I'm an empiricist who fixes houses, co-owns a wood shop, runs, and climbs. insta.trom.tf/willardbroswoo…

Yardley PA
Joined December 2012
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
1
7
3
27
Show this thread
These 1/6 traitors aren't in good shape so they're probably tired a lot. Do you think they talk about being fatigued on social media? If you're tired go to bed! #publicvulnerabilityisweakness #imnottired
0
0
0
1
Ground-source heat pump systems (geothermal) have a horrible track record in residential and light commercial buildings and I'm surprised more people don't talk about this.
1
0
0
1
Resi AC undersizing is rare. When offered as a field diagnosis (of exclusion) it's almost always wrong, and given because a tech lacks the resources to identify a problem. Don't accept this diagnosis!
0
0
0
1
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?
1
1
0
2
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.
1
1
0
2
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?
1
1
0
3
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.
1
1
0
3
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!
1
1
0
6
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.
1
1
0
3
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!
2
1
0
9
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?
1
5
0
11
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!
1
1
0
6
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.
1
2
0
4
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.
2
2
1
7
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.
1
2
0
6
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!
1
1
1
10
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!
1
1
0
11