Tuesday, April 15, 2014

CryoSPRITE HX Stack Test

Click on Image to Enlarge
A few weeks ago I had a very expensive mistake occur, and that was the loss of a brand new miniature Aspen compressor.

I rushed into the first test with far too much optimism, and not enough caution, thinking that this was going to be a walk in the park.

However the problem was that I didn't know as much about this new smaller HX Stack configuration, as I thought I did. So that combined with starting with too high of an Argon charge, caused such a huge up surge in discharge pressure, that the compressor motor current draw opened up one of the motor windings before the controller could safely shut it down.

End result: Dead Compressor.

So having no compressor, and not quite ready to shell out another $450, I needed a new strategy. My solution was to use my Appion G5 Twin recovery pump as a temporary compressor. This way I could better figure out what was going on without killing yet another mini-compressor.

If you look at the picture in the beginning of this post you will see the results of an actual test using the recovery pump as a compressor, and getting some very decent performance (the blue TC Meter is connected to the evaporator coil mid point, which is surrounded by pink fiberglass insulation). In order to get to this point, I had to first make some radical adjustments in cap tube flow. Basically I increased flow.

When I was designing the CryoSPRITE HX Stack, I forgot to take into account just how small the discharge flow path was getting to be. This started to have the effect of the HX tubing acting like a cap tube. So combine this with the actual flow regulating cap tubes, which I had down sized as well, and the end result was a huge restriction in flow. So much so, that even with a moderately charged system, the discharge peak was enormous. And with the recovery pump I could see this before anything broke. After several adjustments, I was able to get everything in proper proportion, and then good results soon followed.

Best results to date using the recovery pump/compressor...

Suction Pressure: 32 psi
Discharge Pressure: 250 psi
Evaporator Temperature: -131°C

Charge: R600a, R1150, R50, Argon

Aspen Customer Service not so good after the sell.
Before I actually placed an order for the Aspen compressor, the President/Owner was very helpful at answering any of my questions. But later the first thing that slipped was the delivery date. This got pushed out by more than a month beyond the month I had already been waiting. So I compromised and suggested that they send me the older design instead, which they did (including a small refund for the price difference). However when my compressor blew up, and I contacted Aspen explaining that something had gone wrong (even admitted that it was most likely my fault), help at figuring out what was truly wrong never came. So I had to diagnose it myself. However I will give them the benefit of the doubt, and assume they just didn't know how to respond due to the unique nature of what I am using the compressor for (definitely not an R134a system). But it would have been nice to get some troubleshooting tips.

ACXZ14DCH 1.5cc/rev Sine Wave DC Inverter Compressor
Being kinda spooked by what happened, I have decided to use an alternative compressor from an alternative source. That source being Rigid Auto via Ali-Express (Store No: 331602).

The compressor model number is: ACXZ14DCH, and it is a 24 VDC Inverter Drive Rotary Compressor. Being a sine wave based system, it promises to be quieter and less vibration prone then its predecessor (ACXZ14DC-S). It also promises to be cheaper then the Aspen, coming in under $380 including FedEx shipping.

The people over at Rigid Auto are very nice to communicate with, and kinda go the extra mile at trying to answer any questions you may have, and/or provide data sheets on what they sell. My plan is to order a sample in about 1-2 weeks for use in my CryoSPRITE prototype unit.