Problems with new build!

Snowman89 · 11-15-2009, 03:47 PM

This weekend i completed my first singelstage. It has a piotres evap and a NL11F and a 0.75kw condensor. Its using r404.

My problem is:
First i had it on while tuning it. Then it held -30/31 with 250w load. Now, 4hours later it pulls down to -54 without load and cant hold 250w for

... It goes to + degrees then i just shut it off... Searched for leaks now but there arent any, also checked for leaks with nitrogen first before vaccum. When it held -30/31 i had 15bar high side and 0.5bar low side. It was filled with about 200g of r404

Im speechless, now it sits at -53.5 and at first there was ice to half the suction acumulator and then it all just defrosted :S Whats really going on? And when i start the dummyload about 90% of the suction line and suction acumulator gets frosted

When it gets to about -25C the line starts to defrost again.. :S

What can really be the problem?

Ozzfest05 · 11-15-2009, 04:06 PM

Whats the length and Diameter of captube your using you may need to trim it down, My suggestion, vacuum the system down again for several hours, use a filter dryer, let us know your captube details.

Snowman89 · 11-15-2009, 04:08 PM

Quote:

Originally Posted by Ozzfest05

Whats the length and Diameter of captube your using you may need to trim it down, My suggestion, vacuum the system down again for several hours, use a filter dryer, let us know your captube details.

I already have a filter dryer. Do you mean i have to change the one i have? What do you think could be the problem? It has 275cm of 0.9mm captube.

[XC] gomeler · 11-15-2009, 04:14 PM

Hook your gauges up to the system and monitor pressures while testing. You need more information before you can make an educated guess as to what is happening.

Snowman89 · 11-15-2009, 04:16 PM

Quote:

Originally Posted by [XC] gomeler

Hook your gauges up to the system and monitor pressures while testing. You need more information before you can make an educated guess as to what is happening.

Must have forgotten to write them.

Under the load where i had -30/-31 temps the high side was 15bar and low side 0.5bar. Although i might know why the temps was kinda stable there, i had crap contact.. :/ We charged it with about 200g of r404

Patrickclouds · 11-15-2009, 04:49 PM

make a test with 150 watts then more watts and see how it behaves. i think this captube of 2,75m is too long to get enough massflow of refrigerant through your evaporator. so test it if it holds a bit less of load.

let it run with 150 watts for maybe 15 minutes
then increase load to 180 watts and see how it behaves. fill more refrigerant in to reach the lowest temp. let it run for 15 minutes
increase load to 200watts and see how it behaves. if temp drops, fill more refrigeration in. and so on and so on.

if there is a point, where more refrigeration doesnt help, you should shorten your capillary tube or raise your highsidepressure by switching of your fans

than you´ll see if more refrigeration goes through the captube and evaporator.
you can also meassure the subcooling (high pressure in °C minus filterdrier temp) and overheating (temp 10cm before suctionport minus low pressure in °C). if captube is too long you have a large subcooling and large overheating.

Snowman89 · 11-15-2009, 04:52 PM

Quote:

Originally Posted by Patrickclouds

make a test with 150 watts then more watts and see how it behaves. i think this captube of 2,75m is too long to get enough massflow of refrigerant through your evaporator. so test it if it holds a bit less of load.

let it run with 150 watts for maybe 15 minutes
then increase load to 180 watts and see how it behaves. fill more refrigerant in to reach the lowest temp. let it run for 15 minutes
increase load to 200watts and see how it behaves. if temp drops, fill more refrigeration in. and so on and so on.

if there is a point, where more refrigeration doesnt help, you should shorten your capillary tube or raise your highsidepressure by switching of your fans

than you´ll see if more refrigeration goes through the captube and evaporator.
you can also meassure the subcooling (high pressure in °C minus filterdrier temp) and overheating (temp 10cm before suctionport minus low pressure in °C). if captube is too long you have a large subcooling and large overheating.

What do you mean with " Low pressure in C" ? High pressure in is about 50C and out around 28-30. Could it be as simple as its to little gas in it?

Patrickclouds · 11-15-2009, 05:28 PM

search in this document the temp for the pressure on your manometers. every pressure has a belonging temperature thats what i mean.
of course could it be that you have not enoug refrigeration in your unit for 250watts. but in my opinion 200g in a small single stage is a very big charge

Ozzfest05 · 11-15-2009, 05:36 PM

Quote:

Originally Posted by Snowman89

I already have a filter dryer. Do you mean i have to change the one i have? What do you think could be the problem? It has 275cm of 0.9mm captube.

