Trying to fine tune this system.... need advice :-)

[cruzer747]

So I finally got my chiller working after about 3 months and countless dollars and hours later. I had started with a freezer but had accidentally busted a line so I had to hire a HVAC guy and buy a new compressor b/c moisture had gotten inside :( So here are the specs:
-1/3HP motor (I think, maybe 1/4) Embraco FF 10HBX
-I am not sure how long the evap is, maybe 10'ish of 3/8
-still using the condenser from the freezer
-HVAC guy added a filter into the line
-2 capilary (appear to be 1/32) lines running in parallel approx 4' each
-Charged with 25oz of R409A
-40%antifreeze 60%distilled H2O
-2.5 Gallons total
-400GPH Hagen pump
-Temp controller (forgot the name... it uses an electric probe and was easy to set up to my liking 5degrees of change
-plumbed 1/2" vinyl to a MCW6002-A (2500+ barton)and a Polarflow TT(9700pro) in my case smothered in conformal coating, topped with liquid electrical tape with a side of dielectric grease and closed cell foam to the best of my abilities. (will build airtight cooled case like FrozenDeath hasif needed)

So my results so far are run the chiller all the time while cpu is on, which nets me 13Cidle cpu temp, and about 20C load or run the compressor less than half the time (I know it is not as good on the compresser but better on power consumption which I am wary of) which nets me a cpu temp of 20C idle low 30s load. I have not measured the water temp yet but I assume its about 20C colder than my cpu temps.

Ok so here is my question, can I fine tune this better or should I be happy with what I have? I asked the HVAC guy how he calculated the heat load and he said something about using hot water??? and advised me to try going to 20% antifreeze to get better temps instead of messin with the charge or anything else. Thanks so much I will include some pics that may be relevant:)

[expansionvalve]

At first glance I would guess the condenser is holding you back, a good forced air condeser would I suspect raise system performance.

[SexyMF]

Why did you run 2 capillary lines?

My chiller cooled a 2500-M @ 200x11 1.6Vcore to 7C under load. The fluid temp was -20C. (max -27C)

[cruzer747]

I suppose I could put better airflow on it (I have the unit in a box on the side of the house with a filtered port at the top w/ a 120mm 90cfm fan pushing out and then the inlet port on the opposite side bottom of the box which is near the condenser but it is by no means forced air. As far as the cap tubing, I have no idea why the HVAC guy did that, I am no expert by any means, come to think of it wouldn't that effectively be just the same as a single .045 cap tube???:confused:

also, just measured coolant temp @ idle is @ -0.8C and cpu is 17 right now according to PCalert.

[expansionvalve]

Hi, outside is a good place :)
I have a system a bit like yours whereby the coolant/compressor are in another room/location, can't be having some nasty compressor in the computer room adding lots of extra heat:D

On a more level note, I think to be real honest it's going to be hard for anyone here to suggest a way to tune if a few variables are not known, like discharge pressue, suction, water temp and the like.

I take it it's not possible for you to fit a guage set?

[cruzer747]

meanwhile I have noticed my system has been crashing at random! I am guessing it is one of two things... the waterblock is not insulated enough (there is a bunch of condensation on the top and the mounting screws but I am sure I have great ammounts where it counts... or being that I have the MSI K7N2 Delta I have to rely on the ZIF socket hold downs and I had to modify the hold down as it is to get good clamping pressure, while I was messing with the lines maybe it has come slightly loose... and superheating is occuring that doesn't show up on the MB monitor. Usually just resets itself after about 40 minutes or so...? reboots just fine. I would not reccomend this MB for chilled water because of this :-(, this weekend I will be building an airtight case so I can strip all that nasty insulation. I will take pics for sure...:)

[RussC]

that convection cooled condensor is holding you back. Thats the biggest problem with the system. They were never meant to be run continually and will overheat badly. This will effect perfromance severly. The dual cap tube seems to be not restrictive enough. If it was being changed, Id go single cap tube using the length formulas from the other forum.

RussC

[cruzer747]

thanks RussC, I am going to put the chiller mod on hold while I finish this case, as I found out why my cpu was rebooting... condensation dripping on video card :eek: so I am getting into the insulated case build with my time. On a different note, what would someone think about just using this chiller as a backup and trying to make one out of a cheap A/C unit for something more effective, I am beginning to think that would be quicker and cheaper being that I lack all the A/C tools and knowledge, as opposed to finding a better condenser (probably as pricey as a used A/C unit) and having the HVAC guy install it...?

