Mach I R404a Conversion Questions (I've read the stickies :) )

[ge|atinousfury]

Well I am now the owner of a Mach I and I want to have the loop evacuated and recharged with R404a. As such, I have some questions about the whole procedure. A friend I graduated high school with has been working at a local heating and cooling company for 4 or so years now as a technician (refilling and servicing household/commercial A/C units, etc., etc.). I called him up the other day and told him about my Mach I and wanting to find someone that could evacuate it and recharge it with R404a. He's a good friend and stated that he would do it for about $30 plus the cost of refrigerant (he said he would do it on the side to keep from having to go through the company and get overcharged by them for labor). I assume since he's a technician/repairman for a heating and cooling company and he does this stuff most every day then he can do this job also. I think the only thing he wanted me to find out was how much refrigerant that the Mach I label says that if has in the unit so he can know how much to put back in it.

For some reason I'm still reluctant (not because I doubt him but because I don't have the money to buy another Mach I if my luck goes south with this one) to have this mod done. I think that if I get some questions answered my reluctance will ease up a bit.

1. Is there ANYTHING that the guy doing the evacuating/recharging needs to know about this procedure that is different than evacuating/recharging typical A/C units that you would see on the job every day as a technician/repairman?

2. I assume he'll want to test it out after it's recharged to see if everything works, correct? I'm not bringing my computer with me to hook it up to so is there any way to test out the unit before or after recharging it without hooking it up to a computer?

3. I have read that there are heat issues with the Mach I compressor after the system has been recharged with R404a. I plan on putting a YS Tech 120mm 130CFM fan in the Mach I as the stock fan replacement. I'm also going to hook this fan up directly into my computer's psu so it will be on 24/7. The unit will be on a tabletop so there will be nothing around to block ventilation. Is this enough compensation for the added heat of the compressor?

4. As of now my Mach I is brand new. I guess this goes back to question 2, but I assume I need to test this thing out to make sure that it's not (god forbid) DOA before I take it to have it modded. I don't have a motherboard and processor right now so I can't test it out on my system. How can I hook this thing up without a computer to see if it works?

MANY MANY thanks for any help!!!

I would think that new Mach I owners would have many of these questions also. I've looked through stickies and searched the archived threads but can't seem to find any of these answers.

[FUGGER]

1. he has to cut the line and install a valve. you will release R134a into the atmosphere unless he has a vampire tap to reclaim the gas.

2. you need a power supply jumpered with a wire to stay on to fire up the mach units without a machine. This is NOT a solid test of the unit for capacity. You need to test the unit under load for at least an hour to see if the unit fails. I have seen units fire up and get past -52 on the display and fail a few minutes later.

Pull down to 250 minron and let it sit for a few minutes to see if you have a leak after valve install.

Nventiv put a silver sticker somewhere on your unit or the box the exact chage of your unit. about 20oz

3. fans alone should be more than enough if you do not pull the unit into a deep vacuum when you pull the gauges off. I suggest around 3 to 5 inches of vacuum before pulling the gauges off. If you do it around 11 inches you will be a lot colder(yes that is what you want but), you will have less capacity(bad) and the compressor will run very hot(bad). Make sure the ac guy does not pull the gauges with the unit on and in a vacuum or it will suck in air (very bad, start over).

Do not hook the gauges back up after charge unless you plan of sucking out the charge and starting over.

lots of answers here including the questions you asked.

Find my other posts on exact charging of the mach units if you need more on the procedure and what to tell the tech.

Check google more info on how to fire up a psu with jumper wire, its the green wire in the center to ground on the large molex connector.

Lastly, consider R507 instead of R404

[ge|atinousfury]

Thanks a TON Fugger. That helped tremendously. Also, I searched for posts by you in this particular forum and came up with a lot more relevant threads than by searching for "R404", "R404a", etc.

So here's what I've gathered to tell the AC guy (questions followed by parentheses means I need a bit of clarification):

1. He will need to install a Shrader valve

2. He will need to pull the system to 250 microns and set the vacuum for 6 inches (although I've read everything from 4 to 8 inches on these forums....)

