Navien 240 combi unit, hot water base board, issue with downstairs heat

[drochford]

We have a navien 240 combi unit. Hot water is fine, usually let it run a few minutes before jumping right in a shower. Our hot water base board downstairs is an issue in the COLD. Upstairs we set the thermostat to 67/68 and it maintains that temp. Downstairs I have the thermostat set to 70 via programmable thermostat at 430am. The other first cold morning, 630am, temp downstairs was at 63. When it is real cold out, the downstairs does not even come close to the temp set. After 9/10 am it will start to rise and maybe hit 68, depends on how cold it is outside. Today the temp downstairs was 67 when we woke up at 630, but its a bit warmer out then the other day, its about 30 this morning. Baseboards are cold or slightly warm when I get up. I expect to hear the crackling sounds of water running through the baseboards since its set to 70 but no. Again this is only when its freezing outside, the other day it was about 20, today 30. I dont know what the issue is. Its been this way since we had it installed. My husband at first said we, NY, never had freezing temps like this, so the unit cant keep up. I do not agree, something must be wrong. I've attached a picture of our setup. Any recommendations is greatly appreciated. Our home is approximately 2600 sq ft. Two zone heating. We live on long island, NY.

 

[Dana]

Are you running the heating water output at some fixed temperature, or do you have the "outdoor reset" option installed?

How many running feet of baseboard do you have on each of the zones, broken down by zone?

Can you tell if the circulation pump is running other than the "crackling sound"? The baseboards should be essentially quiet, with perhaps some ticking metal as the temperature changes, but if there's gurgling it could have air in the system limiting flow, or it could be cavitating at the pump.

It's hard to figure out the near-boiler plumbing in the upside-down picture with other stuff in the foreground. Some close-ups of what happens between the boiler and circulation pump(s) might be worth it. (Oriented right side up too- standing on my head on the desk is more than I'm up for today. )