Oh yeah, so should I post in the chilled liquid forum for advice and tips on that case or the case forum:confused:

[RussC]

Look at the A/C thread in the stickies here. That should give you plenty of ideas on using a A/C unit.

Dont know about the case insulation. Usally its the MB thats the issue with condensation.

RussC

[cruzer747]

The case insulation I am referring too is like FrozenDeath made (http://www.xtremesystems.org/forums/showthread.php?t=64405&highlight=case+airtight) except an acrylic version that has an outer acrylic case ~ 1 1/2 inches away from the inner case for the insulation barrier.... radiator on the inside of inner case in chilled water loop to chill air so no condensation is possible. outer case to insulate "cold inner case" so by the outside of the outercase I hopefully will have no sweating. I have a relatively small room with 135 gallons of fishtanks happenin so its prolly about 100% humidity here!

[SexyMF]

I see two things first of all.

Add fan to the condensor (maybe bottom facing up to aid convection)..

The bottom of the condensor should be liquid. So that liquid is trying to climb that long pipe all the way up to higher than the gas inlet, then through the filter/dryer. I suspect that there isn't enough refrigerant being metered to the evaporator. I would place the filter at the bottom of the condensor pointing down at 45 degrees after a small u-bend. Then use ~1.5m of small diameter (0.028") cap tubing doing the climb up to your evaporator coils.

Given the price that the HVAC guy will charge you I'd get a MAPP torch and step up to DIY land. Since you have the majority build done then you really only need to replace the capillary tube, vacuum it, and refill it. R290 is cheap, ozone friendly and oil compatible.

I've not used R409a as I'm really only new to actually making systems myself. But since R290 is a relatively low working pressure gas then your pressure is way low (gleened from your PM). For R290 things only start to work with around 100PSI difference from high side to low side. I would charge the system to between 10" vacuum to 0" vacuum. Heck I ran 10PSI low side. I would expect at least 150PSI on the high side. Now this is were you need the fan on the condensor. Without it you will see good high-side pressures but this comes from a little gas being very hot and not cooling down much in it's pass through the condensor. The system only shifts heat and it's still down to fans to remove that energy with air power. Adding a fan will lower the condensor temp and hence pressure, which also drives down the low-side pressure (which is great). You can then add more gas to achive better cooling.

Building these systems as you have just found out is an iterative process. You will always need to modify the build. So in the long run it is better to have the facility to do this yourself. I would go find some old fridges and rip out the compressors and rig them in series to make a vacuum pump. I did. It works, its cheap. Slow to vacuum but hey it's not $400.

And my trick to removing the high-side line is to overcharge slightly to negate the loss which inevitably follows :D


Hope this makes some sense.

[cruzer747]

I was afraid you'd say that:cool: ok, so my first question, is this a suitable vacuum pump? it does 28.3 pounds for only 17$
http://i47.photobucket.com/albums/f174/cruzer747/Img_4690.jpg
is there any guide that you know of withn explanation of vacuuming? I suppose being a newbie to it I could make one:) , what state should the compresser be in? off I presume, vacuum hooked up to the high side access valve, refrigerant hooked up to low side, pull vacuum, start charging, turn vacuum off, finish charge, runrun, test, charge & finetune...? hmm, oh and I suppose making the changes to the filter and cap tube should be in there somewhere, at the beginning, I should discharge, (I need container) then cut and solder..., then proceed with vacuuming? oh yeah, isnt that a filter in image 4144 hiding behind the insulated tubing with the two cap tubes running to it? is it ok to reuse it or should I start with a new one?thanks for your quick reply. and in case anyone is wondering, curiosity crippled the chiller :( it had a low charge as I suspected and while unhooking valves I lost too much and now it cant handle a load. If there are no good picture guides I will be obliged to take plenty for more of the noobs like me.
thanks again

[SexyMF]

I wouldn't trust that pump as far as I could throw it. It requires an air compressor to function. You can never pull a proper vacuum with that. It's like buying xray glasses from the back of a comic book.

Real pumps are several hundred dollars and take at least 1/2hour to pull vacuum.

Here is my vac pump. 2 ancient compressors in series.
http://i20.photobucket.com/albums/b224/Unxious/Vacuumpump800.jpg

Search the vapor section and you will find all the answers you need.


