Why did the water heater need replacement during the furnace project?

Chimney orphaning. The previous setup had both furnace and water heater venting through the original brick chimney. When the furnace was replaced with a 96% AFUE condensing model (PVC venting), the water heater alone couldn't generate enough combustion product to drive adequate chimney draft. Result: backdrafting risk — combustion products entering the home rather than exhausting up the chimney. Power vent water heater eliminated this risk by providing dedicated venting.

Why did you choose mid-tier instead of premium or cost-conscious?

Eduardo's selection based on these factors: mid-tier modulating Bryant 925SA gives most of the comfort and efficiency benefits of premium tier at lower initial cost; cost-conscious Goodman would deliver adequate performance but expected equipment life is shorter; premium Carrier 59TP6 would deliver only marginally better part-load performance for $3,000 additional cost; heat pump conversion would have been ideal but customer wanted to wait for matched AC replacement timing.

Why does altitude derate matter for furnace sizing?

Per IFGC Section 304.1, gas equipment requires 4% capacity derate per 1,000 ft above sea level. At the Avenues 4,400 ft elevation, this is 17.6% derate. The Bryant 925SA's 60,000 BTU/hr nameplate input delivers approximately 49,440 BTU/hr effective output at this elevation. Manual J calculated heat load of 42,800 BTU/hr at 9°F design temperature means the altitude-derated capacity meets the load with reasonable safety margin.

Why was MERV 13 filtration upgraded during this project?

The original 1-inch MERV 8 filter housing had no upgrade path beyond MERV 8 due to depth limitation. MERV 13 cartridge filters require deeper housing (4-inch). Replacing the housing during furnace project allowed deeper filter installation without later refit. MERV 13 captures significantly more particulate than MERV 8 supporting improved IAQ, particularly valuable in Salt Lake's PCAPS inversion months.

What's next for this property?

Eduardo's plan: AC replacement summer 2025. Likely heat pump conversion (Mitsubishi P-Series cold-climate) with the matched air handler integration to his existing furnace. Federal IRA 25C tax credit up to $2,000 plus Rocky Mountain Power Wattsmart rebate up to $2,000 stacked rebates make heat pump conversion economically attractive even when the furnace is relatively new.

Avenues Historic Home Furnace Replacement: 1924 B Street Bungalow

Customer:: Eduardo P.
Address area:: Avenues B Street, Salt Lake City — lower Avenues bungalow district
Home characteristics:: 1924 bungalow, approximately 1,650 sq ft on main level plus partially finished basement (~600 sq ft). Wood-framed construction with original lath-and-plaster walls in living areas, drywall in basement. Single-pane wood double-hung windows (original) with storm windows added 1970s. Original brick chimney serving previous boiler (decommissioned 1962 during furnace conversion). Lower Avenues neighborhood with established trees and uphill grade.
Project type:: Furnace replacement (existing equipment at end of life)
Project completion date:: November 12, 2024
Total cost:: $7,800 installed plus $200 Dominion ThermWise rebate = $7,600 net cost

Background

Eduardo P. has been a customer of ours since 2019 with multiple service relationships across his portfolio of Avenues properties. This case study documents the November 2024 furnace replacement at his B Street bungalow. He also owns a Capitol Hill property (boiler service ongoing) and a Quince Street 1926 home with Viessmann boiler (separate case study planned). The B Street bungalow was Eduardo’s residence. His previous service history with us included annual tune-ups (Comfort Care plan), capacitor replacement on the matched 1997 Carrier AC system in summer 2022, and HSI replacement on the existing furnace in December 2021.

Existing Equipment

Furnace:: 1962 Bryant horizontal-flow forced-air furnace (replacement for original 1924 cast iron boiler). 80,000 BTU/hr nameplate capacity. 60% AFUE estimated (1960s equipment, no AFUE rating on nameplate). Natural gas. Located in utility closet at basement level, accessed via main-level pantry. Atmospheric venting through brick chimney (boiler-era flue).
Ductwork:: 1962 sheet metal ductwork installed during conversion from boiler heat to forced-air. Round trunk and branch ducts. R-2 fiberglass insulation on visible ducts; uninsulated where buried in walls. Some original galvanized return air paths.
Thermostat:: 1990s Honeywell Round mechanical thermostat. Original to Eduardo’s purchase of home in 2014.
AC matched:: 1997 Carrier 38CB024 split system AC. Service capacity at time of project: still operational but approaching end of expected service life. Customer planned AC replacement in summer 2025.
Other:: Honeywell Round thermostat (replaced 2008 with then-current model). MERV 8 1-inch filter at return air. No active IAQ equipment. 1996 50-gallon natural gas water heater also venting through brick chimney (orphaned during furnace replacement — addressed in installation scope).

