electric heater. do you know any other option.

[smpsmp45]

We have been using HGDF system with water cooled condensers without any problems. What exactly is the problem? U r not getting enough Hot gas? R Connections OK?

[Tycho]

The condenser is not a part of HG defrost so its not relevant if its cooled by water or air. If your evaporator is flooded one, allow time between LSV closed and HG valve opening to empty all the liquid out. Check the operating of KVL, some of them have strainers on the enterance and if blocked or even partialy, you don't get good suction.

Is this a sudden problem, or it has been for a long time?

And how is the condenser not part of the hotgas defrost?

[Tycho]

Maybe you should tell us a little more of what is happening.


You are saying the water pump is in the off position during defrost. this makes me believe there is not a PM valve on the high pressure line

what refrigerant are you using?

are there a manometer on the evaporator, what pressure do you get on the evap during defrost?

what is the HP of the compressor?

[Shaukat]

at -40°c , we may not use water to defrost cooling coil, as i know there 2 option 1- hot gas ,2- electric heater. do you know any other option.
hi,
no, it is not suddanly , it is from date of installation

[Shaukat]

Maybe you should tell us a little more of what is happening.


You are saying the water pump is in the off position during defrost. this makes me believe there is not a PM valve on the high pressure line

what refrigerant are you using?

are there a manometer on the evaporator, what pressure do you get on the evap during defrost?

what is the HP of the compressor?
f-22 , temp of hot gas is unsufficeent heat to remove ice from coil, i desided to use elecrict heaters.

[Tycho]

f-22 , temp of hot gas is unsufficeent heat to remove ice from coil, i desided to use elecrict heaters.

Maybe with a PM valve on the compressor, during defrost you could make all the hotgas go to the evap, giving you better pressure and heat.


welp...

[Shaukat]

We have been using HGDF system with water cooled condensers without any problems. What exactly is the problem? U r not getting enough Hot gas? R Connections OK?
yh, i m not geting enough hot gas

[Shaukat]

dear frindes, i solved my problem with electric heater, a old man tehnician advice me to not use over size water cooled condenser if you are going for hot gas defrost. .. thanx again

[US Iceman]

...advice me to not use over size water cooled condenser if you are going for hot gas defrost.


That does not have anything to do with the problem. The problem is you don't have enough hot gas. How will an air-cooled condenser or any other type of condenser give you more hot gas?

They won't!

What you have is a fundamental problem with the hot gas defrost system. Are you defrosting more than one evaporator at a time? Or worse, do you only have one evaporator on the compressor?

[Tycho]

That does not have anything to do with the problem. The problem is you don't have enough hot gas. How will an air-cooled condenser or any other type of condenser give you more hot gas?

They won't!

What you have is a fundamental problem with the hot gas defrost system. Are you defrosting more than one evaporator at a time? Or worse, do you only have one evaporator on the compressor?



If the condenser is oversized, and there is a PM valve on the hp line, and the hotgas is connected on the condenser side of the PM ;)

Or if the condenser is correctly sized and there is no PM valve, and the compressor is on low capacity (if there is capacity control on the compressor), compressor on low capacity - little to no hotgas - not enough hp to overcome the hotgas return valve (if it's set to high)



there's not enough info to make anything close to an educated guess :)

[US Iceman]

I don't disagree with you Tycho, but to say a water-cooled condenser is the reason is not correct either.

Something else is wrong.

[Tycho]

I don't disagree with you Tycho, but to say a water-cooled condenser is the reason is not correct either.

Something else is wrong.

he said "over size water cooled condenser"

So we agree, and I wasnt pointing my finger at you, just generally waving it around :)

[US Iceman]

That's fine, I'm a big boy.

There is definitely a system design problem though. Sure an over-sized condenser would make the problem worse instead of better.

I'm going back to my corner now....:D

[Shaukat]

That does not have anything to do with the problem. The problem is you don't have enough hot gas. How will an air-cooled condenser or any other type of condenser give you more hot gas?

They won't!

What you have is a fundamental problem with the hot gas defrost system. Are you defrosting more than one evaporator at a time? Or worse, do you only have one evaporator on the compressor?
i think water quantity in water cooled condensor is more and defrosting time is less , [or ambiant is < 25°c]