Subject : R500

>~~>In early July 1995, the air conditioning failed. The same air conditioning repair company was dispatched by the Home Warranty company. Upon diagnosis, the HVAC company stated that the evaporator coil was designed for R500 refrigerant and the condensing unit was designed for R22 refrigerant. Therefore, the evaporator coil and condensing unit were not compatable. The HVAC company also stated that they were sure the condensing unit that they replaced the previous summer was engineered for R22 refrigerant. (paul milligan) writes:

> SO they admit their error ? By their own statement they say that they installed a condensing unit that is incompatible with the evap they left in ? Are they trying to say that repeating what they claim to be someone elses mistake excuses their own ? Homey don't think so !


Paul, as you may know, converting R-500 a/c systems to R-22 is not an uncommon practice nowadays. Consider the following problems when one has to service an R-500 unit: (1) try finding R-500 refrigerant. It is doable, but not easy. Then try paying for it. :-) (2) try finding a 'drop-in' replacement for R-500. Perhaps refrigerant R-401B (MP66) is as close as you are going to get but, IMHO, R-401B doesn't solve your evaporator coil problems any better than R-22. The expansion device will have to be change in either case. Refrigerant velocities in the evaporator will be significantly lowered (compared to R-500) using either alternative, which tends to degrade coil performance. And R-401B has a large temperature glide one must consider. R-22 doesn't have this problem and, of course, it is much cheaper.

The *ONLY* reason one should convert an R-500 a/c system to R-22 (or R-401B, or whatever) is simply to extend equipment like. With a residential a/c unit, it makes no sense to change the condensing unit to an R-22 type and save the R-500 evaporator. C'mon! what are you saving here? A residential sized evaporator is not that expensive in the grand scheme of things.

On commercial equipment, trying to save R-500 air handlers may make economic sense. Here, I've seen many R-500 to R-22 conversions. I recommend to servicemen doing this work to change out the TEV and resize the refrigerant distributor to improve refrigerant distribution in the coil with R-22. Then hope for the best. Oil return doesn't seem to be a problem--R-22 is a fairly reactive refrigerant and tends to drag oil along in the suction line pretty well at low velocities.

BTW, you think placing R-22 condensing units on R-500 coils is 'challenging', just wait till you see the new condensing units using R-22 alternative refrigerants make it to market. These units, with their polyol ester oil, will likely be hooked up to old, beat up R-22 evaporators. Expansion devices *WILL* have to be changed for the unit to operate properly. And the ester oil may create moisture and foreign material problems not seen before in the residential a/c industry.

Isn't this a great industry????!!!!!!

Andy Schoen

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