3. He will need to put 2 oz. of refrigerant in

4. If possible, go with R507 because it is slightly more efficient and you can vapor charge it instead of liquid charging with R404a

Am I leaving anything out?

[Marci]

Well.... here's what I've found so far... All info was obtained thru the posts here...

NB: All measures quoted are approximations

Prometeia Fresh Captube / Head Replacement - 404a
120" (3.048mtrs) 0.028 Cap Tube (then tweak down in length under load for optimum temps)

Prometeia Captube ADDITION - 404a (Using Stock Head or Baker18 Head)
58.5" (1.500mtrs) 0.028 Cap Tube (after load tweaking done properly, this length can end up reduced to as much as 36" depending on heatload applied to the evap head)

Prometeia Fresh Captube / Head Replacement - 134a/507a
61.5" (1.562mtrs) 0.028 Cap Tube - THIS IS PROMMI STOCK CAP LENGTH

Prometeia Captube ADDITION - 507a (Using Stock Head or Baker18 head)
None Required.

Removing refrigerant with the Prometeia running cannot be accomplished by pushing the valvecore. Air will rush in then... introducing moisture into the system. All old/original gas must be vac'd out.

For optimum temps in both cases, extend total SUCTION line length by approx 5". Suction line is 3/8 Tube. Condenser lines etc are 1/4" Tube. Deepen trap loop on suction line. Replace existing drier with 20g (Captube Conn one side, 1/4" tube conn the other).

404a should be charged as a liquid direct to the high pressure side, or as a liquid thru the compressor's process tube. Fill til both high and low side are approx 40psi. Now we should be ready to fine tune the charge by slowly adding more refrigerant.

When modded to 404 or 507, condenser fans should be run at full speed at all times.

Load testing: XP1700+ (1.4Ghz stock, 133bus, 1.5vcore) at 2.8Ghz (200bus, 2vcore)

There are several methods for the initial charging of an EMPTY unit...

Herefishy says: "Charge until the suction return temperature nears the SST when nothing is connected to the evap. Exact amount, unknown... but in similar custom built units, around 3 - 4 oz of R404A does the trick."

Chilly1 says: "Generally, rough charge the Mach II to a suction pressure (with the highside gauge removed) to 5 inches of vacuum (0.17 bar) and allow it to run unloaded for 15minutes, then top it off to the same amount and test underload of 100W. The pressure should stay the same and the temperature will rise to -50C and stabilize. You can then add or remove gas in .01CC increments to taylor your charge for best temperature. If you are using R404 or don't have a highside tap you must let the unit stand for enough time to fully equalize. You cannot ever charge these with scales as the charge is smaller than that contained in your manifold set."

Gary Lloyd says: "Stick enough refrigerant in there to bring it up to positive pressure. Start the compressor. Add enough to make it run at the low side SST you expect to end up with. Wait until the evaporator reaches it's lowest temp under heavy load, then charge by best CPU Temp at heaviest load.

If you are charging without load, charge to near floodback... say 10 deg C superheat at compressor inlet. This is the maximum safe amount of refrigerant you can put in the system. You will have to remove some of it when you have heavy load on it to get optimum performance."

Under no-load conditions if the bottom of the compressor is cold or even cool there is too much refrigerant in the system. Remove gas a little at a time until the bottom of the compressor is warm. Put system under load. Allow evap to chill to it's lowest and level off. Remove tiny amounts of gas at a time. Temp should continue to fall. When you remove refrigerant and the evap temp starts to rise, you've removed a little too much.

It tends to put the compressor at less risk if you UNDERcharge and ADD gas then overcharge and remove gas... as if you overcharge too much you'll damage the compressor. Between each topup / removal, wait 10 to 15 minutes for the Unit and CPU Temps to settle at the new charge. When working from an initial undercharge, simply keep adding gas until the unit has "peaked" at it's lowest temp and then begins to rise again. As soon as it starts to rise, stop and remove a tiny amount of charge to get it back down to it's lowest again.

Once this is done... hook temp probes up for the following...

