How To: Fix Ignition Problems With Napoleon NPS40 and NPI40

The Napoleon NPS40 pellet stove and the NPI40 pellet insert were the first are two pellet stoves made by Napoleon. Like many pellet stove. Models that existed in the 1990s, these pellet stoves use analog controls (knobs and switches as opposed to digital controllers). There are a lot of these pellet stoves still in use and some online retailers still sell leftover stock. The stove has not been made since 2008. Over the years I have found a huge flaw in the design of these two models that will inevitably cause a serious repair bill if the problem is not corrected and, it’s a really simple and inexpensive fix.

The problem is this, the ignition “OFF” switch Napoleon uses on these units is plastic. It’s mounted on the steel exhaust passage that gets very, very hot. Over time the switch will become brittle and can sometimes melt. The switch is located inside the mechanical cabinet, under the hopper on the backside of the exhaust chamber leading over to the exhaust blower. Facing the stove, you can access the switch from the right side. Attached to it are an orange wire and one of the igniter wires which is usually white. The mounting for this switch is inset into the exhaust passage and actually monitors the exhaust gases.

The switch is normally closed, which makes it a "limit switch”. The designation of the switch is L120-10, which means that in its “normal state” the switch is closed (completes a circuit). At startup, electricity flows through the switch to the igniter. Once the stove has started and the exhaust temperatures reach 120°F, the switch opens and power to the igniter is cut. When the stove is turned off, the fire slowly dies out and the stove begins to cool down. When the air temps in the exhaust drop to 120°F, the proof of fire switch (a different switch) will open and power to the stove will be cut. When the stove falls below 110°F (10°F below 120°F), the igniter switch will now close again but because their proof of fire switch has already shut the power off, the igniter switch will just stay closed waiting for power to flow again once the stove is turned back on.

So here are the problem…lots of folks neglect to keep the convection motor clean or clean their venting frequently. Each of these contributes to excessive heat being built up within the stove. This prolonged heat exposure causes the igniter switch to fail and when it does, the power to the auger will be “ON” the entire time the stove is running. This burns the igniter out. Sometimes when this happens, a short in the igniter will take out the 30 shutdown timer box with it.

Here’s my fix. Simply upgrade to a ceramic igniter switch. Ceramic switches are designed to be used on hot surfaces. If your igniter hasn’t failed, I suggest doing the upgrade. If your igniter has failed, make sure you at least bench test the igniter switch to make sure it’s still working correctly…but I’d replace the switch along with the igniter.