But since you need intervention for the system anyway. I would bend the filter down to a 45 degree angle. Then I would slightly pinch the cap line. This will restrict the flow and raise the pressure differential.

[Jonathan_S]

ummm I have been thinking of tinkering with my chiller and I did a little reading up on it, I am far from an expert..... this is kinda like the blind leading the blind. My understanding is that you pull a vacuum on the system with the system turned off. The reason you pull a vacuum is to boil off all the water in the system. This can take some time to boil off. After you have pulled the vacuum (2 hours or more if the system was completely ruptured) you then remove the vacuum leaving the system in a a vacuum state then you add refrigerant to the low side of the system after you have added some refrigerant you then turn on the compressor and continue to fill the system the compressor pulls a vacuum and pulls refrigerant in as it is pumping.

If you didn't rupture a line and allow moisture into your system you can skip the whole vacuum thing and just add more refrigerant. It is my understanding, you will need to verify this, that you can mix r-22 and r290 (propane) you will not have a perfect system but both boiling points are close enough that they will work well together. You system will be able to achieve lower temps with a r-22, r290 mix than r-22 alone. So maybe it is better than a perfect r-22 system. I do know from my reading that you need to add more propane to your system respectively than you would r-22 and it is recommended that when you do this that you do it gradually and use a temperature monitoring of your cooling cycle instead of volume of the charge being added in comparison to the amount of r-22 that you would have added.

Doing this also eliminates the need to recover the r-22 from your system in a Eco friendly manner (as we all who tinker with our systems do..... RIGHT.....) :D .

So anyway if you do decide to do a mix let me know how it works so I can decide weather to do a mix on my system or just convert strait over to propane. ;)

[cruzer747]

so I bent the filter to 45, crimped one of the 2 cap tubes as best I could (I think there was way too mch in the first place, and crimped the 2nd one slightlyhttp://i47.photobucket.com/albums/f174/cruzer747/Img_4691.jpg
all with no change in pressures, except I noticed that the low side is now drawing 18 pounds vacuum(12 in picture but went to 18 soon after) and the high side is 58. http://i47.photobucket.com/albums/f174/cruzer747/Img_4694.jpg

so now thinking of an easy working solution "for now" could I recover what is in there, and fill with a refrigerant that I can buy myself(as r409a I believe is requiring certification) and fill it up without vacuuming it? R22 I see constitutes 60% of r409a so am thinking they may be compatible...

I am tempted to buy a used 11500 btu daewoo A/C unit for $50 and work on that for the long run so maybe a bandaid for now to keep things cool?

alright I am going to try and read all I can for a while to learn more... thanks so far!

oh yeah! so is that vacuum pump still junk if I have an air compressor to work with?

UPDATE: Thanks for the heads up on looking for guides in the vapor section... why I didn't think to..?? heh heh, anyhow, LardArse is the man with that awesome set of guides!!!

[SexyMF]

When in vacuum the scale is in inches of mercury. I would puchase that A/C unit and work with that. You need more gas into the system.

Get some compressors for the vacuum pump. It's dead easy. Access valve on the first comp suction. second comp suction to first discharge. That's all. There are more pipes on mine because those compressors for oil cooling.

Ask yourself this: Why would HVAC guys purchase an $500 vacuum pump if they could use a $20 gadget? Other people have asked about such pumps and I've not seen anyone using one.

[cruzer747]

so over here you need to be certified to get r22, ahh well, so now I am wondering what I can put back in there, I believe the compresser has poe oil in there as it has a 134a sticker on it and the hvac charged with 409a(which can work with other oils) does anyone have any objections to just putting some propane in there to fill it back up? I read that propane works with any oil anyways. I have been trying to read all I could and can't see why this will not work in the mean time until I have a better Idea of what I am doing :) Running the pc unchilled, with the case open stinks!:( It looks like I should devote some time to going to the dump and seeing if they will let me have any old compressors for the vacuum pump.

