The Problem With Making Assumptions
Don’t assume that all equipment installations will be done under
laboratory conditions.
I don’t know how many years ago it was that I learned that the first three letters in the word assume explain what we make of ourselves whenever we make an assumption. Yet, almost all of us do it on a daily basis and on the most important matters. Personally, I don’t blindly trust in anything that I read or hear in the news, what my religion taught me, what politicians (either liberal or conservative) tell me, what my doctor says is best for me, or what HVACR manufacturers say is the best practice. I guess you could say that I’m cynical, but that’s what my experi-ence in life has taught me.
This cynicism was recently reinforced when I went to visit a major equipment manufacturer’s wholesale outlet to do some research on an article that I was writing about proper charging methods for R410A systems. Since I knew that their service manager was highly paid, factory trained, probably the best technical person in their office, and certainly no kid, I started off by assuming that he would have all the right answers to common and simple questions about air-conditioner refrigerant charging practices - but I was wrong.
He started off on the right foot by telling me that since most R410A systems use thermostatic expansion valves, checking the liquid-line subcooling is the best method (true). But then he started explaining how the installers or servicers should thereafter check the airhandler’s entering and leaving wet-bulb temperatures, and then compare them against the manufacturer-supplied chart to make sure that everything is correct.
Well, as I explained to him, you can’t really trust the entering-and-leaving wet bulb temperatures across an airhan-dler, because the results aren’t based on real-life situations. They are based on laboratory test conditions, which are based on having exactly 400-cfm/ton airflow. Anything other than that results in a wrong refrigerant charge, which reduces system efficiency. This has also been the problem with the manufacturer charging charts supplied for the more-critical R22 systems.
“No,” he exclaimed, “all our dealers check and adjust the airflow until it is exactly at 400-cfm/ton! That’s what we teach them to do in all our classes!” (Quite an assumption.)
Well, I didn’t want to argue with him, but I’ve been in this business for almost 40 years, and I’ve never seen a ba-lometer (the only device for properly checking diffuser air output) on a residential service or installation truck, and I’ve never seen a residential installer or servicer doing air balancing.
Anyhow, before I left (since my A/C system would soon have to be replaced), I asked him to recommend the best dealer to do the job. He suggested one who he said can always be trusted to do it the right way. And eventually I called them to replace my system (I’d rather have the best job than the cheapest installation, and I didn’t want to get up in my hot attic myself).
Well, they left yesterday; and for a fact, the company he recommended did a wonderful job. But they didn’t use the manufacturer’s holding charge, they didn’t check the entering-and-leaving wet bulb temperatures, and they didn’t check or balance the airflow. Yet, this (according to him) is their best dealer! Did I expect it? No! But HVAC manufacturers and trainers still live in their dream worlds and assume that all installations of their equipment will be done under laboratory conditions, which is misleading and kind of silly.
My point? It would be great to see manufacturers and their instructors get their heads out of the clouds and start supplying information that can be practically used in actual field conditions. It can be done, because some have been able to do it in the past. (See the link http://www.wwwebworks.com/ht/fyi/Jim_Wheeler_Charging.pdf).
I don’t know how many years ago it was that I learned that the first three letters in the word assume explain what we make of ourselves whenever we make an assumption. Yet, almost all of us do it on a daily basis and on the most important matters. Personally, I don’t blindly trust in anything that I read or hear in the news, what my religion taught me, what politicians (either liberal or conservative) tell me, what my doctor says is best for me, or what HVACR manufacturers say is the best practice. I guess you could say that I’m cynical, but that’s what my experi-ence in life has taught me.
This cynicism was recently reinforced when I went to visit a major equipment manufacturer’s wholesale outlet to do some research on an article that I was writing about proper charging methods for R410A systems. Since I knew that their service manager was highly paid, factory trained, probably the best technical person in their office, and certainly no kid, I started off by assuming that he would have all the right answers to common and simple questions about air-conditioner refrigerant charging practices - but I was wrong.
He started off on the right foot by telling me that since most R410A systems use thermostatic expansion valves, checking the liquid-line subcooling is the best method (true). But then he started explaining how the installers or servicers should thereafter check the airhandler’s entering and leaving wet-bulb temperatures, and then compare them against the manufacturer-supplied chart to make sure that everything is correct.
Well, as I explained to him, you can’t really trust the entering-and-leaving wet bulb temperatures across an airhan-dler, because the results aren’t based on real-life situations. They are based on laboratory test conditions, which are based on having exactly 400-cfm/ton airflow. Anything other than that results in a wrong refrigerant charge, which reduces system efficiency. This has also been the problem with the manufacturer charging charts supplied for the more-critical R22 systems.
“No,” he exclaimed, “all our dealers check and adjust the airflow until it is exactly at 400-cfm/ton! That’s what we teach them to do in all our classes!” (Quite an assumption.)
Well, I didn’t want to argue with him, but I’ve been in this business for almost 40 years, and I’ve never seen a ba-lometer (the only device for properly checking diffuser air output) on a residential service or installation truck, and I’ve never seen a residential installer or servicer doing air balancing.
Anyhow, before I left (since my A/C system would soon have to be replaced), I asked him to recommend the best dealer to do the job. He suggested one who he said can always be trusted to do it the right way. And eventually I called them to replace my system (I’d rather have the best job than the cheapest installation, and I didn’t want to get up in my hot attic myself).
Well, they left yesterday; and for a fact, the company he recommended did a wonderful job. But they didn’t use the manufacturer’s holding charge, they didn’t check the entering-and-leaving wet bulb temperatures, and they didn’t check or balance the airflow. Yet, this (according to him) is their best dealer! Did I expect it? No! But HVAC manufacturers and trainers still live in their dream worlds and assume that all installations of their equipment will be done under laboratory conditions, which is misleading and kind of silly.
My point? It would be great to see manufacturers and their instructors get their heads out of the clouds and start supplying information that can be practically used in actual field conditions. It can be done, because some have been able to do it in the past. (See the link http://www.wwwebworks.com/ht/fyi/Jim_Wheeler_Charging.pdf).
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