Thread by @JesseTayRiver

Some of the primary challenges to fixing school ventilation systems are totally overlooked, especially in academia. We need a deeper understanding of the main obstacles to HVAC improvement. Thread

Story time! My brother became carpenters in the 90s. Back in 2010 we were dabbling in low-energy/high performance buildings. We had a little training in HVAC, and had just started in NJ's retrofit program, Home Performance with Energy Star.

Mostly this went well. Retrofits routinely saw leakage reductions >40% (we still do this, pics are from yesterday). Ice-damming problems were vanishing, comfort problems improved, energy consumption plummeted.

But we couldn't bring HVAC in line. In fact, our HVAC systems were horrible. We paid big $ to several different subs but the results were always the same.

Our systems were loud. Installing or modifying duct systems made things worse. Temperatures and airflow felt weird. Humidity control was poor. Why was everything so bad? We had top Princeton companies who insisted they did everything right. What was happening?

At the time I had very little practical experience in HVAC, but a decent academic understanding of how systems should work based on training and reading. IOW just enough to be dangerous.

One day I was working on a retrofit where an HVAC sub had performed a heat loss calc and installed a 100 kbtu/hr (🤦) furnace w VS motor but left the existing AC. I had some measurement tools in my truck, but hadn't used them outside of class.

Partly wanting to keep my skills current, I dusted off my TrueFlow grid to measure airflow. The house had a 3 ton AC, so it should have had ~1200 cfm of airflow. My test showed 2000 cfm! Uh oh! No dehumidification! That can't be right, can it?

Knowing I'd probably messed up, I restaged the test. Dismantled everything, checked spacers and settings, I EVEN DRILLED A NEW HOLE FOR THE STATIC PRESSURE PROBE. That feels embarrassing because it's so stupid.

But the 2nd airflow reading was within a few cfm of the first test. Could my 3 ton AC unit be getting 5 tons of air? The manual was sitting next to the machine in an unopened plastic wrapper (🤦we'll come back to this). How to reprogram airflow?

The furnace was programmed by a series of dipswitches on the control board. The installer sets airflow using the switches (on or off), then takes static pressure readings to determine airflow for a given switch configuration. Similar to this pic.

DO YOU SEE WHY THE UNOPENED INSTALLATION INSTRUCTIONS ARE BAD? One set of instructions might include 5 of these charts! No technician can keep these numbers in their head! Enrico Fermi didn't work in HVAC!

After a bit of fussing, it became evident that the dipswitches had never been programmed (quite a bit later I figure out that 'off' is usually very high airflow) That's OK right? Sometimes things get overlooked.

I called the installer (we're chummy) who revealed that he wasn't aware that airflow could be programmed So the best installer for a major commercial/resi HVAC company in Princeton in the year of our Lord 2010 HAD NEVER ONCE PROGRAMMED airflow on a furnace. NEVER!

I was stupid and naïve, but this changed how I spent the next decade. What have I learned since? 1. HVAC techs don't know how to program HVAC systems. Do you think this might be a problem when you need to ventilate your way out of an indoor respiratory pandemic?

2. Almost no HVAC techs can measure airflow or reasonable proxies for airflow (ESP). 5 years later the supervising technician for a multi-million dollar HVAC company would show me his external static pressure measurement by drilling 1 hole (it requires 2) in the wrong location!

3. Almost no HVAC techs follow good protocols for charging refrigerant. I have yet to see one with tools that isolate a micron gauge from a vacuum pump. IOW, I don't know a single tech who can verify a tight, dry AC system, aside from myself.

I see a lot of academics approaching ventilation failures like they're one-offs by competent and honest techs. So they tend to fixate on things like the fraction of recirculated air in a system.

This makes sense because it's a reasonable mistake someone would make to save energy or reduce discomfort. It's the type of mistake an HVAC tech with a PhD might make. But it's not the dominant, real-world mistake.

Real world mistakes are endemic, lazy, stupid, and dishonest. So we need to roll up our sleeves and understand these systems better. Read manuals, or #rtfm as @edjHVAC tells me. Get into the field and put hands on stuff. Figure out programming!

We need to stop taking BS claims at face value. Techs know enough to parrot back to you that ventilation air is set to 100%. Just like every subcool is 10, every AC coil dT is 20, every duct ESP is .5 IWC. These are lies designed people say when they want to escape!

You're all doing important and incredible work! It's just that we need to have this conversation. @ErinBromage @ShellyMBoulder @WBahnfleth @CorsIAQ @HuffmanLabDU @linseymarr @marwa_zaatari @DavidElfstrom @DFisman @CathNoakes @Poppendieck @jljcolorado @j_g_allen