Problems with Mach I and r404a.. please read!

[tombman]

First of all: i have a EUROPEAN Version of the prommie mach I, so the compressor is a little different to the US Version.

It is the NL7F (http://www.danfoss.com/compressors/pdf/datasheets/r134a_220v_50_60hz/n-series/NL7F_R134a_220V_50Hz_08-01_Cg43k202.pdf) 220volt model.

Yesterday my cooling tech. friend got my prommie mach I to refill it with 404a and lengthen the captube, but today he came back with the mach I unmodded, telling me that this compressor would not handle the r404a if filled with full power.
He said it MAY work when only putting small amounts of r404a into it, but since he can´t measure the exact grams of r404a he has to put into he cannot guarantee that the compressor would not be damaged.

So he asked me if i could find out what the pressure should be for mach I + r404a, so that the compressor can handle it.

OPP, bowman, tom holck, can you please help me and name the exact pressure the manometer has to show for mach I + r404a.

HELP!! :(

p.s: could it be, that the european version cannot handle 404a, only the US Version?

[rabeb25]

shoot i wish i could remember, why does 40 grams ring a bell?
They will be in soon to help you.

[Charles Wirth]

We put about 2.5 oz of gas in and brought it down to 4 inches of vaccum, my unit seems to be working great.

I have a US version obviously, but they should be similar.

[herefishy]

...IMO.... :) .... FWIW:




The machine is best charged by monitoring the suction temperature returning to the compressor. You would likely find satisfactory operation with an unloaded suction pressure of about 8"Hg.

Just charging by pressures is not adequate. One (must) have a thermometer reading the temperature of the suction line, while referencing the saturation temperature of the refrigerant at the pressure it is. Only with previous experience could one generalize the operating pressure as to representing a proper charge under any particular conditions.

OH... but did he even attemp it?

If he didn't, just tell him to be brave. The compressor is rated R-12/134A at -10, but -60 with R-404A is the same thing interms of refrigerant density and power output. This explanation is not very good, and I am not well versed in precisely the exact scientific and mathematical explanations for the similarities in the applications between the low and high pressure refrigerants. I just kinda' do it empirically.

Your tech friend should expect the R-12/134A compressor to act nearly like a 404 compressor with the 404 in it (head pressure would be at about 110 psig). Maybe he's expecting to see R-12/134A pressures while putting the 404 in it?

[herefishy]

Originally posted by tombman
....he cannot guarantee that the compressor would not be damaged.....

Tell him that he will not be responsible if the compressor gets damaged, that you assume all the liability shall hold him harmless in the case of compressor fialure (that includes calling him bad names upon such an event). If the cap tube is not changed/lengthened, you certainly will damage the compressor, I assure you. ;)

If you add 4-1/2 feet of cap tube, that should be fine according to many knowledgeble folks, I hear.

[lallend]

Originally posted by herefishy
If the cap tube is not changed/lengthened, you certainly will damage the compressor, I assure you. ;)

If you add 4-1/2 feet of cap tube, that should be fine according to many knowledgeble folks, I hear. Would you say the same holds true for a US spec Mach II refilled wilth R507 and no cap tube mod?

[herefishy]

Yes.

Now, certainly the compressor is not going to be properly cooled, nor the refrigeration system properly charged, one way or the other:

1.) If the compressor properly cooled, we would not obtain the temperatures that we find desireable.


2.) If the system is charged to the desireable effect (at the evaporator) that we want, the compressor is not properly cooled.

.... It is a lot more complicated than that, just listen to Gary... he's got all the reasons "Pat". Really what we are doing when we do a no-cap-tube mod, R-404A thingy, is pick a happy medium (which really at this point, it is the compressor that is still unhappy) to get the system to within some resemblence of .... what we want.

Now, actually manifesting a compressor failure will depend a lot upon usage. If you crank the sucker for 6 hours a day, every day (like some people I know, LOL!), you are more likely to actually experience the failure, rather than in the case of light use.

Cheers

[Charles Wirth]

Superheat under no load was 12 degrees, under load raised it to 20 degrees c.

Im getting an idle temp of -54c with no overclock.

