Burnham Series 3 boiler - 0 psi

Jstorms

Hi everyone, glad to have found this community!

Maybe a week ago our main level started overheating, in an attempt to troubleshoot I drained some water out of the boiler. I know now that was a mistake, and the issue ended up just being the zone valve, but now I've got another problem with the psi staying at 0. We've attempted turning the boiler off and letting it cool, I made sure the water pump filled the tank and when I opened the drain spout briefly just to check, water came out and the pressure valve does let air and water out too. There's a cold water tank but the ball valves on both pipes attached to it were closed. I opened them for maybe 5 or 6 hours because I read that might be necessary, but the pressure gauge didn't budge. 

The obvious answer is to open the fill loop, but I don't know if we have one. We have two metal pipes but I'm pretty sure they're air sensors for outside and there's no valves on them. There's nothing I can see to increase pressure. It's been a couple days now and I'm not sure how to fix it. 

I'm not sure if it's related, but our water was a little chilly so we turned the water heater up and have been adjusting it every so often the last week. I also can't find a pressure gauge on the water heater but I tested the pressure valve on that and it released water as it should. I'm wondering if the water heater could be the problem and that's affecting the boiler now that we've messed with that a bit too.

We haven't fixed the zone valve yet either, it just won't close completely so I don't believe that would cause the issue with the psi remaining at 0. I'll include some pictures and if someone could point me in the right direction, I'd appreciate it!

hot_rod

Something odd looking. The small 1/2" copper line at the left of the pic is the fill line. I see 3 shutoff valves and a backflow device, but no pressure reducing valve?
Often the backflow and fill valve re right next to one another. The fill valve is often set at 12 psi for a small home with two levels or less.

EBEBRATT-Ed

The water line in the first picture does not match the water line in the third picture