Morphing Air Conditioner into Autocascade System

[mytekcontrols]

What do you mean you wonder if the compressor can start without drawing too many amps? Haven't you run it already?

Yes I have run it (how else would I have gotten the data), but the system was originally started up day before yesterday with a lower static BP of 154 psig. I then boosted up its charge while running, in order to tune it for 150 watt operation, and then incrementally reduced the applied load to obtain the load profile curve you saw above.

I shut it down, and watched its pressure build while also observing the temperatures of the stack TC's. When it got to nearly 0C and was just approaching 200 psig, I was satisfied that it was tracking with what I had estimated the additions should increase it by. When I get a chance today, I'll try a re-start and see what happens. I'll also verify what the warmed up BP is as well.

[Polizei]

Oh... so you haven't run it since you initially charged it.

I was going to say...

[mytekcontrols]

Oh... so you haven't run it since you initially charged it.

Yes I have run it. I just haven't re-started it from a warmed up state.

As I said earlier, I made refrigerant additions while it was running and cold. Just haven't verified how these additions will ultimately add up, or how they will affect the start up capability of the unit.

Edit: I think we are of the same understanding... just saying it in different ways.

[Polizei]

Oh. Cut me some slack... I was up early for an extremely boring C++ programming class this morning.

My reading comprehension went back to bed.

[mytekcontrols]

Oh. Cut me some slack... I was up early for an extremely boring C++ programming class this morning.

OK you win But when I turn 70 and the alzheimer's begins to kick in, I'll be expecting the same

[Polizei]

OK you win But when I turn 70 and the alzheimer's begins to kick in, I'll be expecting the same

Sounds fair.

[godmod]

He means that he is wondering if the Amps drawn by the compressor at startup will exceed its maximum rating or if it will be within specifications.

[mytekcontrols]

He means that he is wondering if the Amps drawn by the compressor at startup will exceed its maximum rating or if it will be within specifications.

This is what I still need to find out. Hopefully it will be within specifications, or can be persuaded to by allowing the discharge to bypass into the expansion tank immediately upon start-up. I figure opening a solenoid valve between the compressor discharge line and the expansion tank for maybe the first few seconds would probably do it.

The LG QA090C's motor current rating is 5.2 amps @ 115V, exceeding this by as much as 1.25% (6.5 amps) for a short period of time should do no harm, and is considered acceptable. Going much over this could cause a premature failure.

So I'll see what happens later today.

[RyderOCZ]

Stunning work Michael, top notch stuff. -100 at 25W+ over your initial goal. You must be pretty happy

[godmod]

The LG QA090C's motor current rating is 5.2 amps @ 115V, exceeding this by as much as 1.25% (6.5 amps) for a short period of time should do no harm, and is considered acceptable. Going much over this could cause a premature failure.

5.2A + 1,25% = 6.5A ?
Does not work for me
(It would be 25%)

[RyderOCZ]

I am sure he meant 25%, which you would multiply by 1.25

Just a % sign in the way of a perfect calculation

[godmod]

I am sure he meant 25%, which you would multiply by 1.25
Just a % sign in the way of a perfect calculation

You are right
...like double negation

[mytekcontrols]

Yep, I did mean 1.25 x 5.2 amps, or 25% over spec. Sorry
(damm... Alzheimer's kicking in already)

You can use a solenoid valve on the compressor suction return, in parrallel with which is restrictive length of tubing.

At startup the solenoid valve is closed, causing the return gas to flow through the restriction. The restriction causes a pressure drop between the suction line and compressor suction port.

The developed pressure drop reduces the motor loading on the compressor, because the compressor is doing less work.

When the system has become stable the solenoid is opened and the system opperates as normal.

Interesting idea, and yes I see how this could work (I'll have to write this down)

But not to dismiss it, I will probably do the buffer valve thing I mentioned, for the simple fact that I have used this before in autocascades with great success. Although it does depend on small pressure drop to be effective, where as your idea doesn't.

Stunning work Michael, top notch stuff. -100 at 25W+ over your initial goal. You must be pretty happy

Yes I am!
Thanks for the kudos.

[n00b 0f l337]

Basically the same as an idle load switch in a way. Just a way to connect high and low with little to no restriction. Plumb it into the expansion tank and let the restriction between there and system to equalize and then close the valve once compressors going.

[Jack]

Thanks Chris. I too am amazed at what this little sub 10cc compressor can do


Wait no longer, here they are:

Coil outlet is Evap inlet, in the graph Shouldn't it be Evap outlet?

Anyway 150 Watts! Nice!
Not too shabby!

[mytekcontrols]

Some thoughts...

I have been doing some thinking on why the R-600, R-170, R-14 charge did not work as expected. It appears to all come down to how effective is the separation in my home brew phase separators. I had assumed it would be simply adequate, but not phenomenal, especially in the later stages. But now I'm not too sure about this.

