Gas is Wilmington’s heating story — the overwhelming majority of the city’s boilers burn piped gas, from converted atmospheric units in downtown rowhouses to condensing wall-hungs in the New Castle County suburbs. This page goes deep on how those systems fail: ignition and flame-sensing faults, condensate and venting problems in humid mid-Atlantic winters, and pressure loss on sealed systems.
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And what that means for your boiler’s age and type.
Piped gas reached Wilmington long ago — most of the downtown rowhouse stock converted from coal to gas decades back, and the post-war suburbs were built on gas from the start. The equipment splits into two generations: converted atmospheric units downtown — cast-iron workhorses 25 to 40+ years old, many on their second or third set of ignition components — and sealed and condensing systems in the suburbs — 90s-and-later installs in Brandywine colonials and county subdivisions, with wall-hung condensing units in renovated and newer homes.
That split is why a gas call starts with the unit’s age and type: an atmospheric unit from the conversion era and a condensing unit from a 2015 renovation share a fuel and almost nothing else. Both families are covered here and on the national gas boiler repair page; the tiny oil minority has its own honest treatment on the oil page.
The most common gas failure family.
On gas units, the single most common failure family is ignition and flame sensing. The pattern is unmistakable: the boiler tries to fire, flames for seconds, and drops out — or it locks out every few days and a reset brings it back. The usual suspects, in order of likelihood: a fouled flame sensor (the most common of all — soot and oxidation insulate it until the board can no longer “see” the flame), a worn igniter on units old enough to use them, tired thermocouples on the oldest standing-pilot conversions downtown, and loose or corroded burner wiring in damp basements. Wilmington’s humid climate is quietly hard on electrical connections — green crust on terminals in a downtown rowhouse basement is a local cliché.
The rule for this family: resetting without finding the cause is borrowing trouble. The safety chain is doing its job; clearing the lockout hides the evidence the technician needs. Note the pattern — how often, how long it runs, what the display says — and report it on the call. A flame sensor cleaning is a small job; the control board it gets misdiagnosed as is not.
Wilmington’s humid cold has its own signature fault.
Condensing gas units wring extra heat from exhaust by condensing the water vapor out — and that water has to drain somewhere. In Wilmington’s humid winters, the signature condensing fault is the frozen condensate drain: an externally run drain that works fine in November freezes solid in a January cold snap, backs water into the unit, and shuts it down. The fix is routing discipline — interior discharge or properly insulated runs — not repeated resets.
Venting deserves the same attention. Direct-vent and concentric terminations on suburban homes can be blocked by snow drifts, leaves, or ice; older atmospheric units downtown need their flues and draft in good order. A blocked vent on a modern unit usually produces a pressure-switch lockout — annoying but protective — while a degraded flue on an old atmospheric unit is the scarier failure. Either way, the visit checks combustion air and venting as part of the fuel-side sequence, because the burner is only as healthy as its air supply.
The chronic suburban complaint.
The chronic suburban complaint: the gauge that was at 12–15 psi cold in October reads near zero by December, and someone keeps topping it up. On Wilmington’s sealed Brandywine-colonial and subdivision systems, slow pressure loss almost always traces to one of three places: a waterlogged expansion tank (the bladder fails, the tank fills, and there is nowhere for heated water to expand), a weeping fitting or valve (auto-fill valves, air vents, and radiator valves all weep before they fail outright), or the auto-fill/feed valve itself sticking. Topping up without finding the leak masks the fault and feeds fresh oxygen into the system, which corrodes from the inside.
Gauge literacy helps before you call: the boiler pressure guide explains what a healthy cold reading looks like and what the needle’s behavior is telling you. Report the pattern — how fast it drops, whether the relief valve has ever discharged — and the visit starts with testing, not topping.
Testing, in fuel-specific order.
A proper gas visit moves in order: combustion air and venting first, then ignition and flame (sensor, igniter, wiring, burner condition), then gas supply (pressure and valve operation), then the water side (pressure, expansion tank charge, auto-fill valve, air), and finally distribution. On condensing units the condensate path and error history get their own look — a technician who reads the fault log instead of clearing it will find the intermittent lockout’s cause in the log’s memory.
Expect findings explained before any work is authorized — what failed, why it failed, and the options. If the block itself is finished, the replacement page covers Wilmington fuel-choice and sizing math; a dead unit right now is an emergency call. Unsure whether your unit is condensing or conventional? The model plate answers it — read it aloud on the call and the triage takes it from there.
Straight answers before you call.
Often yes — atmospheric burners on converted coal units are simple and their common wear parts remain available. What retires these units is the heat exchanger or the boiler sections, not the burner hardware. Have the unit's approximate age ready when you call (888) 766-1474; it shapes the parts conversation.
Directly — the exterior condensate run froze on a cold night and the unit shut down as designed rather than flood itself. The boiler is fine; the drain routing is the fault. The lasting fix is rerouting the drain inside the thermal envelope, which the visit should address, not just the restart.
It is losing water: a failed expansion tank that lost its air charge, a weeping joint in the loops, or a faulty auto-fill valve. Regular topping-off is a symptom, not maintenance — and each refill adds oxygen that corrodes the system internally. Get the actual fault found instead.
Condensing units are more efficient, but rowhouses complicate the venting — sidewall terminations need proper clearances from property lines and neighboring windows, and the condensate needs a freeze-proof drain path. An on-site assessment of the venting and drainage decides whether it is straightforward or a project.
No — that short-cycling wastes gas and wears components. Common causes are an oversized unit, a thermostat issue, or low water flow through the heat exchanger. Note the cycle length when you call; it is one of the most useful diagnostic details you can give.
Write down the exact code before touching anything — it maps to ignition, flame sensing, pressure, or condensate faults, and it is the fastest clue you can hand the triage. Do not guess fixes from the code. Report it when you call and the triage will tell you whether it is a reset, a visit, or an emergency.
Go deeper nationally, or sideways in Wilmington.
The national gas boiler repair page covers the full ignition, flame, and condensate fault families in general terms, and the hot-water hydronic page covers the sealed-system water side. In Wilmington, the general diagnosis page is where a misbehaving unit starts, the emergency page is where a dead one goes, and the replacement page handles the end-of-life conversation.
Call (888) 766-1474 — describe the fault pattern and get connected to a local pro.