[SexyMF]

You will also need to make an adapter to go from the 1/4" charge hose to propane bottle head. Most people purchase a cheap propane torch head and braze an access valve onto it. I would also get a charging hose that has an inbuilt tap to seal it. That way you can attach it to the vac pump, do your thing and then seal it and shift it to the propane bottle (retaining the vacuum within the hose)

[cruzer747]

I already got the stuff ready to braze together a propane adapter, but I am unsure by what you mean when you say "a charging hose that has an inbuilt tap to seal it.

when you say "tap" could I not hold a vacuum with the one I build out of blowtorch head using the valve on it? I have not been able to find anything on here that matched that description. I could see if you may know that the valve on there would not be adaquate, so I would be grateful for some elaboration on that one.

thanks:)

[SexyMF]

If you have a standard hose you connect one side to the suction of the manifold and the other to the suction of the vacuum pump. Then you need to get the refrigerant into the system. If you simply turn off the manifold and undo the hose from the vacuum pump you loose all the vacuum inside the hose. If you then attached it to your propane bottle you will inject a hose lengths worth of air into your system.

Sealright (TM) is one brand of charging hose with which seals when you disconnect it.

You really want to vacuum the system and the propane adapter (with the valve closed) at the same time. You will also end up with air from the valve of the adapter up to the access valve.

I will endevour to take some photo's of my setup. But I have recently moved house and the new garage is full. All my gear is in there somewhere.

[cruzer747]

I get it:)

[cruzer747]

but I dont have much time to do extensive testing with it :-/ I filled it up with some r290, little by little untill I felt that it was about close, although perhaps a tad under, but it did take a 16.4oz container, but I do remember the a/c guy saying he had 25oz of 409a in there so if it took this much I must have lost more of it than I thought :-/ last night it was running for a while steady at 10 psi low, 175 high, chiller container temp was 13c and compressor was 62c. sound ok? more charge??

[SexyMF]

How long did you run it for. To pull down several litres of coolant can take hours.

[[XC] MarioMaster]

Especially with a convection condensor.

[cruzer747]

run for approxomately 3 hours so far, ran into trouble with new hard lines I installed and by the time I closed up the case, the gpu cooler seems to have come loose with all the fuss. So I need to take it apart again tonight when I get home and sort that out, and install my new 1/8 wall tubing as couplers to the hardline rather than the 1/16... I wish I could get an evap temperature but that would require some work and I will have to settle for an idle liquid temp later.... but I will run it for a while after I have things sorted out.

[cruzer747]

I have tried various charges and the thing just cant hang with the heatload! :( I am guessing perhps the cap tubes the guy put on there were dialed in to what he charged with, and now the r290 just aint cutting it... ahh well, I will try and get that air conditioner tomorrow and see what that does right off the bat, and if I cant mess with the charge at all to get it to work, I will deffinately be putting one together. So is there anything you guys could think of that would be relatively simple, yet work on r290, and be able to handle the heatload which is a 2500 barton, a 9800 pro, and the radiator cooling everything else... maybe 300 watts? maybe more heatload... who knows. I am not sure what compressor I may be getting with taht thing, we'll see...:confused:

[SexyMF]

I suspect that you have also injected air into the system since you have not got a vacuum setup. Did you just make the adapter, and plug in the hose to the fill port?

You have only a few inches of large bore cap tube. You need to have several meters of restrictive cap tube to get things to work. My money is on the fact that the HVAC guy doesn't know what he is doing for the type of system you have. Otherwise he would have told you about the dryer position and cooling of the condensor.

[SexyMF]

last night it was running for a while steady at 10 psi low, 175 high

To me that looks ok, but with the short cap tube you are running high capacity but high temp. At 10PSI R290 boils @ -29.61C

[cruzer747]

well I spent over half the day converting that A/C unit into a chiller, I am sorry to say in the rush to leave I had forgot my camera so no progressive pics, but I will get one of the unit tomorrow all ready to go. I still will need to bypass all the electrical on it, but that shouldd not be too hard. Oh yeah I am not sure if you read right but there are 2 strands of 4 feet each cap tube on the one that I am running now, not 4 inches... feet=' and inches =" right? anywho, the compressor was a rotary charged with r22 so no easy charging with it :( but I am hoping it will do ok.
the new units evaporator was pretty big, over 16 wide, and 14 tall, so I could not get by using the skinny cooler as a reservior, I had to get a larger unit and will probably need to fill it up with something to displace the extra space as I am thinking 5 gallons may be a little much :-) but then again, I could use that to my advantage by prechilling with the cpu off and that would give me a huge headstart if this one wasn't up to snuff either.
all this work just for a quiet computer, I am starting to think that remote locating the computer may have been more effective time wise, but then again itwouldn't be chilled :rolleyes: more tomorrow... sleeeeep

[SexyMF]

Oh yeah I am not sure if you read right but there are 2 strands of 4 feet each cap tube on the one that I am running now, not 4 inches... feet=' and inches =" right? anywho,

Yup, I read that wrong.

