Getting the Prestige Solo 110 to stop throwing codes
The Triangle Tube Prestige Solo 110 is a solid condensing combi, but once it starts flagging errors, the diagnostic path isn't always obvious. I've spent more weekends than I care to admit wrestling with these units, and most of the time the issue comes down to one of three things: low static pressure, a bad flame sense, or a misrouted sensor. Let's get into it. Before you call a technician, start with the basics that actually matter. Check the domestic water pressure gauge on the front panel. It should sit between 12 and 15 PSI when the system is cold and isolated. If it's below 10, the boiler will lock out on a low-pressure condition before it even attempts ignition. The fill loop valve at the bottom of the unit is easy to miss behind the kickplate. Open it slowly until the gauge climbs, then close it firmly. Don't overfill past 18 PSI or you'll open the relief valve and lose more water than you gained. Error codes on the Solo 110 follow a straightforward pattern. A single red LED flash with a green LED off usually indicates a flame failure during startup. Two flashes points to an overheat condition. Three flashes is a pressure sensor fault. Four flashes means the limit thermostat has tripped. Five flashes is an ignition trial failure. Six flashes indicates a faulty flame signal during operation. The display also cycles through fault memory, so hold the mode button for three seconds to scroll through recent error logs. Most technicians skip this step and replace parts blindly.
Here's a specific case I ran into last fall that illustrates why the obvious fix isn't always the right one. A homeowner reported repeated lockouts on a Prestige Solo 110, and the error was a flame failure code. The gas valve was opening, the igniter was sparking, but the boiler never established a flame. I swapped the flame sensor, cleaned the electrode, checked the gas supply pressure at the manifold (10.5 inches of water column, which is correct), and the problem persisted. After two visits and two unnecessary part replacements, I finally measured the resistance of the flame sensor ground path. The ground wire had corroded at the connection point near the control board. Barely visible corrosion, but enough to raise the resistance to over 50 ohms. The board couldn't detect the microamp signal from the flame. Once I cleaned the terminal and applied dielectric grease, the unit ran for three weeks straight. Replacing the sensor or gas valve would have cost them around $450 and still wouldn't have fixed it.
Common problems and what they actually mean
Hot water works fine but central heating doesn't engage. This is usually the three-way diverter valve sticking or the actuator motor failing. On the Solo 110, the diverter is electrically actuated, not hydraulic. Listen for a small clicking sound from the valve when the heating call activates. No click means the actuator isn't receiving power or the motor is dead. If you hear clicking but the radiators stay cold, the valve spindle may be stripped internally. Valve replacement runs about $80 to $120 for the part, and the job itself is roughly an hour of labor if you're familiar with the removal process. The unit cycles on and off rapidly during heating mode. This is almost always a flow issue, not a control problem. Check the system side valve positions first - both the supply and return isolation valves need to be fully open. Then verify the circulator is actually moving water. Place your hand on the supply pipe near the boiler; it should feel warm within 30 seconds of a heat call, and the return should also be warm. If the supply is hot but the return is cold, the pump isn't circulating. Could be a stuck impeller, a closed zone valve, or air trapped in the system. Bleed the radiators and check the auto-air vent on the boiler header. A clogged air vent creates micro-airlocks that kill flow faster than anything else on these units. Error code flashing in a pattern that doesn't match the manual. The Prestige Solo 110 uses a dual-LED indicator system, and some third-party error code charts online are wrong. The official Triangle Tube documentation lists the codes as flashes of the RED LED only, with the GREEN LED indicating power status. If your LEDs are behaving differently, check whether a recent firmware update changed the flash patterns. Some units shipped with early firmware that misreported certain faults as generic flame failures. A board-level diagnostic mode reveals the actual fault code - disconnect power for 30 seconds, then reconnect while holding the mode and reset buttons simultaneously. The LEDs will display a diagnostic code different from the normal error display. Write it down before powering down.
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Pressure-related issues that aren't what they seem
Pressure drops consistently over a few days with no visible leaks. The first place to check is the expansion tank. Press the Schrader valve on the tank with a tire gauge. If it reads system pressure or lower, the bladder is failed and the tank is waterlogged. This causes the pressure to spike during heating cycles and then drop as the relief valve bleeds excess. Replace the expansion tank - standard size for the Solo 110 is a 4.8 gallon vertical tank. Recharging it won't fix a failed bladder, and I've seen technicians waste two service calls trying to bleed it. If the pressure gauge reads zero but the unit still fires, the sensor tube is likely blocked. The Solo 110 uses a pressure transducer connected to the system via a small copper capillary tube. Over time, this tube can become clogged with sludge or debris from the system, causing false zero readings. Disconnect the tube from the transducer and blow through it with compressed air. It should be clear. If it's blocked, flush it and replace the O-ring seal before reattaching. A clogged sensor tube causes intermittent lockouts that are nearly impossible to diagnose because the pressure appears normal when the technician arrives.