Herefishy, how does it damage the compressor? My engineer here is has doubts. We are charging R507, not 404a. Proms seem to like it better. Compressor runs a little cooler.

Lallend how is your unit running?

[Gary Lloyd]

When you put a higher pressure refrigerant in a system than the system is designed for, you take your chances. It voids the warranty.

R404A carries a higher pressure than R134A, and R507 carries a higher pressure than R404A.

If you don't lengthen the cap tube, then the compressor is pumping a higher capacity, which increases the high side pressure.

Can the compressor take the excess pressure? Maybe, maybe not.

As for the US version vs the European version (50hz vs 60 hz), the US version is more likely to fail.

The greatest danger to the compressor is from liquid charging and/or overcharging.

A system should be vapor charged, unless you are using a zeotropic refrigerant, such as R404A which must be liquid charged to avoid fractionation. In this case, it must be charged a little at a time.

In all cases, it is better to be undercharged and add a little at a time, than to be overcharged and remove a little at a time.

[lallend]

Originally posted by FUGGER

Lallend how is your unit running? Hehe, it's not! Thats because I had to reorder the mounting kit. I think either myself or my wife accidently threw it out with the original box.

Theres 75 bucks down the toilet! :dammit:

But when I get it up and running I will let ya know the results

[herefishy]

Hi Fugger,

My opinion regarding this is

R-507 may act differently, and what I post is my opinion, so no one take it too much as hard fact. I am always welcome to differing opinions, and I am wrong at times. :)

Again, my opinion: :)

The primary factor in the discrepancy of the non-modded cap tube, is that the cap tube is sized for a lower pressure drop in the R-134A application (not enough resistance to the refrigerant flow). The compressor capacity and the cap tube capacity want to balance at a higher evaporating temperature than the -54c temperatures that we want. If we add more refrigerant, the SST (evporator) temperature rises accordingly.

As the suction pressure/temperature rises (adding more refrigerant), the capacity of the compressor increases due to the increase in the density of the returning refrigerant (at higher pressure), and the compressor can compress a greater volume (lbs.Kg) of refrigerant per hour.

The reason that we are able to obtain the -54c and -40c loaded, is we are only applying 110w to 150w of load to the compressor. Essentially the balance between the cap tube and compressor capacity is at a higher evaporating temperature than what we all "lock it in at".

A proper cap tube would increase the pressure drop from the high to the low side of the system, and lower the evaporating temperature to a desired temperature with a properly fed evaporator and proper compressor-motor cooling.

Does that make sense to you?

[Gary Lloyd]

Superheat under no load was 12 degrees, under load raised it to 20 degrees c.

I would view this as the maximum allowable charge.

With this being the maximum charge, you can then find the optimum charge by putting the system under full load and removing very small amounts until the lowest evaporator temp is achieved. If this results in the compressor running too hot, then an accumulator should be considered.

Actually, those numbers sound very close to optimum already. I strongly suspect you have done your homework. Good job. :D

[Charles Wirth]

Granted we went over the happy medium, we know exactly how to get a good charge on the system and where to safely pull vacuum to. I believe it can be done safely if done correctly.

Lallend if you want to bring your unit back for the cap tube lengthend please do. I am not going to lenghten mine and continue to monitor how it operates under benchmarking this weekend.

Opps unit was leaking @ 10 inches of vacuum and sucked in atmosphere. This was the result of a cap tube mod.

lenghting the cap tube will decrease amount of refridgerant going to the evap thus decreasing the coolant raching the compressor. This will also increase the superheat.

404a is about 8% less efficiant that 507, increasing the cap tube 8%.

when charging these with 404 will damage these compressor because they be running outside the specifiactions. Damage occource at 190 degrees to the oil.

We are monitoring superheat and subcooling, that is about the best way to keep the compressor. Another point that has not been covered is amp draw increase from mod.

Take the lock rotor amps divide by 5 = run amp. Running over LRA will burn it out, increasing the cap tube increases the LRA.

404 will increase LRA more than 507

Compresor change is the optimal solution.

[herefishy]

Originally posted by FUGGER
lenghting the cap tube will decrease amount of refridgerant going to the evap thus decreasing the coolant raching the compressor. This will also increase the superheat.

