Piker said:
Numbus board issues with the Econoburn controls are nothing new, even on new boilers. I have had my share of them for sure, and in fact, several "discussions" with the factory about the problem. Apparently they are now saying that the high limit aquastat was never intended to shut down the fan except in emergency cases... this after finding out that switching the fan back on in low fire is drawing too many amps through the nimbus board and burning them out. Problem is, if there is no call for heat, the boiler is absolutely going shut the fan off at some point. They maintain that the boiler will not overheat in low fire... that there is only enough air to keep the coals alive... but when I open the bottom of a 150 on low fire and see an 1800° torch that is 6" long coming out of the nozzle... that seems like more than just keeping the coals alive.
I had one of my customers get service directly from econoburn a week or so ago for this very issue. They swapped the nimbus board, and reset the dip switches so the fan on low fire would just barely turn... this was an attempt to keep the fan running all the time so that you don't have that high amp draw through the numbus board when the high limit aquastat releases... problem is... the boiler doesn't gasify at this slow fan speed... and it creosoted up terribly in just a few days time while burning way more wood than normal. Ultimately, the customer just said forget the low fire, and set his digital aquastat higher than the mechanical... now the mechanical aquastat controls the boiler, and he only has high fire. Econoburn seems okay with this setup.... so now I am considering sending my own letters out to customers telling them about the issue and how to try to prevent it.
The funny thing is, this isn't a hard fix... a time delay relay to run the fan flat out for 5 or 10 seconds on startup would solve the problem in a heartbeat... but doubtful that econoburn will add this feature to older boilers with warranty issues.
cheers
This is interesting stuff Piker, and you certainly have much inside information that the rest of us aren't privy to. I have a different perspective, based only on my own experience. This aquastat/controller thing has been like a Twilight Zone episode for me (yikes, my age is showing there

). This post will be long, but I need to include the background. I've been running my 150 since Nov 2008. During the first few days, the boiler temp would eventually hit what is referred to as "overtemp" - light flashing and buzzer going off. I didn't know what was going on because the boiler was not actually close to boiling over. Then someone with another boiler mentioned that the aquastat needed to be set down, and I also saw the same thing mentioned on the forum. So, I dropped the Honeywell aquastat to around 193*, and the light show stopped happening. I ran the boiler like this for 2 years fat, dumb, and happy - no reason to believe it wasn't correct. The boiler was performing well, and we used essentially no oil for 2 years. Then early this Fall I got the "humming", stopped fan as described previously. So, I called Dale and he told me the Honeywell is only supposed to be a fail-safe. Ok, I said, then tell me what I should be doing. He had me do the dip setting swap (the 5/3, not the one Piker described), and also the TC33 high limit down to 210*, based on our heating needs. Plus the Honeywell raised above 210* to function as the fail-safe. Then I ran a few larger loads, just to see what happened when the upper limit is reached. The TC33 was working ok temp-wise, stopping the fan at 209*, and starting up again around 201 (based on the 10* differential setting that I'm using). The lower fan setting also performed better, so everything was great except for one thing - the light and buzzer were back. I figured there must also be a controller setting to stop the light and buzzer, so I called Dale about that. I was fairly amazed when he told me that the solution was to BREAK the buzzer. He told me to unscrew the cap, and snap the black buzzer in the center with pliers. I did that and no more buzzer - just the blinking red light remains - no problem with that. But there is one more bizarre thing related to this. Dale told me that by setting the Honeywell up, the fan would continue to run on low speed (as Piker mentioned above). I just cannot understand that statement, and sent him an email to see if there was something I'm missing about this. I can't imagine any gasser that could allow a fan to continue running, even at low speed, unless the load always exceeds the boiler output. That's certainly not the case for me - all zones eventually shut off, and the boiler would boil over if the fan continued to run. I was hoping he would reply by saying that the fan continues to run until it hits the TC33 high limit, but based on what Piker wrote above, that's not going to happen. So at this point I don't know what's right or wrong, but as far as I'm concerned, the TC33 seems to be doing everything that it needs to, in the manner that it should, and the boiler is performing better than it ever has. And there is the additional bonus of having a blinking red light whenever it's idling - I've actually come to think of this "overtemp" as the idling indicator light :lol: So, I wonder if the "new" controller is the offspring of the TC33, with a user-friendly way added to shut off the "overtemp" buzzer and the light.