Tuesday, October 30, 2012

CryoBUG new source of R600a

In my last post I mentioned that my Ebay source for the R600a (100% pure Iso-Butane) had unfortunately succumbed to a several month back order. They were gracious enough to quickly refund my purchase price, and also apologized for the lack of inventory. However this temporarily left me with  no way to recharge my CryoBUG demo unit. And on another front, I was still trying to figure out a much better way to charge this into my unit, with repeatable results.

So I started Googling and came across a site called IQ Dental Supply which appeared to have the Wall Lenk 65F Iso-Butane fuel I had been using as my R600a alternative (the MSDS verified it as 100% pure Iso-Butane). And they also sold the burner accessory as well, which I had previously used to fashion a 1/4" refrigerant flare fitting adapter from (no need to make another, but it was good to know that they carried this item as well). The only problem was that, I didn't know if they would sell this to a non-dental person like myself, having run into problems like this before.

Well I decided to place an order for a quantity of six WLC-65F (5.5 oz Wall Lenk Butane Refill), so as to get their quantity discount pricing. Within a few seconds the order was processed, and I received a confirmation email (so far so good). And then about 2-1/2 hours later I received yet another email verifying that the order had been fulfilled and shipped (Woohoo!!!). And yesterday my case of butane refills arrived. The only glitch in ordering from IQ Dental was that the email confirmations did not reflect the additional S&H and HazMat charges that were added to the order, the later of which adds a pretty hefty toll ($25.00 HazMat fee). So in the future I would be wise to double my order in order to help offset this extra cost. On the plus side, their product pricing was the lowest I've seen thus far.

Now that I have my R600a once again, I'm almost ready to get back to my demo unit testing. The only other problem left to resolve is the repeatability issue when charging by weight. As I had mentioned in my last post. Due to the very small quantity of refrigerant to be used, and the near impossibility of negating the influence of the interlinking refrigerant hose connection, the variance in quantity charged vs. what was desired is unacceptable. I needed a better more accurate way of doing this. And that way would be to use what is called a Charging Glass, which is a pressure cylinder having a graduated column. Problem is these can be quite expensive, and are normally of a much higher volume than what I need (hence not as accurate for small refrigerant quantities).

Charge-Check 7001
Enter Thermal Engineering's Charge-Check 7001, which can hold up to 16 ounces of refrigerant. Although at $150+ it was still a little bit more then what I wanted to spend. And by the nature of the beast, it is not something that becomes inaccurate with age, so buying one on the used market seemed like a good option.

Checking Ebay revealed several models made by Thermal, but only a couple were the smallest model 7001 that I was seeking. Out of these, most were being sold for near retail pricing, which always makes me ask "why would I buy this used for the same price as new including a warranty?". Anyway the good news is, that there was one going for $25.00, and I grabbed it.

The Charge-Check I'm getting is most likely graduated for R12 and/or R22 since it appears to be an older model. For my purpose this really doesn't matter, since I doubt that anyone makes one for R600a. So what I'll need to do is fill it with a known weight of R600a (10 ounces), using my electronic scale to verify the before and after weight of the charging glass. Then I'll create my own graduated scale by dividing the liquid column height by 10, and further subdividing this down to show 1/2 ounces. Or if I'm lucky, I'll find that it already matches up with the existing graduated scale (however I'm rarely ever that lucky).

The great thing about using the charging glass method of measuring in my liquid refrigerant, is that it is entirely immune to any outside influence other than a slight variance due to ambient temperature changes (less than 2% error).

All my gaseous refrigerants will be charged in after the liquid using additive pressure. And by weighing the CryoBUG before and after charging is completed, I'll get the total charge weight of all the blended refrigerants. This should work well, and give me repeatable results.


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