I switch over to propane, then do it. Otherwise the capillary can get too hot.
I switch over to propane, then do it. Otherwise the capillary can get too hot.
If you have a cooling question or concern feel free to contact me.
Originally Posted by n00b 0f l337
Snap,it will just burn right though the cap tube if you have the oxy on, just propane so that it just gets hot enough to let the solder flow, the secret is to rap the cap tube as tight as possible and add a small amount of flux so that the solder flows nice.
There's only one problem Ron
You're making it look better than I do
Nice work though, I've always been jealous of your brazing skills and this time is no exception. It reminds me of showhomes I see sometimes. The ones that are too nice for anyone to live there. It's almost a shame to cover all of that up
Looks like you're getting close though, looking forward to some results from this project
Gray
[SIGPIC][/SIGPIC]
Initial charge. The Danfoss NF5.5CLX is really quiet. I haven't pushed any frost back to the compressor yet, no dripping noise what so ever, maybe when I insulate that will change.
Load testing tomorrow.
Looks good ron, but I think your going to have floodback problems when you insulate sadly. Maybe its time we look into proper accumulators, the horizontal ones require a heatload, while the vertical ones use gravity. The problem though is finding the room or where to place it. Too bad we can't get some heaters for the suction line.
If you have a cooling question or concern feel free to contact me.
Why not?
You can use a fridge wire heater
I don't know if it is really needed
O, didn't know fridges had wire heaters. I wonder if we can find something small, say 5watts or something that we can run off a 12v or the like, and could actually be added to a controller. Say at full load when the fan speed increases, the heater drops.
If you have a cooling question or concern feel free to contact me.
What refrigerant are you using Ron? What's the temperature at the exit of the 1" horizontal tube?
NoL - You can't say this without any figures
The charge "looks" fine, the workmanship is superb...
Tom
"What will become of us, will we evolve"
Throw the heat to her Ron!!
That looks so much like the frost response on my unit, made the same way, it's unreal.
Uninsulated completely, I had it frosted right to the compressor, and still had no flood issues. This should end up being a very ideal charge, with a little room for more if you find you need it.
Noob, I don't think you're seeing the point of this.
A horizontal or vertical accumulator is going to be quite similar, and the vertical accumulator will actually worsen the oil logging on startup anyway. I find that setting it up like this, or with a slight inclination, is ideal for all around performance.
Gravity does give a little over to the vertical, but I think that the tradeoff in slower startup due to the oil settling there isn't really worth it.
The compressor is smaller, but I think that the lower noise and power bills will be worth it.
The fact that you'll have a system that's good for very high load, an evap that potentially will work well at a high natural load than others anyway, along with the ability to use it with lower load cpu's without floodback issues, makes it a really versitile system.
I'm very much looking forward to load tests, and the floodback response from high load to low load and no load when the system has been under load for some time.
Looks perfect so far though Ron
Gray
[SIGPIC][/SIGPIC]
NOL - accumulator is tilted down toward suction pipe going to compressor (gravity) I have frost almost all the way back to the compressor without even a plop. So far so good.
This could change right after a heavy load is dropped. We'll see later today. Think positive noob
I'll get you a few temps when I run it again. I wish I had your mind for this Tom.
If your condensor is quite strong, you'll get a more rapid drop in HP and that should help to prevent a liquid front from hitting the compressor at the suction.
I've noticed myself that on the units I've done this way, I can get a bit of floodback for a short period from 270w to 0w until the HP comes down a bit. higher fan speed would cure it, but keeping things quiet too is nice.
Looks like there may be a source here soon for some better condensors though, and that should be enough to keep the load response to a minimum.
What condensor are you using on this system Ron?
[SIGPIC][/SIGPIC]
These are the condensers Jinu got a good while back. It is not the rifled barrel tubing.
Hey Ron, what sort of material is that brush you are using then? Presumably you would use a low RPM too?
<-- Pessimistic, sorry.
As for the brush thing, I couldnt find, so I picked up a grinder wheel.
I think one of the other solutions is to simply run 100% loaded all the time. Have you tried actually having capillary in the Accumulator ron?
