Prestige Solo 110 w/ repeating B26 error code

PMM

Homeowner with a 3 year old Solo 110 serving cast iron radiators upstairs and heated concrete floor in the basement. Now that winter's here in MN, we've been getting a B26 error code almost every day. Easy to start back up by adding pressure, but would really like to know what's causing this. No leaks in the system to my knowledge, have bled all the radiators. What else should I be looking for?

Alan (California Radiant) Forbes

Something

is causing a drop in pressure.  It could be a bad expansion tank, a leak you're not finding........................



Is there an air elimination device on the system or only manual air vents at the radiators?  There is some weirdness going on and you have to think of something unusual going on behind your back.

PMM

OK...

There are two relief valves at the top of the boiler - a screw type and flap type. I've kept the screw type closed, thinking that might even out the pressure, but it doesn't seem to make much difference.

We also have an old expansion tank, ceiling mounted above the boiler. When the Prestige was installed, I asked about removing the exp tank, but the installer said we might as well keep it if it's functional. How can I tell if there's a problem with the tank?

CMadatMe

LWCO

Low water cut off is open. Make sure operating pressure is above 10psi. If it is continually probably going to need to replace the internal lwco.

rm72

expansion tank

that big tank hanging from the ceiling is probably full and needs to be drained or better yet replaced with radiant expansion tank

tim smith

B26 code

Is the pressure dropping below 10 psi every night, if so, you have a leak somewhere? The lwco or expansion tank problem will only be the case if your relief valve is dripping, is that the case? You mention no signs of water?

PMM

Expansion tank is empty...

The expansion tank is dry, and as far as I know, always has been with this boiler. Sounds like it should be full at all times? If the boiler is not filling it, and we have no need for it (?) can I close it off from the system? There's a valve for the expansion tank with a tag that says "This valve should be OPEN at all times..."

Alan (California Radiant) Forbes

Expansion Tank

The expansion tank should be 2/3 full of water and 1/3 full of air at the top.  If it's empty, something is blocking the line from the system to the tank; either a valve is closed or the line is clogged.  Get it fixed or replace it with a properly sized diaphragm tank and see if the problem persists.