I did all of these things:
- Checked the pressure and temperature, which looked OK
- Attempted to "purge" the area. The zone (let's call it Zone 2), was purged by opening the valve on the return. I had incorrectly completed this by opening the valve on the supply return. It didn't seem to make a difference, assuming I did it right (I opened a 5 gallon bucket worth).
What I did notice is that Zone 2 was in a loop/split. Zone 2 split into two pipes, "Back" and "Front". It seems that the baseboard that doesn't work is in "Back" and what did work was in "Front". When I checked the plumbing I also noticed that pipe immediately coming out of the split for Zone 2 was hot, but once the water got to "Front" and "Back" it was only "Back" that was lukewarm.
Here's a diagram (more or less)
(1) There appears to a ball lever here. The left of this lever + is significantly hotter | than the right. It's green +-----------------------------------------+ | Unindentified Pipe | (2) This appears to be some sort | | of outlet/drain. I've tried | +(2) + | draining this. This is red +------------+-----------------+ | | + Zone 2 - Front +(1) | | (3) This is a ball lever. Each | | | side of this is scorching hot. | | | Hotter than Zone 2 - Front. | + | | Turning this off doesn't appear +---------------------+ | | to do much. | Zone 1 +(3) | | | | | | | (4) This is a ball le^er. Turning this +-+ (4) | | | off makes Zone 2 - Front hotter | | | | but only the right. This effect, |Z | | | seems to only be temporary, though. |o + + + |n |e | +| | |2 | + lever
I'm probably going to call a plumber, but feel like this may have a really simple resolution that someone's experience and familiarity could easily solve by simply saying: "Oh hey, just twist this thingy." (I hope.)
One thing I've read on various forums is that it's possible due to the length of pipe that even though I purged the air via the return valve it's not fully out of the system. One suggestion was the temporarily increase the pressure to force everything out. I'm not sure how to do this, however. This is the boiler I have. Going to take a look at the manual online.
One thing I noticed several months ago was a gurgling noise coming from the boiler. In retrospect these two issues may be related as apparently gurgling is a loss of water pressure in some cases. That lack of pressure may explain why two zones are cold (air blockage with combination of low pressure).
Here are some pictures: https://imgur.com/a/gXnkGi7
I tried to be as detailed as I can. If information is needed please let me know :D.