If you have a cooling question or concern feel free to contact me.
nie work there runc, nice to see matching pressures and temps
Kayl, that temps idle, so it definitly should be matching pressure
If you have a cooling question or concern feel free to contact me.
Suggestions please -
Compressor - NF5.5CLX - VapoLS - r404/r507 - LBP/MBP
evaporator - gosmeyer
Refrigerant - r402a
Cap tube - 120" (3.048M)
Ambient temp - 24.5C
Idle
Air into front of condenser - 24.5C
Air out of back of condenser - 28.3C
Evap temp @ idle - 43C
Load block temp @ idle - 43C
Low side pressure - 4psi
High side pressure - 210psi
suction line temp 6 inches from compressor - -38.5C
202Watt load
Evap temp - -26.1C
Load block temp - -21.5C
Low side pressure - 13psi
High side pressure - 240psi
suction line temp 6 inches from compressor - -3.5C
gas temp into top of condenser - 48C
liquid temp out of bottom of condenser - 34C
220Watt load
Evaporator temp - -25.1C
Load block temp - -20.2C
suction line temp 6 inches from compressor - +3.4C
low side pressure - 14psi
high side pressure - 245psi
240 watt load
evaporator temp - -24.2C
block temp - -19.2C
low side pressure - 15psi
high side pressure - 250psi
It held 240watts for about 45 min and then pressures dropped to 12psi low side and 240psi high side and evap and block temp rose up to 60F and that's when I turned off load.
I would like to be able to handle 250watt load without crashing I have a BIG charge on it now - no way I can add more r402a.
Last edited by runmc; 05-05-2007 at 07:40 AM.
I experienced this with many units when I was testing up to 270 and now to 300 watts. The only solution I found was tooo short of a captube for what we'd normally recommend. 8' 6" on nf11fx, 9' on a 3/4hp rotary. This is with r507a though. And our pressures are about the same. I think also a stronger compressor would defniitly improve temperatures.
If you have a cooling question or concern feel free to contact me.
ron, seems to me your only measuring superheat, measure subcooling as well to determine what's the problem. subcooling = measure the temp of outlet of the condensor and convert the discharge pressure to temperature. The temperature difference between these 2 should be within a couple degrees at full load. If it's higher it means the cap tube is to restrictive, if there is almost no difference you need to add more gas. good luck
ron, seems to me your only measuring superheat, measure subcooling as well to determine what's the problem. subcooling = measure the temp of outlet of the condensor and convert the discharge pressure to temperature. The temperature difference between these 2 should be within a couple degrees at full load. If it's higher it means the cap tube is to restrictive, if there is almost no difference you need to add more gas. good luck
I'll strap a probe on the discharge between condenser and filter/drier. Unknown_road - I know you remember Gary Lloyd - well last night I pulled his book out and did some refreshing of my memory -
Measuring subcooling -
Most refrigerants gauges have both pressure and temperature scales. Get into the habit of reading the temperature scales rather than the pressure scales. Start thinking in terms of saturated condensing pressure (SCT) instead of head pressure. This will make diagnosing systems a lot easier.
Subcooling is measured by subtracting the liquid line temperature (at the receiver outlet or between the condenser and filter/drier with cap tube) from the saturated condensing temperature (SCT). Keep in mind that we are comparing two temperatures. Either temperature by itself will not tell us what we need to know.
In most systems anything over 15 degrees F subcooling should be considered excessive. In those rare systems which specify more than 15degrees F (some as high as 20degrees F). 15 degrees will work fine, but will not be quiet as energy efficient. If in doubt, 15degrees is a reasonable limit for subcooling. Excessive subcooling is caused by noncondensibles (usually air), refrigerant overcharge, or restriction.
Excessive refrigerant
If the system does not contain noncondensibles and the subcooling is more than 15degrees F. this tells us that the condenser contains excessive refrigerant. There may be too much refrigerant in the system (overcharged), or the excess refrigerant has been borrowed from the low side (restriction)
Overcharged
At this point in the procedure, it is not necessary to know if the system is overcharged or restrictived. We simply remove refrigerant until the subcooling is 15degree F. If the system was overcharged, we have just taken care of it. If the system is restricted, we will find this when we check the superheat.
