Yesterday, my two year old fancy high efficiency boiler died. The heat has been erratic for a couple of days and the house has been cold. I thought that the circulation pump had failed so I bought another one at almost $200. A little while later I looked at the boiler’s computer display to check that the water was getting hot and I saw the "F05" error flashing. The manual says this is because the output temperature is over 250 degrees. The real reason is that the thermister (usually spelled thermistor, but the part you order has an er at the end) has failed showing the temperature as high, even though the temperature is low.
I had to spend $27 for the the thermister plus the cost of overnighting it.
Last year, I had the exact same problem. This thermister fails once a year. While it is failing the heat is erratic, but there is no way to tell what the cause is. It is an easy fix once it finally dies, but the last time it took two weeks and several emails with the Peerless Pinnacle engineers to figure our which thermister to change and what exactly the "F05" error meant. I ordered two thermisters and I am thinking that I should have bought 5 or 6.
This appears to be a serious design flaw in these boilers, and if I had known about it I would have gone with another brand. Now I am stuck with an expensive boiler that needs fixing constantly. I feel sorry for people who have to hire a plumber to do this.
On top of everything I had to sit up next to the woodstove last night to keep the house warm and prevent the pipes, cats and people from freezing. I got maybe two hours sleep and my back is killing me. I’ve been in meetings all morning where I could not stop yawning.