Diagnostic Findings

Annual tune-up combustion analysis (October 2024):

During scheduled annual tune-up, comprehensive combustion analysis using Testo 320 combustion analyzer.

CO at flue: 285 ppm (concerning — above expected range of under 50 ppm for properly maintained equipment)
CO ambient (in mechanical room): 3 ppm (below WHO 9 ppm chronic exposure threshold but elevated for ambient)
O₂ in flue gas: 11.2% (excess combustion air, consistent with aging equipment)
CO₂ in flue gas: 4.8% (lower than expected, consistent with elevated O₂)
Flue gas temperature: 425°F (high — indicates poor heat transfer)
Steady-state efficiency: 58.4% (declining from estimated 65% original)

Heat exchanger borescope inspection:

Performed during tune-up. Three locations on primary heat exchanger sections showed surface oxidation but no through-cracks visible at inspection. Combination of declining combustion efficiency, elevated CO at flue, and 62-year equipment age supports replacement decision.

Ductwork inspection:

1962 sheet metal ductwork in serviceable condition. Some R-2 insulation deterioration on visible ducts. Static pressure measurement: 0.62″ WC at supply plenum (within acceptable range for the existing furnace blower).

Gas line inspection:

1962 black iron gas piping serving furnace and water heater. Inspection identified no leaks or compromised connections. CSST bonding present and code-compliant per NEC 250.104(B).

Chimney/flue assessment:

Original 1924 brick chimney serving both furnace and water heater. Chimney lining: clay flue tile, original. Condition: serviceable but showing some surface deterioration. Critical finding: with replacement furnace (90%+ AFUE) requiring PVC venting, water heater would become orphaned in chimney (insufficient combustion product to drive adequate draft). Scope expanded to include water heater venting reconfiguration.

Decision Framework

Repair vs. replacement analysis:

62-year-old furnace at end of expected service life. Combustion analysis indicating declining efficiency and elevated CO at flue. No specific component repair would address the systemic age-related performance decline. Repair option not viable.

Replacement options evaluated:

Cost-conscious tier: Goodman GMVM97 96% AFUE modulating — $5,400 installed. Adequate for the home’s heat load.
Mid-tier modulating: Bryant 925SA 96% AFUE modulating — $7,800 installed. Better part-load performance, longer expected equipment life, communicating control compatibility.
Premium modulating: Carrier 59TP6 96.7% AFUE modulating with Carrier Infinity controls — $10,800 installed. Premium tier with full smart control integration.
Heat pump conversion: Mitsubishi P-Series cold-climate heat pump — $19,400 installed, $15,400 net after rebates. Considered but customer planning summer 2025 AC replacement and wanted to defer heat pump decision until then.

Customer selection:

Eduardo selected mid-tier Bryant 925SA. Reasoning: Bryant 925SA modulating output provides better part-load comfort for the home (Manual J load varies significantly between mild and design winter days). Expected equipment life 20-25 years justifies investment over cost-conscious tier (15-18 years). Defers heat pump decision until summer 2025 AC replacement timing.

Equipment Specifications

Furnace selected: Bryant 925SA

Model: 925SA48060V17 (60,000 BTU/hr input, 96% AFUE, modulating 35-100%)
Variable-speed ECM blower
Communicating control compatible (Bryant Evolution platform)
PVC concentric venting (intake + exhaust)
10-year parts warranty, 5-year labor warranty
Altitude-derated for 4,400 ft elevation (17.6% derate): nameplate 60,000 BTU/hr delivers approximately 49,440 BTU/hr effective output

Manual J calculation results:

Per ACCA Manual J protocol with home characteristics: total heating load 42,800 BTU/hr at ASHRAE 99% winter design (9°F at this elevation). Required nameplate capacity (with 17.6% altitude derate): 42,800 / (1 – 0.176) = 51,942 BTU/hr. Bryant 925SA 60,000 BTU/hr nameplate is appropriately sized with reasonable safety margin.

Thermostat:

Honeywell T6 Pro programmable thermostat (basic programmable replacement for the legacy Honeywell Round). Customer chose Honeywell T6 Pro rather than smart thermostat (didn’t want internet-connected device for this property).