High Superheat
High superheat is caused by undercharged (leak) or restriction. If we add refrigerant until subcooling is normal and the superheat is still high, the system is restricted.
For diagnostic purposes we may consider an underfeeding metering device to be a form of restriction.
If superheat is no longer high, the system was undercharged. Locate and repair the leak before proceeding.
Low Superheat
Low superheat (floodback) is caused by overcharge, overfeeding metering device, or insufficient compressor. If we remove refrigerant until the superheat is normal, and the system still has measured subcooling, the system was overcharged. If the system has no subcooling, check the compressor efficiency. If the compressor is OK, the metering device is overfeeding.
I really miss Gary, and I've been meaning for about a year to chase him up and buy one of those books.
Right, if your captube is just over 3m and it's .031" then with that compressor you ARE a little too long.
What you can do though, is to give it 240w, slowly increase both load, and your charge, and watch for a pressure spike.
I find that if I end up with more load than the captube will allow for in a system, regardless of compressor type, I get a serious rise in high pressure at a given charge. That's when I know that I'm at my limit for the captube I have, and have to either live with the capacity, or shorten the captube and start over.
On a smaller compressor, I'd be looking at around 2.75m to be honest. I've been going longer on the NL11F to around 2.9 to 3.0m and been able to tune for 270w, but only barely. I like to be close to the max tuning for the captube though, it tends to give the best results in terms of temp vs. capacity.
As far as your system goes, can you try to charge it to hold 250w, and see if you get 'spiked' on the high side.
If you don't, and you can get it to hold that load, back off to about 50w and see if you have any floodback.
Then, after about 5 min at 50w, go to 0w and see if, and how badly, you are flooding, by the noise and by the amount of fluctuation on the low pressure scale.
Your system is doing very well, and you aren't far off, but you may find that you don't need to change anything to get it to hold the 250w, just give that a try and find out whether you need shorter captube, or more suction volume to deal with it.
Gray
[SIGPIC][/SIGPIC]
Gary Lloyd Book
Maybe this is still the right information. This is the one I ordered -
Last edited by runmc; 05-05-2007 at 04:18 PM.
*ordering*
If you have a cooling question or concern feel free to contact me.
Jurgen said it perfectly, you need to measure subcooling to check capillary tube sizing.
The text from Gary's book:
To get that high subcooling you're filling the bottom rows of the condensor with liquid which is now getting cooled to a temperature a lot below saturation (heavy subcooling).Measuring subcooling -
Most refrigerants gauges have both pressure and temperature scales. Get into the habit of reading the temperature scales rather than the pressure scales. Start thinking in terms of saturated condensing pressure (SCT) instead of head pressure. This will make diagnosing systems a lot easier.
Subcooling is measured by subtracting the liquid line temperature (at the receiver outlet or between the condenser and filter/drier with cap tube) from the saturated condensing temperature (SCT). Keep in mind that we are comparing two temperatures. Either temperature by itself will not tell us what we need to know.
In most systems anything over 15 degrees F subcooling should be considered excessive. In those rare systems which specify more than 15degrees F (some as high as 20degrees F). 15 degrees will work fine, but will not be quiet as energy efficient. If in doubt, 15degrees is a reasonable limit for subcooling. Excessive subcooling is caused by noncondensibles (usually air), refrigerant overcharge, or restriction.
With the condensor now containing a large amount of liquid (indicated by heavy subcooling) the effective area of the condensor which gas can condense in is reduced - a lot. This causes the discharge pressure to rise - a lot.
The increased discharge pressure causes the flow in the capillary tube to increase, so in a way the system adjusts a little - but you've now got an increased compression ratio and therefore reduced compressor performance.
In short subcooling is the key to capillary tube sizing
Nice to see a system described with pressures and temperatures by the way
Tom
"What will become of us, will we evolve"
Posting Permissions
Reply With Quote
is the remedy 
Bookmarks