No I was just making sure as you didn't mention that you were using a filter in the OP, around 9 feet of cap tube your using , your pressures seem good, so you may want to see what cooling capacity you have right now, is your load tester variable, try 150 watts, a system can hold 150 watts at -45 and not hold 180 watts at all, we call this crashing, your overshooting the cooling capacity.

My guess is you need more time I would still vacuum the system just to ensure no moisture is affecting it, then recharge like I said your pressures are good monitor them at load and at idle, my guess is not enough refrigerant is flooding the evap to hold the load , test the system until increasing the watt load until it crashes shorten the cap tube recharge and give it another go.

Finally make sure your mounting is good, temp probe is accurate, and do not use too much thermal paste silly mistakes cant affect your tuning.

bartx · 11-15-2009, 09:59 PM

Problem with captube. When compressor isn't hot is ok, but situation is changing when temperature goes to 70-80C. I've got the same in my rotary build now - at the beginning it holds -43 @ 250W but temperature is rising up to -36C after couple of hours and discharge pressure is going really high. Now I have 2.1-2.2m of 0.8mm captube, but I'm going to shorten it. Look here http://www.xtremesystems.org/forums/...d.php?t=201986 - he has very short captube, but almost 3 times more powerful compressor and it's holding load so easy even in 25C ambient (with my unit in 14C ambient everything was ok, but not in 21C).

EDIT: How looks you loaded temp after 4 hours? - because you didn't tell us. If it's rising together with pressures -> too long captube in my opinion.

Snowman89 · 11-16-2009, 01:01 AM

Thanks for all the help.

The problem is that i dont have a tools at all or acess to them where iam now. I dont even have gauges here

I also have to pay to get it vaccumed/refilled

The load tester is not variable but im going to get a thing so i can make it variable

The first time i tried the unit here it got to like +3C after 20min load. Second time it was at -13C after like 40min

sdumper · 11-16-2009, 04:27 AM

Quote:

Originally Posted by Snowman89

This weekend i completed my first singelstage. It has a piotres evap and a NL11F and a 0.75kw condensor. Its using r404.

My problem is:
First i had it on while tuning it. Then it held -30/31 with 250w load. Now, 4hours later it pulls down to -54 without load and cant hold 250w for

... It goes to + degrees then i just shut it off... Searched for leaks now but there arent any, also checked for leaks with nitrogen first before vaccum. When it held -30/31 i had 15bar high side and 0.5bar low side. It was filled with about 200g of r404

Im speechless, now it sits at -53.5 and at first there was ice to half the suction acumulator and then it all just defrosted :S Whats really going on? And when i start the dummyload about 90% of the suction line and suction acumulator gets frosted

When it gets to about -25C the line starts to defrost again.. :S

What can really be the problem?

How sure are you really that you didnt leak some refrigerant because that sounds to me like lack of pressure. You could also have a block in your cap tube possibly but it doesnt sound like its just the length of the cap because if it was you would have repeatablity from the first test and not something entirely different the next time...

--edit-- I just read the first post and responded. Yep if you had "Crap contact" then the cap tube sizing does make sense if when you tried again you had cured paste or you adjusted your contact. Regardless i jumped in late to this thread...

piotres · 11-16-2009, 06:59 AM

Snowman's suction line have 275cm of 0.9mm captube, that lenght work very good for me with NL11F . I'm sure that's not problem with captube lenght . I think that's rather problem with humidity inside unit.

quintus · 11-16-2009, 07:35 AM

Yepp Piotres is right, captube is fine. Bartx you are comparing big a$s 1hp rotasys with 1/3hp nl11f...
Contact between heat loader and evap may be also.

Quote:

Originally Posted by Snowman89

When it held -30/31 i had 15bar high side and 0.5bar low side.

This is wrong at 1bar you must have -44c, you cant go higher on temps with lower presure in normal conditions.

Where are you measuring the temps? Where is your manometer?:P Make yourself a variable load tester

Good Luck!!!

Snowman89 · 11-16-2009, 02:54 PM

Quote:

Originally Posted by quintus

Yepp Piotres is right, captube is fine. Bartx you are comparing big a$s 1hp rotasys with 1/3hp nl11f...
Contact between heat loader and evap may be also.

This is wrong at 1bar you must have -44c, you cant go higher on temps with lower presure in normal conditions.

Where are you measuring the temps? Where is your manometer?:P Make yourself a variable load tester

Good Luck!!!

Im measuring the temp on the evap. The manometer is right after the comp/before.