Monitoring Points:
1 - CPU Diode Temp & Undersocket Temp
2 - Evap head temp
3 - SST (Saturated Suction Temp) OR Low Side Pressure (and type of refrigerant)
4 - Condenser Air in Temp (Ambient Air Temp)
5 - Condenser Air out Temp
6 - SCT (Saturated Condenser Temp) OR High Side Pressure (and type of refrigerant)
7 - Liquid line temp near Condenser Outlet

There is NO POINT taking all these measurements on an uninsulated system, as insulation changes all the temps and you have to start again from scratch. If charging uninsulated, overgas so that you can start the system and remove gas rather than undercharging and adding gas. Insulate, then once completed fine tune the gas load removing a little at a time...

Main Reference Threads:
http://www.xtremesystems.org/forums/showth...ht=prommie+404a (http://www.xtremesystems.org/forums/showthread.php?s=&threadid=22147&highlight=prommie+404a)
http://www.xtremesystems.org/forums/showth...&threadid=24797 (http://www.xtremesystems.org/forums/showthread.php?s=&threadid=24797)
http://www.xtremesystems.org/forums/showth...&threadid=25956 (http://www.xtremesystems.org/forums/showthread.php?s=&threadid=25956)
http://phase-change.com/index.php?action=A...at=Guides&id=23 (http://phase-change.com/index.php?action=Articles_page&cat=Guides&id=23)
http://www.xtremesystems.org/forums/showth...rheat+measuring (http://www.xtremesystems.org/forums/showthread.php?s=&threadid=29923&highlight=superheat+measuring)


Afterthoughts... AESTHETICS

Flexy Sleeving (Braid)
http://www.wirecare.com/wc_splashpage.asp?prodline=ho
http://www.techflex.com

Insulation
Armaflex (see http://www.armaflex.com)
Builders' Foam (local B&Q / DIY Shop)

If using custom Baker18 Evap Heads, enclosures will soon be available to provide a mounting / insulation solution from xtwerks.com

[Gary Lloyd]

To clarify on the cap tube additions:

R404A and R507 use the same cap tube lengths.

Cap tube length is a tradeoff between temperature and capacity. Longer cap tube gives you lower temperature, but cannot handle as heavy a heat load. Shorter cap tube can handle a heavier heat load, but the temperature will not be quite as low.

Without the cap tube addition, using R404A or R507, the system can handle about 200watts heat load.

With the cap tube addition, it can handle about 150watts heat load.

I have no idea what the temperature differences are, but I suspect no more than 1-2C. Perhaps others have tested this.

Personally, I think the cap tube addition is not cost effective. If you are just changing refrigerants, the system doesn't need a deep evacuation, since it is not open to the air. Just suck out the old, pull a rough evacuation, and put in the new.

With the cap tube addition, the drier should be changed, and a deep vacuum (preferably a triple evacuation) should be pulled on the system. Unless you are doing the work yourself, this is going to be much more expensive.

[Marci]

Righty... in which case I wish I'd read that earlier! If stock captube will increase the units heat dispersion capacity then I'll leave mine as is and just stick the 404a in there!

I'll try my hand at the cap tube swap-out etc at a later date...

[ge|atinousfury]

Wow. Many thanks for the info. Looks like I've got some reading to do :toast:

[phobos]

So I think I'll call my A/C guy tody ;)

[Gary Lloyd]

What would be a very good thing is a load simulator. If you can put the right load on the evaporator, hold the evaporator in the right position, and charge for best evap temp, then the charge will be just right for that amount of heat load.

[phobos]

Yeah, I thought about that some time ago. May be we could realize it with a 170W peltier or something like that.

[DaBit]

A load simulator?

A 0-180W adjustable dummy load can be found here:
http://www.icecoldcomputing.com/text/show_page.php?id=80

It's simple and not too accurate, but processor output is not accurate down to a tenth of a Watt either.

[Marci]

....and that diagram means naff all to me!! */me wanders off to find the electronics handbook again*

[phobos]

Really simple load simulator :)
Nice!
But how would you produce a 180W heat load, because Ptot of the TIP14X is 125W?!