No, it will balance the system at a lower evaporating temperature/pressure and you will add more refrigerant. You will increase subcooling in you condenser. You will get a colder return gas at a lower pressure with the proper cap tube.



Compresor change is the optimal solution.

Actually the compressor whose rating at -10degF R-134A is a perfect choice for R-404A/507 at -50F evaporating temperature. It is the cap tube change that is the optimal solution. IMHO the compressor is perfect!

You will not find any compressor on the market rated at a -50 to -60F evaporating temperature. The ice cream merchandiser manufacturers use low temp 134A compressors in R-404A very low temp applications. :)

[Gary Lloyd]

We are monitoring superheat and subcooling, that is about the best way to keep the compressor.

No argument here. I am a BIG fan of subcooling and superheat, as well as delta-T's and TD's. My books revolve around these concepts.

[herefishy]

Originally posted by FUGGER
Superheat under no load was 12 degrees, under load raised it to 20 degrees c.

How are you calculating your superheat? R-507 @ 5"Hg has a Saturation temperature of -60F.

[Gary Lloyd]

Cap tube length is critical. Too restrictive results in excessive subcooling. Not restrictive enough results in excessive capacity during pulldown. Either can result in higher evaporator temp and greater strain on the compressor. Everything is balances and trade-offs, especially when you are pushing the limits.

The trick is to provide the exact amount of refrigerant flow needed for the load and for compressor cooling, with an acceptable amount of subcooling.

[Charles Wirth]

Were taking the pressure and converting it to temp and subtracting the actual temp on the suction close to the evaporator since the suction line is about 18 inches long.

Proms are sealed so he is using the evap head temp and adjusting calculation.

[Charles Wirth]

The trick is to provide the exact amount of refrigerant flow needed for the load and for compressor cooling, with an acceptable amount of subcooling.

That is exactly what we are shooting for, the engineer that I am working with is retired and knows this stuff inside and out.

I am confident that Lallend's unit was optimally charged.

[Gary Lloyd]

That is exactly what we are shooting for, the engineer that I am working with is retired and knows this stuff inside and out.

Yep, it sure sounds like he knows his stuff. Must be one of my customers... LOL

[tombman]

Oh man, this is difficult...

I have red the whole thread and understood just too few :(

Could you guys just tell exactly step for step what he has to do to perfectly charge the mach I and exactly how long the whole captube has to be.

All those "whens" and "ifs" don´t get me nowhere, cause i need a fool-prove step by step instruction.

I really appreciate your help, and THIS thread could be the ultimate "mach I to r404a mod" tutorial :D

p.s.: the european compressor is rated different then the US version.... just check the link i gave you...

[Gary Lloyd]

If I could explain fine tuning in a few paragraphs, then I wouldn't need to write books, and if I revealed it all in an online tutorial, then I wouldn't be able to sell books. It's how I put food on my table. :D

[Charles Wirth]

I am not fully up to speed on working the gauges, so the technique used on mine would be a uselss partial guess.

[tombman]

So is there no one on this Forum that actually DID successfully
mod a Mach I with r404a and DIDN´T break it?

@gary, aehmm, this thread is not intended to advertise your books, but to help others to mod a particular unit with a particular amount of r404a. So i guess passing that information to this forum will 100% not make you gonna lose customers...

Please get me right: i don´t need to know why things work, or how they work, i just need to know what has to be done to get a running mach I modded with r404a and longer cap tube.

[Charles Wirth]

I will know for sure by this weekend if my mod was 100% sucessfull when I put my system under full load for many hours of benching.

[tombman]

Originally posted by FUGGER
I will know for sure by this weekend if my mod was 100% sucessfull when I put my system under full load for many hours of benching.

Great :D

And then tell everybody how to do it AND how to keep it safe ;)

[herefishy]

Originally posted by FUGGER
We're taking the pressure and converting it to temp and subtracting the actual temp on the suction "close to the evaporator" since the suction line is about 18 inches long.

:stick:

JMHO


:)


I am NOT purposefully trying to stir the pot, here. I am amiable to the fact that what is done may well be right... and I am often wrong...... (....) and perhaps I miss something... but.....