Good luck with the AC unit

[cruzer747]

the A/C unit is pretty much what I should have done in the first place IMO. for the $50 unit, a days work, and a $40 cooler, the rig idles at -12C running computer, -15C was the lowest temp it hit without computer and with 3 gallons, under 30 minutes pulldown from 55C, I think it will go a tad cooler with more fluid as the evaporater is only 1/4 submerged, no? So I really goofed on not bringing my camera, it is so hard to get decent pics after the fact. here is the best one I have.
http://i47.photobucket.com/albums/f174/cruzer747/Img_4700.jpg

case temps are slowly creeping down, currently @4.1C and as the cold saturates the part I expect it to go a tad further. With the cpu and videocard on the loop, cpu shows 11C I know that is almost 20 degree differential but the case temps are more important to me than a couple degrees on the chip. when I take the unit out (I need to modify my outdoor enclosure for it I will get some better piccies...:)

[[XC] MarioMaster]

I'm guessing the air conditioner has R22? Anyway, you could recharge it with another gas or tune the refrigerant charge and get even lower temps. It may be more hassle than you really care for but just thought I'd toss that idea around.

[cruzer747]

so I go and get some more distilled and antifreeze to fill it up, finished wiring it to the temperature controller, and start letting it pull down... keeping an eye on everything, I notice by peeking under the lid with a light that the evaporator is all iced over... I am guessing this impairs the cooling abilities, so I am wondering if that means that the A/F and H20 are not fully mixed, should I try running it warm and then pulling it down again to see if that helps? Anyone else have experience with this? I can plainly see that the unfrozen stuff is having no problems and the pump is circulating. And now for my next hurdle, I go to turn it back on, (it had already pulled down from 12C to -10C in 40 minutes, and that is 7 and 1/2 gallons!) and BAM! circuit breaker blows! the starting amps must be pretty beefy on this puppy, plus my and my brother's rooms are on this 15A circuit so I guess that means installing another fuse in the main box :-/ been meaning to but not this soon! The breaker had been heated pretty good (my bro had turned his heater off and it still blew it a few times so I gave up for tonight, with that much liquid, I will have no problems for tonight:D oh yeah, I am running a 40/60 mix antifreeze/distilled water
here is all the ice around the evap...
http://i47.photobucket.com/albums/f174/cruzer747/Img_4708.jpg


UPDATE: I just checked and my worst fears are confirmed... smurfs, EVERYWHERE! I have an all out infestation and the lil buggers are too smart for mousetraps!:eek:

[[XC] MarioMaster]

Two rooms on one 15A breaker? With your brother running a heater it's no wonder it tripped. How many BTU's is the air conditioner? I know a 5000 uses around 5-6 amps and even small heaters can use 10 amps or more. Throw in some lights, your computer etc..... New circuit for both rooms = good idea. I just have a 15A for myself.

[SexyMF]

Did you wait for the pressure to equalise before turning the compressor back on.

I suspect your AF mix isn't pure. Sounds like you are mixing already diluted stuff.

Look good tho.

[cruzer747]

ok, so I ran a dedicated fuse from the box straight to the chiller :-D about an hour and a half into running it with the computer idling and she's a dropping, with 7 gallons of antifreeze, the temp started @ 13C and is now showing a couple different temperatures(two temp gauges in the res) I am not sure which one to trust, probably both as the colder one is more in a low flow spot probably trapped in frozen AF, the other one is closer to the surface away from the ice. That one reads -17.6C and the colder one is now @ -22.7, and steadily but slowly dropping :) my guess is that the stuff that is actually being pumped is @ the warmer temerature... my cpu shows 4C, system 16C, and case 0.5C I think I am going to have to call it good with the chiller work thus far, as my estimated costs were well... surpassed about a month ago or so :rolleyes: now all that is left to do is change the size of the outdoor enclosure, insulate lines better, put the thing on piers so it does not send vibrations through the wall, and perhaps pick up some of the ultimate dessecant, molecular sieves... probably to pull it a lot lower with that and they are rechargeable :p: alright! just hit 0C case temp, liquid is down to -18.6 and I now am getting a slight hint of condensation on the outside of the inner case closest the radiator, should add fan in there too. Alright, 15 minutes later, coldest temp(iced up probe) is now -24C, liquid temp -20C and I think that I am going to save some power and set the temp controller to -15, maybe I will putt another gallon of AF in there to bring the ratio up to 45/55... see if that helps
http://i47.photobucket.com/albums/f174/cruzer747/newscreen.jpg
http://i47.photobucket.com/albums/f174/cruzer747/Img_4731.jpg

