1st test of my cascade's I stage...

[berkut]

Hello


I made a first test of my baby a moment ago, some pics and im hoping for some help and suggestions

The standart thing...

Refrigerant: R22
Room temp: 17C
SCT: 25C (9.5 bar/140 psi)
Condenser outlet: 19C
Subcool: 6C

SST: -41C (0/1bar/ 0psi)
Pipe 10" from the compressor: -37C
TXV Bulb: -37C
Evaporator temp: -40C
Superheat: 4C

Air entering the condenser: 17C
Air leaving the condenser: 21C

You can find the pics here. I wont post the beacause they are preety bad quality and theres not much to see...

And one thing to all you kids over there, refrigeration is preety dangerous, even a I stage system. Making asian swords (katana's), turbine engines, gokarts and a few more things too...:




berkut

[berkut]

Oh and one more thing...

U guys remember when i said i cant read the vacuum scale too good when i talked about my prevoroius cascade tests ?

Maybe this will show you why...:



Ill buy a new mainfold and a better gauge with a good vacuum scale.. Unfourtenetly the only gas wich is attaineble for now is R23

[Gary Lloyd]

Reduce your condenser airflow until the SCT is about 12C above the room temp. This can be done by simply blocking off part of the condenser, or by reducing the fan speed. Then adjust the refrigerant charge (if needed) until the subcooling is 8C.

[Gary Lloyd]

In the pics, it looks like the TXV bulb is not insulated. It must be heavily insulated so that it is sensing only the suction line temp and not the air temp.

[berkut]

Are you testing something or is it just badly calibrated ? I would love to know ^^

Ill post some info tomorrow when the poliurethane foam hardens on the HX...

[Gary Lloyd]

It would be a good idea to soft solder part of the liquid line to the suction line. This suction/liquid heat exchange would make the interstage more efficient and warm the suction vapor a little before it gets to the compressor. It is running very close to floodback. Is the bottom of the compressor cold?

[Gary Lloyd]

There is only 8C difference between the SCT and the room temperature, therefore it is not possible for the subcooling to be more than 8C. The difference between room temp and SCT is the condenser TD.

If we raise the SCT by blocking airflow we raise that difference. Then we can tell if there is solid liquid by the condenser outlet subcooling.

Given sufficient condenser TD, solid liquid occurs at 6-8C subcooling. More than 8C means liquid is starting to back up into the condenser, reducing its capacity. If we adjust the charge to 8C subcooling, then we know we have the maximum amount of refrigerant in the system, without filling the condenser.

Your condenser is oversized, therefore the airflow can be reduced. The difference between the air in temp and the air out temp is the condenser delta-T, and is an indicator of airflow. The delta-T should be no more than 12C. I like to keep it below 10C. Your delta-T is 4C, so your fan speed can be reduced for quieter operation, while still staying below 10C dT.

[berkut]

No, the compressors bottom is 40C, the top is 48C

I can attach a HX tomorrow to work as a subcooler or how should it be called.

Its funny... a heat exchanger from a failed first attempt will work in the MK6 revision... Whats funnyer... i forgot about it and i had a dream this night about my old hx in the new cascade Its a nice thing when old parts can be used in new systems, makes your work less harder ;]

And where should i place the TXV bulb after i attach the HX, before or after it ?

[Gary Lloyd]

The TXV bulb should be at the outlet of the evaporator.

[berkut]

Originally posted by Gary Lloyd There is only 8C difference between the SCT and the room temperature, therefore it is not possible for the subcooling to be more than 8C.

If we raise the SCT by blocking airflow we raise that difference. Then we can tell if there is solid liquid by the condenser outlet subcooling.

Solid liquid occurs at 6-8C subcooling. More than 8C means liquid is starting to back up into the condenser, reducing its capacity. If we adjust the charge to 8C, then we know we have the maximum amount of refrigerant in the system, without filling the condenser.

