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HVAC

Our upstairs Bryant HVAC, original to the house,
looks awful but amazingly still works.

Goodman main HVAC installed in 2013.
Goodman originally had a poor reputation,
perhaps because they honored warranty for DIY installs.
Essentially rebranded Amana, my KY Goodman was fine.

static pressure Static pressure, generated by fans or blowers, moves air.
Pitot tubes measure moving air's velocity pressure, which I ignore.

Taps for static pressure, measured by manometer in inches of water,
installed at A and B,
encompass pressure drops for both filter and AC coil,
along with airflow direction changes (not shown),
each of which also drop pressure by 0.1 or so.

Taps at C and D measure total external static pressure.

Main furnace ASPF426016EA has a 100.0 AFUE rating,
based on 0.3" water column pressure between D and C:

D tap above 22x23x1 filter

Our furnace has Motor Speed Tap 4 set:

22x23x1 filter slot at furnace bottom is rusted and collapsed,
confounding replacements.
4-inch media filter upgrade was anyway intended,
with 22x23x1 inadequate for wanted airflow...
With total external static pressure seemingly specified
excluding built-in provision for it, 22x23x1 was
presumably not intended to be used for many configurations.

Manometer measures pressure differences, e.g. for timing filter changes.
Manometer mounting screws are for sheet metal,
accommodated by taping aluminum flashing to duct board:
 
Included taps are also for sheet metal;
spade bit cut a 7/8" hole for pressure tap B,
 
then tap in flashing scrap was taped over it.
 

Manometer zero adjustment has minimal range;
this small amount of fluid determined ability to zero or NOT:
 
Lexington HVAC filter gage showed air pressure
increases, but not actual water column values.

As with most projects involving aluminum duct tape,
paper backing removal is the hardest part;
a utility knife and illuminated magnifier help...

0.9" pressure drop measured by manometer:

... to AC coil exit A:
 
from tap B in ductboard, before planned new filter location,
seems excessive, explaining high electric bill
and operating noise louder than Lexington installation.
Another manometer tap C at air mover exit
would reveal even worse pressure drop...

Plenum below ASPF426016EA probably lacks deflectors
to help air make 180 degree turn, increasing pressure drop.
3.5 ton systems want about 1400 cfm air flow
with 700 square inches of 1-inch filter.
22x23x1 filter < 500 square inches...
25x15x4" filter is good for about 1300 cfm

Honeywell Media Air Cleaner F100F1625
One reviewer noted gap between cover and included filter lets air by.
1x3/4" foam tape fills that gap:

Cheaper and better Filtrete MPR 1550 filters will leave about 1/4" wider gap..
13 Oct:  creating a home for F100F1625
Cut at top end of vertical return exposed sides;
when exposed, cut other sides (from inside return).

Cut down about 16 inches along vertical corners of exposed sides;
flare 11" and 22" exposed sides to F100F1625 (17x24).

ductboard surgery (horizontal cuts for flare)
Utility knife blade from inside should not pierce ductboard foil.

butcher knife
Harbor Freight purchase, to cut Cindy Blair attic insulation,
also used to cut styrofoam for Weaverville move packing.

opened

less dirty than expected

clamps and wood to bend flashing into angle strips
for hanging F100F1625 from horizontal return.

Basement return at vertical return bottom will bypass F100F1625;

14x14 return air filter grille ordered.

F100F1625 hung
supported on back sides by vertical return duct board;
screws thru horizontal return duct board and flashing angle strips.

ductboard wedges
flare 11x22" vertical return to 17x25" F100F1625

taped and masticated (or whatever is the right word)

Two 10 oz tubes of Red Devil RD-DS 181 Duct Sealant sufficed.
This took less time (< 2 hours) and was less messy than expected
(3 paper towels, 1 pair of nitrile gloves, a sacrificial 2-inch brush)

Caulking gun forced mastic beads into interior duct board seams.
Fiberglass mesh tape failed, would not stick around corners.
Internet has little about mastic inside fiberglass duct board,
but was already used in this return:

My mastic application, by caulking gun into seams,
is mostly not visible in this image.
Mastic is both sealant and structural, after curing,
which takes up to 72 hours.

18 Oct: empty F100F1625 cabinet,
open 12x6" furnace room return
(minimizing pressure on mastic for another day or so...)
~ .85" with Filtrete in basement return, 0.9" without.
Opening F100F1625 did not decrease pressure drop.
Closing 12x6" furnace room vent slightly decreased it.

22 Oct:   New 1/8" barbed taps measure pressures at
B' in return plenum below 1" filter (to be removed),
C in supply plenum above furnace, and
D below AC coil, which required some hacking:
B - A 0.9"
B - B' 0.01 - 0.03" (fluctuates)
C - room 0.13"
C - B' 0.36"
B' - D 0.75" drop across 22x23x1 filter
room - B' 0.23"
C - D 1.1" total "external":

Honeywell FC100A1029 installed;  22x23x1 removed
B - A 0.45" half of 1"
B - B' 0.16" drop across 4" filter
room - D 0.51"
C - room 0.??"
C - B' 0.6"
B' - D 0.18" drop across empty 1" filter slot
room - B 0.21-0.23"
C - D 0.8" total "external"; not great but 0.3" better

Thermostat - furnace - wanted operation

27 Oct:  ST55 and OT18-60A installation
Control wires at heat pump were too dingy
and faded to tell black from brown;
  used gray wire to both thermostats for W2.

Heat pump electrical corner is very cramped;
  barely room for OT18-60A thermostat.
Heat pump uses 45/5uF 440VAC capacitor;
  its clamp screw now also holds OT18-60A.

OT18-60A wire color coding is wrong;
  blue and yellow are connected above set point.
  I guessed that blue is to pole of SPDT;
  W2 will not activate below set point if pole is yellow.
However, heat pump will get disabled below 5°,
then ST55 will set W2 as required to maintain set temperature.