Laars Heat Diagnose

boulderz

Hello,
I am having an issue with our Laars Endurance EBP 110 not heating. The problem was happening only intermittently but now seems permanent. At first, I would notice the house was cold (only maintaining temps in the 60-65 degree range - and the whole house, not just the single zone I had an earlier thread about). The boiler does heat but is not circulating hot water fully. I can feel the outlet pipe just on top of the boiler is very hot (first 6" or so) and then downstream pipes are only lukewarm. Domestic water heating works fine. I contacted a heating contractor who suggested it could be the anticondensing valve failed or sticking in domestic water mode. He suggested I manually operate the switch on top of the ACV a few times. I tried it and it seemed to work once. The next time it happened toggling the switch didn't help. I tried testing to see if the ACV was stuck closed by isolating the primary loop by closing valves at the beginning of all zones. After closing the valves, the hot water circulates through the primary loop. So it seems to me the ACV is not stuck closed. Open the downstream valves and then water in the primary loop goes back to lukewarm. The boiler is just not sending the hot water through the zones. All 4 zones are calling for heat (red LEDs on Taco lit). Any ideas on how to diagnose or what could be the issue?

boulderz

Back to an intermittent problem as it is working this morning. Which makes diagnosing much harder..