.... the fact that the cap tube was originally designed for a 150psi drop with R-134A, and to use the same cap tube and expect a 250psig drop with R-(507).... that's where I just don't get it.... please explain..... my understanding is that the differences in capillarity of (any) flouro/hydro-carbon refrigerants is negligible......

[Gary Lloyd]

.... the fact that the cap tube was originally designed for a 150psi drop with R-134A, and to use the same cap tube and expect a 250psig drop with R-(507).... that's where I just don't get it.... please explain..... my understanding is that the differences in capillarity of (any) flouro/hydro-carbon refrigerants is negligible......

You are not wrong, herefishy. The 250 psig drop is achieved by eliminating subcooling and passing a liquid/vapor mixture through the cap tube. Can this work? Yes. Would lengthening the cap tube work better? Yes. Of course, this assumes that chip-con got the cap tube right for R134A.

[herefishy]

Hi Gary,

Is it functionally feasible to actually splice a cap tube?

I've got a prolem with the concept of "splicing cap tubes"... can you relieve my pain? :(

Is this practice actually suitable to proper operation of a refrigeraton system? I've never done it, and consider it taboo, as opposed to replacing the entire refrigerant control in whole (cap tube).

thanks in advance. :)

[Hobocrow]

Herefishy! :) I truely love this exchange...it's sooo educational and simply interesting! You guys' are very knowledgeable and info us with way more data than we need...please continue! :D

edit:// I do not...can not...would not in my wildest dream try to speak for Gary or any one else in this area!

Oh!..if I remember correctly from an earlier thread..it's almost impossible the joint cap tubes and not get "tiny bubbles"..is that not correct?

[herefishy]

......DELETED......

[lallend]

Originally posted by herefishy
LOL!!! ... That reminds me of Lawrence Welk.... Am I old? :confused: I think its actually Don Ho, err umm....guess that makes me the old fart for knowing that!

I too am curious about splicing cap tubes. Theres gotta be a way to do it without turbulance or crap like that.

How bout compression fittings, or flaring tools and stuff like that? Just shots in the dark cause I ain't got a clue! :confused:

[herefishy]

........DELETED........

[Hobocrow]

Originally posted by herefishy
LOL!!! ... That reminds me of Lawrence Welk.... Am I old? :confused:


No! No....It was Lawrence Welk and Don H. with special guest host Ed Sullivan! :toast: :D ILMAO...Ok! back to business before we get in trouble. ;)

edit:// I was trying to follow along, but, da^n dialup places me outside the conversation sometimes...

The "tiny Bubbles" was a good joke and I was trying to have a little fun, but I will not be any part of putting Gary in a bad light...I'm sure he can take care of himself...I just wan't be part of anything that demeans him or puts down in any way! He spends many hours helping ppl and IMHO really cares! If this arrives out of place, forgive me...if I have over-reacted forgive me..if not , then back to business!

[Gary Lloyd]

I'm thinking Dean Martin, but then I'm getting senile. They all kinda blur together into a Dean Ho Sullivan, talking to Mr. Ed... LOL

Splicing cap tubes? Can you do it without turbulence?

Ideal would be a tight fitting sleeve, with the cap tube ends wide open and butted against each other, being careful not to get any brazing material where it shouldn't be.

Best would be to replace the entire cap tube. This is what pros do because they have to guarantee their work. It has to be right the first time.

For those who can afford to screw around a little, splice it a little longer than needed, check the subcooling/superheat balance and trim to perfection (or thereabouts).

[Hobocrow]

Originally posted by Gary Lloyd
I'm thinking Dean Martin, but then I'm getting senile. They all kinda blur together into a Dean Ho Sullivan, talking to Mr. Ed... LOL

Thanks the best one yet! :p:

[tombman]

STOP!!

Please open a new thread if you want to discuss cap tube splicing and other things... otherwise this is just spam in THIS thread...

Please stay on topic!

[SAE]

Originally posted by tombman
First of all: i have a EUROPEAN Version of the prommie mach I, so the compressor is a little different to the US Version.