Water heater venting reconfiguration:

Scope addition addressing chimney orphaning. Replacement 50-gallon power vent water heater (A.O. Smith FCG-50 power vent) installed during furnace project. Power venting through new exterior wall vent rather than original chimney. Chimney decommissioned for combustion equipment use.

Air filtration upgrade:

Original 1-inch MERV 8 filter housing replaced with 4-inch MERV 13 filter cabinet (AprilAire 213). Better filtration for IAQ. Customer education on filter change frequency.

Installation Scope and Timeline

Day 1 (November 11, 2024):

Existing furnace removal and disposal
Existing water heater removal and disposal
Chimney inspection and decommissioning
Site preparation for new equipment

Day 2 (November 12, 2024):

New furnace installation
PVC concentric venting installation through south exterior wall
Gas connection (black iron pipe, leak test with manometer)
Electrical work (new dedicated 15A circuit for ECM blower)
Condensate drain to existing basement sanitary drain
New 50-gallon power vent water heater installation
Power vent installation through south exterior wall
MERV 13 filter cabinet installation
Thermostat installation and programming
Commissioning

Commissioning measurements (after installation):

Manifold pressure: Set to 3.4″ WC (altitude-adjusted from nameplate 3.5″ WC)
CO at flue: 18 ppm (well within acceptable range)
CO ambient: 0 ppm
O₂ in flue gas: 8.4% (typical for properly tuned modulating furnace)
CO₂ in flue gas: 8.2%
Flue gas temperature: 132°F (typical for 96% AFUE condensing furnace)
Steady-state efficiency: 95.8% (within manufacturer expected range)
Static pressure at supply plenum: 0.48″ WC (improved from 0.62″ with new blower)

AHJ inspection:

Salt Lake City Building Department inspection November 14, 2024. Passed inspection. Permit documentation: Salt Lake City permit #B-2024-25871. Inspector noted clean PVC venting installation and proper combustion air provision.

Cost Breakdown

Itemized project cost:

Bryant 925SA furnace equipment: $3,800
Bryant furnace installation labor: $1,400
PVC venting materials and installation: $385
Gas connection and leak testing: $285
Electrical work (new 15A circuit): $185
A.O. Smith FCG-50 power vent water heater: $1,200
Water heater installation labor: $485
Power vent installation: $245
MERV 13 filter cabinet (AprilAire 213): $385
Honeywell T6 Pro thermostat: $185
Permit fees: $245
Subtotal: $8,800
Comfort Care plan discount (15%): -$1,000
Total customer cost: $7,800 installed

Rebates and incentives:

Dominion Energy ThermWise rebate (Bryant 925SA 96% AFUE eligible): $200
Federal IRA 25C tax credit: 30% of qualifying furnace cost ($3,800) = $1,140 federal tax credit available (Eduardo applied at 2024 tax filing)

Net out-of-pocket cost:

$7,800 – $200 ThermWise = $7,600 net cost after rebate. Federal tax credit additional $1,140 reduction at tax filing.

Post-Installation Outcomes

Gas bill comparison (winter 2024-2025 vs. winter 2023-2024):

Winter 2023-2024 (5 months Dec-April): 712 therms total ($684 at $0.96/therm Dominion rate)
Winter 2024-2025 (5 months Dec-April): 488 therms total ($488 at $1.00/therm Dominion rate)
Therm reduction: 31.5% (largely attributable to 96% AFUE vs. estimated 58% AFUE replacement, plus power vent water heater improvement)
Cost reduction: $196 across the 5-month heating season despite Dominion rate increase

Comfort improvements (customer-reported):

Eduardo reported significantly improved comfort during mild winter weather (modulating output matches actual demand, eliminating the cycling pattern of fixed-output legacy equipment). Less temperature swing between thermostat cycles. Quieter blower operation (variable-speed ECM vs. fixed PSC).

Air quality:

MERV 13 filter cabinet captures significantly more particulate than previous MERV 8. Combined with sealed-combustion 96% AFUE furnace (no longer drawing combustion air from indoor space), interior air quality improved. Eduardo reported less dust accumulation on furniture between cleaning cycles.

Eduardo’s overall assessment:

Customer satisfaction with the work. Plans to proceed with AC replacement summer 2025, potentially with heat pump conversion (Mitsubishi P-Series cold-climate) given the rebate stacking economics he evaluated during this project.

Ongoing service relationship:

Eduardo continued his Comfort Care plan into 2025. Next scheduled service: annual tune-up October 2025.

