A Personal Experience: The Mismatched Compressor and Air Distribution System in My Home

Mismatched fluid handling machinery and the systems they service are a frequent occurrence in industrial, municipal and commercial fluid transfer installations. And, as I found out this morning, in residential installations. Specifically, in the residential installation in which I personally live.

Two summers ago I bought a new home in the Colorado Spring area. It has an air conditioning unit that only distributes air to the upstairs. Upstairs has only bedrooms and a bathroom.

Colorado Springs is a beautiful city that sits at the base of the world famous Pikes Peak. The local elevation of the city is 6000 ft (1800 m) and my home is at 7200 ft (2200 m). The high elevation results in a more mild summer climate such that the need for air conditioning in homes is not very strong. We do not use our air conditioning upstairs very often.

However, in recent weeks (it is now August) the air conditioning has been used - and stopped working two days ago. Well, everything was working except almost no air was blowing out of the vents. This morning an air conditioning technician came to my house for what I thought would be a one hour service call. This call turned into a four hour call.

What we found out was that there was not enough warm air flowing over the cooling coils to keep the coils from freezing the moisture from the air. Eventually so much moisture froze on the coils it formed an ice blockage which prevented air from flowing resulting in virtually no air flow to the upstairs rooms. The technician did some calculations which suggested the air flow needed to be about double its current capacity in order to keep the freezing from happening. I need to build an AFT Fathom or AFT Arrow model of my air distribution system to confirm what the technician told me. He suggested removing the current distribution system and installing larger ducts to the rooms.

After some discussion he solved the problem with "a band-aid solution". Sound familiar? The band-aid solution was to put a "freeze stat" on the coil and shut down the compressor when the coil got too cold. As all technicians seem to do, he complained about the designer of the system and their lack of competence.

A large part our business at Applied Flow Technology is selling software solutions which help engineers make their fluid handling machinery better match their systems. When properly used at the design stage our software can help avoid the type of problem I have at my home. In the long run this of course saves money by increasing the efficiency of the system and reducing the need for maintenance as well as reducing down time.

We have written several case studies of how our software has helped companies do exactly that - matching fluid handling machinery to the system. Here are a few example case studies from around the world in the municipal, power generation, mining, oil and chemical industries:

• AFT Fathom Instrumental in District Cooling System Planning, Development & Operation (in the USA)
• Mine Dewatering System Design Validated Using AFT Fathom (in Australia)
• Optimization of Seawater Pumping System (in the Middle East)
• Resolving Operational Problems in Pumping Non-Settling Slurries (in the USA)
• Flue Gas Desulfurization System Expansion Design Optimized with AFT Arrow (in Eastern Europe)
  • Also see the follow-up technical paper to this case study showing the installed system measured results: Knocking the SOx off emissions

As discussed in these case studies, some resulted in the saving of many millions of dollars for their owners. On the other hand my HVAC woes cost me $700. And four hours of my time plus some downtime of the system and resulting discomfort for a few days for some of those living upstairs in my home. 

We want others to avoid what I experienced today. This is a good opportunity to state AFT's Mission:

To provide fluid dynamic expertise through world-class software, dedicated technical support and effective training that enables engineers to design and operate fluid transfer systems that are more efficient, cost effective and reliable.