Remember the 3600 Watt "Big Brother" unit I showed in a previous photo? A unit similar to this was my first test bed for an R-600 charge. It worked unbelievably better, and with only half the liquid (R-600) than the previous R123/R22 combo. So I just assumed that I would see similar results with my AC-2 unit when using R-600. Why didn't I? well I think that proportionally speaking, all my phase separators are much much larger then what is used on the "Big Brother" unit. How much larger? At least 13 times the volume (based on compressor mass flow differences).

So it would stand to reason that the AC-2 unit would be far superior in its ability to separate the liquids from the gases at each phase separation point. Having poor phase separation allowed the "Big Brother" unit to get by without a mid-carrier refrigerant between R-600 and R-170 (80 degree C difference in boiling points).

But the AC-2 unit with its superior phase separation, ended up disconnecting between the lower and upper stages, mainly due to excessive amounts of R-170 being dissolved into the R-600 and robbed from the downstream stages. And later as the lower stage got even colder due to it's isolation from upper stage loads, the temperature dropped to the level that even R-14 was being gobbled up as well. Probably the best way to over come this would have been to add a mid-carrier refrigerant such as R-290 or R-22. Another way was by using brute force, and adding excessive amounts of R-170 and R-14 in order to compensate (this is what I did on my first tests). But from a thermodynamic aspect, this probably just ends up making 3 phase separated autocascade, into something that acts more like 2 phase separated design due to inter-stage flooding.

R-600 should still be better at moving heat then an HCFC. So perhaps I'll try a future test with an R-600/R-22 combination to see what happens. If I had R-290 I'd try that as well.

I still might get even more out of the AC-2 unit

[mytekcontrols]

Coil outlet is Evap inlet, in the graph Shouldn't it be Evap outlet?

Yes you are right It's now fixed

Thanks Jack

[mytekcontrols]

Basically the same as an idle load switch in a way. Just a way to connect high and low with little to no restriction. Plumb it into the expansion tank and let the restriction between there and system to equalize and then close the valve once compressors going.

Adam... Yep you got it!

[n00b 0f l337]

R290 is insanely easy to get in decently high purity. Hop to homedepot, blue bottles from bernzomatic, like $2 a pop. Then pickup a $10 propane soldering/brazing torch, cut off the end of the torch, and braze an access valve to the bottle attachment side. Tada R290

[mytekcontrols]

R290 is insanely easy to get in decently high purity. Hop to homedepot, blue bottles from bernzomatic, like $2 a pop. Then pickup a $10 propane soldering/brazing torch, cut off the end of the torch, and braze an access valve to the bottle attachment side. Tada R290

Great idea! And so simple.

How pure do you think it is?

[Jack]

I figure opening a solenoid valve between the compressor discharge line and the expansion tank for maybe the first few seconds would probably do it.

I know that with huge ammonia chillers they use pretty much the same thing.
There's a pipe going from the the top of oil separator the the suctionline, just before the compressor. That pipe has a valve which opens for 1,5 minutes after start-up. After the 1,5 minutes the compressor has reached enough rpm to overcome the static charge.

[godmod]

Technical Propane has got a purity of 95%.
The 5% are unknown, other HCs, Water.

I can tell you for Propane 2.5:
Purity 99.5%
O2 max. 100 vpm
CO + CO2 max. 10 vpm
H2O max. 12 vpm
KW C1,C2,C4 max. 0,7 Vol%

[n00b 0f l337]

Bernzomatic is 97.5% according to them, other stuff is HC's and air in small quantities. Run through a filter on the way in. I use that and its more then pure enough to run full singles and cascades on 290 only.

[wdrzal]

Bernzomatic is 97.5% according to them, other stuff is HC's and air in small quantities. Run through a filter on the way in. I use that and its more then pure enough to run full singles and cascades on 290 only.

How about a explanation of the law in the USA of using propane in refrigeration systems..........or pure HC's. It's actually illegal to modify(say a torch) to use it other than for it's intended purpose.


Are refrigeration units being designed/built to satisfy all the regulatory bodies,Or are potential bombs being built.

Even systems designed with every safety precaution possible/thinkable occasionally things still go boom "$hit happens" doesn't get you a "Get out of jail free card".

I don't know......... Once you start selling/shipping units you just opened yourself up to exposure from all government regulations.


What do you guy's Think ??????

[n00b 0f l337]

I never sell units charged with propane Walt. Don't be jabbing at me. What do you think ethylene is? And no its not illegal to modify tools for other purposes. And from tests, and after seeing window ac's explode (see thread still available to read in first two pages here in vapor phase forum), impinged and "atomized" oil in refrigerants is much more deadly.

And what about hydrocarbons in other refrigerants? Many have r290 in them. And autocascades, mytek would you like to explain the legality of using butane? I don't see a problem.