It is the NL7F (http://www.danfoss.com/compressors/pdf/datasheets/r134a_220v_50_60hz/n-series/NL7F_R134a_220V_50Hz_08-01_Cg43k202.pdf) 220volt model.


Hmm. I have the NL11F :confused:

P.S. Following the thread very curiously... :D

[Nico]

Originally posted by Gary Lloyd
I'm thinking Dean Martin, but then I'm getting senile. They all kinda blur together into a Dean Ho Sullivan, talking to Mr. Ed... LOL

Splicing cap tubes? Can you do it without turbulence?

Ideal would be a tight fitting sleeve, with the cap tube ends wide open and butted against each other, being careful not to get any brazing material where it shouldn't be

You'd think they would make cap tube joiners, as you say a short length of tight fitting tube with cleanly cut cap tube ends.

[tombman]

And still no step-by-step instructions here.... :(

[herefishy]

Originally posted by tombman
And still no step-by-step instructions here.... :(

Step by step, the way that herefishy has done it. This procedure has a high degree of difficulty, and you may wish to pursue a less effective procedure in order to not risk the destruction of your machine:

1.) Open the refrigeration system

2.) remove the filter-drier (with cap tube attached is OK, the cap tube will be discarded)

3.) Disconnect the sensor and heater wires from the block at the 4-pin connector (it might be best to simply mark the wires and cut them to re-solder and shrink-tube insulate after the mod)

4.) un-sweat/remove the suction line from the compressor and remove entirely from the prommie case and remove the insulation.

5.) Pry the plastic cover from the cooling side of the block to expose the expanded foam insulation surrounding the copper evaporator.

6.) snip the cap tube right at the point it enters into the suction line/evaporator (when convenient, the esposed cap tue still in the suction line/block is braxed over to seal). Remove cap tube from suction line and discard.

7.) Carefully, and I mean very carefully, slice around the copper block in order to release the adhesion of the foam to the copper. Be very careful not to stray too far from the block with your blade, because the temp sensor wires and 2 sets of heater wires are inbedded in the foam. Be prepared to solder any cut wires back together upon re assembly. At one corner of the block, you will notice a bulge which prevents you from cutting right up to the copper. Don't force it as to not damage the sensor.

8.) release the block from the expanded foam and plastic enclosure/mount, and slide completely off of the suction line.

9.) Carefully pry the temp sensor from the copper block (it is embedded in an epoxy like substance to the block). Remove and clean the temp sensor bonding material from the copper

10.) Drill a small hole about the size of the NEW cap tube, in a lower corner of the block on the suction line connection side of the block (back) (I wouuld use 12' of .028" cap tube. with the NL7F, you may be cutting down to about 10' ).

If you look at the block from the side that the suction line is connected, you will notice that the suction connection favors one end of block in relation to it's longest dimension. you will pick a corner of the other side of the longest dimension in order to drill a hole to slide your cap tube into and braze it in. Make sure that the location that you choose for the cap tube entry does not interfere with the stand-offs that are molded into the mount head.

Be carefull while drilling, because there are internal little copper fingers in the block that can bind the drill bit once you have drilled throught the copper into the internal void, that can break your bit, damage the internals, or otherwise just be a pain (I guess, I didn't have a problem just a high level of awareness).

11.) Braze cap tube in, in a manner that the tube runs flush along the (top) surface of the block over to the suction inlet, where the cap tube will begin to wrap the suction line. (A lot heat is required to get the large mass of copper block heated to the melting point of the alloy - be careful not to overheat the fragile cap tube)

12.) Widen the hole in the molded plastic block mount in order to ease re-assembly, and prevent damage to sensor and heater wires.

13.) Repair any wires that were damaged upon disassembly.

14.) Use 2-part epoxy to re-adhere the temperature sensor to the block, as it was beofre.

15.) Fish the uncoiled cap tube through the enlarged hole in the plastic mount, followed by the wires and the suction line. Be careful not to bind the wires and copper which may strip insulation off of the wires. Additional removal of foam in the mount may be required to accomodate re-assembly.

16.) Fit block into mount. Take time to assure that fit isproper, removing additional foam if required. Check alignment and proper seating by placing the previously removed white plastic foam cover to give a good reference to the original configuration.