Nice to know, i love to listen to such things...

Your condenser is oversized, therefore the airflow can be reduced. The difference between the air in temp and the air out temp is the delta-T, and is an indicator of airflow. The delta-T should be no more than 12C. I like to keep it below 10C. Your delta-T is 4C, so your fan speed can be reduced for quieter operation, while still staying below 10C dT.

Now the system is working in a "idled" mode, meaning that the condenser doesent have to pump too much heat (heat losses + wattage of the compressor), i assume that when we turn on the II stage we will have to adjust the fan speed ?

Im also concerned about the efficiency of the compressor. Wont the higher compression ratios reduce it too much ?

[Gary Lloyd]

Think of this as the rough tuning phase. We will need to look at all of this again after we get the low stage rough tuned. Then after fine tuning the high stage, we fine tune the low stage. The two systems are interdependent. Each step brings us closer to optimum.

[berkut]

Reduce your condenser airflow until the SCT is about 12C above the room temp. This can be done by simply blocking off part of the condenser, or by reducing the fan speed. Then adjust the refrigerant charge (if needed) until the subcooling is 8C.

As i said before- the system wasnt insulated. Now theres 5cm + insulation on the hx, pipes too, the txv bulb also, no frost, no cold, not even slightly cool to the touch.

Had some problems... (nevermind leaks)...
When i blocked the air flow on the condenser, the SCT went up to ~12C above room temp as you ordered and:
-the system starts to oscilate, going from -45C sst / 7C superheat to -40C sst / 4C superheat
-the compressors temp. skyrockets from 45C to ~ 60C

Now, about that subcool... am i supposed to add or let out refrigerant ? I dont want to do anything light headed...

Oh and 1 thing... the compressor is so loud that it doesent make any difference if the fan on the condenser goes full blast or its off...

[Gary Lloyd]

What is the SCT and the liquid line temp? Subtract one from the other and that's the subcooling.

If the subcooling is less than 8C, add refrigerant. If the subcooling is more than 8C, remove refrigerant.

The TXV is hunting, because it is oversized for the load. Not too surprising since there is no load at the moment.

[Gary Lloyd]

Did you add the suction/liquid heat exchanger?

BTW, the ideal temp for the bottom of the compressor is 60-70C.

[berkut]

Ok....

I added refrigerant and:

-SCT went to 34C
-Subcool is 7C
-SST is -36C
-Superheat is 6C....
-Ambient is 19C

The discharge temps fell down to 39C and compressor is ~43C

[Gary Lloyd]

Okay, that's pretty close to maximum charge then. Now unblock the condenser airflow and start the low stage system. Then let us know what all of the high stage temps and pressures are with a minimum (idle) load.

[berkut]

Theres now low stage yet ;]

I had to unblock the flow, this is with full blast, im working on it a little still....

[Gary Lloyd]

What is the complete list of temperatures and pressures, now?

[berkut]

ill post the info later... I talked with my dad and i think i found something wich is a blessing for me: my Dad has a hydrocarbon detector.

Now i can fill the system up with a little propane (add it to R22/R23), set the tester and "sniff" the whole system, pipe by pipe, part bby part.... omg im so happy no more undecteble leaks

[berkut]

SCT 32C
Subcool 6C
SST -40C
Superheat 5C

The compressor is ~ 38C and from the sound i can tell it doesent suck liquid...

[Gary Lloyd]

The liquid line is 26C?

[berkut]

Yes, how ill is the system doctor ?

Do you have mIRC ?

[Gary Lloyd]

It seems odd that the liquid line temp would be that much higher than the room temp. Is there warm air blowing on the temp sensor? Is the temp sensor insulated so that it is measuring line temp and not air temp?

[berkut]

The room temp is 20C.

I can insulate it, right now its attached with some masking tape and HTSP thermal paste

[Gary Lloyd]

Does the system have a receiver? If so, measure the temp at the receiver outlet.