Amtrol BoilerMate Indirect Problems
The Short Answer: An Amtrol BoilerMate stores potable water and steals heat from the boiler through a finned coil. Cold showers with a hot boiler mean the aquastat or Smart Control, the DHW circulator or zone valve, air in the coil, or a coil packed with scale. A wet jacket is a dead inner bottle. Do not treat it like a gas tank with a pilot.
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Search Intent & The Real Problem
The radiators are hot. The Amtrol next to them is not. Or the opposite: the boiler short-cycles all afternoon because the tank thinks it is always cold. BoilerMate (WH-series, CH / TD 41- and 80-gallon class, RTR Smart Control) is a polymer or glass inner tank inside a steel jacket with a finned heat exchanger — not a SuperStor smooth coil, not a Buderus Logalux, not a Weil-McLain AquaPlus. Hard water loves those fins. Cousins: SuperStor, Buderus, Weil-McLain. A coil inside the boiler block is a tankless coil.
What other guides get wrong
They tell you to relight a pilot on a tank that has no burner. They vinegar-flush the domestic side and call the fins “descaled.” Acid through an Amtrol coil is a licensed isolation job, not a garden hose in a faucet. They treat a warm outer jacket as proof the inner bottle failed — foam is thin on these; a healthy tank can feel warmer than a 2-inch-foam SuperStor. And they skip DHW priority, which is why a “dead” BoilerMate appears every heating season.
Step-by-Step Troubleshooting
Step 1: Confirm it is a BoilerMate, then split no-heat vs leak vs scald
| What you have | Path |
|---|---|
| Top connections, Amtrol / BoilerMate plate, 41 or 80 class | This page |
| Digital Smart Control, Er1 / Er2 / Er3 | Step 2 |
| Mechanical aquastat in a well, 90–150°F dial | Step 2 |
| Stainless indirect, inspection plate, Weil-McLain badge | Wrong article |
| Two domestic lines into the boiler block, no tank | Tankless coil |
| Jacket wet, rust at the base, inner bottle collapsed | Replacement |
- What to look for: Rating plate. Sensor well vs drywell. Circulator or zone valve on the boiler loop. Mixing valve on the domestic hot outlet. Photograph the piping before anyone “straightens it out.”
- Required tools: Phone camera, flashlight.
Step 2: Is the boiler being asked to heat DHW?
- What to look for: Aquastat or Smart Control calling. DHW pump spinning or zone valve open. Boiler in DHW priority. Many “dead BoilerMates” are a probe that fell out of the well, a pulled thermistor plug, or priority disabled after a thermostat swap.
- Required tools: Eyes on pump LEDs and the boiler display. The sticker on that Amtrol control.
Smart Control (confirm your manual):
| Code | Meaning | First move |
|---|---|---|
| Er1 | Thermistor open / unplugged / damaged | Reseat the probe in the well, then licensed |
| Er2 | Stored water over ~155°F | Mixing valve, stuck zone, probe location — scald risk |
| Er3 | Did not reach setpoint in about an hour | Coil scale, air, dead circulator, undersized boiler, then licensed |
Wrong well = the control thinks the tank is always hot or always cold. I find probes under insulation at least once a month.
Step 3: Circulator, zone valve, and coil delta-T
- What to look for: Supply pipe hot, return cooler if the tank is taking heat. Both pipes hot and the tank cold = air or a closed coil. Both pipes cold during a call = pump, relay, stuck flow-check, or control output. Isolation valves actually open. After a boiler drain, these coils air-lock.
- Required tools: Contact thermometer on both coil pipes.
Purging the hydronic side is a boiler procedure. Do not open domestic faucets to “bleed the coil.” Do not crack gas fittings on the boiler — do not purge gas.
Step 4: Mixing valve, recirc, and “not enough hot water”
- What to look for: Scald at one fixture, tepid at another. Recirc returning into the cold inlet and stripping the tank. Mixing valve failed closed on the hot port. Setpoint on a mechanical aquastat that someone left at 110°F. House static over ~80 psi dumping the T&P on every heat cycle — T&P on a new heater, expansion tank full. Typical relief 150 psi / 210°F. Never cap it.
- Required tools: Thermometer at tank-out vs mixed-out. Hose-bib gauge if the T&P is wet.
Lukewarm with a hot tank is not “buy an 80-gallon.” Measure. Fixture-side cousin: Bradford White not hot enough as physics, Amtrol parts as parts.
Step 5: Scale on the fins, coil leak, vessel leak
- What to look for: Boiler that never shuts up on DHW, rising fuel use, tank that will not hit setpoint (Er3). Finned coils scale into an insulator in hard water — that is the Amtrol-specific funeral. Coil leak: boiler losing pressure while the domestic side gains pressure or discolors — shut domestic and the boiler; that is a health issue. Foam jacket wet at the base with fittings dry = inner bottle. Polymer bottles do not get an anode; glass-lined cousins still might. Do not inject stop-leak into an indirect.
- Required tools: Paper towel. Pressure gauges on the boiler are licensed territory if you are not the boiler tech.
A pinholed coil is a tank, not a flush. Isolate — apartment shutoff if you need the house water off. No floor drain? This drain procedure.
When DIY Ends: Calling a Licensed Pro
Stop at boiler programming, hydronic purging, gas combustion, Er2 scald, and any leak from the vessel or coil. You may verify valves are open, reseat a probe that is obviously out of the well, and read Er codes. EMS / aquastat wiring, coil isolation for descaling, and replacement of a BoilerMate are licensed boiler work. Amtrol warranties are allergic to DIY control jumps and stop-leak.
Frequently Asked Questions
Q: Why is my Amtrol BoilerMate not making hot water? A: The boiler is not getting a DHW call (sensor, aquastat, or priority), the circulator or zone valve is dead, the coil is air-bound, or the fins are scaled. House heat working does not prove the tank circuit.
Q: What does Er1, Er2, or Er3 mean on a BoilerMate Smart Control? A: Er1 is the thermistor. Er2 is over-temperature — treat it as a scald risk. Er3 is a tank that never reached setpoint (coil, pump, or boiler). Confirm against the manual on that unit.
Q: Can I repair a leaking Amtrol indirect? A: Unions, valves, and T&P yes. A wet jacket or a coil leaking boiler water into potable is replacement. Do not epoxy the shell or dump stop-leak in the loop.