17.) When satisfied with new fit, apply expanding foam insulation into voids created by block removal and fitting. Seat white plastic foam cover over curing expanding foam (the stuff in the spray can is fine - use cautiously, it makes a big mess). As foam cures, expands, press on plastic to squeeze excess out and wipe away occasionally. TIP: Use foam that is specifically indicated as "low expansion", or what-have-you. you don't need that much expansion, and super-expanding foam will be very messy and give poor results.

18.) After foam has cured, wrap cap tube up suction line as before, secure the wires, and if it is wanted at this time, and continous and uncut/slitted peice of tubular insulation can be slid onto the suction line up to the head (be sure to cap the open end of the suction line so as not to contaminate with insulation stuff or dirt).

19.) slide/compress insulation up suction line, so as not to melt while brazing suction back to compressor, then do so.

20.) coil cap tube in about a 3" coil, and braze end into new filter-drier.

21.) evacuate and re-charge R-404A

[DarKcyde]

uhhh... wow. /me bookmarks.

One question, what benefit do we get from running the cap tube thru the suction line, and how much difference does it make to the new tube that doesnt run inside the suction?

[herefishy]

Originally posted by DarKcyde
how much difference does it make to the new tube that doesnt run inside the suction?

Absolutely NO difference. The only reason that the cap tube is run inside the suction just before the block, in the original configuration, is for a cleaner look/setup from the plant without having to cramm the cap tube through the plastic hole that is already crowded with wires. ;) Internally the cap tube actually is routed to one of the corners of the block in the original configuration (as the illustrated mod accomplishes). There is only about 1.5" of cap tube inside the evaporator block/suction line.

:toast:

[bowman1964]

herefishy your way looks fine to me,close to how i did some.i just unbrased the block and put the cap in the same spot.but your way is easier....:D

and i never saw one keep itself in a big vacuum while it was fully loaded at least on mine.usally they run around -4hg to 0 psi on mine.that seams to be the best load bearing..charge for me anyways.the high side seams to me around 210psi under a full load .i can make it run it a vacuum but the evaperator starts to starve under a load.as it you can put enough heat to one you will watch it all of a sudden hit a point where it can not keep up and the temp will suddenly start to rise ,and keep on rising untill you drop the heat output some,to a point it can handle.

it is always about checks and ballances.to give you more to one side you have to take some from somewhere.

[herefishy]

Hi Bowman..... and HAPPY BIRTHDAY :D

Your observations are right on the money (with my observations) regarding a loaded system. at about 4"Hg we have an SST of about -56F. I haven't charged a prommie with a cap tube change-out (entire) using the stock compressor. I had done the job I illustrated above during the course of a campressor change-out resulting from valve failure (that I attribute to a R-404 mod w/o cap tube mod). I replaced the Danfoss NF9FX with a Tecumseh TPA1390. The comrpessor was real happy. ;) . I'm sure the Danfoss would do the same.

Idle on the bench, no card, I will see about 8"Hg, and call it good. That seems to really get it in the ballpark. That's not in stone, however, because I apply compressors ranging from R-12/134A capacities @ -10F of 850btuh to 1,050 btuh, and the idle (NO load) suction pressure runs between 8"Hg to 10"Hg for the higher capacity little compressors.


Cheers

:toast:

[bowman1964]

thanks ...herefishy....yea i am a little older..:D

yea too many people watch the gauges,they only tell a small part of the story.....yea Gary i got that from you.....
I am like you and that i really dont care how much of vacuum it pulls just how much heat it can absorb.and just so happens i leave the gauges on to help me fine tune it by letting some in and out.i do notice the pressures...LOL:) and i dont like removing and hooking up gauges as you let small amounts of air in,but that cannt be helpped so i leave them on until the last adjustment has been made.
i personlly dont like having a compressor run in a deep vacuum running all the time.it is hard on it.

[SAE]

Happy Bday from my side too, Bowman.

Keep up the good work... I know you are the best professional phasechange builder/modder I know of. Wish I could send you my prom so you could mod it for me... but it would cost me an arm and a leg ;)

Bye

Stefan