Flame rectification and ground integrity
Intermittent flame failure codes that resolve themselves after a few cycles. This is a ground path issue more often than a sensor issue. The flame sensor on the Prestige Solo 110 operates in the microamp range - typically 1.5 to 4 microamps for a healthy flame. If your multimeter shows anything below 1 microamp during operation, the ground path is compromised. Check every ground connection in the chain: the sensor to the burner assembly, the burner to the heat exchanger, the heat exchanger to the chassis ground, and the chassis to the control board ground. A single loose terminal in that chain drops the signal below the board's detection threshold. The flame sensor itself can be fouled by condensation inside the combustion chamber. On condensing boilers like the Solo 110, water vapor condenses on the heat exchanger tubes and drips toward the burner area. Over months of operation, this leaves a thin film of mineral deposits on the sensor probe. Clean it with fine emery cloth or 0000 steel wool - not sandpaper, which leaves abrasive residue. Wipe with a clean rag afterward. Do not use chemical cleaners on the sensor. Replacement sensors run about $15 to $25 and are worth changing every other year as preventive maintenance, even if the old one looks fine.
Gas valve and combustion performance
The boiler fires but shuts down after 10 to 20 seconds. Check the combustion air and flue gas readings with a manometer or multimeter probe. The Solo 110 targets a flue gas CO2 level of approximately 9.2 percent on natural gas at sea level. If CO2 reads below 8.5 percent, the air-to-fuel ratio is too lean, which triggers a high-limit shutdown. This can be caused by a partially blocked intake air filter, a deteriorated draft inducer motor seal, or a cracked heat exchanger allowing excess air ingress. Inspect the intake filter first - it's a foam pad behind the front access panel. A clogged filter restricts combustion air enough to destabilize the flame. The gas valve on these units is a modulating valve controlled by the main board. If the board is sending proper 24V signals to the valve but the valve isn't responding, the valve coil may be failing. Measure the resistance across the gas valve terminals with power disconnected. The expected range is 35 to 45 ohms. Values outside that range indicate a bad valve. However, before replacing the valve, verify the board is actually outputting the modulation signal. Use a multimeter on DC voltage mode while the boiler is calling for heat. You should see a varying voltage between 0 and 24V DC at the gas valve terminals. If the board outputs a solid 24V or a solid 0V instead of a modulating signal, the control board is faulty, not the gas valve. Swapping parts without this test is how you end up with both a new gas valve and a new board that you don't need.
Control board diagnostics
The main control board on the Prestige Solo 110 is relay-based with a microprocessor. Common failure points are the relay contacts for the gas valve and the 24V transformer secondary. If the unit has no power at all - no display, no LED activity - check the 3-amp slow-blow fuse on the board first. It's a standard automotive blade fuse visible under a small plastic cover. A blown fuse usually indicates a short downstream, commonly from a failed circulator or gas valve coil. Replace the fuse and recheck resistance on those components before closing the circuit again, or the new fuse will blow immediately. If the display works but the boiler won't ignite despite correct voltage at the transformer and spark electrode, check the thermal fuses on the heat exchanger assembly. There are two: the primary high-limit and the secondary operating limit. Both are 185°F-rated one-time fuses with push-on terminals. Test continuity with an ohmmeter. Either one open means no ignition sequence. These are located behind the burner access panel and are easily overlooked because they look identical to the wiring harness connectors they attach to. The parts cost is minimal - about $8 each - and replacement takes ten minutes.
When to stop troubleshooting and call someone
Cracked heat exchanger. If combustion analysis shows elevated CO levels above 100 ppm on natural gas, or if you see water leaking from the heat exchanger joints, the aluminum-silicon alloy passages may be cracked. These units use a plate-type heat exchanger that can develop stress fractures from repeated thermal cycling, especially if the system sidestream flow is insufficient. Repair isn't possible - replacement of the heat exchanger assembly runs $600 to $900 for the part alone. At that point, evaluate whether the cost of repair justifies the age of the unit. Most Solo 110s last 15 to 20 years with proper maintenance. Mold or moisture smell from the flue. Condensate neutralizer media (calcium carbonate) in the condensate treatment kit depletes over time. When it's exhausted, acidic condensate passes through the drain line and can corrode the flue connections. The smell is distinct and usually precedes a visible rust stain near the flue collar. Inspect the condensate trap and neutralizer cartridge annually. The neutralizer kit should be replaced every 12 to 18 months depending on usage. A clogged condensate trap causes the boiler to shut down on a pressure switch fault, which adds another fault code to the mix and makes diagnosis slower. The Delta T across the heat exchanger is a useful diagnostic metric that most homeowners never check. Place two temperature probes on the supply and return pipes near the boiler during a heating call. The Solo 110 targets a Delta T of approximately 15 to 20 degrees Fahrenheit between supply and return. A Delta T below 10 degrees indicates excessive flow - the water is moving too fast through the heat exchanger and not absorbing enough heat. This can happen if a zone valve is stuck open or if the system was recently repiped with undersized balancing. A Delta T above 25 degrees indicates insufficient flow, which triggers high-limit cuts. Balancing the system valves usually resolves this within an hour.
Maintenance that prevents most problems
Annual servicing on the Solo 110 should include: cleaning the flame sensor and electrode, inspecting the combustion air filter, checking the expansion tank pre-charge pressure, verifying flue gas readings, inspecting the condensate trap and neutralizer, and testing the high-limit and operating limit thermostats. This takes about 45 minutes for someone who knows the unit and costs nothing if you do it yourself beyond the $15 replacement sensor if you choose to swap it proactively. The user manual recommends draining and refilling the system every three years to remove sludge buildup. This is good advice for older systems but unnecessary for properly treated new installations. If your system water is clear and the pH is between 7 and 8 when you check it, skip the drain. If the water is dark and has visible particulate, a flush is warranted regardless of age. The Prestige Solo 110's plate heat exchanger channels are small enough that sludge accumulation can restrict flow significantly over time.
