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Field notes · From the trucks

What we'd tell you at the kitchen table.

Short, illustrated explainers on how your system actually works — drawn so you can see it. No jargon, no upsell.

Cutaway of an air handler showing a neglected clogged filter beside a new one

Start here

Maintenance · 3 min

The $12 part that decides your August bill.

A clogged filter is behind more "my AC quit" calls than any single failed component. Here is what it does to the coil, the blower, and your bill.

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Diagram of a Wi‑Fi router, signal strength and a smart thermostat with power cycling steps

Thermostats · 2 min

Thermostat dropped off Wi‑Fi? Do this before you call.

Nine times out of ten it is the router, not the thermostat. Five steps, in order, that fix it.

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Cutaway of a single-storey house showing attic ductwork, supply registers and return grille with airflow arrows

How it works · 4 min

How air actually moves through a San Antonio house.

Supply, return, and the loop between them. Once you can see it, every noise and warm room starts making sense.

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Attic cutaway with supply plenum, main trunk, branch ducts and dampers over pink insulation

Ductwork · 3 min

Where 20% of your cold air goes.

Attic ductwork in Texas lives in 140° air. Every leak, gap and crushed run is money you paid to cool the attic.

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Two-column spring/summer and fall/winter HVAC maintenance checklist on a chalkboard

Maintenance · 2 min

The two-season checklist we run on every tune-up.

Spring and fall, in this order. Print it, or let us do it.

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Labelled diagram of an outdoor condenser: disconnect box, safety shutoff, sealed sleeve, foam-insulated suction line, service valves

Installs · 3 min

What a proper condenser install looks like.

Anyone can set a box on a pad. The details around it are what decide whether it lasts 8 years or 18.

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Cutaway of a bathroom and attic showing exhaust fan ducting to the roof, humidity sensor and return air

How it works · 3 min

Why the bathroom fan matters to your AC.

Every shower puts about a pint of water into the air. Where it goes decides how hard your system works.

Read →

Diagram of a motorised fresh-air damper connecting an outdoor intake to the return plenum, with control wiring to the thermostat

Air quality · 3 min

Fresh-air dampers, explained.

New homes are built tight. That is great for the bill and bad for the air — unless something is letting the outside in on purpose.

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Diagram of a refrigerant line set from condenser through a wall penetration, showing liquid line, flare fittings and lineset cover

How it works · 2 min

What the copper lines outside are doing.

Two pipes connect the outdoor unit to the attic. One is cold and sweating, one is warm. Here is why, and what to look for.

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Exploded view of a smart thermostat display, base plate and wiring on a wall

Thermostats · 2 min

Inside a smart thermostat install.

It takes 45 minutes when it is done right. Here is what those 45 minutes are.

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← All field notes

Maintenance · 3 min read

The $12 part that decides your August bill.

A clogged filter is behind more "my AC quit" calls than any single failed component. Here is what it does to the coil, the blower, and your bill.

5–15%Less AC energy with a clean filter (U.S. DOE)

30–90 dChange interval in SA

Cutaway of an air handler showing a neglected clogged filter beside a new one — Neglected vs. new — same air handler

What a filter is really protecting

It is not there for your lungs first — it is there for the evaporator coil. The coil sits right behind the filter and is wet whenever the system runs. Dust that gets past a loaded filter sticks to that wet coil, insulates it, and the system slowly loses its ability to pull heat out of the house.

Why the blower pays for it

A packed filter is like breathing through a pillow. The blower motor pulls harder against it, runs hotter, and wears its bearings early. On variable-speed systems it will ramp up to compensate, which is why the bill climbs before you notice anything is wrong.

The San Antonio number

With our pollen, cedar season and a dog or two, a 1-inch pleated filter is usually done in 30 to 45 days between May and September. A 4-inch media filter goes 6 months. If you hold it up to a light and cannot see through it, it is past due.

The frozen-coil call

Restricted airflow drops the coil temperature below freezing. Ice builds, airflow drops further, and eventually the house gets warm while the outdoor unit runs nonstop. Plenty of "no cold air" calls in July turn out to be a filter and a frozen coil — which is why we always ask you to check it before we roll a truck.

← All field notes

Thermostats · 2 min read

Thermostat dropped off Wi‑Fi? Do this before you call.

