Is there a refrigeration engineer in the house?

[gsxrsquid]

IF someone knows and would like to edjumacate an old geezer like me:

example, you have a reach in cooler with cap tube system. this is a critically charged system. If someone (no not me) replaced the condenser unit with one that has a liquid receiver can it be made to work as a non critically charged system?

[tjc76]

i am no engineer, but find this interesting anyway. i do not believe there is anyway to make this work as a non critical system, as all cap tubes are critical. unit would need an expansion valve. a contractor i used to work for changed many a traulsen unit from cap to txv

[k-fridge]

If it's still a cap tube system, the receiver has to go. A cap tube will not function properly with a receiver.

You could change to a TXV, but that creates other issues like starting torque, possible head pressure problems, etc.

[kerndt]

check out this thread..........it answers your question

http://www.hvac-talk.com/vbb/showthread.php?t=116028&highlight=kerndt+receiver

[cybercontadino]

I have seen reachins with cap tubes and receivers and they worked well and lasted for years. Don't know the reasoning behind the "engineering" of this.
There are dropin cold pans at KFC which came in this way from the manufacturer. Go Figure...

[TGoodrich]

The Truth... A cap tube system will work fine with a receiver. The amount of refrigerant charged may have to be slightly higher to compensate for the volume required to fill the bottom of the condenser to cover the outlet tube. I'm only talking about an ounce or two. The risk, however, is that it will be easy to overcharge the system. There will be no precipitous rise in head pressure, bacause the liquid will simply fill the receiver. If the compressor is off for very long, the excess liquid will flow through the cap tube into the evaporator and cause problems on start-up. Liquid may flood back to the compressor, eventually causing bearing failure or the compressor will repeatedly cycle on the motor overload. The overload will then ultimately fail. These systems are usually built without receivers for the cost savings.

[k-fridge]

The Truth... A cap tube system will work fine with a receiver. The amount of refrigerant charged may have to be slightly higher to compensate for the volume required to fill the bottom of the condenser to cover the outlet tube. I'm only talking about an ounce or two. The risk, however, is that it will be easy to overcharge the system. There will be no precipitous rise in head pressure, bacause the liquid will simply fill the receiver. If the compressor is off for very long, the excess liquid will flow through the cap tube into the evaporator and cause problems on start-up. Liquid may flood back to the compressor, eventually causing bearing failure or the compressor will repeatedly cycle on the motor overload. The overload will then ultimately fail. These systems are usually built without receivers for the cost savings.
Perhaps you should read the "sticky" thread at the top of the page.:)

[TGoodrich]

I am speaking the truth. Many posts report OEM installations with receivers present. A agree that a system will reach equlibrium sooner without a receiver in the mix and that they are not necessary in the circuit. However, I disagree that, in a system with all else normal, they will cause any problems. That is, assuming nobody overcharges it.:cool:

[k-fridge]

I am speaking the truth. Many posts report OEM installations with receivers present. A agree that a system will reach equlibrium sooner without a receiver in the mix and that they are not necessary in the circuit. However, I disagree that, in a system with all else normal, they will cause any problems. That is, assuming nobody overcharges it.:cool:
OK, Let's think through this. It's a given that a cap tube is a fixed orifice....right?

How does a fixed orifice control superheat at different load conditions?

[gsxrsquid]

Thanks guys It has been a long time but I got it. and to answer kfridge, a cap tube doesn't control superheat at different load conditions.

I knew why TXV needed the receiver but was trying to figure why it would hurt a cap tube system. its the superheat and subcooling stupid. DOH

What prompted the question was a reach in we went to. Boss was was me and he noticed it right off. I hadn't noticed the receiver. I had noticed the CU had been changed and the cap tube replaced. And they installed a longer smaller cap tube. Seems to me they went the wrong direction. smaller should be shorter, bigger should have been longer. but of course you have to stay within limits. we pulled the receiver and replaced cap tube with original size and length. Put the juice to it and it is working fine now.

That what I love about this site, the cure for a brain fart. lol
now.......what is a sticky?

[Freezeking2000]

Thanks guys It has been a long time but I got it. and to answer kfridge, a cap tube doesn't control superheat at different load conditions.

I knew why TXV needed the receiver but was trying to figure why it would hurt a cap tube system. its the superheat and subcooling stupid. DOH

What prompted the question was a reach in we went to. Boss was was me and he noticed it right off. I hadn't noticed the receiver. I had noticed the CU had been changed and the cap tube replaced. And they installed a longer smaller cap tube. Seems to me they went the wrong direction. smaller should be shorter, bigger should have been longer. but of course you have to stay within limits. we pulled the receiver and replaced cap tube with original size and length. Put the juice to it and it is working fine now.

That what I love about this site, the cure for a brain fart. lol
now.......what is a sticky?


It would have worked ok without removing the reciever, the cap tube was the issue. Still better to remove them..........in a rush I have forgotten to remove a few in my days.

[k-fridge]

and to answer kfridge, a cap tube doesn't control superheat at different load conditions.
Actually it does, but it relies on some other factors to do so. In a properly designed system a cap tube modulates its flow according to pressure differential, subcooling, and the ration of vapor and liquid entering the cap tube. The latter is a crucial factor, as vapor entering the cap tube restricts the amount of liquid that can flow through it. When a receiver is introduced to the system, the liquid seal takes takes this factor away. It also limits the fluctuation in head pressure and it sets subcooling at a fairly constant rate.

As I stated in the other thread; a cap tube system with a receiver may work, but it won't work right.

[MikeySq]

Many posts report OEM installations with receivers present. :

I have come across that aswell, OEM with cap + Reciever, on a side note these OEM suppliers are in the custom kitchen equipment department and then you gotta think of what they actually know/do

Ever see a reputable equipment manufacture with this set up?
-Mike