Code Compliance Documentation

Applicable codes for this project:

2024 IMC with Utah amendments: Mechanical equipment installation
IFGC Section 304.1: Altitude derate at 4,400 ft elevation (17.6% derate, manifold pressure adjustment from 3.5″ WC to 3.4″ WC)
UMC Section 510: Combustion air provision (sealed-combustion design supplies outside air through PVC intake)
ACCA Manual J: Heat load calculation (42,800 BTU/hr at 9°F design temperature)
ACCA Manual S: Equipment selection (60,000 BTU/hr nameplate properly sized for altitude-derated load)
ACCA Manual D: Ductwork analysis (existing ductwork serviceable, no modifications required)
NEC 250.104(B): CSST bonding (existing bonding verified compliant)
2021 IECC: Energy efficiency requirements (96% AFUE exceeds minimum)

Permit number:

Salt Lake City Building Department permit #B-2024-25871

Permit issuance:

November 8, 2024

Inspection passed:

November 14, 2024

Frequently Asked Questions

Why did the water heater need replacement during the furnace project?: Chimney orphaning. The previous setup had both furnace and water heater venting through the original brick chimney. When the furnace was replaced with a 96% AFUE condensing model (PVC venting), the water heater alone couldn’t generate enough combustion product to drive adequate chimney draft. Result: backdrafting risk — combustion products entering the home rather than exhausting up the chimney. Power vent water heater eliminated this risk by providing dedicated venting.
Why did you choose mid-tier instead of premium or cost-conscious?: Eduardo’s selection based on these factors: (a) mid-tier modulating Bryant 925SA gives most of the comfort and efficiency benefits of premium tier at lower initial cost; (b) cost-conscious Goodman would deliver adequate performance but expected equipment life is shorter; (c) premium Carrier 59TP6 would deliver only marginally better part-load performance for $3,000 additional cost; (d) heat pump conversion would have been ideal but customer wanted to wait for matched AC replacement timing.
Why does altitude derate matter for furnace sizing?: Per IFGC Section 304.1, gas equipment requires 4% capacity derate per 1,000 ft above sea level. At the Avenues 4,400 ft elevation, this is 17.6% derate. The Bryant 925SA’s 60,000 BTU/hr nameplate input delivers approximately 49,440 BTU/hr effective output at this elevation. Manual J calculated heat load of 42,800 BTU/hr at 9°F design temperature means the altitude-derated capacity meets the load with reasonable safety margin. Equipment sized at nameplate without altitude consideration would have been significantly undersized.
Why was MERV 13 filtration upgraded during this project?: The original 1-inch MERV 8 filter housing had no upgrade path beyond MERV 8 due to depth limitation. MERV 13 cartridge filters require deeper housing (4-inch). Replacing the housing during furnace project allowed deeper filter installation without later refit. MERV 13 captures significantly more particulate than MERV 8 (1-3 micron particles vs. 3-10 micron) supporting improved IAQ. Particularly valuable in Salt Lake’s PCAPS inversion months.
What’s next for this property?: Eduardo’s plan: AC replacement summer 2025. Likely heat pump conversion (Mitsubishi P-Series cold-climate) with the matched air handler integration to his existing furnace. Federal IRA 25C tax credit up to $2,000 plus Rocky Mountain Power Wattsmart rebate up to $2,000 stacked rebates make heat pump conversion economically attractive even when the furnace is relatively new.

Project Details Summary

Customer:: Eduardo P. (consent for documentation given)
Property:: Avenues B Street 1924 bungalow, lower Avenues district, Salt Lake City
Project:: Furnace replacement with mid-tier modulating equipment
Completion date:: November 12, 2024
Total cost:: $7,800 installed, $7,600 net after Dominion ThermWise rebate
Equipment installed:: Bryant 925SA48060V17 96% AFUE modulating furnace, A.O. Smith FCG-50 power vent water heater, AprilAire 213 MERV 13 filter cabinet, Honeywell T6 Pro programmable thermostat
Outcome:: 31.5% therm reduction following winter, improved comfort during mild weather (modulating output), improved IAQ (MERV 13 filtration), eliminated combustion air contamination risk (sealed combustion + power vent water heater)
Ongoing service relationship:: Continued Comfort Care plan member. Annual tune-up scheduled October 2025.

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Phone: (385) 300-1867
Address: 756 E Winchester St #322, Salt Lake City, UT 84107
Email: info@saltlakecityheatingairconditioning.xyz
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Avenues 1924 Bungalow Furnace Replacement Case Study