Nine times out of ten it is the router, not the thermostat. Five steps, in order, that fix it.

30 sRouter power-off wait

2.4 GHzBand most thermostats need

Diagram of a Wi‑Fi router, signal strength and a smart thermostat with power cycling steps — Router · signal · thermostat

Step 1 — Power-cycle the router, not the thermostat

Unplug the router, wait a full 30 seconds so the capacitors drain, plug it back in and give it two minutes to stabilise. Most drop-offs are the router handing out a new address and the thermostat not catching it.

Step 2 — Check the band

Most thermostats only talk on 2.4 GHz. If your router merges both bands under one name, temporarily split them or move the thermostat to the 2.4 GHz network in its Wi‑Fi settings.

Step 3 — Look at signal strength

Open the thermostat's network screen. Two bars or fewer through a couple of walls means it will keep dropping. A $30 mesh node in the hallway fixes it permanently.

Step 4 — Confirm the C-wire

A thermostat without a common wire runs off a trickle of power stolen from the furnace. Wi‑Fi radios are hungry — the screen stays on but the radio sleeps. If yours drops every night, it probably needs a C-wire or a power extender kit.

Step 5 — Then call us

If it still won't hold a connection after those four, the board or radio is failing. That is a warranty conversation, and we can usually tell over the phone.

← All field notes

How it works · 4 min read

How air actually moves through a San Antonio house.

Supply, return, and the loop between them. Once you can see it, every noise and warm room starts making sense.

400CFM per ton, roughly

1 : 1Supply should equal return

Cutaway of a single-storey house showing attic ductwork, supply registers and return grille with airflow arrows — Supply in blue · return in orange

It is a loop, not a fan

The air handler in your attic pulls air out of the house through the return grille, pushes it across a cold coil, and sends it back through the supply registers. The same air goes around thousands of times a day. Nothing is being "made" — heat is being carried out.

Why one room is always warm

Long duct runs, crushed flex duct, or a register at the end of the line with no damper adjustment all starve a room. The fix is usually in the attic, not the thermostat — rebalancing dampers or replacing a kinked run.

Returns are the forgotten half

Most San Antonio tract homes have one return for a 2,000 sq ft house. Close a bedroom door and that room pressurises, air leaks out through the ceiling, and hot attic air leaks in elsewhere to replace it. Adding a return or a jumper duct is one of the cheapest comfort upgrades there is.

What we measure

Static pressure — the resistance the blower is fighting — tells us in two minutes whether the ductwork is the problem. Above 0.8 inches of water column and the system is choking no matter how new the equipment is.

← All field notes

Ductwork · 3 min read

Where 20% of your cold air goes.

Attic ductwork in Texas lives in 140° air. Every leak, gap and crushed run is money you paid to cool the attic.

140°Typical SA attic in July

20–30%Loss in leaky systems

Attic cutaway with supply plenum, main trunk, branch ducts and dampers over pink insulation — Plenum · trunk · branch · damper

The trunk and branch system

Air leaves the plenum on top of the air handler, travels a main trunk, then splits into branch ducts to each register. Every joint is a place for tape to fail, and builder-grade flex duct sags and kinks over 15 years.

Leaks you cannot see

A duct leak in a 140° attic does two things: it dumps conditioned air you paid for, and it pulls attic air and dust back in on the return side. Dusty house plus high bill is the classic symptom.

Sealing vs. replacing

If the ducts are structurally sound, mastic-sealing the joints and boots recovers most of the loss for a fraction of the cost. If flex has collapsed or the inner liner is shredded, replacement is the honest answer — we will show you which with a camera.

Insulation matters too

In an attic that hot, R-8 duct wrap pays for itself, and burying the runs under blown insulation keeps them far cooler.

← All field notes

Installs · 3 min read

What a proper condenser install looks like.

Anyone can set a box on a pad. The details around it are what decide whether it lasts 8 years or 18.

R-454BRefrigerant in new Trane systems

12 inClearance minimum, all sides

Labelled diagram of an outdoor condenser: disconnect box, safety shutoff, sealed sleeve, foam-insulated suction line, service valves — Disconnect · sleeve · line-hide · valves

The pad and the level

A composite pad on compacted, level ground. Out of level and the compressor oil pools on one side and starves the bearings. Twelve inches of clearance on all sides and five feet above so the fan is not pulling its own hot exhaust back in.

