Need your help with tuning

[bartx]

Hi everyone

I need some help with tuning my phase unit. It isn't my first single stage, but for the first time I'm trying to tune it properly.

Specs:

10755 btu rotary (Teco 17.6cc)
25x25x6 cm condenser, two 12v 0,5a fans (San Aces)
2.35m of captube 0.8 mm
SLHX (80 cm 12 mm pipe with captube inside)
captube wrapped around suction line
gas is propane-butane (70/30 mix, maybe more propane, I'm not sure)

Idle:

-45.9c
-0.2 bar
11.8 bar

http://img29.imageshack.us/img29/7452/idle2.jpg

Suction accumulator is all frozen, I heard that it must be frozen so all good now I think

Load 150w:

-32.1c
0.2 bar
14.8 bar

http://img32.imageshack.us/img32/368/load3.jpg

Still 150w, but less amount of refrigerant:

-33.1c
0.1bar
14.0bar

http://img210.imageshack.us/img210/9133/p1090862.jpg

But frost on suction accumulator is going back :) It causes sometimes overheat the compressor.

Are these temps are good on this gas mix? What else can I do?

[bartx]

Anyone?

[ultralo1]

Sorry bartx, I have been having fun with chew toy in another thread.

Why do you say that the compressor is over heating?

I am not familiar with rotaries, I use mostly recips. With them having frost within 1-6 inches of the comp is good. But there shell is common to the suction line where as with rotaries I think their shell is common to the discharge.

I think I calculated your discharge to be close to 200PSI under load. ( I Know, damn Americans will not switch to metric). From looking at your pics you may have an airflow problem over the condensor. I can really tell but from the looks you may have 1/3 of the condensor not having air flow. That would have a definate effect on your discharge pressure.

[EvoCarlos]

depending on the comp make some rotos can run in excess of 100c +

i also agree with ultralo1 you shold make shroud for tyhe condencer it will improve air flow over it :p

presures look a bit high for propain imo :)

[tiborrr]

Watch out, if it's regular cooking gas like we have (70/30 Propane/Isobutane), it will contain quite a lot of impurities, the most unwanted of all would be water. When you charge your unit with cooking gas as a refrigerant, run it through big ass filter/driver.

As the guys suggested, improve your airflow over the condenser. The temperatures are normal for that mix I think, but the discharge pressure is a tad high. Get some R-22 for this cooling device, it's really cheap as every HVAC shop has some you can probably get for free. But watch out for oil compatibility, don't know what oil is in your compressor - may be POE but most likely AB.

[bartx]

Thanks :) Two Sanyo fans which I have now produce 350 m3/h airflow. Standard 250mm fan has performance 1460 m3/h so that's difference.

I'm going to buy bottle for refrigerants (7 kg) but before I must ask if any local HVAC service sell me some r507.

What about suction accumulator? Should it be all frozen or it's not necessary? I suppose that when I use better gas (colder) accumulator will be freezeing easily.

[Postal Dude]

I doubt with all the new regulations you can just go and buy R507 without the proper documents ( i tried last week)

The suction accumulator will be frozen to a different degree depending on the load placed on the system. Ideally with no load you should have frost covering it. When you put a load on the unit, it wouldnt be unusual for some of this frost to melt, as more liquid refrigerant is being evaporated in the evap. It should still be pretty cold though.

Try to get pure R290 or even just regular propane from a bottle (sifted through a filter drier before charging into unit) I think that 30% butane you have in your system is hurting its potention performance to some degree as its got a much higher BP than Propane alone

[tiborrr]

I assume you don't need any licence(s) for obtaining R-507 in Poland, so this won't be an issue. Just watch out for refrigerant oil compatibility. R-507 requires POE (polyol ester) lubricant.

[bartx]

License isn't needed. Which refrigerant do you recommend? I can buy r507 r404a r407c in the same price - 7.5 eur/kg. Price is good, but I have to buy 10kg and pay for a bottle 40 eur.

[Postal Dude]

Go for the 507 mate. Thats definately your best option. Avoid 407c at all costs. 404a is basically 507 with an added shot of r134a. Works nicely, but not as nice at pure 507.

PS: im moving to poland... unrestricted refrigerant ftw