Problem with DD, high temp :(

[Kayoz]

Well, I finished my first DD, I used a small 1/5HP R12 compressor and about 19.5 Feet of 0.041" ( eh, I know i know.. ) , the evap is an Own made onem nothing special but it works :p: , Well, I charged it at 155psi at the end, and the temp without heatload goes down till -47/-48 ° , thats pretty good for using R22 pure as refrigerant, but the problem is that I managed to get only to -7 with heat load of about 150Watt on CPU, I tryed adding more refrigerant but the best I could get was that silly -7°, now I know that the base of My evap is not very flat and no perfectly lapped, but, can The compressor size and Capillary be part of the low performances under load?
Another thing, it seems my compressor cant hold high side pressures higher than 150 psi for long, it can go to 190 psi if I keep charging, but after 24 hours ~ it get back to 150 and stay on tha pressure, dunno why, but the sistem gotta be leak free, cos if it wasnt my pressure would be 0 so far, and it is still 150psi on high side after more then 1 week of tests.. please Pro's, any advice is of vital importance to me, thx in advance :)

[Malachia]

e bella camelluzzo :D

[gkiing]

I'ts possible that it only leaks significantly at high side pressures over 150.

[chilly1]

Please post the rest of the system stats. Like suction temp 3 inches from the compressor inlet and outlet temps on the condenser.
For capillary tubsizing for R22 and 1/5 hp compressor you need 130 inches of 0.028 capillary tube for around 180W.
Was this a new or used compressor.

What is the static pressure at what room temperature.

[kayl]

is that in degs c or F?

[Malachia]

is that in degs c or F?


here in italy we use °C :D

[Kayoz]

Well, it is an old used compressor, which has been exposed to the atmospehre for quite a bit ;) , now Im costructing another DD, with a very new 1/5hp compressor, this time im gonna use .031" cap tube, with r22, i think 157" is the right lenght right? I will use a bigger condenser as well, cos the one im using now is quite small, only 12 copper pipes (6 U), lets say this first project was for testing and skillin up a lil with brasing and joints etc, I'll try to drill a classic maze evap asap (gotta find some specific tool), this time I will minimize the use of flare+ teflon and try to make as more direct brazing as I can, so i'll be sure there are no leaks at all, gonna post soon ;)

[Kayoz]

I'ts possible that it only leaks significantly at high side pressures over 150.I think ur right, Im sure Ive found the tiny leak, it should be the Low SideShrader valve, cause I brazed it without screwing out the pin+teflon part before brazing, so the little teflon ring have melted, and It leaks a bit, and stop leaking around 150psi! But do u think 150psi are enaugh for best temps under load? I heard somewhere that u need at least 180-190 psi on high side with r22 to have nice temps under load, ambient temperature is always somewhere btw 24° and 19° (the condenser is very small)

[chilly1]

120inches of 0.028 cap tube if that is the equivilant of 0.031 then yes.

[gkiing]

IO think starting with .028" captube you multiply by .7 for .026, by 1.3 for .031, and remove one foot for a high pressure gas (r22/r290) and remove one foot for each additional heat load over 150w.

[hatemi]

IIRC the right multiplier for .31 was 1.6

[Kayoz]

So It will be 150" , about your experiences, which is ~ a right High Side pressure for R22 with 1/5 compressor? 200, 180 or?

[gkiing]

i might be wrong but I doubt it I got my calculations from gary lloyd's post on cap tube lengths on the phase-change.com forums.

[chilly1]

Don't worry about the highside pressure, Look at the temperatures and hte suction pressure.

[gkiing]

I dont know but my 1/4hp lbp compressor runs 195high 4" low on propane adn around 205high 4" low on r22/~7%propane.

[hatemi]

Quote from Garys post at Team Puss:
"For .026 cap tube, multiply by .7.

For .031 cap tube, multiply by 1.6."

[gkiing]

"For R404A/R507:

Using a center point of 150 watts load I would guestimate 10 feet (3 M) of .028 inch (.7 mm) cap tube.

For each increase of 15 watts, I would shorten the cap tube by 1 foot (30 cm).

For each decrease of 15 watts, I would lengthen the cap tube by 1 foot (30 cm).

Then for R22/R290 (propane) shorten 1 foot (30 cm).

For .026 cap tube, multiply by .7.

For .031 cap tube, multiply by 1.6.

It is best to stay between 5 feet (1.5 M) and 16 feet (5 M), with center range of 10 feet (3 M) being ideal.
"

yah your right

[Kayoz]

Ok, so it should be somewhere around 200, last time I tested it under load I was around 190 coz adding more made the under load temp increase a lil