Thermal expansion valve adjustment (txv)

[Fred Ficarra]

Richard, I submitted a question last week when your services were announced. I don't see it listed anymore. My question is how do I adjust the freezer TXV on my system. I've installed a much larger plate after our rebuild but it seems to have no more capacity that the original plate. Ice cubes are not made any faster. You can get an idea of what my system is (custom)on my web site. Assuming that the superheat adjuster will cause the TXV to act like it has a larger orifice (tonnage) what should I look for in pressures when the system is running? Do I want to see the high side go down and the low side rise? The TXV is externally equalized. Or should I install a larger valve? Or,,? (the gas is now HotShot)

 

[Richard Kollmann]

Need More Info.

I did answer your request and It will come up in a day or two. But I copyed and pasted my answer:I am sorry I don’t remember your refrigeration system. I either look at systems or answer fifteen refrigeration email questions per week so I can’t remember each one.  Your system should work now as well as it did before and yes fine tuning of the system should correct the current problem. The best way for me to help you is for you to send a description of your system: type compressor, type of condenser, type refrigerant and the type of electrical controls that can start and stop the compressor. Also advise if you have a servicing gauge set.I am confused, you listed one freezer plate and one refrigerator plate and then you say the Three together? Also there is only one expansion valve and it is externally equalized? Where in the equalizing line connected?

 

[Phil Herring]

If you don't see your question...

Hi all,If you submitted a question to Richard and you don't see it yet, don't worry. All the questions submitted are "time released" into the forum, a few each day. This helps keep the momentum going and avoids slamming our moderators with 50 questions in a day.Thanks for your patience!ph.

 

[Fred Ficarra]

Oh Boy,, I see what you mean, you're busy!

On my web site are several pictures of the components. The system is engine driven. I built most of it. The 10cu.in. 'Tecumseh' compressor goes to an oil separator that leads to the condenser (water cooled, in-line to engine cooling) that leads to the receiver (12lbs) that routes gas to the filter/dryer then to the sight glass then to the solenoid valves. These are individually wired so as to be able to run each separately or together in any combination as desired. One controls the freezer plate, another the refer plate and the last, the air conditioning evaporator. The fridge and the AC have suction control valves at the inlet manifold of the accumulator. The freezer suction is wide open. The refer and freezer solenoids are controlled by a timer (up to 60 min.). The AC control is free to run as long as needed. It does have a thermometer so as not to freeze the evaporator. It'll cut out the compressor until the evaporator warms. Let's see, oh, the whole system is wired to the ignition so that if the engine is shut down (SW off) the main power relay turns off so as not to have the system start when the engine is restarted. System pressures are monitored full time by built in gauges. The system is controlled by a standard electric clutch on the compressor. The original refrigerant was R12 of course but is now HotShot. Replacement of any component is not a problem. I have a 'shadow company'. Gas is also not a problem. I have EPA certification. (universal) Oh, and a nearly new vacuum pump too.  Probably more than you wanted to hear, huh Richard? Anyway, you helped me with pressures last summer after I switched to HotShot. All values were good but we didn't know what the freezer plate would do until now. I'm sure it needs some tweaking. Thanks for reading this far. Standing by,,,P.S. Thanks Phil, got it.P.S.2. The equalizer bulbs are located just past the respective evaporators with clamps to the pipes. Each evaporator has its' own TXV. They are each adjustable as are the suction control valves.

 

[Richard Kollmann]

One unit trying to do three things at once

You have a very interesting refrigerant system, but what happened to the old sailors words KEEP IT SIMPLE.I have seen two separator suction pressure evaporators in the same system before but never three.You said in the other message that the expansion valves were externally equalized so where are these lines connected to the suction pressure? They must be connected to read only that evaporator’s pressure.I think the only way to balance each of the three systems and set their superheats is to isolate each one from the other. As I understand it, there is no way to stop the refrigerant flow to the A/C unit. Each expansion valve’s wide open orifice needs to be sized for that areas heat load. I would set each units superheat with only that unit flowing refrigerant.I would then set the two suction pressure regulators again with only that system running. Be sure to set the pressure regulators with a pressure gauge connected to the valve you are adjusting.

 

[Fred Ficarra]

Richard, some of your questions are addressed

in my previous post. I was editing for several minutes after putting it up. Hit refresh. As far as suction control valve adjustment, no where in any of the component documentation, is a adjustment value given. One is expected to be an engineer. As a matter of fact, an engineer spec'd those things out and ordered them for me back in the late '80s. That's when the system moved to "industrial grade". In any case, I'm not complaining. If you where off the coast of Nicaragua one night, in the conditions we were in, the cost of the system was worth it, just for the AC that night alone. To say we were the envy of the fleet is accurate.

 

[Richard Kollmann]

Evaporator pressures for Hot shot

Adjusted Suction vapor pressure range in the evaporators when using Hot Shot refrigerant is:•For AC evaporator 39 to 25 psi.•Refrigerator evaporator 12 to 6 psi •Freezer evaporator 6 to a vacuum of 4 inches.The high pressure will depend on seawater temperature and amount of Btus of heat to be removed. If the high pressure is below110 psi. the seawater is too cold to adjust the separate evaporator pressures.

 

[Fred Ficarra]

Thanks Richard

That's a keeper. It's copied and saved. I'll check it out ASAP.