[Jonathan_S]

hmmm I think you have too much H2o in your mixture, I am running 60% strait anti freeze (undulated) and then 50% denatured alcohol to 50% H20 added for the other 40%. Making my H20 only like 20% of my total volume. I do not have ice up at those temps at all in fact I can cool it down to -40c without ice forming except condensation on the hoses in the reservoir that are out of the liquid.

[cruzer747]

thats what I need, I was thinking about it but then I could not use it in my car :( thats the broblem with having 7 gallons in your res! it aint cheap, about 40$ in fluids right there!! but I will bet I will get quicker pulldowns b/c of the better flow through the condenser, I am wondering if it will be detrimental to my cpu temps tho..? Any thoughts on that? At what percentage does the liquid temp conductivity become noticable? I have been going it seems around 15 minutes no chiller, 10 minutes w/ from -17.5 to -15. Come to think of it, that Ice may act as a sort of cold battery, if the ice is what appears to be 5c colder than the liquid, it would buffer the warm up time a little, and aid the enormous 7 gallon temp capacity...maybe yes? no?:confused:

[cruzer747]

I looked outside in the res the next morning and the ice was so thick at the top of the res, maybe 2 inches deep! (I had to run my computer for 5 or 6 hours to warm up the coolant enough to melt it!!!:eek: ) I concluded that my coolent flow is causing the seperation (my return line comes in and goes under the liquid line about 2 inches as to avoid siphoning the liquid out of my loop when I turn the computer (pump) off. I contemplated a check valve but with temperatures that cold, I am not sure if that is a safe way to go, but I like the computer being above the reservior for the added saftey if there is a leak there is minimal pressure and it will not fill my case up if I am away. Also it makes draining the lines a snap in case of tubing changes. So I emptied a gallon of denatured alcohol into the res bringing my total capacity up to 9 1/2 gallons, cut the return hose in the res so it is above the liquid line thereby agitating the surface and keeping good circulation.... at the expense of having it drain when I shut it of... hrmmmm,. maybe I will look @ check valves tomorrow... anyhow, I just checked the res and there is not nearly as much ice on the exposed portion of the evap, and not a hint of ice at all, givin that the percentage of alcohol in thereis only 10.5%. Id say that the coolant flow is just as critical to your mix as what you got in it.

[cruzer747]

I think anyone with a larger style reservior and a thermostat/temp controller on their chiller might find this interesting... I have been noting pulldown time vs temps and figured I could easily convert that into a rate at given temperature to see what temp the chiller performs best @ and a good bit of info to keep in mind for setting your thermostat.
takeing the time and temperature a feww times during a pulldown, you can take the temp drop from one reading to the next and divide that by the elapsed time during that drop and come up with a degrees per minute rating. For example, when I started my chiller, liquid was 10.9C 12 minutes later it was 2C, so that gives me an 8.9C drop in 12 minutes.... 8.9/12=.74 degrees per minute, I kept taking measurements for over an hour and a half until the thing had almost bottomed out, and then I worked it out to see the DpM readings were clearly saying the obvious, it was easy to get that 10C to 2C, and almost twice as hard to get that 2c to -14C, and over twice as hard to get from there to -16.4C but when it was obviousely wasting energy and effort was around -20C when i was getting .1DpM, at -21.1 it was .06! so....a decent temp range for my chiller to quickly pull down is around -15... with the thing set to go down 3 degrees further. If I wanted to save $$$ on electricity, I would have to run things much warmer, but I would rarely have to run them at all... also using this you can track your usage degrees... monitering how quickly it warms up when off... I see my avg is .075DpM divide that by the 3 degree differential and that will give me 40 minutes of compressorless running and my avg chill DpM in that range was .1 giving me a 30 minute run time. Make sense?:confused: ;)