Harman pb 105 overheat zone issue.

[Tdiguy]

I have a harman pb 105 that i have had for a few years now. Getting it installed and working was a pain. The local dealer near me does not really install these per say. They simply pipe them and by that only the intake and exhaust. So I had the dealer drop it off. I had a master plumber come to do the install and he was nice enough to connect it to power and plumb it up and such. I recently noticed that the overheat zone had never been connected. Course i noticed this because i just switched to a different brand of pellets that seem to burn hotter because several times now my boiler has stopped working and been flashing overheat.
So i looked into it a little bit and i found a relay in box product which is a self contained dpdt relay so i figured i could have the boiler trigger that to fire up the circulator pump and open a zone.
I got it all wired up but now the overheat zone is always on. Mind you the led itself isnt always on but the circuit is always on. The wiring i dont think could be easier really. 2 wires for the coil and then the switched wires. When i disconnect the blue wire from harman of course the relay shuts off but when i connect it it goes right back on. I am having a hard time thinking that its anything other than a bad logic board since there is so little that could be wrong. I am also not sure if i call the dealer if i will get any help with it at all since they wouldn't connect it to power to start with.

 

[PassionForFire&Water]

I guess there is the overheat temperature sensor that is set at a to low temperature.
Increase that set point to 185F or 190F.
If it has a differential setting, set that at 5F
If all this is not possible, I would just install a strap on overheat aquastat to control the overheat circulator/zone valve

 

[Tdiguy]

I guess there is the overheat temperature sensor that is set at a to low temperature.
Increase that set point to 185F or 190F.
If it has a differential setting, set that at 5F
If all this is not possible, I would just install a strap on overheat aquastat to control the overheat circulator/zone valve

The overheat temp for this boiler is hard set in the logic board i have no way to change it. Also even when the overheat light is off there is power to the overheat zone which i think it the real problem.
Any idea what a new logic board costs? I am having a heck of a time finding the pricing. If they are over 90$ i will probably go with a different solution like an aquastat. I figure i can still use my dpdt relay with the aquastat and have it cut power to the boiler (while its too hot that is) turn on the circulator and open a zone valve. Maybe cutting power to the boiler is unneeded but whats a little overkill here and there when it comes to recovering from a condition that brings equipment close to design limits.

 

[Tdiguy]

Wow found a price for the logic board. I hope i never actually have to replace this puppy at $239.99 (broken image removed) I think i wil go with using a aquastat in its place. I am pretty sure i can get those for about 80-90$.