Disconnect and whip

A weatherproof disconnect within sight of the unit, the correct breaker size from the nameplate, and a liquid-tight whip to the unit. Undersized breakers trip in August; oversized ones let a failing compressor cook.

The line set

Suction line fully insulated with closed-cell foam, no gaps, UV-protected, and run through a sealed wall sleeve. Copper against brick sweats, then rots. Line-hide cover is not decoration — it protects the insulation from sun and string trimmers.

Commissioning

This is the step that gets skipped. Nitrogen pressure test, vacuum to 500 microns, weigh in the charge, then verify superheat and subcooling with the system running. A system that "seems fine" without those numbers is a coin flip.

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How it works · 3 min read

Why the bathroom fan matters to your AC.

Every shower puts about a pint of water into the air. Where it goes decides how hard your system works.

50%Target indoor humidity

20 minRun fan after a shower

Cutaway of a bathroom and attic showing exhaust fan ducting to the roof, humidity sensor and return air — Exhaust · humidity sensor · return

Your AC is a dehumidifier first

In San Antonio the system spends as much energy pulling water out of the air as it does dropping the temperature. Every pint of moisture you keep out of the house is cooling capacity you get back.

Fans that vent into the attic

A shocking number of exhaust fans end in the attic instead of at the roof. Humid air soaks the insulation, feeds mould on the underside of the decking, and the moisture finds its way back into the house through can lights.

The humidity sensor switch

A $40 humidity-sensing switch runs the fan until the room drops below 50% and then shuts off. No one has to remember. It is the highest-return upgrade in most master baths.

When the house still feels clammy

If indoor humidity sits above 55% with the AC running, the system may be oversized — it cools the air too fast to wring the water out. That is a sizing conversation before it is an equipment one, and it is why we do a load calculation on every replacement.

← All field notes

Air quality · 3 min read

Fresh-air dampers, explained.

New homes are built tight. That is great for the bill and bad for the air — unless something is letting the outside in on purpose.

2–5×Indoor vs outdoor pollutant levels (EPA)

30–50%Indoor humidity EPA recommends

Diagram of a motorised fresh-air damper connecting an outdoor intake to the return plenum, with control wiring to the thermostat — Damper motor · fresh air duct · mixed air

Why tight houses need it

Modern construction barely leaks. Cooking, showers, cleaning products and people all load the indoor air, and with nowhere to go CO₂ and VOCs climb. A controlled fresh-air intake fixes that without leaving a window open in August.

How the damper works

A small insulated duct runs from a screened hood outside to the return plenum. A motorised damper opens it on a schedule or when the thermostat calls for ventilation, so the incoming air is filtered and conditioned before it reaches a room.

The controller is the whole point

Without a controller the damper is just a hole. Set to run a few minutes an hour, it brings in roughly the volume code asks for and closes when it is 102° outside or raining.

Filtration goes with it

Outdoor air brings pollen and dust. Pair the damper with a 4-inch media filter or an electronic air cleaner at the return so the fresh air is actually clean air.

← All field notes

How it works · 2 min read

What the copper lines outside are doing.

Two pipes connect the outdoor unit to the attic. One is cold and sweating, one is warm. Here is why, and what to look for.

2Lines, liquid and suction

10 yrTrane parts warranty, registered

Diagram of a refrigerant line set from condenser through a wall penetration, showing liquid line, flare fittings and lineset cover — Liquid line · suction line · lineset cover

Liquid and suction

The small line carries warm liquid refrigerant from the condenser to the coil in the attic. The big insulated line brings cold gas back. If the big one is not insulated end to end, it sweats, drips on the ceiling and loses capacity.

Insulation and UV

Foam insulation crumbles after a few summers in direct sun. Bare copper on the suction line is the single most common thing we see on a 10-year-old install, and it costs efficiency every hour the system runs.

The wall penetration

The hole where the lines enter the house should be sleeved and sealed. Open penetrations let hot attic air, insects and moisture in. Line-hide cover keeps the foam out of the sun and the string trimmer.

Reuse or replace?

With a new system we pressure-test the existing line set. If it holds and is the right diameter for the new equipment, we flush and reuse it. If it has ever had a compressor burnout or is undersized, we run new — reusing a contaminated line set voids the warranty.

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